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Functional Hydrogels for Biomedical Applications

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

Deadline for manuscript submissions: closed (25 March 2023) | Viewed by 23633

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Special Issue Editors

Dr. Aleeza Farrukh

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Guest Editor

Department of Chemical and Biomolecular Engineering, University of California Irvine, Irvine, CA 92697, USA
Interests: biomaterial engineering; responsive hydrogels; bioelectronics; bioinspired materials; bioconjugation chemistries; polymer/organic chemistry; nanomaterials

Dr. Roshna Vakkeel

E-Mail Website
Guest Editor

Ph.D. National Chemical Laboratory, CSIR, Pune 411008, India
Interests: bio-organic chemistry; synthetic organic/peptide chemistry; bioconjugation; biomaterial functionalisation

Special Issue Information

Dear Colleagues,

This special issue on “Functional Hydrogels for Biomedical Applications” is dedicated to recent developments in the synthesis, design, tailoring, and fabrication of hydrogels for applications in biomedical fields. Hydrogels are three-dimensional hydrophilic polymeric networks that have the ability to absorb large volumes of water. The inherent biocompatibility, stiffness, porosity, biodegradability, flexibility, and versatility of hydrogels closely mimics the tissue environment. These properties make hydrogels excellent material for biomedicine and tissue regeneration applications such as drug delivery, biosensors, bio-adhesives, cell culture platforms, wound dressings, contact lenses, and scaffolds for regeneration of hard and soft tissues. Despite, their potential, the applications of hydrogels in biomedicines and biotechnologies are limited due to their poor mechanical properties, hard processability, low tunability, and lack of multifunctionality. Although various strategies has been explored to understand, tune and develop advanced hydrogels with superior mechanical properties and multifunctionalities, such as hybrid polymers, nanocomposite hydrogels, stimuli-responsive materials (e.g., pH, light, electricity, and temperature), and degradable polymers, as well as bioconjugation chemistries for reversible crosslinking to make hydrogels self-healing, injectable and suitable for post-processing and additive manufacturing; still many synthetic and design aspects are left to discover. We hope that this special issue will stimulate new research and strategies to enhance hydrogels´ material properties, processability, and dynamic functionalities, to fully unlock the potential and translation of hydrogels in biomedical and clinical applications. We look forward to new studies ranging from the synthesis of new or hybrid polymers, the design of smart or functional hydrogels, computation or characterization of their tunable properties, and advanced manufacturing techniques to fabricate implantable biomaterial scaffolds. We will welcome the submission of both theoretical and experimental results.

Dr. Aleeza Farrukh
Dr. Roshna Vakkeel
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

nanocomposite hydrogels
responsive hydrogels
shape memory hydrogels
bioelectronic hydrogels
tissue adhesive hydrogels
injectable/implantable hydrogels
self-healing hydrogels
degradable hydrogels
translation of hydrogels in biomedicine

Published Papers (10 papers)

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Research

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22 pages, 9852 KiB

Open AccessArticle

Antibacterial Activity of PVA Hydrogels Embedding Oxide Nanostructures Sensitized by Noble Metals and Ruthenium Dye

by Diana Pelinescu, Mihai Anastasescu, Veronica Bratan, Valentin-Adrian Maraloiu, Catalin Negrila, Daiana Mitrea, Jose Calderon-Moreno, Silviu Preda, Ioana Catalina Gîfu, Adrian Stan, Robertina Ionescu, Ileana Stoica, Crina Anastasescu, Maria Zaharescu and Ioan Balint

Gels 2023, 9(8), 650; https://doi.org/10.3390/gels9080650 - 11 Aug 2023

Viewed by 1091

Abstract

Nanostructured oxides (SiO₂, TiO₂) were synthesized using the sol–gel method and modified with noble metal nanoparticles (Pt, Au) and ruthenium dye to enhance light harvesting and promote the photogeneration of reactive oxygen species, namely singlet oxygen (¹O₂) and hydroxyl radical (•OH). The resulting nanostructures were embedded in a transparent polyvinyl alcohol (PVA) hydrogel. Morphological and structural characterization of the bare and modified oxides was performed using scanning electron microscopy (SEM), transmission electron microscopy (TEM), atomic force microscopy (AFM), UV–Vis spectroscopy, and X-ray photoelectron spectroscopy (XPS). Additionally, electrokinetic potential measurements were conducted. Crystallinity data and elemental analysis of the investigated systems were obtained through X-ray diffraction and X-ray fluorescence analyses, while the chemical state of the elements was determined using XPS. The engineered materials, both as simple powders and embedded in the hydrogel, were evaluated for their ability to generate reactive oxygen species (ROS) under visible and simulated solar light irradiation to establish a correlation with their antibacterial activity against Staphylococcus aureus. The generation of singlet oxygen (¹O₂) by the samples under visible light exposure can be of significant importance for their potential use in biomedical applications. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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23 pages, 2223 KiB

Open AccessArticle

Formulation of Chitosan Microparticles for Enhanced Intranasal Macromolecular Compound Delivery: Factors That Influence Particle Size during Ionic Gelation

by Morné Weyers, Bianca Peterson, Josias H. Hamman and Jan H. Steenekamp

Gels 2022, 8(11), 686; https://doi.org/10.3390/gels8110686 - 23 Oct 2022

Cited by 8 | Viewed by 1935

Abstract

Therapeutic macromolecules (e.g., protein and peptide drugs) present bioavailability challenges via extravascular administration. The nasal route presents an alternative non-invasive route for these drugs, although low bioavailability remains challenging. Co-administration of permeation enhancers is a promising formulation approach to improve the delivery of poorly bioavailable drugs. The aim of this study was to prepare and characterize chitosan microparticulate formulations containing a macromolecular model compound (fluorescein isothiocyanate dextran 4400, FD-4) and a bioenhancer (piperine). Ionic gelation was used to produce chitosan microparticle delivery systems with two distinct microparticle sizes, differing one order of magnitude in size (±20 µm and ±200 µm). These two microparticle delivery systems were formulated into thermosensitive gels and their drug delivery performance was evaluated across ovine nasal epithelial tissues. Dissolution studies revealed a biphasic release pattern. Rheometry results demonstrated a sol-to-gel transition of the thermosensitive gel formulation at a temperature of 34 °C. The microparticles incorporating piperine showed a 1.2-fold increase in FD-4 delivery across the excised ovine nasal epithelial tissues as compared to microparticles without piperine. This study therefore contributed to advancements in ionic gelation methods for the formulation of particulate systems to enhance macromolecular nasal drug delivery. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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21 pages, 6279 KiB

Open AccessArticle

Bioinspired Remineralization of Artificial Caries Lesions Using PDMAEMA/Carbomer/Calcium Phosphates Hybrid Microgels

by Alexander Bonchev, Marin Simeonov, Pavletta Shestakova, Radosveta Vasileva, Rositsa Titorenkova, Anton Apostolov, Elena Dyulgerova and Elena Vassileva

Gels 2022, 8(10), 681; https://doi.org/10.3390/gels8100681 - 21 Oct 2022

Cited by 3 | Viewed by 1959

Abstract

Dental caries remains one of the most prevalent bacterium-caused chronic diseases affecting both adults and children worldwide. The development of new materials for enhancing its remineralization is one of the most promising approaches in the field of advanced dental materials as well as one of the main challenges in non-invasive dentistry. The aim of the present study is to develop novel hybrid materials based on (PDMAEMA)/Carbomer 940 microgels with in situ deposited calcium phosphates (CaP) and to reveal their potential as a remineralization system for artificial caries lesions. To this purpose, novel PDMAEMA/Carbomer 940 microgels were obtained and their core–shell structure was revealed by transmission electron microscopy (TEM). They were successfully used as a matrix for in situ calcium phosphate deposition, thus giving rise to novel hybrid microgels. The calcium phosphate phases formed during the deposition process were studied by X-ray diffraction and infrared spectroscopy, however, due to their highly amorphous nature, the nuclear magnetic resonance (NMR) was the method that was able to provide reliable information about the formed inorganic phases. The novel hybrid microgels were used for remineralization of artificial caries lesions in order to prove their ability to initiate their remineralization. The remineralization process was followed by scanning electron microscopy (SEM), X-ray diffraction, infrared and Raman spectroscopies and all these methods confirmed the successful enamel rod remineralization upon the novel hybrid microgel application. Thus, the study confirmed that novel hybrid microgels, which could ensure a constant supply of calcium and phosphate ions, are a viable solution for early caries treatment. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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9 pages, 2661 KiB

Open AccessArticle

Silk Fibroin/Tannin/ZnO Nanocomposite Hydrogel with Hemostatic Activities

by Chul Min Yang, Jeehee Lee, Su Yeon Lee, Haeshin Lee, Kiramage Chathuranga, Jongsoo Lee and Wonho Park

Gels 2022, 8(10), 650; https://doi.org/10.3390/gels8100650 - 12 Oct 2022

Cited by 7 | Viewed by 2233

Abstract

The inevitable bleeding and infections caused by disasters and accidents are the main causes of death owing to extrinsic trauma. Hemostatic agents are often used to quickly suppress bleeding and infection, and they can solve this problem in a short time. Silk fibroin (SF) has poor processibility in water, owing to incomplete solubility therein. In this study, aiming to overcome this disadvantage, a modified silk fibroin (SF-BGE), easily soluble in water, was prepared by introducing butyl glycidyl ether (BGE) into its side chain. Subsequently, a small amount of tannic acid (TA) was introduced to prepare an SF-BGE /TA solution, and ZnO nanoparticles (NPs) were added to the solution to form the coordination bonds between the ZnO and TA, leading to an SF-based nanocomposite hydrogel. A structural characterization of the SF-BGE, SF-BGE/TA, SF-BGE/TA/ZnO, and the coordination bonds between ZnO/TA was observed by attenuated total reflectance-Fourier transform infrared spectroscopy (ATR-FTIR), and the phase change was observed by rheological measurements. The pore formation of the SF-BGE/TA/ZnO hydrogel and dispersibility of ZnO were verified through energy-dispersive X-ray spectroscopy (EDS) and scanning electron microscopy (SEM). The cytocompatible and hemostatic performances of the SF-BGE/TA/ZnO NPs composite hydrogels were evaluated, and the hydrogels showed superior hemostatic and cytocompatible activities. Therefore, the SF-based nanocomposite hydrogel is considered as a promising material for hemostasis. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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15 pages, 2967 KiB

Open AccessArticle

Synthesis of Novel Hyaluronic Acid Sulfonated Hydrogels Using Safe Reactants: A Chemical and Biological Characterization

by Elisa Sturabotti, Silvia Consalvi, Luca Tucciarone, Elisa Macrì, Valerio Di Lisio, Iolanda Francolini, Carmen Minichiello, Antonella Piozzi, Claudia Vuotto and Andrea Martinelli

Gels 2022, 8(8), 480; https://doi.org/10.3390/gels8080480 - 30 Jul 2022

Cited by 3 | Viewed by 2474

Abstract

Here, we present a one-pot procedure for the preparation of hyaluronic acid (HA) sulfonated hydrogels in aqueous alkaline medium. The HA hydrogels were crosslinked using 1,4-butanedioldiglycidyl ether (BDDE) alone, or together with N-bis(2-hydroxyethyl)-2-aminoethanesulfonic acid (Bes), as a safe sulfonating agent. Conditions for the simultaneous reaction of HA with BDDE and Bes were optimized and the resulting hydrogels were characterized under different reaction times (24, 72, and 96 h). The incorporation of sulfonic groups into the HA network was proven by elemental analysis and FTIR spectroscopy and its effect on water uptake was evaluated. Compared with the non-sulfonated sample, sulfonated gels showed improved mechanical properties, with their compressive modulus increased from 15 to 70 kPa, higher stability towards hyaluronidase, and better biocompatibility to 10T1/2 fibroblasts, especially after the absorption of collagen. As main advantages, the procedure described represents an easy and reproducible methodology for the fabrication of sulfonated hydrogels, which does not require toxic chemicals and/or solvents. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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13 pages, 2812 KiB

Open AccessArticle

Preparation of a Bioadhesive Poly(Acrylic Acid)/Polyvinylpyrrolidone Complex Gel and Its Clinical Effect on Dental Hemostasis

by Tomoko Ito, Shingo Yamaguchi, Daisuke Soga, Takayuki Yoshimoto and Yoshiyuki Koyama

Gels 2022, 8(8), 462; https://doi.org/10.3390/gels8080462 - 23 Jul 2022

Cited by 7 | Viewed by 2718

Abstract

Poly(acrylic acid) (PAA) is a water-soluble synthetic polymer that exhibits bioadhesive properties and has been applied in various novel medical devices, such as drug-delivery carriers and hemostatic agents. PAA forms a water-insoluble complex when mixed with polyvinylpyrrolidone (PVP). If PAA and PVP are mixed in water, they form an aggregated precipitate, which neither swells nor adheres to tissues. The formation of the hydrophobic complex was caused by hydrophobic interactions between the main chains of both polymers aligned the same as a zipper. To hinder the zipper-like alignment of the polymer main chains, hyaluronic acid (HA), a macromolecular viscous polysaccharide, was added to the PVP solution prior to complex formation. When the initial concentration of PAA was lower than 0.05%, HA effectively prevented the aggregation of PAA/PVP complexes and resulted in a slightly clouded suspension. Freeze-drying of the mixture yielded a soft white sponge, which could immediately swell in water to form a highly bioadhesive hydrogel. The PAA/PVP complex prepared with HA exhibited high hemostatic efficiency in clinical studies, even in patients on antithrombotic drugs. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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19 pages, 3830 KiB

Open AccessArticle

Eco-Friendly Synthesized PVA/Chitosan/Oxalic Acid Nanocomposite Hydrogels Embedding Silver Nanoparticles as Antibacterial Materials

by Irina Popescu, Marieta Constantin, Irina M. Pelin, Dana M. Suflet, Daniela L. Ichim, Oana M. Daraba and Gheorghe Fundueanu

Gels 2022, 8(5), 268; https://doi.org/10.3390/gels8050268 - 25 Apr 2022

Cited by 17 | Viewed by 3037

Abstract

PVA/chitosan (PVA/CS) composite hydrogels incorporating silver nanoparticles (AgNPs) were prepared by double-cross-linked procedures: freeze–thawing and electrostatic interactions. Oxalic acid (OA) was used both for solubilization and ionic cross-linking of CS. AgNPs covered by CS (CS-AgNPs) with an average diameter of 9 nm and 18% silver were obtained in the presence of CS, acting as reducing agent and particle stabilizer. The increase of the number of freeze–thaw cycles, as well as of the PVA:CS and OA:CS ratios, resulted in an increase of the gel fraction and elastic modulus. Practically, the elastic modulus of the hydrogels increased from 3.5 kPa in the absence of OA to 11.6 kPa at a 1:1 OA:CS weight ratio, proving that OA was involved in physical cross-linking. The physicochemical properties were not altered by the addition of CS-AgNPs in low concentration; however, concentrations higher than 3% resulted in low gel fraction and elastic modulus. The amount of silver released from the composite hydrogels is very low (<0.4%), showing that AgNPs were well trapped within the polymeric matrix. The composite hydrogels displayed antimicrobial activity against S. aureus, K. pneumoniae or P. gingivalis. The low cytotoxicity and the antibacterial efficacy of hydrogels recommend them for wound and periodontitis treatment. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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13 pages, 2501 KiB

Open AccessArticle

A Co-Polymerizable Linker for the Covalent Attachment of Fibronectin Makes pHEMA Hydrogels Cell-Adhesive

by Laura Schumacher, Katharina Siemsen, Clement Appiah, Sunil Rajput, Anne Heitmann, Christine Selhuber-Unkel and Anne Staubitz

Gels 2022, 8(5), 258; https://doi.org/10.3390/gels8050258 - 21 Apr 2022

Cited by 2 | Viewed by 2334

Abstract

Hydrogels are attractive biomaterials because their chemical and mechanical properties can be tailored to mimic those of biological tissues. However, many hydrogels do not allow cell or protein attachment. Therefore, they are post-synthetically functionalized by adding functional groups for protein binding, which then allows cell adhesion in cell culture substrates. However, the degree of functionalization and covalent binding is difficult to analyze in these cases. Moreover, the density of the functional groups and the homogeneity of their distribution is hard to control. This work introduces another strategy for the biofunctionalization of hydrogels: we synthesized a polymerizable linker that serves as a direct junction between the polymeric structure and cell adhesion proteins. This maleimide-containing, polymerizable bio-linker was copolymerized with non-functionalized monomers to produce a bioactive hydrogel based on poly(2-hydroxyethyl methacrylate) (pHEMA). Therefore, the attachment site was only controlled by the polymerization process and was thus uniformly distributed throughout the hydrogel. In this way, the bio-conjugation by a protein-binding thiol-maleimide Michael-type reaction was possible in the entire hydrogel matrix. This approach enabled a straightforward and highly effective biofunctionalization of pHEMA with the adhesion protein fibronectin. The bioactivity of the materials was demonstrated by the successful adhesion of fibroblast cells. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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Review

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28 pages, 3516 KiB

Open AccessReview

Natural Polymeric Composites Derived from Animals, Plants, and Microbes for Vaccine Delivery and Adjuvant Applications: A Review

by Abu Hassan Nordin, Siti Muhamad Nur Husna, Zuliahani Ahmad, Muhammad Luqman Nordin, Rushdan Ahmad Ilyas, Ahmad Khusairi Azemi, Noraznawati Ismail, Nordin Hawa Siti, Norzita Ngadi, Mohammad Saifulddin Mohd Azami, Abdin Shakirin Mohamad Norpi, Mohd Farhan Hanif Reduan, Abdinasir Yusuf Osman, Dyah Ayu Oktavianie A. Pratama, Walid Nabgan and Rumaizi Shaari

Gels 2023, 9(3), 227; https://doi.org/10.3390/gels9030227 - 15 Mar 2023

Cited by 1 | Viewed by 1903

Abstract

A key element in ensuring successful immunization is the efficient delivery of vaccines. However, poor immunogenicity and adverse inflammatory immunogenic reactions make the establishment of an efficient vaccine delivery method a challenging task. The delivery of vaccines has been performed via a variety of delivery methods, including natural-polymer-based carriers that are relatively biocompatible and have low toxicity. The incorporation of adjuvants or antigens into biomaterial-based immunizations has demonstrated better immune response than formulations that just contain the antigen. This system may enable antigen-mediated immunogenicity and shelter and transport the cargo vaccine or antigen to the appropriate target organ. In this regard, this work reviews the recent applications of natural polymer composites from different sources, such as animals, plants, and microbes, in vaccine delivery systems. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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31 pages, 13292 KiB

Open AccessReview

The Role of the Sol-Gel Synthesis Process in the Biomedical Field and Its Use to Enhance the Performance of Bioabsorbable Magnesium Implants

by Juan Pablo Fernández-Hernán, Belén Torres, Antonio Julio López and Joaquín Rams

Gels 2022, 8(7), 426; https://doi.org/10.3390/gels8070426 - 7 Jul 2022

Cited by 11 | Viewed by 2686

Abstract

In the present day, the increment in life expectancy has led to the necessity of developing new biomaterials for the restoration or substitution of damaged organs that have lost their functionalities. Among all the research about biomaterials, this review paper aimed to expose the main possibilities that the sol-gel synthesis method can provide for the fabrication of materials with interest in the biomedical field, more specifically, when this synthesis method is used to improve the biological properties of different magnesium alloys used as biomaterials. The sol-gel method has been widely studied and used to generate ceramic materials for a wide range of purposes during the last fifty years. Focused on biomedical research, the sol-gel synthesis method allows the generation of different kinds of biomaterials with diverse morphologies and a high potential for the biocompatibility improvement of a wide range of materials commonly used in the biomedical field such as metallic implants, as well as for the generation of drug delivery systems or interesting biomaterials for new tissue engineering therapies. Full article

(This article belongs to the Special Issue Functional Hydrogels for Biomedical Applications)

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