Special Issue "Self-Assembly of Polymers"

A special issue of Micromachines (ISSN 2072-666X). This special issue belongs to the section "D:Materials and Processing".

Deadline for manuscript submissions: closed (31 August 2018)

Special Issue Editors

Guest Editor
Prof. Dmitry Volodkin

Associate Professor, College of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, UK
Website | E-Mail
Phone: (864) 656-2201
Interests: polymer self-assembly; encapsulation and colntrolled release; microfluidics; hard templating; advanced drug delivery systems; polymer scaffolds; cell-surface engineering; 2D and 3D cell culture, hydrogels; organic inorganic hybrids
Guest Editor
Dr. Anna Vikulina

Postdoctoral research fellow, College of Science and Technology, Nottingham Trent University, Clifton Lane, Nottingham, NG11 8NS, United Kingdom
E-Mail
Interests: lipid assembly; lipid chemistry and analysis; liposomes; molecular transport; diffusion phenomenon; controlled release; drug delivery; biomedical applications

Special Issue Information

Dear Colleagues,

Nowadays, polymer self-assembly has become extremely attractive for both biological (drug delivery, tissue engineering, scaffolds) and non-biological (packaging, semiconductors) applications. In nature, a number of key biological processes are driven by polymer self-assembly, for instance protein folding. Impressive morphologies can be assembled from polymers thanks to a diverse range of interactions involved, e.g., electrostatics, hydrophobic, hots-guest interactions, etc. Both 2D and 3D tailor-made assemblies can be designed through modern powerful techniques and approaches such as the layer-by-layer and the Langmuir-Blodgett deposition, hard and soft templating.

This Special Issue highlights contributions (research papers, short communications, review articles) that focus on recent developments in polymer self-assembly for both fundamental understanding the assembly phenomenon and real applications. Particular attention is paid to:

  • microfluidic-assisted self-assembly
  • design of (bio)polymer based devices and films
  • colloidal particles and multilayers
  • core-shell structures
  • bio-functional self-assembled structures
  • hybrid polymer assemblies with lipids and nanoparticles
  • polymer mobility and structure of self-assemblies
  • mechanism of polymer self-assembly

Contributions related to new technologies and material aspects of polymer assemblies are very welcome.

Prof. Dr. Dmitry Volodkin
Dr. Anna Vikulina
Guest 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 special issue 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. Micromachines is an international peer-reviewed open access monthly 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 1400 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

  • Self-assembly
  • Polymer
  • Multilayers
  • Core-shell
  • Hybrid Materials
  • Lipids
  • Nanoparticles
  • Biopolymers

Published Papers (9 papers)

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Research

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Open AccessArticle
Marine Polysaccharide-Collagen Coatings on Ti6Al4V Alloy Formed by Self-Assembly
Micromachines 2019, 10(1), 68; https://doi.org/10.3390/mi10010068
Received: 30 November 2018 / Revised: 16 January 2019 / Accepted: 18 January 2019 / Published: 19 January 2019
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Abstract
Polysaccharides of marine origin are gaining interest as biomaterial components. Bacteria derived from deep-sea hydrothermal vents can produce sulfated exopolysaccharides (EPS), which can influence cell behavior. The use of such polysaccharides as components of organic, collagen fibril-based coatings on biomaterial surfaces remains unexplored. [...] Read more.
Polysaccharides of marine origin are gaining interest as biomaterial components. Bacteria derived from deep-sea hydrothermal vents can produce sulfated exopolysaccharides (EPS), which can influence cell behavior. The use of such polysaccharides as components of organic, collagen fibril-based coatings on biomaterial surfaces remains unexplored. In this study, collagen fibril coatings enriched with HE800 and GY785 EPS derivatives were deposited on titanium alloy (Ti6Al4V) scaffolds produced by rapid prototyping and subjected to physicochemical and cell biological characterization. Coatings were formed by a self-assembly process whereby polysaccharides were added to acidic collagen molecule solution, followed by neutralization to induced self-assembly of collagen fibrils. Fibril formation resulted in collagen hydrogel formation. Hydrogels formed directly on Ti6Al4V surfaces, and fibrils adsorbed onto the surface. Scanning electron microscopy (SEM) analysis of collagen fibril coatings revealed association of polysaccharides with fibrils. Cell biological characterization revealed good cell adhesion and growth on bare Ti6Al4V surfaces, as well as coatings of collagen fibrils only and collagen fibrils enhanced with HE800 and GY785 EPS derivatives. Hence, the use of both EPS derivatives as coating components is feasible. Further work should focus on cell differentiation. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Open AccessArticle
Internal Structure of Matrix-Type Multilayer Capsules Templated on Porous Vaterite CaCO3 Crystals as Probed by Staining with a Fluorescence Dye
Micromachines 2018, 9(11), 547; https://doi.org/10.3390/mi9110547
Received: 28 September 2018 / Revised: 19 October 2018 / Accepted: 23 October 2018 / Published: 25 October 2018
Cited by 1 | PDF Full-text (3653 KB) | HTML Full-text | XML Full-text
Abstract
Multilayer capsules templated on decomposable vaterite CaCO3 crystals are widely used as vehicles for drug delivery. The capsule represents typically not a hollow but matrix-like structure due to polymer diffusion into the porous crystals during multilayer deposition. The capsule formation mechanism is [...] Read more.
Multilayer capsules templated on decomposable vaterite CaCO3 crystals are widely used as vehicles for drug delivery. The capsule represents typically not a hollow but matrix-like structure due to polymer diffusion into the porous crystals during multilayer deposition. The capsule formation mechanism is not well-studied but its understanding is crucial to tune capsule structure for a proper drug release performance. This study proposes new approach to noninvasively probe and adjust internal capsule structure. Polymer capsules made of poly(styrene-sulfonate) (PSS) and poly(diallyldimethylammonium chloride) (PDAD) have been stained with fluorescence dye rhodamine 6G. Physical-chemical aspects of intermolecular interactions required to validate the approach and adjust capsule structure are addressed. The capsules consist of a defined shell (typically 0.5–2 µm) and an internal matrix of PSS-PDAD complex (typically 10–40% of a total capsule volume). An increase of ionic strength and polymer deposition time leads to the thickening of the capsule shell and formation of a denser internal matrix, respectively. This is explained by effects of a polymer conformation and limitations in polymer diffusion through the crystal pores. We believe that the design of the capsules with desired internal structure will allow achieving effective encapsulation and controlled/programmed release of bioactives for advanced drug delivery applications. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Open AccessArticle
Self-Assembled Mucin-Containing Microcarriers via Hard Templating on CaCO3 Crystals
Micromachines 2018, 9(6), 307; https://doi.org/10.3390/mi9060307
Received: 9 May 2018 / Revised: 1 June 2018 / Accepted: 11 June 2018 / Published: 19 June 2018
Cited by 2 | PDF Full-text (4866 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Porous vaterite crystals of CaCO3 are extensively used for the fabrication of self-assembled polymer-based microparticles (capsules, beads, etc.) utilized for drug delivery and controlled release. The nature of the polymer used plays a crucial role and discovery of new perspective biopolymers is [...] Read more.
Porous vaterite crystals of CaCO3 are extensively used for the fabrication of self-assembled polymer-based microparticles (capsules, beads, etc.) utilized for drug delivery and controlled release. The nature of the polymer used plays a crucial role and discovery of new perspective biopolymers is essential to assemble microparticles with desired characteristics, such as biocompatibility, drug loading efficiency/capacity, release rate, and stability. Glycoprotein mucin is tested here as a good candidate to assemble the microparticles because of high charge due to sialic acids, mucoadhesive properties, and a tendency to self-assemble, forming gels. Mucin loading into the crystals via co-synthesis is twice as effective as via adsorption into preformed crystals. Desialylated mucin has weaker binding to the crystals most probably due to electrostatic interactions between sialic acids and calcium ions on the crystal surface. Improved loading of low-molecular-weight inhibitor aprotinin into the mucin-containing crystals is demonstrated. Multilayer capsules (mucin/protamine)3 have been made by the layer-by-layer self-assembly. Interestingly, the deposition of single mucin layers (mucin/water)3 has also been proven, however, the capsules were unstable, most probably due to additional (to hydrogen bonding) electrostatic interactions in the case of the two polymers used. Finally, approaches to load biologically-active compounds (BACs) into the mucin-containing microparticles are discussed. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Open AccessArticle
A Facile Interfacial Self-Assembly of Crystalline Colloidal Monolayers by Tension Gradient
Micromachines 2018, 9(6), 297; https://doi.org/10.3390/mi9060297
Received: 11 May 2018 / Revised: 8 June 2018 / Accepted: 10 June 2018 / Published: 13 June 2018
Cited by 2 | PDF Full-text (6759 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Many self-assembly approaches of colloidal monolayers have flourished but with some shortages, such as complexity, time-consumption, parameter sensitivity, and high-cost. This paper presents a facile, rapid, well-controlled, and low-cost method to prepare monolayers by directly adding silica particle suspensions containing water and ethanol [...] Read more.
Many self-assembly approaches of colloidal monolayers have flourished but with some shortages, such as complexity, time-consumption, parameter sensitivity, and high-cost. This paper presents a facile, rapid, well-controlled, and low-cost method to prepare monolayers by directly adding silica particle suspensions containing water and ethanol to different liquids. A detailed analysis of the self-assembly process was conducted. The particles dove into water firstly, then moved up under the effect of the buoyancy and the tension gradient. The tension gradient induced the Marangoni convection and the relative motion between the water and the particles. At last, the particles were adsorbed at the air-water interface to minimize the free energy. The quality of the monolayers depended on the addition of sodium dodecyl sulfonate or ethanol in the water subphase. An interfacial polymerization of ethyl 2-cyanoacrylate was used to determine the contact angles of the particles at different subphase surfaces. The value of the detachment energy was positively associated with the contact angle and the surface tension. When the detachment energy decreased to a certain value, some particles detached from the surface, leading to the formation of a quasi-double layer. We also observed that the content of ethanol in suspensions influenced the arrangement of particles. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Open AccessArticle
High-Precision Solvent Vapor Annealing for Block Copolymer Thin Films
Micromachines 2018, 9(6), 271; https://doi.org/10.3390/mi9060271
Received: 19 April 2018 / Revised: 16 May 2018 / Accepted: 25 May 2018 / Published: 29 May 2018
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Abstract
Despite its efficacy in producing well-ordered, periodic nanostructures, the intricate role multiple parameters play in solvent vapor annealing has not been fully established. In solvent vapor annealing a thin polymer film is exposed to a vapor of solvent(s) thus forming a swollen and [...] Read more.
Despite its efficacy in producing well-ordered, periodic nanostructures, the intricate role multiple parameters play in solvent vapor annealing has not been fully established. In solvent vapor annealing a thin polymer film is exposed to a vapor of solvent(s) thus forming a swollen and mobile layer to direct the self-assembly process at the nanoscale. Recent developments in both theory and experiments have directly identified critical parameters that govern this process, but controlling them in any systematic way has proven non-trivial. These identified parameters include vapor pressure, solvent concentration in the film, and the solvent evaporation rate. To explore their role, a purpose-built solvent vapor annealing chamber was designed and constructed. The all-metal chamber is designed to be inert to solvent exposure. Computer-controlled, pneumatically actuated valves allow for precision timing in the introduction and withdrawal of solvent vapor from the film. The mass flow controller-regulated inlet, chamber pressure gauges, in situ spectral reflectance-based thickness monitoring, and low flow micrometer relief valve give real-time monitoring and control during the annealing and evaporation phases with unprecedented precision and accuracy. The reliable and repeatable alignment of polylactide cylinders formed from polystyrene-b-polylactide, where cylinders stand perpendicular to the substrate and span the thickness of the film, provides one illustrative example. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Open AccessArticle
Self-Assembly Behavior and pH-Stimuli-Responsive Property of POSS-Based Amphiphilic Block Copolymers in Solution
Micromachines 2018, 9(6), 258; https://doi.org/10.3390/mi9060258
Received: 1 May 2018 / Revised: 16 May 2018 / Accepted: 17 May 2018 / Published: 24 May 2018
Cited by 1 | PDF Full-text (3742 KB) | HTML Full-text | XML Full-text | Supplementary Files
Abstract
Stimuli-responsive polymeric systems containing special responsive moieties can undergo alteration of chemical structures and physical properties in response to external stimulus. We synthesized a hybrid amphiphilic block copolymer containing methoxy polyethylene glycol (MePEG), methacrylate isobutyl polyhedral oligomeric silsesquioxane (MAPOSS) and 2-(diisopropylamino)ethyl methacrylate (DPA) [...] Read more.
Stimuli-responsive polymeric systems containing special responsive moieties can undergo alteration of chemical structures and physical properties in response to external stimulus. We synthesized a hybrid amphiphilic block copolymer containing methoxy polyethylene glycol (MePEG), methacrylate isobutyl polyhedral oligomeric silsesquioxane (MAPOSS) and 2-(diisopropylamino)ethyl methacrylate (DPA) named MePEG-b-P(MAPOSS-co-DPA) via atom transfer radical polymerization (ATRP). Spherical micelles with a core-shell structure were obtained by a self-assembly process based on MePEG-b-P(MAPOSS-co-DPA), which showed a pH-responsive property. The influence of hydrophobic chain length on the self-assembly behavior was also studied. The pyrene release properties of micelles and their ability of antifouling were further studied. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Open AccessArticle
Microstructure Formation of Functional Polymers by Evaporative Self-Assembly under Flexible Geometric Confinement
Micromachines 2018, 9(3), 124; https://doi.org/10.3390/mi9030124
Received: 30 January 2018 / Revised: 2 March 2018 / Accepted: 8 March 2018 / Published: 12 March 2018
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Abstract
Polymer microstructures are widely used in optics, flexible electronics, and so forth. We demonstrate a cost-effective bottom-up manner for patterning polymer microstructures by evaporative self-assembly under a flexible geometric confinement at a high temperature. Two-parallel-plates confinement would become curve-to-flat shape geometric confinement as [...] Read more.
Polymer microstructures are widely used in optics, flexible electronics, and so forth. We demonstrate a cost-effective bottom-up manner for patterning polymer microstructures by evaporative self-assembly under a flexible geometric confinement at a high temperature. Two-parallel-plates confinement would become curve-to-flat shape geometric confinement as the polydimethylsiloxane (PDMS) cover plate deformed during solvent swelling. We found that a flexible cover plate would be favorable for the formation of gradient microstructures, with various periodicities and widths obtained at varied heights of clearance. After thermal annealing, the edge of the PMMA (Poly-methylmethacrylate) microstructures would become smooth, while the RR-P3HT (regioregular-poly(3-hexylthiophene)) might generate nanocrystals. The morphologies of RR-P3HT structures included thick films, straight lines, hierarchical stripes, incomplete stripes, and regular dots. Finally, a simple field-effect transistor (FET) device was demonstrated with the RR-P3HT micropattern as an active layer. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Review

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Open AccessReview
Biocatalysis by Transglutaminases: A Review of Biotechnological Applications
Micromachines 2018, 9(11), 562; https://doi.org/10.3390/mi9110562
Received: 10 October 2018 / Accepted: 23 October 2018 / Published: 31 October 2018
Cited by 1 | PDF Full-text (2313 KB) | HTML Full-text | XML Full-text
Abstract
The biocatalytic activity of transglutaminases (TGs) leads to the synthesis of new covalent isopeptide bonds (crosslinks) between peptide-bound glutamine and lysine residues, but also the transamidation of primary amines to glutamine residues, which ultimately can result into protein polymerisation. Operating with a cysteine/histidine/aspartic [...] Read more.
The biocatalytic activity of transglutaminases (TGs) leads to the synthesis of new covalent isopeptide bonds (crosslinks) between peptide-bound glutamine and lysine residues, but also the transamidation of primary amines to glutamine residues, which ultimately can result into protein polymerisation. Operating with a cysteine/histidine/aspartic acid (Cys/His/Asp) catalytic triad, TGs induce the post-translational modification of proteins at both physiological and pathological conditions (e.g., accumulation of matrices in tissue fibrosis). Because of the disparate biotechnological applications, this large family of protein-remodelling enzymes have stimulated an escalation of interest. In the past 50 years, both mammalian and microbial TGs polymerising activity has been exploited in the food industry for the improvement of aliments’ quality, texture, and nutritive value, other than to enhance the food appearance and increased marketability. At the same time, the ability of TGs to crosslink extracellular matrix proteins, like collagen, as well as synthetic biopolymers, has led to multiple applications in biomedicine, such as the production of biocompatible scaffolds and hydrogels for tissue engineering and drug delivery, or DNA-protein bio-conjugation and antibody functionalisation. Here, we summarise the most recent advances in the field, focusing on the utilisation of TGs-mediated protein multimerisation in biotechnological and bioengineering applications. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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Open AccessReview
Progress in Photo-Responsive Polypeptide Derived Nano-Assemblies
Micromachines 2018, 9(6), 296; https://doi.org/10.3390/mi9060296
Received: 25 May 2018 / Revised: 6 June 2018 / Accepted: 11 June 2018 / Published: 13 June 2018
Cited by 12 | PDF Full-text (5655 KB) | HTML Full-text | XML Full-text
Abstract
Stimuli-responsive polymeric materials have attracted significant attention in a variety of high-value-added and industrial applications during the past decade. Among various stimuli, light is of particular interest as a stimulus because of its unique advantages, such as precisely spatiotemporal control, mild conditions, ease [...] Read more.
Stimuli-responsive polymeric materials have attracted significant attention in a variety of high-value-added and industrial applications during the past decade. Among various stimuli, light is of particular interest as a stimulus because of its unique advantages, such as precisely spatiotemporal control, mild conditions, ease of use, and tunability. In recent years, a lot of effort towards the synthesis of a biocompatible and biodegradable polypeptide has resulted in many examples of photo-responsive nanoparticles. Depending on the specific photochemistry, those polypeptide derived nano-assemblies are capable of crosslinking, disassembling, or morphing into other shapes upon light irradiation. In this mini-review, we aim to assess the current state of photo-responsive polypeptide based nanomaterials. Firstly, those ‘smart’ nanomaterials will be categorized by their photo-triggered events (i.e., crosslinking, degradation, and isomerization), which are inherently governed by photo-sensitive functionalities, including O-nitrobenzyl, coumarin, azobenzene, cinnamyl, and spiropyran. In addition, the properties and applications of those polypeptide nanomaterials will be highlighted as well. Finally, the current challenges and future directions of this subject will be evaluated. Full article
(This article belongs to the Special Issue Self-Assembly of Polymers)
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