Project Collection "Polyelectrolytes"

A project collection of Polymers (ISSN 2073-4360). This project collection belongs to the section "Polymer Chemistry".

Papers displayed on this page all arise from the same project. Editorial decisions were made independently of project staff and handled by the Editor-in-Chief or qualified Editorial Board members.

Editors

Dr. Christine Wandrey
Website
Collection Editor
Ecole Polytechnique Fédérale de Lausanne, EPFL SB ISIC-GE, CH C1 392, station 6, CH-1015 Lausanne, Switzerland
Interests: water-soluble polymers; polyelectrolytes; polyelectrolyte complexes; hydrogels; biomaterials; radical polymerization/copolymerization; characterization of charged macromolecule; analytical ultracentrifugation
Special Issues and Collections in MDPI journals
Prof. Dr. Ruth Freitag
Website
Collection Editor
Chair for Process Biotechnology, Faculty of Engineering Sciences, University of Bayreuth, 95440 Bayreuth, Germany
Interests: stimuli-responsive; materials; bioconjugates; synthetic biodelivery systems; bioseparation engineering; scaffolds for tissue engineering; encapsulation; monolithic stationary phases for chromatography and electrochromatography
Dr. Ulrich Scheler
Website
Collection Editor
Head of teh Department Polyelectrolytes and Dispersions, Leibniz-Institut für Polymerforschung Dresden e.V., D-01069 Dresden, Germany
Interests: structure, dynamics and charge in complex polymer and polyelectrolytes systems magnetic resonance (NMR & EPR) including methods developments
Special Issues and Collections in MDPI journals

Project Overview

Dear Colleagues,

Polyelectrolytes are the subject of very active research and development in fields such as chemistry, physics, biology, medicine, materials science, food science, and nanotechnology. Polyelectrolyte properties are intrinsic, not only to a multitude of single macromolecules, but also to their organized structures and molecular assemblies. Biopolymers, such as proteins, DNA, and polysaccharides, which are available in almost unlimited quantity in nature, as well as many synthetic polymers, which are industrially produced on a large scale, belong to this fascinating class of polymers. The importance of polyelectrolyte research is best documented by the exponential annual increase of scientific publications dedicated to polyelectrolytes.

This Topical Collection of Polymers intends to serve as an interdisciplinary platform addressing all polyelectrolyte related aspects. Overcoming the hurdles of single research disciplines will be the major goal of this platform. Original articles reporting recent progress on polyelectrolyte related research from different disciplines and review papers highlighting in particular interdisciplinary aspects are both invited. Launched in 2015, this Topical Collection remains open for submissions. We are looking forward to receiving your paper at any time.

Dr. Christine Wandrey
Prof. Dr. Ruth Freitag
Dr. Ulrich Scheler
Collection Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the collection website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Polymers is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2200 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • polyelectrolyte synthesis, modification and functionalization
  • advanced analysis and characterization of polyelectrolytes and their assemblies
  • thermodynamics, solubility, and phase diagrams
  • polyelectrolytes in solution and at interfaces
  • theory and simulations
  • polyelectrolyte phenomena
  • assemblies and multilayers
  • complexes and particles
  • conformation and counterions: theory vs. experiment
  • natural polyelectrolytes
  • synthetic polyelectrolytes
  • hybrid materials
  • polyelectrolytes in food and cosmetics
  • polyelectrolytes for biomaterials and pharmaceuticals
  • polyelectrolytes for industrial and environmental processes

Related Special Issues

Published Papers (90 papers)

2020

Jump to: 2019, 2018, 2017, 2016, 2015, 2014, 2011, 2010

Open AccessReview
Strategies to Functionalize the Anionic Biopolymer Na-Alginate without Restricting Its Polyelectrolyte Properties
Polymers 2020, 12(4), 919; https://doi.org/10.3390/polym12040919 - 15 Apr 2020
Cited by 4
Abstract
The natural anionic polyelectrolyte alginate and its derivatives are of particular interest for pharmaceutical and biomedical applications. Most interesting for such applications are alginate hydrogels, which can be processed into various shapes, self-standing or at surfaces. Increasing efforts are underway to functionalize the [...] Read more.
The natural anionic polyelectrolyte alginate and its derivatives are of particular interest for pharmaceutical and biomedical applications. Most interesting for such applications are alginate hydrogels, which can be processed into various shapes, self-standing or at surfaces. Increasing efforts are underway to functionalize the alginate macromolecules prior to hydrogel formation in order to overcome the shortcomings of purely ionically cross-linked alginate hydrogels that are hindering the progress of several sophisticated biomedical applications. Particularly promising are derivatives of alginate, which allow simultaneous ionic and covalent cross-linking to improve the physical properties and add biological activity to the hydrogel. This review will report recent progress in alginate modification and functionalization with special focus on synthesis procedures, which completely conserve the ionic functionality of the carboxyl groups along the backbone. Recent advances in analytical techniques and instrumentation supported the goal-directed modification and functionalization. Full article
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Open AccessArticle
Electrical Field-Assisted Gene Delivery from Polyelectrolyte Multilayers
Polymers 2020, 12(1), 133; https://doi.org/10.3390/polym12010133 - 06 Jan 2020
Cited by 2
Abstract
To sustain gene delivery and elongate transgene expression, plasmid DNA and cationic nonviral vectors can be deposited through layer-by-layer (LbL) assembly to form polyelectrolyte multilayers (PEMs). Although these macromolecules can be released for transfection purposes, their entanglement only allows partial delivery. Therefore, how [...] Read more.
To sustain gene delivery and elongate transgene expression, plasmid DNA and cationic nonviral vectors can be deposited through layer-by-layer (LbL) assembly to form polyelectrolyte multilayers (PEMs). Although these macromolecules can be released for transfection purposes, their entanglement only allows partial delivery. Therefore, how to efficiently deliver immobilized genes from PEMs remains a challenge. In this study, we attempt to facilitate their delivery through the pretreatment of the external electrical field. Multilayers of polyethylenimine (PEI) and DNA were deposited onto conductive polypyrrole (PPy), which were placed in an aqueous environment to examine their release after electric field pretreatment. Only the electric field perpendicular to the substrate with constant voltage efficiently promoted the release of PEI and DNA from PEMs, and the higher potential resulted in the more releases which were enhanced with treatment time. The roughness of PEMs also increased after electric field treatment because the electrical field not only caused electrophoresis of polyelectrolytes and but also allowed electrochemical reaction on the PPy electrode. Finally, the released DNA and PEI were used for transfection. Polyplexes were successfully formed after electric field treatment, and the transfection efficiency was also improved, suggesting that this electric field pretreatment effectively assists gene delivery from PEMs and should be beneficial to regenerative medicine application. Full article
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2019

Jump to: 2020, 2018, 2017, 2016, 2015, 2014, 2011, 2010

Open AccessArticle
Enhanced Pervaporation Properties of PVA-Based Membranes Modified with Polyelectrolytes. Application to IPA Dehydration
Polymers 2020, 12(1), 14; https://doi.org/10.3390/polym12010014 - 19 Dec 2019
Cited by 1
Abstract
In this work, dense and supported pervaporation polyvinyl alcohol (PVA)-based membranes modified with poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate)(PSS)/PAH top nanolayers were synthesized. Two main points were investigated: the role of the polyelectrolyte PAH on water selectivity of the selective polymer matrix and [...] Read more.
In this work, dense and supported pervaporation polyvinyl alcohol (PVA)-based membranes modified with poly(allylamine hydrochloride) (PAH) and poly(sodium 4-styrenesulfonate)(PSS)/PAH top nanolayers were synthesized. Two main points were investigated: the role of the polyelectrolyte PAH on water selectivity of the selective polymer matrix and the impact of the porous substrate based on polyacrylonitrile (PAN) and aromatic polysulfone amide (UPM-20®), used to get supported high-performance membranes. Various methods of analysis (fourier-transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), atomic force microscopy (AFM), small-angle X-ray scattering (SAXS), porosity, contact angles, ultrafiltration) were applied to study the developed membranes. Transport characteristics of the developed membranes were studied in isopropanol dehydration by pervaporation. Obtained results are discussed in the light of the structure and physicochemical characteristics of these PVA/PAH membranes and the types of porous substrate. It was shown that the PAN-supported membrane with the selective layer based on PVA/PAH modified by 10 polyelectrolyte PSS/PAH bilayers possessed ~4.5 times higher permeation flux with the same high selectivity level (99.9 wt % water in the permeate) for the dehydration of the isopropanol (20 wt % water) at 60 °C compared to the commercial analog PERVAPTM 1201. Full article
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Open AccessArticle
Revealing Adsorption Behaviors of Amphoteric Polyacrylamide on Cellulose Fibers and Impact on Dry Strength of Fiber Networks
Polymers 2019, 11(11), 1886; https://doi.org/10.3390/polym11111886 - 15 Nov 2019
Cited by 1
Abstract
Amphoteric polyacrylamide (AmPAM) has been widely used in a variety of industrial areas and the adsorption behavior of AmPAM plays a crucial role in its applications. In this study, a series of AmPAMs with various molecular weights (MW) were synthesized; and their impact [...] Read more.
Amphoteric polyacrylamide (AmPAM) has been widely used in a variety of industrial areas and the adsorption behavior of AmPAM plays a crucial role in its applications. In this study, a series of AmPAMs with various molecular weights (MW) were synthesized; and their impact on dry strength of fiber networks or paper was assessed. The results showed that the optimal MW of AmPAM for strength enhancement ranged between 300 and 500 k. More importantly, the adsorption behaviors of three typical AmPAM samples on silica (model substrate) and cellulose surfaces were revealed using a quartz crystal microbalance with dissipation monitoring (QCM-D) in situ and in real time. The adsorption dynamics of AmPAM and the conformation of the adlayers were further derived. The results indicated that a relatively high adsorption amount was achieved under the conditions of a high polymer concentration, a medium pH close to its isoelectric point (IEP), a mild ionic strength, and a high charged surface; whereas the MW of AmPAM had little effect on the equilibrium adsorption mass of AmPAM, but significantly affected the conformation of adsorbed layer on substrates. Based on the adsorption behaviors of AmPAM, the explanation of the best dry strength achieved in a narrow range of MW of AmPAM is proposed. It was concluded that the appropriate balance between bridging and flocculation, penetration into fiber pores, and conformation were only achieved in the optimal MW range of AmPAM. The findings obtained from in this work enable us to better understand the adsorption behaviors of polyampholyte, and provide a guideline on molecular design of AmPAM and its applications from both fundamental and practical points of view. Full article
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Open AccessArticle
Synthesis, Characterisation and Biological Evaluation of Ampicillin–Chitosan–Polyanion Nanoparticles Produced by Ionic Gelation and Polyelectrolyte Complexation Assisted by High-Intensity Sonication
Polymers 2019, 11(11), 1758; https://doi.org/10.3390/polym11111758 - 25 Oct 2019
Cited by 5
Abstract
Recently, one of the promising strategies to fight sensitive and resistant bacteria, and decrease the morbidity and mortality rates due to non-nosocomial infections, is to use antibiotic-loaded nanoparticles. In this study, ampicillin-loaded chitosan–polyanion nanoparticles were produced through the techniques of ionic gelation and [...] Read more.
Recently, one of the promising strategies to fight sensitive and resistant bacteria, and decrease the morbidity and mortality rates due to non-nosocomial infections, is to use antibiotic-loaded nanoparticles. In this study, ampicillin-loaded chitosan–polyanion nanoparticles were produced through the techniques of ionic gelation and polyelectrolyte complexation assisted by high-intensity sonication, using several crosslinking agents, including phytic acid (non-polymeric polyanion), sodium and potassium salts of poly(maleic acid-alt-ethylene) and poly(maleic acid-alt-octadecene) (polymeric polyanions). These nanoparticles were analysed and characterised in terms of particle size, polydispersity index, zeta potential and encapsulation efficiency. The stability of these nanosystems was carried out at temperatures of 4 and 40 °C, and the antimicrobial effect was determined by the broth microdilution method using sensitive and resistant Staphylococcus aureus strains. The results reveal that most of the nanosystems have sizes <220 nm, positive zeta potential values and a monodisperse population, except for the nanoparticles crosslinked with PAM-18 polyanions. The nanometric systems exhibited adequate stability preventing aggregation and revealed a two-fold increase in antimicrobial activity when compared with free ampicillin. This study demonstrates the potential application of synthesised nanoparticles in the field of medicine, especially for treating infections caused by pathogenic S. aureus strains. Full article
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Open AccessEditor’s ChoiceArticle
Employing of Trukhan Model to Estimate Ion Transport Parameters in PVA Based Solid Polymer Electrolyte
Polymers 2019, 11(10), 1694; https://doi.org/10.3390/polym11101694 - 16 Oct 2019
Cited by 18
Abstract
In the current paper, ion transport parameters in poly (vinyl alcohol) (PVA) based solid polymer electrolyte were examined using Trukhan model successfully. The desired amount of lithium trifluoromethanesulfonate (LiCF3SO3) was dissolved in PVA host polymer to synthesis of solid [...] Read more.
In the current paper, ion transport parameters in poly (vinyl alcohol) (PVA) based solid polymer electrolyte were examined using Trukhan model successfully. The desired amount of lithium trifluoromethanesulfonate (LiCF3SO3) was dissolved in PVA host polymer to synthesis of solid polymer electrolytes (SPEs). Ion transport parameters such as mobility (μ), diffusion coefficient (D), and charge carrier number density (n) are investigated in detail using impedance spectroscopy. The data results from impedance plots illustrated a decrement of bulk resistance with an increase in temperature. Using electrical equivalent circuits (EEC), electrical impedance plots (ZivsZr) are fitted at various temperatures. The results of impedance study demonstrated that the resistivity of the sample decreases with increasing temperature. The decrease of resistance or impedance with increasing temperature distinguished from Bode plots. The dielectric constant and dielectric loss values increased with an increase in temperature. The loss tangent peaks shifted to higher frequency region and the intensity increased with an increase in temperature. In this contribution, ion transport as a complicated subject in polymer physics is studied. The conductivity versus reciprocal of temperature was found to obey Arrhenius behavior type. The ion transport mechanism is discussed from the tanδ spectra. The ion transport parameters at ambient temperature are found to be 9 × 10−8 cm2/s, 0.8 × 1017 cm−3, and 3 × 10−6 cm2/Vs for D, n, andμ respectively. All these parameters have shown increasing as temperature increased. The electric modulus parameters are studied in an attempt to understand the relaxation dynamics and to clarify the relaxation process and ion dynamics relationship. Full article
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Open AccessArticle
Novel Ruthenium-Silver PTA-Based Polymers and Their Behavior in Water
Polymers 2019, 11(8), 1249; https://doi.org/10.3390/polym11081249 - 28 Jul 2019
Cited by 3
Abstract
New coordination polymers based on two metal-containing moieties Ru–Ag are synthesized: Na[RuCpX(PTA)-μ-(PTA)-1κP:2κ2N-AgX2] (X = Cl (1), Br (2), I (3)). Characterization is performed by NMR, UV-visible and FT-IR spectroscopy, [...] Read more.
New coordination polymers based on two metal-containing moieties Ru–Ag are synthesized: Na[RuCpX(PTA)-μ-(PTA)-1κP:2κ2N-AgX2] (X = Cl (1), Br (2), I (3)). Characterization is performed by NMR, UV-visible and FT-IR spectroscopy, optical-electron microscopy, and elemental analyses (C, H, N, S). Light scattering is employed to characterize the colloidal particles growth by polymer self-assembling. These structures are stable over a broad range of pH and exhibit thermally-driven swelling, thus resembling a typical thermosensitive hydrogel. Full article
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Open AccessArticle
Effects of Chain Length of Chitosan Oligosaccharides on Solution Properties and Complexation with siRNA
Polymers 2019, 11(8), 1236; https://doi.org/10.3390/polym11081236 - 25 Jul 2019
Cited by 1
Abstract
In the context of gene delivery, chitosan has been widely used as a safe and effective polycation to complex DNA, RNA and more recently, siRNA. However, much less attention has been paid to chitosan oligosaccharides (COS) despite their biological properties. This study proposed [...] Read more.
In the context of gene delivery, chitosan has been widely used as a safe and effective polycation to complex DNA, RNA and more recently, siRNA. However, much less attention has been paid to chitosan oligosaccharides (COS) despite their biological properties. This study proposed to carry out a physicochemical study of COS varying in degree of polymerization (DP) from 5 to 50, both from the point of view of the solution properties and the complexing behavior with siRNA. The main parameters studied as a function of DP were the apparent pKa, the solubility versus pH, the binding affinity with siRNA and the colloidal properties of complexes. Some parameters, like the pKa or the binding enthalpy with siRNA, showed a marked transition from DP 5 to DP 13, suggesting that electrostatic properties of COS vary considerably in this range of DP. The colloidal properties of siRNA/COS complexes were affected in a different way by the COS chain length. In particular, COS of relatively high DP (≥50) were required to form small complex particles with good stability. Full article
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Open AccessArticle
Role of Protein Self-Association on DNA Condensation and Nucleoid Stability in a Bacterial Cell Model
Polymers 2019, 11(7), 1102; https://doi.org/10.3390/polym11071102 - 29 Jun 2019
Cited by 1
Abstract
Bacterial cells do not have a nuclear membrane that encompasses and isolates the genetic material. In addition, they do not possess histone proteins, which are responsible for the first levels of genome condensation in eukaryotes. Instead, there is a number of more or [...] Read more.
Bacterial cells do not have a nuclear membrane that encompasses and isolates the genetic material. In addition, they do not possess histone proteins, which are responsible for the first levels of genome condensation in eukaryotes. Instead, there is a number of more or less specific nucleoid-associated proteins that induce DNA bridging, wrapping and bending. Many of these proteins self-assemble into oligomers. The crowded environment of cells is also believed to contribute to DNA condensation due to excluded volume effects. Ribosomes are protein-RNA complexes found in large concentrations in the cytosol of cells. They are overall negatively charged and some DNA-binding proteins have been reported to also bind to ribosomes. Here the effect of protein self-association on DNA condensation and stability of DNA-protein complexes is explored using Monte Carlo simulations and a simple coarse-grained model. The DNA-binding proteins are described as positively charged dimers with the same linear charge density as the DNA, described using a bead and spring model. The crowding molecules are simply described as hard-spheres with varying charge density. It was found that applying a weak attractive potential between protein dimers leads to their association in the vicinity of the DNA (but not in its absence), which greatly enhances the condensation of the model DNA. The presence of neutral crowding agents does not affect the DNA conformation in the presence or absence of protein dimers. For weakly self-associating proteins, the presence of negatively charged crowding particles induces the dissociation of the DNA-protein complex due to the partition of the proteins between the DNA and the crowders. Protein dimers with stronger association potentials, on the other hand, stabilize the nucleoid, even in the presence of highly charged crowders. The interactions between protein dimers and crowding agents are not completely prevented and a few crowding molecules typically bind to the nucleoid. Full article
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Open AccessReview
Protein–Polyelectrolyte Complexes and Micellar Assemblies
Polymers 2019, 11(7), 1097; https://doi.org/10.3390/polym11071097 - 28 Jun 2019
Cited by 8
Abstract
In this review, we highlight the recent progress in our understanding of the structure, properties and applications of protein–polyelectrolyte complexes in both bulk and micellar assemblies. Protein–polyelectrolyte complexes form the basis of the genetic code, enable facile protein purification, and have emerged as [...] Read more.
In this review, we highlight the recent progress in our understanding of the structure, properties and applications of protein–polyelectrolyte complexes in both bulk and micellar assemblies. Protein–polyelectrolyte complexes form the basis of the genetic code, enable facile protein purification, and have emerged as enterprising candidates for simulating protocellular environments and as efficient enzymatic bioreactors. Such complexes undergo self-assembly in bulk due to a combined influence of electrostatic interactions and entropy gains from counterion release. Diversifying the self-assembly by incorporation of block polyelectrolytes has further enabled fabrication of protein–polyelectrolyte complex micelles that are multifunctional carriers for therapeutic targeted delivery of proteins such as enzymes and antibodies. We discuss research efforts focused on the structure, properties and applications of protein–polyelectrolyte complexes in both bulk and micellar assemblies, along with the influences of amphoteric nature of proteins accompanying patchy distribution of charges leading to unique phenomena including multiple complexation windows and complexation on the wrong side of the isoelectric point. Full article
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Open AccessArticle
Structure and Rheology of Polyelectrolyte Complexes in the Presence of a Hydrogen-Bonded Co-Solvent
Polymers 2019, 11(6), 1053; https://doi.org/10.3390/polym11061053 - 17 Jun 2019
Cited by 3
Abstract
Intermolecular interactions as well as macromolecular conformation affect the rheological and microstructural properties of polyelectrolyte complexes (PECs) solutions. The properties of semi-dilute solutions of weakly charged PECs can be controlled by the degree of ionization and solvent composition. In this work, we examined [...] Read more.
Intermolecular interactions as well as macromolecular conformation affect the rheological and microstructural properties of polyelectrolyte complexes (PECs) solutions. The properties of semi-dilute solutions of weakly charged PECs can be controlled by the degree of ionization and solvent composition. In this work, we examined the effect of ethanol as a co-solvent on PECs composed of poly(allylamine hydrochloride) (PAH) and poly(acrylic acid) (PAA) at low pH. The aqueous PECs solution was turbid, indicating formation of large aggregates, whereas PECs solution in water/ethanol (60:40 w/w) was transparent, implying no aggregation, and demonstrated higher relative viscosity than the aqueous solution, implying pronounced network formation. Imaging PECs solution by transmission electron microscopy (TEM) demonstrated aggregation, whereas the solution prepared with the mixed solvent revealed almost no phase contrast. Small-angle X-ray scattering (SAXS) of PECs in the aqueous solution indicated the presence of aggregates, while PECs in mixed solvent demonstrated a swelled macromolecular conformation with diminished aggregation. PECs with no ionic interactions in the mixed solvent assumes a homogenous network structure, which enables PECs solution processing by electrospinning. Full article
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Open AccessEditor’s ChoiceReview
Intrinsic Disorder-Based Emergence in Cellular Biology: Physiological and Pathological Liquid-Liquid Phase Transitions in Cells
Polymers 2019, 11(6), 990; https://doi.org/10.3390/polym11060990 - 04 Jun 2019
Cited by 18
Abstract
The visible outcome of liquid-liquid phase transitions (LLPTs) in cells is the formation and disintegration of various proteinaceous membrane-less organelles (PMLOs). Although LLPTs and related PMLOs have been observed in living cells for over 200 years, the physiological functions of these transitions (also [...] Read more.
The visible outcome of liquid-liquid phase transitions (LLPTs) in cells is the formation and disintegration of various proteinaceous membrane-less organelles (PMLOs). Although LLPTs and related PMLOs have been observed in living cells for over 200 years, the physiological functions of these transitions (also known as liquid-liquid phase separation, LLPS) are just starting to be understood. While unveiling the functionality of these transitions is important, they have come into light more recently due to the association of abnormal LLPTs with various pathological conditions. In fact, several maladies, such as various cancers, different neurodegenerative diseases, and cardiovascular diseases, are known to be associated with either aberrant LLPTs or some pathological transformations within the resultant PMLOs. Here, we will highlight both the physiological functions of cellular liquid-liquid phase transitions as well as the pathological consequences produced through both dysregulated biogenesis of PMLOs and the loss of their dynamics. We will also discuss the potential downstream toxic effects of proteins that are involved in pathological formations. Full article
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Open AccessArticle
Interactions of Casein and Polypeptides in Multilayer Films Studied by FTIR and Molecular Dynamics
Polymers 2019, 11(5), 920; https://doi.org/10.3390/polym11050920 - 25 May 2019
Cited by 5
Abstract
Multilayer films containing α- and β-casein and polypeptides, poly-L-lysine (PLL), and poly-L-arginine (PLArg) were formed by the layer-by-layer technique and Fourier Transform InfraRed spectroscopy with Attenuated Total Reflection (FTIR-ATR) and FTIR/Grazing Angle analyzed their infrared spectra. We investigated the changes of conformations of [...] Read more.
Multilayer films containing α- and β-casein and polypeptides, poly-L-lysine (PLL), and poly-L-arginine (PLArg) were formed by the layer-by-layer technique and Fourier Transform InfraRed spectroscopy with Attenuated Total Reflection (FTIR-ATR) and FTIR/Grazing Angle analyzed their infrared spectra. We investigated the changes of conformations of casein and polypeptides in the complexes formed during the build-up of the films. To elucidate the differences in the mechanism of complex formation leading to various growths of (PLL/casein)n and (PLArg/casein)n films, we performed the molecular dynamics simulations of the systems consisting of short PLL and PLArg chains and the representative peptide chains—casein fragments, which consists of several aminoacid sequences. The results of the simulation indicated the preferential formation of hydrogen bonds of poly-L-arginine with phosphoserine and glutamic acid residues of caseins. FTIR spectra confirmed those, which revealed greater conformational changes during the formation of casein complex with poly-L-arginine than with poly-L-lysine resulting from stronger interactions, which was also reflected in the bigger growth of (PLArg/casein)n films with the number of deposited layers. Full article
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Open AccessArticle
Simultaneous Measurements of Structure and Water Permeability in an Isolated Human Skin Stratum Corneum Sheet
Polymers 2019, 11(5), 829; https://doi.org/10.3390/polym11050829 - 08 May 2019
Cited by 2
Abstract
Stratum corneum (SC), the outermost layer of human skin, acts as an intelligent physicochemical interface between the inside and the outside of our body. To make clear the relationship between structure and physical barrier properties of SC, we developed a method that enables [...] Read more.
Stratum corneum (SC), the outermost layer of human skin, acts as an intelligent physicochemical interface between the inside and the outside of our body. To make clear the relationship between structure and physical barrier properties of SC, we developed a method that enables us to simultaneously acquire X-ray diffraction (XD) patterns and transepidermal water loss (TEWL) values using a spread SC sheet isolated from human skin. The synchrotron X-ray was incident on the SC sheet surface at an angle of 45° to avoid interference between the two kinds of measurements. Detailed comparison between XD and TEWL data suggested that the thermal behavior of water permeability is closely related to the thermal expansion of the lattice spacings of the hexagonal phases above 40 °C and to the existence ratio of the orthorhombic phase below 40 °C. Thus, the new method we developed can give useful information on the mechanism of water permeation in SC without ambiguity caused by separate measurements of structure and water permeability with different samples. Full article
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Open AccessEditor’s ChoiceArticle
Effect of Solution Composition Variables on Electrospun Alginate Nanofibers: Response Surface Analysis
Polymers 2019, 11(4), 692; https://doi.org/10.3390/polym11040692 - 16 Apr 2019
Cited by 9
Abstract
Alginate is a promising biocompatible and biodegradable polymer for production of nanofibers for drug delivery and tissue engineering. However, alginate is difficult to electrospin due to its polyelectrolyte nature. The aim was to improve the ‘electrospinability’ of alginate with addition of exceptionally high [...] Read more.
Alginate is a promising biocompatible and biodegradable polymer for production of nanofibers for drug delivery and tissue engineering. However, alginate is difficult to electrospin due to its polyelectrolyte nature. The aim was to improve the ‘electrospinability’ of alginate with addition of exceptionally high molecular weight poly(ethylene oxide) (PEO) as a co-polymer. The compositions of the polymer-blend solutions for electrospinning were varied for PEO molecular weight, total (alginate plus PEO) polymer concentration, and PEO proportion in the dry alginate–PEO polymer mix used. These were tested for rheology (viscosity, complex viscosity, storage and loss moduli) and conductivity, and the electrospun nanofibers were characterized by scanning electron microscopy. One-parameter-at-a-time approach and response surface methodology (RSM) were used to optimize the polymer-blend solution composition to obtain defined nanofibers. Both approaches revealed that the major influence on nanofiber formation and diameter were total polymer concentration and PEO proportion. These polymer-blend solutions of appropriate conductivity and viscosity enabled fine-tuning of nanofiber diameter. PEO molecular weight of 2–4 million Da greatly improved the electrospinnability of alginate, producing nanofibers with >85% alginate. This study shows that RSM can be used to design nanofibers with optimal alginate and co-polymer contents to provide efficient scaffold material for regenerative medicine. Full article
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Open AccessArticle
Upper Critical Solution Temperature (UCST) Behavior of Coacervate of Cationic Protamine and Multivalent Anions
Polymers 2019, 11(4), 691; https://doi.org/10.3390/polym11040691 - 16 Apr 2019
Cited by 2
Abstract
Complex coacervation is an emerging liquid/liquid phase separation (LLPS) phenomenon that behaves as a membrane-less organelle in living cells. Yet while one of the critical factors for complex coacervation is temperature, little analysis and research has been devoted to the temperature effect on [...] Read more.
Complex coacervation is an emerging liquid/liquid phase separation (LLPS) phenomenon that behaves as a membrane-less organelle in living cells. Yet while one of the critical factors for complex coacervation is temperature, little analysis and research has been devoted to the temperature effect on complex coacervation. Here, we performed a complex coacervation of cationic protamine and multivalent anions (citrate and tripolyphosphate (TPP)). Both mixtures (i.e., protamine/citrate and protamine/TPP) underwent coacervation in an aqueous solution, while a mixture of protamine and sodium chloride did not. Interestingly, the complex coacervation of protamine and multivalent anions showed upper critical solution temperature (UCST) behavior, and the coacervation of protamine and multivalent anions was reversible with solution temperature changes. The large asymmetry in molecular weight between positively charged protamine (~4 kDa) and the multivalent anions (<0.4 kDa) and strong electrostatic interactions between positively charged guanidine residues in protamine and multivalent anions were likely to contribute to UCST behavior in this coacervation system. Full article
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Open AccessEditor’s ChoiceReview
Polyelectrolyte Complexes of Natural Polymers and Their Biomedical Applications
Polymers 2019, 11(4), 672; https://doi.org/10.3390/polym11040672 - 12 Apr 2019
Cited by 13
Abstract
Polyelectrolyte complexes (PECs), composed of natural and biodegradable polymers, (such as positively charged chitosan or protamine and negatively charged glycosaminoglycans (GAGs)) have attracted attention as hydrogels, films, hydrocolloids, and nano-/micro-particles (N/MPs) for biomedical applications. This is due to their biocompatibility and biological activities. [...] Read more.
Polyelectrolyte complexes (PECs), composed of natural and biodegradable polymers, (such as positively charged chitosan or protamine and negatively charged glycosaminoglycans (GAGs)) have attracted attention as hydrogels, films, hydrocolloids, and nano-/micro-particles (N/MPs) for biomedical applications. This is due to their biocompatibility and biological activities. These PECs have been used as drug and cell delivery carriers, hemostats, wound dressings, tissue adhesives, and scaffolds for tissue engineering. In addition to their comprehensive review, this review describes our original studies and provides an overview of the characteristics of chitosan-based hydrogel, including photo-cross-linkable chitosan hydrogel and hydrocolloidal PECs, as well as molecular-weight heparin (LH)/positively charged protamine (P) N/MPs. These are generated by electrostatic interactions between negatively charged LH and positively charged P together with their potential biomedical applications. Full article
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Open AccessArticle
Aqueous Liquid-Liquid Phase Separation of Natural and Synthetic Polyguanidiniums
Polymers 2019, 11(4), 649; https://doi.org/10.3390/polym11040649 - 09 Apr 2019
Cited by 3
Abstract
Protamines are natural polyguanidiniums, arginine(R)-rich proteins involved in the compaction of chromatin during vertebrate spermatogenesis. Salmine, a protamine isolated from salmon sperm, contains 65 mol% R residues, with positively charged guanidino (Gdm+) sidechains, and no other amino acids with ionizable or [...] Read more.
Protamines are natural polyguanidiniums, arginine(R)-rich proteins involved in the compaction of chromatin during vertebrate spermatogenesis. Salmine, a protamine isolated from salmon sperm, contains 65 mol% R residues, with positively charged guanidino (Gdm+) sidechains, and no other amino acids with ionizable or aromatic sidechains. Salmine sulfate solutions undergo liquid-liquid phase separation (LLPS) with a concentration-dependent upper critical solution temperature (UCST). The condensed liquid phase comprises 50 wt % water and >600 mg·mL−1 salmine with a constant 1:2 ratio of sulfate (SO42−) to Gdm+. Isothermal titration calorimetry, titrating Na2SO4 into salmine chloride above and below the UCST, allowed isolation of exothermic sulfate binding to salmine chloride from subsequent endothermic condensation and exothermic phase separation events. Synthetic random polyacrylate analogs of salmine, with 3-guanidinopropyl sidechains, displayed similar counterion dependent phase behavior, demonstrating that the LLPS of polyguanidiniums does not depend upon subunit sequence or polymer backbone chirality, and was due entirely to Gdm+ sidechain interactions. The results provide experimental evidence for like-charge pairing of Gdm+ sidechains, and an experimental approach for further characterizing these interactions. Full article
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Open AccessArticle
Effect of Multivalent Cations on Intermolecular Association of Isotactic and Atactic Poly(Methacrylic Acid) Chains in Aqueous Solutions
Polymers 2019, 11(4), 605; https://doi.org/10.3390/polym11040605 - 02 Apr 2019
Cited by 2
Abstract
The formation of nanoparticles of two poly(methacrylic acid) (PMA) isomers, atactic (aPMA) and isotactic (iPMA), was investigated in aqueous solutions in the presence of mono- (Na+) and multivalent cations (Mg2+ and La3+). Using dynamic (DLS) and static light [...] Read more.
The formation of nanoparticles of two poly(methacrylic acid) (PMA) isomers, atactic (aPMA) and isotactic (iPMA), was investigated in aqueous solutions in the presence of mono- (Na+) and multivalent cations (Mg2+ and La3+). Using dynamic (DLS) and static light scattering (SLS), we show that PMA nanoparticles have characteristics of microgel-like particles with a denser core and a swollen corona. iPMA aggregates are stable at a much higher degree of neutralization (αN) than the aPMA ones, indicating a much stronger association between iPMA chains. This is explained by proposing segregation of ionized and unionized carboxyl groups within the iPMA aggregates and subsequent cooperative hydrogen-bonding between COOH groups. The calculated shape parameter (ρ) suggests different behavior of both isomers in the presence of Mg2+ ions on one hand and Na+ and La3+ on the other. The microgel-like particles formed in the presence of Mg2+ ions have a more even mass distribution (possibly a no core-shell structure) in comparison with those in the presence of Na+ and La3+ ions. Differences between the aggregate structures in the presence of different ions are reflected also in calorimetric experiments and supported by pH and fluorimetric measurements. Reasons for different behavior in the presence of Mg2+ ions lie in specific properties of this cation, in particular in its strong hydration and preference towards monodentate binding to carboxylate groups. Full article
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Open AccessArticle
Effect of Material Composition on Tunable Surface Roughness of Magnetoactive Elastomers
Polymers 2019, 11(4), 594; https://doi.org/10.3390/polym11040594 - 01 Apr 2019
Cited by 8
Abstract
We investigated magnetic-field-induced modifications of the surface roughness of magnetoactive elastomers (MAEs) with four material compositions incorporating two concentrations of ferromagnetic microparticles (70 wt% and 80 wt%) and exhibiting two shear storage moduli of the resulting composite material (about 10 kPa and 30 [...] Read more.
We investigated magnetic-field-induced modifications of the surface roughness of magnetoactive elastomers (MAEs) with four material compositions incorporating two concentrations of ferromagnetic microparticles (70 wt% and 80 wt%) and exhibiting two shear storage moduli of the resulting composite material (about 10 kPa and 30 kPa). The analysis was primarily based on spread optical reflection measurements. The surfaces of all four materials were found to be very smooth in the absence of magnetic field (RMS roughness below 50 nm). A maximal field-induced roughness modification (approximately 1 μm/T) was observed for the softer material with the lower filler concentration, and a minimal modification (less than 50 nm/T) was observed for the harder material with the higher filler concentration. All four materials showed a significant decrease in the total optical reflectivity with an increasing magnetic field as well. This effect is attributed to the existence of a distinct surface layer that is depleted of microparticles in the absence of a magnetic field but becomes filled with particles in the presence of the field. We analyzed the temporal response of the reflective properties to the switching on and off of the magnetic field and found switching-on response times of around 0.1 s and switching-off response times in the range of 0.3–0.6 s. These observations provide new insight into the magnetic-field-induced surface restructuring of MAEs and may be useful for the development of magnetically reconfigurable elastomeric optical surfaces. Full article
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Open AccessEditor’s ChoiceReview
Macro- and Microphase Separated Protein-Polyelectrolyte Complexes: Design Parameters and Current Progress
Polymers 2019, 11(4), 578; https://doi.org/10.3390/polym11040578 - 29 Mar 2019
Cited by 14
Abstract
Protein-containing polyelectrolyte complexes (PECs) are a diverse class of materials, composed of two or more oppositely charged polyelectrolytes that condense and phase separate near overall charge neutrality. Such phase-separation can take on a variety of morphologies from macrophase separated liquid condensates, to solid [...] Read more.
Protein-containing polyelectrolyte complexes (PECs) are a diverse class of materials, composed of two or more oppositely charged polyelectrolytes that condense and phase separate near overall charge neutrality. Such phase-separation can take on a variety of morphologies from macrophase separated liquid condensates, to solid precipitates, to monodispersed spherical micelles. In this review, we present an overview of recent advances in protein-containing PECs, with an overall goal of defining relevant design parameters for macro- and microphase separated PECs. For both classes of PECs, the influence of protein characteristics, such as surface charge and patchiness, co-polyelectrolyte characteristics, such as charge density and structure, and overall solution characteristics, such as salt concentration and pH, are considered. After overall design features are established, potential applications in food processing, biosensing, drug delivery, and protein purification are discussed and recent characterization techniques for protein-containing PECs are highlighted. Full article
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Open AccessArticle
Ferrocene-Modified Polyelectrolyte Film-Coated Electrode and Its Application in Glucose Detection
Polymers 2019, 11(3), 551; https://doi.org/10.3390/polym11030551 - 22 Mar 2019
Cited by 5
Abstract
A polyelectrolyte film-coated electrode for the quantitative detection of glucose was reported. Carbon nanotubes, graphene oxide and polyelectrolyte with a ferrocenyl group were used to modify an enzyme electrode to facilitate the electron transfer between glucose oxidase and the electrode. Cyclic voltammetry and [...] Read more.
A polyelectrolyte film-coated electrode for the quantitative detection of glucose was reported. Carbon nanotubes, graphene oxide and polyelectrolyte with a ferrocenyl group were used to modify an enzyme electrode to facilitate the electron transfer between glucose oxidase and the electrode. Cyclic voltammetry and amperometric methods were adopted to investigate the effects of different polyelectrolytes and carbon nanomaterials on the electrochemical properties of enzyme electrodes. The results indicate that the ferrocenyl groups on a polyelectrolyte skeleton act as a mediator between the redox center of glucose oxidase and the electrode, which efficiently enhances the electron transfer between a glassy carbon electrode and glucose oxidase. The calibration curve of the sensor shows a linear range from 0.2 to 5 mM for glucose response. The sensor can achieve 95% of the steady-state current within 10 s. The electrodes also present high operational stability and long-term storage stability. Full article
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Open AccessArticle
Gelatin Films Modified with Acidic and Polyelectrolyte Polymers—Material Selection for Soft Gastroresistant Capsules
Polymers 2019, 11(2), 338; https://doi.org/10.3390/polym11020338 - 15 Feb 2019
Cited by 1
Abstract
The following investigation comprised the formation of acid-resistant gelatin-based films, intended for future use in soft-capsule technology. Such film compositions were obtained by including nonionized forms of acid-insoluble polymers in a gelatin-based film-forming mixture. The selected films were additionally modified with small amounts [...] Read more.
The following investigation comprised the formation of acid-resistant gelatin-based films, intended for future use in soft-capsule technology. Such film compositions were obtained by including nonionized forms of acid-insoluble polymers in a gelatin-based film-forming mixture. The selected films were additionally modified with small amounts of anionic polysaccharides that have potential to interact with gelatin, forming polyelectrolyte complexes. The obtained film compositions were subjected to, e.g., disintegration tests, adhesiveness tests, differential scanning calorimetry (DSC), and a transparency study. As a result of the performed study, some commercial enteric polymers (acrylates), as well as cellulose acetate phthalate, were selected as components that have the ability to coalesce and form a continuous phase within a gelatin film. The use of a small amount (1.5%) of additional gelling polymers improved the rheological characteristics and adhesive properties of the obtained films, with ί-carrageenan and gellan gum appearing to be the most beneficial. Full article
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Open AccessArticle
Upper Critical Solution Temperature (UCST) Behavior of Polystyrene-Based Polyampholytes in Aqueous Solution
Polymers 2019, 11(2), 265; https://doi.org/10.3390/polym11020265 - 04 Feb 2019
Cited by 3
Abstract
Strong polyampholytes comprising cationic vinylbenzyl trimethylammonium chloride (VBTAC) bearing a pendant quaternary ammonium group and anionic sodium p-styrenesulfonate (NaSS) bearing a pendant sulfonate group were prepared via reversible addition-fragmentation chain-transfer polymerization. The resultant polymers are labelled P(VBTAC/NaSS)n, where n indicates [...] Read more.
Strong polyampholytes comprising cationic vinylbenzyl trimethylammonium chloride (VBTAC) bearing a pendant quaternary ammonium group and anionic sodium p-styrenesulfonate (NaSS) bearing a pendant sulfonate group were prepared via reversible addition-fragmentation chain-transfer polymerization. The resultant polymers are labelled P(VBTAC/NaSS)n, where n indicates the degree of polymerization (n = 20 or 97). The percentage VBTAC content in P(VBTAC/NaSS)n is always about 50 mol%, as revealed by 1H NMR measurements, meaning that P(VBTAC/NaSS)n is a close to stoichiometrically charge-neutralized polymer. Although P(VBTAC/NaSS)n cannot dissolve in pure water at room temperature, the addition of NaCl or heating solubilizes the polymers. Furthermore, P(VBTAC/NaSS)n exhibits upper critical solution temperature (UCST) behavior in aqueous NaCl solutions. The UCST is shifted to higher temperatures by increasing the polymer concentration and molecular weight, and by decreasing the NaCl concentration. The UCST behavior was measured ranging the polymer concentrations from 0.5 to 5.0 g/L. Full article
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Open AccessArticle
Layer-by-Layer Assembly and Electrochemical Study of Alizarin Red S-Based Thin Films
Polymers 2019, 11(1), 165; https://doi.org/10.3390/polym11010165 - 18 Jan 2019
Cited by 3
Abstract
Electroactive organic dyes incorporated in layer-by-layer (LbL) assemblies are of great interest for a variety of applications. In this paper, Alizarin Red S (ARS), an electroactive anthraquinone dye, is employed to construct LbL (BPEI/ARS)n films with branched poly(ethylene imine) (BPEI) as the [...] Read more.
Electroactive organic dyes incorporated in layer-by-layer (LbL) assemblies are of great interest for a variety of applications. In this paper, Alizarin Red S (ARS), an electroactive anthraquinone dye, is employed to construct LbL (BPEI/ARS)n films with branched poly(ethylene imine) (BPEI) as the complementary polymer. Unconventional LbL methods, including co-adsorption of ARS and poly(4-styrene sulfonate) (PSS) with BPEI to assemble (BPEI/(ARS+PSS))n, as well as pre-complexation of ARS with BPEI and further assembly with PSS to fabricate ((BPEI+ARS)/PSS)n, are designed for investigation and comparison. Film growth patterns, UV–Vis spectra and surface morphology of the three types of LbL assemblies are measured and compared to reveal the formation mechanism of the LbL films. Electrochemical properties including cyclic voltammetry and spectroelectrochemistry of (BPEI/ARS)120, (BPEI/(ARS+PSS))120 and ((BPEI+ARS)/PSS)120 films are studied, and the results show a slight color change due to the redox reaction of ARS. ((BPEI+ARS)/PSS)120 shows the best stability among the three samples. It is concluded that the manner of dye- incorporation has a great effect on the electrochemical properties of the resultant films. Full article
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Open AccessEditor’s ChoiceArticle
Polyelectrolyte Complexation of Oligonucleotides by Charged Hydrophobic—Neutral Hydrophilic Block Copolymers
Polymers 2019, 11(1), 83; https://doi.org/10.3390/polym11010083 - 07 Jan 2019
Cited by 13
Abstract
Polyelectrolyte complex micelles (PCMs, core-shell nanoparticles formed by complexation of a polyelectrolyte with a polyelectrolyte-hydrophilic neutral block copolymer) offer a solution to the critical problem of delivering therapeutic nucleic acids, Despite this, few systematic studies have been conducted on how parameters such as [...] Read more.
Polyelectrolyte complex micelles (PCMs, core-shell nanoparticles formed by complexation of a polyelectrolyte with a polyelectrolyte-hydrophilic neutral block copolymer) offer a solution to the critical problem of delivering therapeutic nucleic acids, Despite this, few systematic studies have been conducted on how parameters such as polycation charge density, hydrophobicity, and choice of charged group influence PCM properties, despite evidence that these strongly influence the complexation behavior of polyelectrolyte homopolymers. In this article, we report a comparison of oligonucleotide PCMs and polyelectrolyte complexes formed by poly(lysine) and poly((vinylbenzyl) trimethylammonium) (PVBTMA), a styrenic polycation with comparatively higher charge density, increased hydrophobicity, and a permanent positive charge. All of these differences have been individually suggested to provide increased complex stability, but we find that PVBTMA in fact complexes oligonucleotides more weakly than does poly(lysine), as measured by stability versus added salt. Using small angle X-ray scattering and electron microscopy, we find that PCMs formed from both cationic blocks exhibit very similar structure-property relationships, with PCM radius determined by the cationic block size and shape controlled by the hybridization state of the oligonucleotides. These observations narrow the design space for optimizing therapeutic PCMs and provide new insights into the rich polymer physics of polyelectrolyte self-assembly. Full article
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Open AccessEditor’s ChoiceReview
Protein–Polyelectrolyte Interaction: Thermodynamic Analysis Based on the Titration Method
Polymers 2019, 11(1), 82; https://doi.org/10.3390/polym11010082 - 07 Jan 2019
Cited by 10
Abstract
This review discussed the mechanisms including theories and binding stages concerning the protein–polyelectrolyte (PE) interaction, as well as the applications for both complexation and coacervation states of protein–PE pairs. In particular, this review focused on the applications of titration techniques, that is, turbidimetric [...] Read more.
This review discussed the mechanisms including theories and binding stages concerning the protein–polyelectrolyte (PE) interaction, as well as the applications for both complexation and coacervation states of protein–PE pairs. In particular, this review focused on the applications of titration techniques, that is, turbidimetric titration and isothermal titration calorimetry (ITC), in understanding the protein–PE binding process. To be specific, by providing thermodynamic information such as pHc, pHφ, binding constant, entropy, and enthalpy change, titration techniques could shed light on the binding affinity, binding stoichiometry, and driving force of the protein–PE interaction, which significantly guide the applications by utilization of these interactions. Recent reports concerning interactions between proteins and different types of polyelectrolytes, that is, linear polyelectrolytes and polyelectrolyte modified nanoparticles, are summarized with their binding differences systematically discussed and compared based on the two major titration techniques. We believe this short review could provide valuable insight in the understanding of the structure–property relationship and the design of applied biomedical PE-based systems with optimal performance. Full article
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2018

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Open AccessReview
Intermolecular Interactions in Polyelectrolyte and Surfactant Complexes in Solution
Polymers 2019, 11(1), 51; https://doi.org/10.3390/polym11010051 - 31 Dec 2018
Cited by 31
Abstract
Polyelectrolytes are an important class of polymeric materials and are increasingly used in complex industrial formulations. A core use of these materials is in mixtures with surfactants, where a combination of hydrophobic and electrostatic interactions drives unique solution behavior and structure formation. In [...] Read more.
Polyelectrolytes are an important class of polymeric materials and are increasingly used in complex industrial formulations. A core use of these materials is in mixtures with surfactants, where a combination of hydrophobic and electrostatic interactions drives unique solution behavior and structure formation. In this review, we apply a molecular level perspective to the broad literature on polyelectrolyte-surfactant complexes, discussing explicitly the hydrophobic and electrostatic interaction contributions to polyelectrolyte surfactant complexes (PESCs), as well as the interplay between the two molecular interaction types. These interactions are sensitive to a variety of solution conditions, such as pH, ionic strength, mixing procedure, charge density, etc. and these parameters can readily be used to control the concentration at which structures form as well as the type of structure in the bulk solution. Full article
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Open AccessReview
Exploring Structure–Property Relationships of GAGs to Tailor ECM-Mimicking Hydrogels
Polymers 2018, 10(12), 1376; https://doi.org/10.3390/polym10121376 - 11 Dec 2018
Cited by 1
Abstract
Glycosaminoglycans (GAGs) are a class of linear polysaccharides that are ubiquitous in the extracellular matrix (ECM) and on cell surfaces. Due to their key role in development, homeostasis, pathogenesis, and regeneration, GAGs are increasingly used in the design of ECM-mimicking hydrogels to stimulate [...] Read more.
Glycosaminoglycans (GAGs) are a class of linear polysaccharides that are ubiquitous in the extracellular matrix (ECM) and on cell surfaces. Due to their key role in development, homeostasis, pathogenesis, and regeneration, GAGs are increasingly used in the design of ECM-mimicking hydrogels to stimulate tissue formation and regenerative processes via specifically orchestrated cell-instructive signals. These applications first and foremost build on the ability of GAGs to effectively bind, protect, and release morphogens. The specificity and strength of morphogen-GAG interactions are largely governed by the number and spatial distribution of negatively charged sulfate groups carried by GAGs. Herein, we summarize a mean-field approach to quantify the density of ionizable groups, GAG concentration, and cross-linking degree of GAG-containing hydrogels on the basis of microslit electrokinetic experiments. We further present and discuss a continuum model of mucosa that accounts for charge regulation by glycan-ion pairing in biological contexts and under conditions of macromolecular crowding. Finally, we discuss the modulation of the morphogen binding and transport in GAG hydrogels by selective desulfation of the GAG component. Full article
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Open AccessArticle
Separation and Characterization of Highly Charged Polyelectrolytes Using Free-Solution Capillary Electrophoresis
Polymers 2018, 10(12), 1331; https://doi.org/10.3390/polym10121331 - 02 Dec 2018
Cited by 1
Abstract
The characterization of statistical copolymers of various charge densities remains an important and challenging analytical issue. Indeed, the polyelectrolyte (PE) effective electrophoretic mobility tends to level off above a certain charge density, due to the occurrence of Manning counterion condensation. Surprisingly, we demonstrate [...] Read more.
The characterization of statistical copolymers of various charge densities remains an important and challenging analytical issue. Indeed, the polyelectrolyte (PE) effective electrophoretic mobility tends to level off above a certain charge density, due to the occurrence of Manning counterion condensation. Surprisingly, we demonstrate in this work that it is possible to get highly resolutive separations of charged PE using free-solution capillary electrophoresis, even above the critical value predicted by the Manning counterion condensation theory. Full separation of nine statistical poly(acrylamide-co-2-acrylamido-2-methylpropanesulfonate) polymers of different charge densities varying between 3% and 100% was obtained by adjusting the ionic strength of the background electrolyte (BGE) in counter electroosmotic mode. Distributions of the chemical charge density could be obtained for the nine PE samples, showing a strong asymmetry of the distribution for the highest-charged PE. This asymmetry can be explained by the different reactivity ratios during the copolymerization. To shed more light on the separation mechanism, effective and apparent selectivities were determined by a systematic study and modeling of the electrophoretic mobility dependence according to the ionic strength. It is demonstrated that the increase in resolution with increasing BGE ionic strength is not only due to a closer matching of the electroosmotic flow magnitude with the PE electrophoretic effective mobility, but also to an increase of the dependence of the PE effective mobility according to the charge density. Full article
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Open AccessArticle
Switchable Release of Bone Morphogenetic Protein from Thermoresponsive Poly(NIPAM-co-DMAEMA)/Cellulose Sulfate Particle Coatings
Polymers 2018, 10(12), 1314; https://doi.org/10.3390/polym10121314 - 27 Nov 2018
Cited by 6
Abstract
Thermoresponsive coatings of poly(N-isopropylacrylamide-co-DMAEMA)/cellulose sulfate (PNIPAM-DMAEMA/CS) complexes are reported eluting bone-morphogenetic-protein-2 (BMP-2) on demand relevant for implant assisted local bone healing. PNIPAM-DMAEMA/CS dispersions contained colloid particles with hydrodynamic radii RH = 170–288 nm at T = 25 °C [...] Read more.
Thermoresponsive coatings of poly(N-isopropylacrylamide-co-DMAEMA)/cellulose sulfate (PNIPAM-DMAEMA/CS) complexes are reported eluting bone-morphogenetic-protein-2 (BMP-2) on demand relevant for implant assisted local bone healing. PNIPAM-DMAEMA/CS dispersions contained colloid particles with hydrodynamic radii RH = 170–288 nm at T = 25 °C shrinking to RH = 74–103 nm at T = 60 °C. Obviously, PNIPAM-DMAEMA/CS undergoes volume phase transition (VPT) analogously to pure PNIPAM, when critical VPT temperature (VPTT) is exceeded. Temperature dependent turbidity measurements revealed broad VPT and VPTT 47 °C for PNIPAM-DMAEMA/CS colloid dispersions at pH = 7.0. FTIR spectroscopy on thermoresponsive PNIPAM-DMAEMA/CS particle coatings at germanium model substrates under HEPES buffer indicated both wet-adhesiveness and VPT behavior based on diagnostic band intensity increases with temperature. From respective temperature courses empirical VPTT ≈ 42 °C for PNIPAM-DMAEMA/CS coatings at pH = 7.0 were found, which were comparable to VPTT found for respective dispersions. Finally, the PNIPAM-DMAEMA/CS coatings were loaded with BMP-2 and model protein papain (PAP). Time dependent FTIR spectroscopic measurements showed, that for T = 37 °C there was a relative protein release of ≈30% for PAP and ≈10% for BMP-2 after 24 h, which did not increase further. Heating to T = 42 °C for PAP and to 47 °C for BMP-2 further secondary protein release of ≈20% after 24 h was found, respectively, interesting for clinical applications. BMP-2 eluted even at 47 °C was found to be still biologically active. Full article
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Open AccessArticle
Effect of the Surface Hydrophobicity Degree on the In Vitro Release of Polar and Non-Polar Drugs from Polyelectrolyte Matrix Tablets
Polymers 2018, 10(12), 1313; https://doi.org/10.3390/polym10121313 - 27 Nov 2018
Abstract
This work is the continuation of a series of studies focused on establishing the relationship between the surface thermodynamic properties of polyelectrolyte matrix tablets and drug release mechanisms. In this case, two model drugs with different polarity features, such as carbamazepine (non-polar) and [...] Read more.
This work is the continuation of a series of studies focused on establishing the relationship between the surface thermodynamic properties of polyelectrolyte matrix tablets and drug release mechanisms. In this case, two model drugs with different polarity features, such as carbamazepine (non-polar) and metoprolol succinate (polar) were used in combination with polymeric material hydroxypropyl-methyl cellulose (HPMC) and two polyelectrolytes derived from maleic anhydride corresponding to the sodium salts of poly(maleic acid-alt-ethylene) and poly(maleic acid-alt-octadecene) named PAM-0Na and PAM-18Na, respectively. The polymers were obtained and characterized as reported previously. Surface studies were performed by the sessile drop method, whilst the surface free energy was determined through Owens, Wendt, Rable and Kaeble (OWRK) semi-empirical model. By contrast, the drug release studies were performed by in vitro dissolution tests, where data were analyzed through dissolution efficiency. The results showed that, depending on the drug polarity, type and polymer proportion, surface properties and drug release processes are significantly affected. Full article
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Open AccessArticle
Design of Oligonucleotide Carriers: Importance of Polyamine Chain Length
Polymers 2018, 10(12), 1297; https://doi.org/10.3390/polym10121297 - 23 Nov 2018
Cited by 1
Abstract
Amine containing polymers are extensively studied as special carriers for short-chain RNA (13–25 nucleotides), which are applied as gene silencing agents in gene therapy of various diseases including cancer. Elaboration of the oligonucleotide carriers requires knowledge about peculiarities of the oligonucleotide–polymeric amine interaction. [...] Read more.
Amine containing polymers are extensively studied as special carriers for short-chain RNA (13–25 nucleotides), which are applied as gene silencing agents in gene therapy of various diseases including cancer. Elaboration of the oligonucleotide carriers requires knowledge about peculiarities of the oligonucleotide–polymeric amine interaction. The critical length of the interacting chains is an important parameter which allows us to design sophisticated constructions containing oligonucleotide binding segments, solubilizing, protective and aiming parts. We studied interactions of (TCAG)n, n = 1–6 DNA oligonucleotides with polyethylenimine and poly(N-(3-((3-(dimethylamino)propyl)(methyl)amino)propyl)-N-methylacrylamide). The critical length for oligonucleotides in interaction with polymeric amines is 8–12 units and complexation at these length can be accompanied by “all-or-nothing” effects. New dimethylacrylamide based polymers with grafted polyamine chains were obtained and studied in complexation with DNA and RNA oligonucleotides. The most effective interaction and transfection activity into A549 cancer cells and silencing efficiency against vascular endothelial growth factor (VEGF) was found for a sample with average number of nitrogens in polyamine chain equal to 27, i.e., for a sample in which all grafted chains are longer than the critical length for polymeric amine–oligonucleotide complexation. Full article
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Open AccessArticle
Conformation Study of Dual Stimuli-Responsive Core-Shell Diblock Polymer Brushes
Polymers 2018, 10(10), 1084; https://doi.org/10.3390/polym10101084 - 30 Sep 2018
Cited by 2
Abstract
Stimuli-responsive nanoparticles are among the most popular research topics. In this study, two types of core-shell (polystyrene with a photoiniferter (PSV) as the core and diblock as the shell) polymer brushes ([email protected]b-PAA and [email protected]b-PNIPA) were designed and prepared using [...] Read more.
Stimuli-responsive nanoparticles are among the most popular research topics. In this study, two types of core-shell (polystyrene with a photoiniferter (PSV) as the core and diblock as the shell) polymer brushes ([email protected]b-PAA and [email protected]b-PNIPA) were designed and prepared using surface-initiated photoiniferter-mediated polymerization (SI-PIMP). Moreover, their pH- and temperature-stimuli responses were explored by dynamic light scattering (DLS) and turbidimeter under various conditions. The results showed that the conformational change was determined on the basis of the competition among electrostatic repulsion, hydrophobic interaction, hydrogen bonding, and steric hindrance, which was also confirmed by protein adsorption experiments. These results are not only helpful for the design and synthesis of stimuli-responsive polymer brushes but also shed light on controlled protein immobilization under mild conditions. Full article
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Open AccessArticle
Sulfonated Poly(Arylene Ether Sulfone) and Perfluorosulfonic Acid Composite Membranes Containing Perfluoropolyether Grafted Graphene Oxide for Polymer Electrolyte Membrane Fuel Cell Applications
Polymers 2018, 10(6), 569; https://doi.org/10.3390/polym10060569 - 23 May 2018
Cited by 7
Abstract
Sulfonated poly(arylene ether sulfone) (SPAES) and perfluorosulfonic acid (PFSA) composite membranes were prepared using perfluoropolyether grafted graphene oxide (PFPE-GO) as a reinforcing filler for polymer electrolyte membrane fuel cell (PEMFC) applications. PFPE-GO was obtained by grafting poly(hexafluoropropylene oxide) having a carboxylic acid end [...] Read more.
Sulfonated poly(arylene ether sulfone) (SPAES) and perfluorosulfonic acid (PFSA) composite membranes were prepared using perfluoropolyether grafted graphene oxide (PFPE-GO) as a reinforcing filler for polymer electrolyte membrane fuel cell (PEMFC) applications. PFPE-GO was obtained by grafting poly(hexafluoropropylene oxide) having a carboxylic acid end group onto the surface of GO via ring opening reaction between the carboxylic acid group in poly(hexafluoropropylene oxide) and the epoxide groups in GO, using 4-dimethylaminopyridine as a base catalyst. Both SPAES and PFSA composite membranes containing PFPE-GO showed much improved mechanical strength and dimensional stability, compared to each linear SPAES and PFSA membrane, respectively. The enhanced mechanical strength and dimensional stability of composite membranes can be ascribed to the homogeneous dispersion of rigid conjugated carbon units in GO through the increased interfacial interactions between PFPE-GO and SPAES/PFSA matrices. Full article
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Open AccessArticle
Effect of Counterion Valence on Conformational Behavior of Spherical Polyelectrolyte Brushes Confined between Two Parallel Walls
Polymers 2018, 10(4), 363; https://doi.org/10.3390/polym10040363 - 24 Mar 2018
Cited by 2
Abstract
We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. [...] Read more.
We study the conformational behavior of spherical polyelectrolyte brushes in the presence of monovalent and trivalent counterions in a confined environment. The confinement is exerted by two parallel walls on the brushes. The enhancement of the confinement induces the extension of grafted chains. For the monovalent case, the increase of the charge fraction leads to extended brush conformation for different slit width (distance between two walls) but collapsed brush in the presence of trivalent counterions is observed. The confinement does not affect electrostatic correlation between trivalent counterions and charged monomers. However, it was found that narrow slit width contributes to stronger electrostatic correlation for the monovalent case. This is because more monovalent counterions are inside the brush at strong confinement, but almost all trivalent counterions are trapped into the brush independently of the slit width. The diffusion of counterions under the confinement is related to the electrostatic correlation. Our simulations also reveal that the brush thickness depends on the slit width nonlinearly. Full article
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2017

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Open AccessArticle
Preparation and Characterization of Water-Soluble Xylan Ethers
Polymers 2017, 9(4), 129; https://doi.org/10.3390/polym9040129 - 31 Mar 2017
Cited by 8
Abstract
Xylan is a predominant hemicellulose component that is found in plants and in some algae. This polysaccharide is made from units of xylose (a pentose sugar). One promising source of xylan is oat spelt. This feedstock was used for the synthesis of two [...] Read more.
Xylan is a predominant hemicellulose component that is found in plants and in some algae. This polysaccharide is made from units of xylose (a pentose sugar). One promising source of xylan is oat spelt. This feedstock was used for the synthesis of two xylan ethers. To achieve water soluble products, we prepared dihydroxypropyl xylan as a non-ionic ether on the one hand, and carboxymethyl xylan as an ionic derivative on the other hand. Different preparation methods like heterogeneous, pseudo-homogeneous, and homogeneous syntheses were compared. In the case of dihydroxypropyl xylan, the synthesis method did not significantly affect the degree of substitution (DS). In contrast, in the case of carboxymethyl xylan, clear differences of the DS values were found in dependence on the synthesis method. Xylan ethers with DS values of >1 could be obtained, which mostly show good water solubility. The synthesized ionic, as well as non-ionic, xylan ethers were soluble in water, even though the aqueous solutions showed slight turbidity. Nevertheless, stable, transparent, and stainable films could be prepared from aqueous solutions from carboxymethyl xylans. Full article
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Open AccessArticle
Hydrophilic Polyelectrolyte Multilayers Improve the ELISA System: Antibody Enrichment and Blocking Free
Polymers 2017, 9(2), 51; https://doi.org/10.3390/polym9020051 - 12 Feb 2017
Cited by 8
Abstract
In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as [...] Read more.
In this study, polyelectrolyte multilayers were fabricated on a polystyrene (PS) plate using a Layer-by-Layer (LbL) self-assembly technique. The resulting functional platform showed improved performance compared with conventional enzyme-linked immunosorbent assay (ELISA) systems. Poly(diallyldimethylammonium chloride) (PDDA) and poly(acrylic acid) (PAA) were used as cationic and anionic polyelectrolytes. On the negatively-charged (PDDA/PAA)3 polyelectrolyte multilayers the hydrophilic PAA surface could efficiently decrease the magnitude of the noise signal, by inhibiting nonspecific adsorption even without blocking reagent adsorption. Moreover, the (PDDA/PAA)3 substrate covalently immobilized the primary antibody, greatly increasing the amount of primary antibody adsorption and enhancing the specific detection signal compared with a conventional PS plate. The calibration curve of the (PDDA/PAA)3 substrate showed a wide linear range, for concentrations from 0.033 to 33 nM, a large specific signal change, and a detection limit of 33 pM, even though the conventional blocking reagent adsorption step was omitted. The (PDDA/PAA)3 substrate provided a high-performance ELISA system with a simple fabrication process and high sensitivity; the system presented here shows potential for a variety of immunosensor applications. Full article
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Open AccessArticle
The Effect of Molar Mass and Charge Density on the Formation of Complexes between Oppositely Charged Polyelectrolytes
Polymers 2017, 9(2), 50; https://doi.org/10.3390/polym9020050 - 04 Feb 2017
Cited by 9
Abstract
The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(l-lysine) (PLL) [...] Read more.
The interactions between model polyanions and polycations have been studied using frontal continuous capillary electrophoresis (FACCE) which allows the determination of binding stoichiometry and binding constant of the formed polyelectrolyte complex (PEC). In this work, the effect of the poly(l-lysine) (PLL) molar mass on the interaction with statistical copolymers of acrylamide and 2-acrylamido-2-methyl-1-propanesulfonate (PAMAMPS) has been systematically investigated for different PAMAMPS chemical charge densities (15% and 100%) and different ionic strengths. The study of the ionic strength dependence of the binding constant allowed the determination of the total number of released counter-ions during the formation of the PEC, which can be compared to the total number of counter-ions initially condensed on the individual polyelectrolyte partners before the association. Interestingly, this fraction of released counter-ions, which was strongly dependent on the PLL molar mass, was almost independent of the PAMAMPS charge density. These findings are useful to predict the binding constant according to the molar mass and charge density of the polyelectrolyte partners. Full article
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Open AccessArticle
Polyion Complex Vesicles with Solvated Phosphobetaine Shells Formed from Oppositely Charged Diblock Copolymers
Polymers 2017, 9(2), 49; https://doi.org/10.3390/polym9020049 - 04 Feb 2017
Cited by 14
Abstract
Diblock copolymers consisting of a hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) block and either a cationic or anionic block were prepared from (3-(methacrylamido)propyl)trimethylammonium chloride (MAPTAC) or sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS). Polymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization using a PMPC macro-chain transfer [...] Read more.
Diblock copolymers consisting of a hydrophilic poly(2-(methacryloyloxy)ethyl phosphorylcholine) (PMPC) block and either a cationic or anionic block were prepared from (3-(methacrylamido)propyl)trimethylammonium chloride (MAPTAC) or sodium 2-(acrylamido)-2-methylpropanesulfonate (AMPS). Polymers were synthesized via reversible addition-fragmentation chain transfer (RAFT) radical polymerization using a PMPC macro-chain transfer agent. The degree of polymerization for PMPC, cationic PMAPTAC, and anionic PAMPS blocks was 20, 190, and 196, respectively. Combining two solutions of oppositely charged diblock copolymers, PMPC-b-PMAPTAC and PMPC-b-PAMPS, led to the spontaneous formation of polyion complex vesicles (PICsomes). The PICsomes were characterized using 1H NMR, static abd dynamic light scattering, transmittance electron microscopy (TEM), and atomic force microscopy. Maximum hydrodynamic radius (Rh) for the PICsome was observed at a neutral charge balance of the cationic and anionic diblock copolymers. The Rh value and aggregation number (Nagg) of PICsomes in 0.1 M NaCl was 78.0 nm and 7770, respectively. A spherical hollow vesicle structure was observed in TEM images. The hydrodynamic size of the PICsomes increased with concentration of the diblock copolymer solutions before mixing. Thus, the size of the PICsomes can be controlled by selecting an appropriate preparation method. Full article
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Open AccessReview
Engineering Cell Surfaces with Polyelectrolyte Materials for Translational Applications
Polymers 2017, 9(2), 40; https://doi.org/10.3390/polym9020040 - 28 Jan 2017
Cited by 7
Abstract
Engineering cell surfaces with natural or synthetic materials is a unique and powerful strategy for biomedical applications. Cells exhibit more sophisticated migration, control, and functional capabilities compared to nanoparticles, scaffolds, viruses, and other engineered materials or agents commonly used in the biomedical field. [...] Read more.
Engineering cell surfaces with natural or synthetic materials is a unique and powerful strategy for biomedical applications. Cells exhibit more sophisticated migration, control, and functional capabilities compared to nanoparticles, scaffolds, viruses, and other engineered materials or agents commonly used in the biomedical field. Over the past decade, modification of cell surfaces with natural or synthetic materials has been studied to exploit this complexity for both fundamental and translational goals. In this review we present the existing biomedical technologies for engineering cell surfaces with one important class of materials, polyelectrolytes. We begin by introducing the challenges facing the cell surface engineering field. We then discuss the features of polyelectrolytes and how these properties can be harnessed to solve challenges in cell therapy, tissue engineering, cell-based drug delivery, sensing and tracking, and immune modulation. Throughout the review, we highlight opportunities to drive the field forward by bridging new knowledge of polyelectrolytes with existing translational challenges. Full article
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Open AccessArticle
Polymer Conformations in Ionic Microgels in the Presence of Salt: Theoretical and Mesoscale Simulation Results
Polymers 2017, 9(1), 15; https://doi.org/10.3390/polym9010015 - 05 Jan 2017
Cited by 26
Abstract
We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account [...] Read more.
We investigate the conformational properties of polymers in ionic microgels in the presence of salt ions by molecular dynamics simulations and analytical theory. A microgel particle consists of coarse-grained linear polymers, which are tetra-functionally crosslinked. Counterions and salt ions are taken into account explicitly, and charge-charge interactions are described by the Coulomb potential. By varying the charge interaction strength and salt concentration, we characterize the swelling of the polyelectrolytes and the charge distribution. In particular, we determine the amount of trapped mobile charges inside the microgel and the Debye screening length. Moreover, we analyze the polymer extension theoretically in terms of the tension blob model taking into account counterions and salt ions implicitly by the Debye–Hückel model. Our studies reveal a strong dependence of the amount of ions absorbed in the interior of the microgel on the electrostatic interaction strength, which is related to the degree of the gel swelling. This implies a dependence of the inverse Debye screening length κ on the ion concentration; we find a power-law increase of κ with the Coulomb interaction strength with the exponent 3 / 5 for a salt-free microgel and an exponent 1 / 2 for moderate salt concentrations. Additionally, the radial dependence of polymer conformations and ion distributions is addressed. Full article
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2016

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Open AccessArticle
Influence of Polyelectrolyte Multilayer Properties on Bacterial Adhesion Capacity
Polymers 2016, 8(10), 345; https://doi.org/10.3390/polym8100345 - 26 Sep 2016
Cited by 16
Abstract
Bacterial adhesion can be controlled by different material surface properties, such as surface charge, on which we concentrate in our study. We use a silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The corresponding surface roughness and hydrophobicity were [...] Read more.
Bacterial adhesion can be controlled by different material surface properties, such as surface charge, on which we concentrate in our study. We use a silica surface on which poly(allylamine hydrochloride)/sodium poly(4-styrenesulfonate) (PAH/PSS) polyelectrolyte multilayers were formed. The corresponding surface roughness and hydrophobicity were determined by atomic force microscopy and tensiometry. The surface charge was examined by the zeta potential measurements of silica particles covered with polyelectrolyte multilayers, whereby ionic strength and polyelectrolyte concentrations significantly influenced the build-up process. For adhesion experiments, we used the bacterium Pseudomonas aeruginosa. The extent of adhered bacteria on the surface was determined by scanning electron microscopy. The results showed that the extent of adhered bacteria mostly depends on the type of terminating polyelectrolyte layer, since relatively low differences in surface roughness and hydrophobicity were obtained. In the case of polyelectrolyte multilayers terminating with a positively charged layer, bacterial adhesion was more pronounced than in the case when the polyelectrolyte layer was negatively charged. Full article
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Open AccessCommunication
Rheological Properties of DNA Molecules in Solution: Molecular Weight and Entanglement Influences
Polymers 2016, 8(8), 279; https://doi.org/10.3390/polym8080279 - 03 Aug 2016
Cited by 5
Abstract
Molecular weight, stiffness, temperature, and polymer and ionic concentrations are known to widely influence the viscosity of polymer solutions. Additionally, polymer molecular weight—which is related to its dimensions in solution—is one of its most important characteristics. In this communication, low molecular weight DNA [...] Read more.
Molecular weight, stiffness, temperature, and polymer and ionic concentrations are known to widely influence the viscosity of polymer solutions. Additionally, polymer molecular weight—which is related to its dimensions in solution—is one of its most important characteristics. In this communication, low molecular weight DNA from salmon sperm was purified and then studied in solutions in a wide concentration range (between 0.5 and 1600 mg/mL). The intrinsic viscosity of this low molecular weight DNA sample was firstly determined and the evidence of the overlap concentration was detected around the concentration of 125 mg/mL. The chain characteristics of these short molecules were studied in terms of the influence of their molecular weight on the solution viscosities and on the overlap parameter CDNA[η]. Furthermore, to complete previously reported experimental data, solutions of a large molecular weight DNA from calf-thymus were studied in a high concentration range (up to 40 mg/mL). The rheological behavior is discussed in terms of the generalized master curve obtained from the variation of the specific viscosity at zero shear rate (ηsp,0) as a function of CDNA[η]. Full article
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Open AccessCommunication
Rapid Mercury(II) Removal by Electrospun Sulfur Copolymers
Polymers 2016, 8(7), 266; https://doi.org/10.3390/polym8070266 - 20 Jul 2016
Cited by 48
Abstract
Electrospinning was performed with a blend of commercially available poly(methyl methacrylate) (PMMA) and a sulfur-rich copolymer based on poly(sulfur-statistical-diisopropenylbenzene), which was synthesized via inverse vulcanization. The polysulfide backbone of sulfur-containing polymers is known to bind mercury from aqueous solutions and can [...] Read more.
Electrospinning was performed with a blend of commercially available poly(methyl methacrylate) (PMMA) and a sulfur-rich copolymer based on poly(sulfur-statistical-diisopropenylbenzene), which was synthesized via inverse vulcanization. The polysulfide backbone of sulfur-containing polymers is known to bind mercury from aqueous solutions and can be utilized for recycling water. Increasing the surface area by electrospinning can maximize the effect of binding mercury regarding the rate and maximum uptake. These fibers showed a mercury decrease of more than 98% after a few seconds and a maximum uptake of 440 mg of mercury per gram of electrospun fibers. These polymeric fibers represent a new class of efficient water filtering systems that show one of the highest and fastest mercury uptakes for electrospun fibers reported. Full article
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Open AccessArticle
Physicochemical Properties of Biopolymer Hydrogels Treated by Direct Electric Current
Polymers 2016, 8(7), 248; https://doi.org/10.3390/polym8070248 - 12 Jul 2016
Cited by 11
Abstract
The objective of this study was to evaluate the changes within the physicochemical properties of gelatine (2%; 4%; 8%), carrageenan (1.5%; 2%; 2.5%) and sodium alginate (0.75%; 1%; 1.25%) hydrogels with different sodium chloride concentrations that were triggered by applying direct current (DC) [...] Read more.
The objective of this study was to evaluate the changes within the physicochemical properties of gelatine (2%; 4%; 8%), carrageenan (1.5%; 2%; 2.5%) and sodium alginate (0.75%; 1%; 1.25%) hydrogels with different sodium chloride concentrations that were triggered by applying direct current (DC) of 400 mA for a duration of five minutes. There were three types of gels prepared for the purpose of the study: C, control; H, gels on the basis of hydrosols that were treated with DC; and G, gels treated with DC. In the course of the study, the authors carried out the following analyses: Texture Profile Analysis (TPA), Fourier Transform Infrared spectroscopy (FTIR), Scanning Electron Microscopy (SEM) and Swelling Ratio (SR). Furthermore, the color and pH of hydrogels were measured. The FTIR spectra showed that the structures of gelatine, carrageenan and sodium alginate do not significantly change upon applying DC. The results of TPA, SR, color and pH measurement indicate that hydrogels’ properties are significantly dependent on the type of polymer, its concentration and the type of the gel. By changing those parameters, the characteristics of such gels can be additionally tuned, which extends their applicability, e.g., in the food industry. Moreover, the analysis revealed that SR of H gel gelatine after 72 h of storage was 1.84-times higher than SR of the control sample, which indicated that this gel may be considered as a possible component for wound dressing materials. Full article
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Open AccessArticle
Effect of Very High Charge Density and Monomer Constitution on the Synthesis and Properties of Cationic Polyelectrolytes
Polymers 2016, 8(6), 234; https://doi.org/10.3390/polym8060234 - 16 Jun 2016
Cited by 1
Abstract
The free-radical homopolymerization of 1,3-bis(N,N,N-trimethylammonium)-2-propylmethacrylate dichloride (di-M) and 1,3-bis(N,N,N-trimethylammonium)-2-propylacrylate dichloride (di-A) in aqueous solution yields cationic polyelectrolytes (PEL) with theoretical/structural charge spacing of only ≈0.12 nm. The high charge density causes condensation of ≈82% of the chloride counterions. The [...] Read more.
The free-radical homopolymerization of 1,3-bis(N,N,N-trimethylammonium)-2-propylmethacrylate dichloride (di-M) and 1,3-bis(N,N,N-trimethylammonium)-2-propylacrylate dichloride (di-A) in aqueous solution yields cationic polyelectrolytes (PEL) with theoretical/structural charge spacing of only ≈0.12 nm. The high charge density causes condensation of ≈82% of the chloride counterions. The high level of counterion condensation reduces the ionic strength in the polymerizing batch when the monomer molecules connect to PEL chains. This has the consequence that the hydrodynamic and excluded volume of the PEL molecules will change. Studies of the free radical polymerization revealed non-ideal polymerization kinetics already at low conversion and additionally autoacceleration above a certain monomer concentration and conversion. Similar autoacceleration was not observed for monomers yielding PEL with charge spacing of 0.25 or 0.5 nm. Coulomb interactions, monomer association, steric effects, and specific features of the monomer constitution have been evaluated concerning their contributions to the concentration dependence and conversion dependence of kinetic parameters. The different backbone constitutions of di-M and di-A not only influence the polymerization kinetics but also equip poly(di-M) with higher hydrolytic stability. The experimental results confirm the impact of electrochemical parameters and the necessity to reconsider their inclusion in kinetic models. Full article
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Open AccessArticle
pH- and Metal Ion- Sensitive Hydrogels based on N-[2-(dimethylaminoethyl)acrylamide]
Polymers 2016, 8(6), 233; https://doi.org/10.3390/polym8060233 - 15 Jun 2016
Cited by 11
Abstract
Smart hydrogels are promising materials for actuators and sensors, as they can respond to small changes in their environment with a large property change. Hydrogels can respond to a variety of stimuli, for example temperature, pH, metal ions, etc. In this article, [...] Read more.
Smart hydrogels are promising materials for actuators and sensors, as they can respond to small changes in their environment with a large property change. Hydrogels can respond to a variety of stimuli, for example temperature, pH, metal ions, etc. In this article, the synthesis and characterization of polyampholyte hydrogels based on open chain ligands showing pH and metal ion sensitivity are described. Copolymer and terpolymer gels using different mixtures of monomers i.e., N-[2-(dimethylaminoethyl)acrylamide] (DMAEAAm), N,N-dimethylacrylamide (DMAAm), acrylic acid (AA) and 2-acrylamido-2-methyl-1-propanesulphonic acid (AMPS), have been synthesized. The effect of copolymer composition, i.e., the ratio and amount of ionic monomers and the degree of crosslinking on the swelling characteristics, was evaluated as a function of pH. On this basis, metal ion sensitivity measurements were performed at selected pH values. The metal ion sensitivity was measured by varying the concentration of Cu2+, Zn2+ and Ag+ ions under acidic pH conditions. Full article
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Open AccessArticle
SANS from Salt-Free Aqueous Solutions of Hydrophilic and Highly Charged Star-Branched Polyelectrolytes
Polymers 2016, 8(6), 228; https://doi.org/10.3390/polym8060228 - 08 Jun 2016
Cited by 6
Abstract
Scattering functions of sodium sulfonated polystyrene (NaPSS) star-branched polyelectrolytes with high sulfonation degrees were measured from their salt-free aqueous solutions, using the Small Angle Neutron Scattering (SANS) technique. Whatever the concentration c, they display two maxima. The first, of abscissa q1 [...] Read more.
Scattering functions of sodium sulfonated polystyrene (NaPSS) star-branched polyelectrolytes with high sulfonation degrees were measured from their salt-free aqueous solutions, using the Small Angle Neutron Scattering (SANS) technique. Whatever the concentration c, they display two maxima. The first, of abscissa q1*, is related to a position order between star cores and scales as q1* ∝ c1/3. The second, of abscissa q2*, is also observed in the scattering function of a semi-dilute solution of NaPSS linear polyelectrolytes. In the dilute regime (c < c*, non-overlapping stars), peak abscissa does not depend on concentration c and is just an intramolecular characteristic associated with the electrostatic repulsion between arms of the same star. In the semi-dilute regime, due to the star interpenetration, the scattering function – through the peak position, reflects repulsion between arms of the same star or of different stars. The c threshold between these distinct c-dependencies of q2* in the dilute and semi-dilute regimes is estimated as c*. Just as simple is the measurement of the geometrical radius R of the star obtained from the q1* value at c* through the relation 2R = 2π/q1*. By considering NaPSS stars of the same functionality with different degrees of polymerization per arm Na, we find R scaling linearly with Na, suggesting an elongated average conformation of the arms. This is in agreement with theoretical predictions and simulations. Meanwhile the value of q2* measured in the dilute regime does not allow any inhomogeneous counterion distribution inside the stars to be revealed. Full article
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Open AccessArticle
Influence of Polyplex Formation on the Performance of Star-Shaped Polycationic Transfection Agents for Mammalian Cells
Polymers 2016, 8(6), 224; https://doi.org/10.3390/polym8060224 - 06 Jun 2016
Cited by 11
Abstract
Genetic modification (“transfection”) of mammalian cells using non-viral, synthetic agents such as polycations, is still a challenge. Polyplex formation between the DNA and the polycation is a decisive step in such experiments. Star-shaped polycations have been proposed as superior transfection agents, yet have [...] Read more.
Genetic modification (“transfection”) of mammalian cells using non-viral, synthetic agents such as polycations, is still a challenge. Polyplex formation between the DNA and the polycation is a decisive step in such experiments. Star-shaped polycations have been proposed as superior transfection agents, yet have never before been compared side-by-side, e.g., in view of structural effects. Herein four star-shaped polycationic structures, all based on (2-dimethylamino) ethyl methacrylate (DMAEMA) building blocks, were investigated for their potential to deliver DNA to adherent (CHO, L929, HEK-293) and non-adherent (Jurkat, primary human T lymphocytes) mammalian cells. The investigated vectors included three structures where the PDMAEMA arms (different arm length and grafting densities) had been grown from a center silsesquioxane or silica-coated γ-Fe2O3-core and one micellar structure self-assembled from poly(1,2-butadiene)-block PDMAEMA polymers. All nano-stars combined high transfection potential with excellent biocompatibility. The micelles slightly outperformed the covalently linked agents. For method development and optimization, the absolute amount of polycation added to the cells was more important than the N/P-ratio (ratio between polycation nitrogen and DNA phosphate), provided a lower limit was passed and enough polycation was present to overcompensate the negative charge of the plasmid DNA. Finally, the matrix (NaCl vs. HEPES-buffered glucose solution), but also the concentrations adjusted during polyplex formation, affected the results. Full article
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Open AccessArticle
Polypeptide-Nanoparticle Interactions and Corona Formation Investigated by Monte Carlo Simulations
Polymers 2016, 8(6), 203; https://doi.org/10.3390/polym8060203 - 25 May 2016
Cited by 13
Abstract
Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and [...] Read more.
Biomacromolecule activity is usually related to its ability to keep a specific structure. However, in solution, many parameters (pH, ionic strength) and external compounds (polyelectrolytes, nanoparticles) can modify biomacromolecule structure as well as acid/base properties, thus resulting in a loss of activity and denaturation. In this paper, the impact of neutral and charged nanoparticles (NPs) is investigated by Monte Carlo simulations on polypeptide (PP) chains with primary structure based on bovine serum albumin. The influence of pH, salt valency, and NP surface charge density is systematically studied. It is found that the PP is extended at extreme pH, when no complex formation is observed, and folded at physiological pH. PP adsorption around oppositely-charged NPs strongly limits chain structural changes and modifies its acid/base properties. At physiological pH, the complex formation occurs only with positively-charged NPs. The presence of salts, in particular those with trivalent cations, introduces additional electrostatic interactions, resulting in a mitigation of the impact of negative NPs. Thus, the corona structure is less dense with locally-desorbed segments. On the contrary, very limited impact of salt cation valency is observed when NPs are positive, due to the absence of competitive effects between multivalent cations and NP. Full article
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