Preparation, Properties and Applications of Functional Hydrogels

A special issue of Gels (ISSN 2310-2861). This special issue belongs to the section "Gel Applications".

Deadline for manuscript submissions: closed (20 May 2023) | Viewed by 23770

Special Issue Editors


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Guest Editor
Centre de recherche en biomédecine de Strasbourg, 67000 Strasbourg, France
Interests: hydrogels; biomaterials; antimicrobial gels; peptide self-assembly; enzyme or chemically fuelled self-assembly; functional gels
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Guest Editor
Polymer and Biomaterials Chemistry Laboratories, School of Chemistry and Biosciences, University of Bradford, Bradford BD7 1DP, UK
Interests: functional polymers; stimuli-responsive systems; moisture control; vapour permeability; grafting
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Guest Editor
Karlsruhe Institute of Technology, Institute of Functional Interfaces, Hermann-von-Helmholtz-Platz 1, 76344 Eggenstein-Leopoldshafen, Germany
Interests: surface functionalization; biomaterials; biointerfaces; layer-by-layer assembly; antimicrobial films; cell–material interactions; hydrogels; polyelectrolytes; nanomaterials
Special Issues, Collections and Topics in MDPI journals

Special Issue Information

Dear Colleagues,

This Special Issue on “Preparation, Properties and Application of Functional Hydrogels” is dedicated to recent advances in the hydrogels field. Within this context, a broad range of subjects, including structure and characterization, molecular modelling and simulation, and applications will be discussed. Over the past decade, hydrogels have received significant research attention due to their unique type of scaffolds and broad application prospects, such as in biomaterials and biointerfaces, coatings, drug/gene delivery, tissue engineering, and soft matter. Several types of hydrogels have been prepared from naturally derived biomaterials, synthetic polymers, 2D nanomaterials, or their combination, showing promising functions through the precise control of molecular and supramolecular architecture. Progress in this field requires an interdisciplinary effort to accomplish a more detailed understanding of the structure and interactions that define the different scaffolds and complex behaviour, and to make it possible to tailor the properties of these materials.

This Special Issue will contain only a few representative examples of the possibilities of hydrogels. It is hoped that through this Special Issue, novel research and discoveries will be stimulated and will lead to new preparation methods, properties, and functions.

Note: If you would like to contribute a related paper, please consider our 2nd Edition: Preparation, Properties and Applications of Functional Hydrogels (2nd Edition)

Dr. Jennifer Rodon-Fores
Dr. Thomas Swift
Dr. Iqbal Muhammad Haseeb
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 submissions that pass pre-check are 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. Gels 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 2600 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

  • hydrogels
  • dynamic properties
  • structure–property relationship
  • synthesis and characterization
  • biomaterials and biointerfaces
  • polymers and nanomaterials
  • functional materials and surfaces
  • applications

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Published Papers (10 papers)

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Research

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13 pages, 1750 KiB  
Article
Water-Content-Dependent Switching of the Bending Behavior of Photoresponsive Hydrogels Composed of Hydrophilic Acrylamide-Based Main Chains and Hydrophobic Azobenzene
by Junsu Park, Yuki Shimizu, Xin Zhou, Ryohei Ikura, Go Matsuba and Yoshinori Takashima
Gels 2023, 9(8), 658; https://doi.org/10.3390/gels9080658 - 16 Aug 2023
Viewed by 1793
Abstract
Photoresponsiveness is a promising characteristic of stimulus-responsive materials. Photoresponsiveness can be achieved by incorporating photoresponsive molecules into polymeric materials. In addition, multiple-stimuli-responsive materials have attracted scientists’ interest. Among the numerous multiple-stimuli-responsive materials, moisture- and photoresponsive materials are the focus of this report. These [...] Read more.
Photoresponsiveness is a promising characteristic of stimulus-responsive materials. Photoresponsiveness can be achieved by incorporating photoresponsive molecules into polymeric materials. In addition, multiple-stimuli-responsive materials have attracted scientists’ interest. Among the numerous multiple-stimuli-responsive materials, moisture- and photoresponsive materials are the focus of this report. These stimuli-responsive materials responded to the stimuli synergistically or orthogonally. Unlike most stimulus-responsive materials utilizing moisture and light as stimuli, the materials studied herein switch their photoresponsiveness in the presence of moisture. Appropriate copolymers consisting of hydrophilic acrylamide-based monomers for the main chain and hydrophobic azobenzene moieties switched their bending behaviors at 6–9 wt% water contents. At water contents lower than 6 wt%, the polymeric materials bent away from the light source, while they bent toward the light source at water contents higher than 10 wt%. At a low water content, the bending behaviors can be described on the molecular scale. At a high water content, the bending behavior requires consideration of the phase scale, not only the molecular scale. By controlling the balance between hydrophilicity and hydrophobicity, the switching behavior was achieved. This switching behavior may inspire additional strategies for the application of polymeric material as actuators. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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13 pages, 2290 KiB  
Article
Hollow Particles Obtained by Prilling and Supercritical Drying as a Potential Conformable Dressing for Chronic Wounds
by Maria Rosaria Sellitto, Chiara Amante, Rita Patrizia Aquino, Paola Russo, Rosalía Rodríguez-Dorado, Monica Neagu, Carlos A. García-González, Renata Adami and Pasquale Del Gaudio
Gels 2023, 9(6), 492; https://doi.org/10.3390/gels9060492 - 16 Jun 2023
Cited by 3 | Viewed by 1227
Abstract
The production of aerogels for different applications has been widely known, but the use of polysaccharide-based aerogels for pharmaceutical applications, specifically as drug carriers for wound healing, is being recently explored. The main focus of this work is the production and characterization of [...] Read more.
The production of aerogels for different applications has been widely known, but the use of polysaccharide-based aerogels for pharmaceutical applications, specifically as drug carriers for wound healing, is being recently explored. The main focus of this work is the production and characterization of drug-loaded aerogel capsules through prilling in tandem with supercritical extraction. In particular, drug-loaded particles were produced by a recently developed inverse gelation method through prilling in a coaxial configuration. Particles were loaded with ketoprofen lysinate, which was used as a model drug. The core-shell particles manufactured by prilling were subjected to a supercritical drying process with CO2 that led to capsules formed by a wide hollow cavity and a tunable thin aerogel layer (40 μm) made of alginate, which presented good textural properties in terms of porosity (89.9% and 95.3%) and a surface area up to 417.0 m2/g. Such properties allowed the hollow aerogel particles to absorb a high amount of wound fluid moving very quickly (less than 30 s) into a conformable hydrogel in the wound cavity, prolonging drug release (till 72 h) due to the in situ formed hydrogel that acted as a barrier to drug diffusion. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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15 pages, 2456 KiB  
Article
Chain-Extendable Crosslinked Hydrogels Using Branching RAFT Modification
by Stephen Rimmer, Paul Spencer, Davide Nocita, John Sweeney, Marcus Harrison and Thomas Swift
Gels 2023, 9(3), 235; https://doi.org/10.3390/gels9030235 - 17 Mar 2023
Cited by 1 | Viewed by 1842
Abstract
Functional crosslinked hydrogels were prepared from 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA). The acid monomer was incorporated both via copolymerization and chain extension of a branching, reversible addition–fragmentation chain-transfer agent incorporated into the crosslinked polymer gel. The hydrogels were intolerant to high [...] Read more.
Functional crosslinked hydrogels were prepared from 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA). The acid monomer was incorporated both via copolymerization and chain extension of a branching, reversible addition–fragmentation chain-transfer agent incorporated into the crosslinked polymer gel. The hydrogels were intolerant to high levels of acidic copolymerization as the acrylic acid weakened the ethylene glycol dimethacrylate (EGDMA) crosslinked network. Hydrogels made from HEMA, EGDMA and a branching RAFT agent provide the network with loose-chain end functionality that can be retained for subsequent chain extension. Traditional methods of surface functionalization have the downside of potentially creating a high volume of homopolymerization in the solution. Branching RAFT comonomers act as versatile anchor sites by which additional polymerization chain extension reactions can be carried out. Acrylic acid grafted onto HEMA–EGDMA hydrogels showed higher mechanical strength than the equivalent statistical copolymer networks and was shown to have functionality as an electrostatic binder of cationic flocculants. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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11 pages, 1977 KiB  
Article
Physical Chemistry Study of Collagen-Based Multilayer Films
by Yi-Wei Chen, Muhammad Haseeb Iqbal, Florent Meyer, Vincent Ball and Fouzia Boulmedais
Gels 2023, 9(3), 192; https://doi.org/10.3390/gels9030192 - 2 Mar 2023
Cited by 1 | Viewed by 1708
Abstract
The surface properties of a biomaterial play an important role in cell behavior, e.g., recolonization, proliferation, and migration. Collagen is known to favor wound healing. In this study, collagen (COL)-based layer-by-layer (LbL) films were built using different macromolecules as a partner, i.e., tannic [...] Read more.
The surface properties of a biomaterial play an important role in cell behavior, e.g., recolonization, proliferation, and migration. Collagen is known to favor wound healing. In this study, collagen (COL)-based layer-by-layer (LbL) films were built using different macromolecules as a partner, i.e., tannic acid (TA), a natural polyphenol known to establish hydrogen bonds with protein, heparin (HEP), an anionic polysaccharide, and poly(sodium 4-styrene sulfonate) (PSS), an anionic synthetic polyelectrolyte. To cover the whole surface of the substrate with a minimal number of deposition steps, several parameters of the film buildup were optimized, such as the pH value of the solutions, the dipping time, and the salt (sodium chloride) concentration. The morphology of the films was characterized by atomic force microscopy. Built at an acidic pH, the stability of COL-based LbL films was studied when in contact with a physiological medium as well as the TA release from COL/TA films. In contrast to COL/PSS and COL/HEP LbL films, COL/TA films showed a good proliferation of human fibroblasts. These results validate the choice of TA and COL as components of LbL films for biomedical coatings. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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18 pages, 8825 KiB  
Article
Fibrillogenesis and Hydrogel Formation from Fibrinogen Induced by Calcium Salts
by Dominik Hense and Oliver I. Strube
Gels 2023, 9(3), 175; https://doi.org/10.3390/gels9030175 - 22 Feb 2023
Cited by 2 | Viewed by 1761
Abstract
Fibrin is considered a highly promising biomaterial for manifold medical applications. Although it is a well-established material in this field, the required enzyme thrombin bears some striking downsides such as high costs and health risks. Current research discovers more and more ways to [...] Read more.
Fibrin is considered a highly promising biomaterial for manifold medical applications. Although it is a well-established material in this field, the required enzyme thrombin bears some striking downsides such as high costs and health risks. Current research discovers more and more ways to use fibrin’s precursor fibrinogen as a substitute. Fibrinogen’s full potential is, however, only retained when using it as fibrous gel, as it is the case for fibrin. In our previous work, we introduced such a kind of material for the first time. This material, called pseudo-fibrin, shows striking similarities to fibrin regarding its supramolecular structure and is created in a facile salt-induced process, which we further improved in this study. In particular, we shine light on the role of Ca2+ in pseudo-fibrin buildup, which turned out to drastically improve the outcome. Never before has it been observed that Ca2+ can induce fibrillogenesis and the gelation of native, enzyme-free fibrinogen. Enzyme catalysis was ruled out by the addition of thrombin and factor XIII inhibitors. Even more striking, Ca2+ induces gelation even under physiological conditions, leading again to stable and fibrous hydrogels. Although this latter approach is possibly co-induced by residual factor XIII, the resulting gels are for the first time recognized as promising materials and not discounted as unwanted side effects. The finding that these gels again consist of fibers especially renders a new perspective on the role of factor XIII and fibrinogen’s well-known Ca2+ binding sites. In this study, we aim to provide first insights into this highly feasible material and its characteristics. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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14 pages, 1927 KiB  
Article
Detection of Gel-Forming Polymers via Calcium Crosslinking, Applied to the Screening of Extracellular Polymeric Substances Extracted from Biological Aggregates
by Abdo Bou-Sarkis, Etienne Paul, Elisabeth Girbal-Neuhauser, Nicolas Derlon and Yolaine Bessiere
Gels 2023, 9(2), 157; https://doi.org/10.3390/gels9020157 - 16 Feb 2023
Cited by 1 | Viewed by 1829
Abstract
The valorization of biological aggregates through the extraction of hydrogel-forming polymers can enhance the economics and sustainability of various processes in which bacteria are involved in organic waste transformation, such as wastewater treatment. Achieving these goals requires the development of a method capable [...] Read more.
The valorization of biological aggregates through the extraction of hydrogel-forming polymers can enhance the economics and sustainability of various processes in which bacteria are involved in organic waste transformation, such as wastewater treatment. Achieving these goals requires the development of a method capable of detecting the presence of gel-forming polymers in complex mixtures containing biopolymers that are most often unknown and uncharacterized. A miniaturized screening method capable of detecting gelation via ionic crosslinking using only 1 to 3 mg of the tested samples (commercial molecules or extracellular polymeric substances, EPSs) is proposed. The method consists of calculating a percentage of reactivity (%R) through UV-vis spectra and determining the percentage of gel volume (%Vg) formed after the addition of calcium. Both factors were combined to give a gelling factor (GF), and the test was applied to pure commercial molecules (BSA, DNA, alginate (ALV), and a mixture of them), allowing the classification of the following solutions according to their gel-forming capacity: GF(ALV) > GF(ALV+DNA) > GF(BSA+ALV+DNA) > GF(BSA+ALV) > GF(DNA) > GF(BSA+DNA) > GF(BSA). As a relevant tool for screening hydrogel-forming solutions, the method was applied to the EPS extracted from aerobic granular sludge. The EPS (0.5% w/v) had a GF of 0.16 ± 0.03, equivalent to approximately half of the GF of ALV (0.38 ± 0.02 at 0.5% w/v). The developed test pushes the limits of the existing gel-detection techniques because it allows for quicker, less consuming, and more informative gelation detection through the use of simple methods that do not require sophisticated equipment. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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8 pages, 1708 KiB  
Article
Tuning of Optical Stopband Wavelength and Effective Bandwidth of Gel-Immobilized Colloidal Photonic Crystal Films
by Ami Amano and Toshimitsu Kanai
Gels 2023, 9(1), 56; https://doi.org/10.3390/gels9010056 - 11 Jan 2023
Cited by 1 | Viewed by 1743
Abstract
We show that both the optical stopband wavelength and effective bandwidth of films of gel-immobilized loosely packed colloidal photonic crystals can be controlled over a wide range. When the gelation reagent of the charge-stabilized colloidal crystals was photopolymerized under ultraviolet light using different [...] Read more.
We show that both the optical stopband wavelength and effective bandwidth of films of gel-immobilized loosely packed colloidal photonic crystals can be controlled over a wide range. When the gelation reagent of the charge-stabilized colloidal crystals was photopolymerized under ultraviolet light using different upper- and bottom-light intensities, it resulted in a gel-immobilized colloidal crystal film with a broadened Bragg reflection peak. Moreover, the width of the Bragg peak increased from 30 to 190 nm as the difference between the light intensities increased. Films with wider Bragg peaks exhibited a brighter reflection color because of the superposition of the shifted Bragg reflections. Furthermore, the Bragg wavelength could be varied over a wide range (500–650 nm) while maintaining the same broadened effective bandwidth by varying the swelling solvent concentration. These findings will expand the applicability of colloidal crystals for use in photonic devices and color pigments. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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13 pages, 2125 KiB  
Article
Does Supramolecular Gelation Require an External Trigger?
by Ruben Van Lommel, Julie Van Hooste, Johannes Vandaele, Gert Steurs, Tom Van der Donck, Frank De Proft, Susana Rocha, Dimitrios Sakellariou, Mercedes Alonso and Wim M. De Borggraeve
Gels 2022, 8(12), 813; https://doi.org/10.3390/gels8120813 - 10 Dec 2022
Cited by 2 | Viewed by 1807
Abstract
The supramolecular gelation of small molecules is typically preceded by an external stimulus to trigger the self-assembly. The need for this trigger stems from the metastable nature of most supramolecular gels and can limit their applicability. Herein, we present a small urea-based molecule [...] Read more.
The supramolecular gelation of small molecules is typically preceded by an external stimulus to trigger the self-assembly. The need for this trigger stems from the metastable nature of most supramolecular gels and can limit their applicability. Herein, we present a small urea-based molecule that spontaneously forms a stable hydrogel by simple mixing without the addition of an external trigger. Single particle tracking experiments and observations made from scanning electron microscopy indicated that triggerless gelation occurred in a similar fashion as the archetypical heat-triggered gelation. These results could stimulate the search for other supramolecular hydrogels that can be obtained by simple mixing. Furthermore, the mechanism of the heat-triggered supramolecular gelation was elucidated by a combination of molecular dynamics simulations and quantitative NMR experiments. Surprisingly, hydrogelation seemingly occurs via a stepwise self-assembly in which spherical nanoparticles mature into an entangled fibrillary network. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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Review

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24 pages, 3834 KiB  
Review
Polysaccharide-Based Multifunctional Hydrogel Bio-Adhesives for Wound Healing: A Review
by Jiahao Yang and Shige Wang
Gels 2023, 9(2), 138; https://doi.org/10.3390/gels9020138 - 6 Feb 2023
Cited by 40 | Viewed by 5967
Abstract
Wound healing is a long-term and complex biological process that involves multiple hemostasis, inflammation, proliferation, and remodeling stages. In order to realize comprehensive and systematic wound management, appropriate wound treatment bio-adhesives are urgently needed. Hydrogel bio-adhesives have excellent properties and show unique and [...] Read more.
Wound healing is a long-term and complex biological process that involves multiple hemostasis, inflammation, proliferation, and remodeling stages. In order to realize comprehensive and systematic wound management, appropriate wound treatment bio-adhesives are urgently needed. Hydrogel bio-adhesives have excellent properties and show unique and remarkable advantages in the field of wound management. This review begins with a detailed description of the design criteria and functionalities of ideal hydrogel bio-adhesives for wound healing. Then, recent advances in polysaccharide-based multifunctional hydrogel bio-adhesives, which involve chitosan, hyaluronic acid, alginate, cellulose, dextran, konjac glucomannan, chondroitin sulfate, and other polysaccharides, are comprehensively discussed. Finally, the current challenges and future research directions of polysaccharide-based hydrogel bio-adhesives for wound healing are proposed to stimulate further exploration by researchers. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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23 pages, 5493 KiB  
Review
Application of Polymer Hydrogels in the Prevention of Postoperative Adhesion: A Review
by Jie Cai, Jiaming Guo and Shige Wang
Gels 2023, 9(2), 98; https://doi.org/10.3390/gels9020098 - 23 Jan 2023
Cited by 21 | Viewed by 3182
Abstract
Postoperative adhesion is a common post-surgery complication formed between the surface of the body cavity, ranging from a layer of connective tissue to a fibrous bridge containing blood vessels and nerve tissue. Despite achieving a lot of progress, the mechanisms of adhesion formation [...] Read more.
Postoperative adhesion is a common post-surgery complication formed between the surface of the body cavity, ranging from a layer of connective tissue to a fibrous bridge containing blood vessels and nerve tissue. Despite achieving a lot of progress, the mechanisms of adhesion formation still need to be further studied. In addition, few current treatments are consistently effective in the prevention of postoperative adhesion. Hydrogel is a kind of water-expanding crosslinked hydrophilic polymer network generated by a simple reaction of one or more monomers. Due to the porous structure, hydrogels can load different drugs and control the drug release kinetics. Evidence from existing studies has confirmed the feasibility and superiority of using hydrogels to counter postoperative adhesions, primarily due to their outstanding antifouling ability. In this review, the current research status of hydrogels as anti-adhesion barriers is summarized, the character of hydrogels in the prevention of postoperative adhesion is briefly introduced, and future research directions are discussed. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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