Special Issue "Bioinspired and Biomimetic Polymers"

A special issue of Polymers (ISSN 2073-4360).

Deadline for manuscript submissions: 30 June 2020.

Special Issue Editors

Prof. Dr. Elisabetta Ranucci
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Guest Editor
Department of Chemistry, University of Milan, Milan, Italy
Interests: biodegradable and biocompatible polymers for applications in nanomedicine; bioinspired polymers with flame-retardant activity; multifunctional composite resins for the absorption of inorganic and organic pollutants from wastewater; composite hydrogels as scaffolds for tissue regeneration; polymers from renewable sources
Prof. Dr. Paolo Ferruti
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Guest Editor
Department of Chemistry, University of Milan, Milan, Italy
Interests: functionalization of polymers; polymer nanoparticles; biocompatible and biodegradable polymers, bioinspired polymers, biomedical and biotechnological applications of functional polymers, polymers for drug delivery, Polymeric hydrogels as scaffolds for cell culturing and tissue regeneration, flame retardant functional polymers, polyelectrolytes, heavy metal ion complexing polymers
Dr. Amedea Manfredi
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Guest Editor
Department of Chemistry, University of Milan, Milan, Italy
Interests: biodegradable and biocompatible polymers for applications in nanomedicine; bioinspired polymers with flame-retardant activity; multifunctional composite resins for the absorption of inorganic and organic pollutants from wastewater; composite hydrogels as scaffolds for tissue regeneration; polymers from renewable sources
Dr. Jenny Alongi
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Guest Editor
Università degli Studi Di Milano, Dipartimento di Chimica, Via C. Golgi 19, 20133 Milano, Italy
Interests: polymers with high thermal stability; flame retarded polymers; biocompatible and biometic polymers; multifunctional resins for the adsorption of heavy metals from wastewaters; multifunctional coatings; layer by Layer assembly

Special Issue Information

Dear Colleagues,

Natural polymers, such as polysaccharides, proteins, and DNA, regulate key functions of biological systems owing to their sophisticated structures endowing them with extraordinary properties. The molecular functionalities of natural polymers, and their macromolecular structures and properties, provide inspiration for designing different classes of high-performance polymeric materials that aim to reproduce specific functions of natural polymers, such as adaptability, self-healing, adhesiveness, surface superwettability and superhydrophobicity, chiral recognition, and bioactivity. The field of bioinspired and biomimetic polymers is rapidly expanding in diverse technological sectors, including pharmacology, tissue engineering, the aerospace industry, optical materials and lightweight structural materials, and biosensors. Biomimetic synthetic polymers and hybrid polymer-materials have the advantage of combining desired functions with tailored morphology and superior chemical and physical stability.

Bioinspired and biomimetic polymers aims to cover all aspects of the subject, including, for instance, the synthesis of hybrid polymer/biomolecule conjugates and blends, self-assembling polymers, chiral polymers and surfaces, films, functional polymer brushes, nanocomposites and nanocomposite hydrogels, and supramolecular polymer structures, without forgetting studies of structure-property relationships, fabrication of materials with precise structural control and advanced properties, and applications of bioinspired polymers in all the different fields mentioned above.

This Special Issue welcomes reports on recent findings and reviews from experts in this frontier sector.

Prof. Elisabetta Ranucci
Prof. Paolo Ferruti
Dr. Amedea Manfredi
Dr. Jenny Alongi
Guest Editors

Keywords

  • chiral polymers and interfaces
  • polypeptides
  • glycopolypeptides
  • polypeptoids
  • polyoxazolines
  • vinylic α-aminoacid derivatives
  • biomaterials
  • tissue engineering
  • gene therapy
  • drug targeting
  • optical materials
  • lightweight structural materials
  • composites and nanocomposites
  • bioadhesive polymers and hydrogels
  • mechanically adapting polymers
  • sensors and biosensors

Published Papers (8 papers)

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Research

Open AccessArticle
A Biomimetic Approach to Increasing Soft Actuator Performance by Friction Reduction
Polymers 2020, 12(5), 1120; https://doi.org/10.3390/polym12051120 - 14 May 2020
Abstract
While increasing power output is the most straight-forward solution for faster and stronger motion in technology, sports, or elsewhere, efficiency is what separates the best from the rest. In nature, where the possibilities of power increase are limited, efficiency of motion is particularly [...] Read more.
While increasing power output is the most straight-forward solution for faster and stronger motion in technology, sports, or elsewhere, efficiency is what separates the best from the rest. In nature, where the possibilities of power increase are limited, efficiency of motion is particularly important; the same principle can be applied to the emerging biomimetic and bio-interacting technologies. In this work, by applying hints from nature, we consider possible approaches of increasing the efficiency of motion through liquid medium of bilayer ionic electroactive polymer actuations, focusing on the reduction of friction by means of surface tension and hydrophobicity. Conducting polyethylene terephthalate (PET) bilayers were chosen as the model actuator system. The actuation medium consisted of aqueous solutions containing tetramethylammonium chloride and sodium dodecylbenzenesulfonate in different ratios. The roles of ion concentrations and the surface tension are discussed. Hydrophobicity of the PET support layer was further tuned by adding a spin-coated silicone layer to it. As expected, both approaches increased the displacement—the best results having been obtained by combining both, nearly doubling the bending displacement. The simple approaches for greatly increasing actuation motion efficiency can be used in any actuator system operating in a liquid medium. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Open AccessArticle
pH-Dependent Chiral Recognition of D- and L-Arginine Derived Polyamidoamino Acids by Self-Assembled Sodium Deoxycholate
Polymers 2020, 12(4), 900; https://doi.org/10.3390/polym12040900 - 13 Apr 2020
Abstract
D- and L-arginine-based polyamidoamino acids, called D- and L-ARGO7, retain the chirality and acid/base properties of the parent α-amino acids and show pH-dependent self-structuring in water. The ability of the ARGO7 chiral isomers to selectively interact with chiral biomolecules [...] Read more.
D- and L-arginine-based polyamidoamino acids, called D- and L-ARGO7, retain the chirality and acid/base properties of the parent α-amino acids and show pH-dependent self-structuring in water. The ability of the ARGO7 chiral isomers to selectively interact with chiral biomolecules and/or surfaces was studied by choosing sodium deoxycholate (NaDC) as a model chiral biomolecule for its ability to self-assembly into globular micelles, showing enantio-selectivity. To this purpose, mixtures of NaDC with D-, L- or D,L-ARGO7, respectively, in water were analysed by circular dichroism (CD) spectroscopy and small-angle neutron scattering (SANS) at different levels of acidity expressed in terms of pD and concentrations. Differences in the CD spectra indicated chiral discrimination for NaDC/ARGO7 mixtures in the gel phase (pD 7.30) but not in the solution phase (pD 9.06). SANS measurements confirmed large scale structural perturbation induced by this chiral discrimination in the gel phase yet no modulation of the structure in the solution phase. Together, these techniques shed light on the mechanism by which ARGO7 stereoisomers modify the morphology of NaDC micelles as a function of pH. This work demonstrates chirality-dependent interactions that drive structural evolution and phase behaviour of NaDC, opening the way for designing novel smart drug delivery systems. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Open AccessArticle
Hydrogen Bonding in a l-Glutamine-Based Polyamidoamino Acid and its pH-Dependent Self-Ordered Coil Conformation
Polymers 2020, 12(4), 881; https://doi.org/10.3390/polym12040881 - 10 Apr 2020
Abstract
This paper reports on synthesis, acid–base properties, and self-structuring in water of a chiral polyamidoamino acid, M-l-Gln, obtained from the polyaddition of N,N′-methylenebisacrylamide with l-glutamine, with the potential of establishing hydrogen bonds through its prim-amide pendants. The M- [...] Read more.
This paper reports on synthesis, acid–base properties, and self-structuring in water of a chiral polyamidoamino acid, M-l-Gln, obtained from the polyaddition of N,N′-methylenebisacrylamide with l-glutamine, with the potential of establishing hydrogen bonds through its prim-amide pendants. The M-l-Gln showed pH-responsive circular dichroism spectra, revealing ordered conformations. Structuring was nearly insensitive to ionic strength but sensitive to denaturing agents. The NMR diffusion studies were consistent with a population of unimolecular nanoparticles thus excluding aggregation. The M-l-Gln had the highest molecular weight and hydrodynamic radius among all polyamidoamino acids described. Possibly, transient hydrogen bonds between l-glutamine molecules and M-l-Gln growing chains facilitated the polyaddition reaction. Theoretical modeling showed that M-l-Gln assumed pH-dependent self-ordered coil conformations with main chain transoid arrangements reminiscent of the protein hairpin motif owing to intramolecular dipole moments and hydrogen bonds. The latter were most numerous at the isoelectric point (pH 4.5), where they mainly involved even topologically distant main chain amide N–H and side chain amide C=O brought to proximity by structuring. Hydrogen bonds at pH 4.5 were also suggested by variable temperature NMR. The 2D NOESY experiments at pH 4.5 confirmed the formation of compact structures through the analysis of the main chain/side chain hydrogen contacts, in line with MD simulations. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Open AccessArticle
Hybrid Complex Coacervate
Polymers 2020, 12(2), 320; https://doi.org/10.3390/polym12020320 - 04 Feb 2020
Abstract
Underwater adhesion represents a huge technological challenge as the presence of water compromises the performance of most commercially available adhesives. Inspired by natural organisms, we have designed an adhesive based on complex coacervation, a liquid–liquid phase separation phenomenon. A complex coacervate adhesive is [...] Read more.
Underwater adhesion represents a huge technological challenge as the presence of water compromises the performance of most commercially available adhesives. Inspired by natural organisms, we have designed an adhesive based on complex coacervation, a liquid–liquid phase separation phenomenon. A complex coacervate adhesive is formed by mixing oppositely charged polyelectrolytes bearing pendant thermoresponsive poly(N-isopropylacrylamide) (PNIPAM) chains. The material fully sets underwater due to a change in the environmental conditions, namely temperature and ionic strength. In this work, we incorporate silica nanoparticles forming a hybrid complex coacervate and investigate the resulting mechanical properties. An enhancement of the mechanical properties is observed below the PNIPAM lower critical solution temperature (LCST): this is due to the formation of PNIPAM–silica junctions, which, after setting, contribute to a moderate increase in the moduli and in the adhesive properties only when applying an ionic strength gradient. By contrast, when raising the temperature above the LCST, the mechanical properties are dominated by the association of PNIPAM chains and the nanofiller incorporation leads to an increased heterogeneity with the formation of fracture planes at the interface between areas of different concentrations of nanoparticles, promoting earlier failure of the network—an unexpected and noteworthy consequence of this hybrid system. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Open AccessArticle
Bio-Inspired Amphiphilic Block-Copolymers Based on Synthetic Glycopolymer and Poly(Amino Acid) as Potential Drug Delivery Systems
Polymers 2020, 12(1), 183; https://doi.org/10.3390/polym12010183 - 10 Jan 2020
Cited by 1
Abstract
In this work, a method to prepare hybrid amphiphilic block copolymers consisting of biocompatible synthetic glycopolymer with non-degradable backbone and biodegradable poly(amino acid) (PAA) was developed. The glycopolymer, poly(2-deoxy-2-methacrylamido-D-glucose) (PMAG), was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Two methods for modifying [...] Read more.
In this work, a method to prepare hybrid amphiphilic block copolymers consisting of biocompatible synthetic glycopolymer with non-degradable backbone and biodegradable poly(amino acid) (PAA) was developed. The glycopolymer, poly(2-deoxy-2-methacrylamido-D-glucose) (PMAG), was synthesized via reversible addition-fragmentation chain transfer (RAFT) polymerization. Two methods for modifying the terminal dithiobenzoate-group of PMAG was investigated to obtain the macroinitiator bearing a primary aliphatic amino group, which is required for ring-opening polymerization of N-carboxyanhydrides of hydrophobic α-amino acids. The synthesized amphiphilic block copolymers were carefully analyzed using a set of different physico-chemical methods to establish their composition and molecular weight. The developed amphiphilic copolymers tended to self-assemble in nanoparticles of different morphology that depended on the nature of the hydrophobic amino acid present in the copolymer. The hydrodynamic diameter, morphology, and cytotoxicity of polymer particles based on PMAG-b-PAA were evaluated using dynamic light scattering (DLS) and transmission electron microscopy (TEM), as well as CellTiter-Blue (CTB) assay, respectively. The redox-responsive properties of nanoparticles were evaluated in the presence of glutathione taken at different concentrations. Moreover, the encapsulation of paclitaxel into PMAG-b-PAA particles and their cytotoxicity on human lung carcinoma cells (A549) and human breast adenocarcinoma cells (MCF-7) were studied. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Open AccessArticle
Gamma Ray-Induced Polymerization and Cross-Linking for Optimization of PPy/PVP Hydrogel as Biomaterial
Polymers 2020, 12(1), 111; https://doi.org/10.3390/polym12010111 - 05 Jan 2020
Cited by 1
Abstract
Conducting polymer (CP)-based hydrogels exhibit the behaviors of bending or contraction/relaxation due to electrical stimulation. They are similar in some ways to biological organs and have advantages regarding manipulation and miniaturization. Thus, these hydrogels have attracted considerable interest for biomedical applications. In this [...] Read more.
Conducting polymer (CP)-based hydrogels exhibit the behaviors of bending or contraction/relaxation due to electrical stimulation. They are similar in some ways to biological organs and have advantages regarding manipulation and miniaturization. Thus, these hydrogels have attracted considerable interest for biomedical applications. In this study, we prepared PPy/PVP hydrogel with different concentrations and content through polymerization and cross-linking induced by gamma-ray irradiation at 25 kGy to optimize the mechanical properties of the resulting PPy/PVP hydrogel. Optimization of the PPy/PVP hydrogel was confirmed by characterization using scanning electron microscopy, gel fraction, swelling ratio, and Fourier transform infrared spectroscopy. In addition, we assessed live-cell viability using live/dead assay and CCK-8 assay, and found good cell viability regardless of the concentration and content of Py/pTS. The conductivity of PPy/PVP hydrogel was at least 13 mS/cm. The mechanical properties of PPy/PVP hydrogel are important factors in their application for biomaterials. It was found that 0.15PPy/PVP20 (51.96 ± 6.12 kPa) exhibited better compressive strength than the other samples for use in CP-based hydrogels. Therefore, it was concluded that gamma rays can be used to optimize PPy/PVP hydrogel and that biomedical applications of CP-based hydrogels will be possible. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Open AccessArticle
Controlled Synthesis of Linear Polyamidoamino Acids
Polymers 2019, 11(8), 1324; https://doi.org/10.3390/polym11081324 - 08 Aug 2019
Cited by 1
Abstract
Polyamidoamino acids (PAACs) are synthetic polymers prepared by the polyaddition of bisacrylamides with natural α-amino acids, which in the process maintain both their chirality and their amphoteric nature. This polymerization process is slow, but has the merits of taking place in water and [...] Read more.
Polyamidoamino acids (PAACs) are synthetic polymers prepared by the polyaddition of bisacrylamides with natural α-amino acids, which in the process maintain both their chirality and their amphoteric nature. This polymerization process is slow, but has the merits of taking place in water and of neither involving protection/de-protection steps nor releasing by-products. However, it leads to polydisperse polymers and, using α-amino acids mixtures, random copolymers. This paper presents a step-by-step polyaddition process leading to homo- and copolymeric PAACs with controlled sequences and controlled molecular weights. It exploits the much different rates of the two Michael addition steps of NH2 of α-amino acids with acrylamides, and the low solubility in organic solvents of the α-amino acid addition products. As a proof of principle, the controlled synthesis of the PAAC from l-arginine and N,N′-methylenebisacrylamide was performed up to a monodisperse product with 11 monomeric units and molecular weight 1840. This synthetic procedure was also tested with l-alanine. All intermediates were isolated and characterized. Noticeably, all of them were α,ω-difunctionalized with either acrylamides or sec-amines and were, in fact, building blocks with potential for preparing complex macromolecular architectures. In a first instance, copolymers with controlled sequences of amidoamine- and amidoamino acid units were prepared. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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Open AccessArticle
d-, l- and d,l-Tryptophan-Based Polyamidoamino Acids: pH-Dependent Structuring and Fluorescent Properties
Polymers 2019, 11(3), 543; https://doi.org/10.3390/polym11030543 - 22 Mar 2019
Cited by 6
Abstract
Chiral polyamidoamino acids were obtained by polyaddition of N,N’-methylenebisacrylamide with d-, d,l- and l-tryptophan (M-d-Trp, M-d,l-Trp and M-l-Trp). l-tryptophan/glycine copolymers, M-G-l-Trp5, M-G-l-Trp [...] Read more.
Chiral polyamidoamino acids were obtained by polyaddition of N,N’-methylenebisacrylamide with d-, d,l- and l-tryptophan (M-d-Trp, M-d,l-Trp and M-l-Trp). l-tryptophan/glycine copolymers, M-G-l-Trp5, M-G-l-Trp10, M-G-l-Trp20 and M-G-l-Trp40, were prepared from l-tryptophan/glycine mixtures. These polymers were amphoteric, with acid-base properties similar to those of the parent amino acids. The l-tryptophan/glycine copolymers with high glycine content were water soluble in the pH range 2-12. M-G-l-Trp40 showed a solubility gap centred at pH 4.5 and all tryptophan homopolymers were soluble only at pH > 7. Dynamic light scattering measurements performed in their solubility ranges, namely 2-11 M-G-l-Trp5, M-G-l-Trp10 and M-G-l-Trp20 and 7-11 for M-G-l-Trp40, M-d-Trp, M-l-Trp and M-d,l-Trp, showed that the size of all samples did not significantly vary with pH. Both M-l-Trp and M-G-l-Trp copolymers showed pH-dependent circular dichroism spectra in the wavelength interval 200–280 nm, revealing structuring. All samples were fluorescent. Their emission spectra were unstructured and, if normalized for their tryptophan content, almost superimposable at the same pH, providing evidence that only tryptophan governed the photoluminescence properties. Changing pH induced in all cases a slight shift of the emission wavelength maximum ascribed to the modification of the microenvironment surrounding the indole ring induced by different protonation degrees. Full article
(This article belongs to the Special Issue Bioinspired and Biomimetic Polymers)
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