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Volume 10
Issue 4
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Gels, Volume 10, Issue 4 (April 2024) – 72 articles

Cover Story (view full-size image): Hydrogels based on cross-linking hydrazide-gelatin (hGel) with either oxidized hyaluronic acid (oxHA) or alginic acid (oxALG) were studied for their suitability to host hepatocyte cell cultures. Rheological studies demonstrated short gelation times and mechanical properties indicating suitability for liver cell culture. Gels were stable for more than 14 days, which is an important prerequisite for application. Studies with HepG2 hepatoblastoma cells showed that both types of gels were not cytotoxic and permitted proliferation of hepatocytes. These findings suggest the use of these hydrogels for establishing in vitro models of liver diseases and treatment, but also potential applications for engineering liver and other tissues. View this paper
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26 pages, 4074 KiB  
Review
Liposome–Hydrogel Composites for Controlled Drug Delivery Applications
by Roya Binaymotlagh, Farid Hajareh Haghighi, Laura Chronopoulou and Cleofe Palocci
Gels 2024, 10(4), 284; https://doi.org/10.3390/gels10040284 - 22 Apr 2024
Cited by 5 | Viewed by 2403
Abstract
Various controlled delivery systems (CDSs) have been developed to overcome the shortcomings of traditional drug formulations (tablets, capsules, syrups, ointments, etc.). Among innovative CDSs, hydrogels and liposomes have shown great promise for clinical applications thanks to their cost-effectiveness, well-known chemistry and synthetic feasibility, [...] Read more.
Various controlled delivery systems (CDSs) have been developed to overcome the shortcomings of traditional drug formulations (tablets, capsules, syrups, ointments, etc.). Among innovative CDSs, hydrogels and liposomes have shown great promise for clinical applications thanks to their cost-effectiveness, well-known chemistry and synthetic feasibility, biodegradability, biocompatibility and responsiveness to external stimuli. To date, several liposomal- and hydrogel-based products have been approved to treat cancer, as well as fungal and viral infections, hence the integration of liposomes into hydrogels has attracted increasing attention because of the benefit from both of them into a single platform, resulting in a multifunctional drug formulation, which is essential to develop efficient CDSs. This short review aims to present an updated report on the advancements of liposome–hydrogel systems for drug delivery purposes. Full article
(This article belongs to the Special Issue Liposomal and Ethosomal Gels: From Design to Application (2nd Edition))
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22 pages, 6890 KiB  
Article
High Modulus, Strut-like poly(ether ether ketone) Aerogels Produced from a Benign Solvent
by Glenn A. Spiering, Garrett F. Godshall and Robert B. Moore
Gels 2024, 10(4), 283; https://doi.org/10.3390/gels10040283 - 22 Apr 2024
Viewed by 1770
Abstract
Poly(ether ether ketone) (PEEK) was found to form gels in the benign solvent 1,3-diphenylacetone (DPA). Gelation of PEEK in DPA was found to form an interconnected, strut-like morphology composed of polymer axialites. To our knowledge, this is the first report of a strut-like [...] Read more.
Poly(ether ether ketone) (PEEK) was found to form gels in the benign solvent 1,3-diphenylacetone (DPA). Gelation of PEEK in DPA was found to form an interconnected, strut-like morphology composed of polymer axialites. To our knowledge, this is the first report of a strut-like morphology for PEEK aerogels. PEEK/DPA gels were prepared by first dissolving PEEK in DPA at 320 °C. Upon cooling to 50 °C, PEEK crystallizes and forms a gel in DPA. The PEEK/DPA phase diagram indicated that phase separation occurs by solid–liquid phase separation, implying that DPA is a good solvent for PEEK. The Flory–Huggins interaction parameter, calculated as χ12 = 0.093 for the PEEK/DPA system, confirmed that DPA is a good solvent for PEEK. PEEK aerogels were prepared by solvent exchanging DPA to water then freeze-drying. PEEK aerogels were found to have densities between 0.09 and 0.25 g/cm3, porosities between 80 and 93%, and surface areas between 200 and 225 m2/g, depending on the initial gel concentration. Using nitrogen adsorption analyses, PEEK aerogels were found to be mesoporous adsorbents, with mesopore sizes of about 8 nm, which formed between stacks of platelike crystalline lamellae. Scanning electron microscopy and X-ray scattering were utilized to elucidate the hierarchical structure of the PEEK aerogels. Morphological analysis found that the PEEK/DPA gels were composed of a highly nucleated network of PEEK axialites (i.e., aggregates of stacked crystalline lamellae). The highly connected axialite network imparted robust mechanical properties on PEEK aerogels, which were found to densify less upon freeze-drying than globular PEEK aerogel counterparts gelled from dichloroacetic acid (DCA) or 4-chlorphenol (4CP). PEEK aerogels formed from DPA were also found to have a modulus–density scaling that was far more efficient in supporting loads than the poorly connected aerogels formed from PEEK/DCA or PEEK/4CP solutions. The strut-like morphology in these new PEEK aerogels also significantly improved the modulus to a degree that is comparable to high-performance crosslinked aerogels based on polyimide and polyurea of comparable densities. Full article
(This article belongs to the Special Issue Advances in Synthetic and Bio-Based Aerogels: Mechanical Properties, Thermal Insulation, and Environmental Remediation)
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18 pages, 2451 KiB  
Article
Influence of Gelatin and Propolis Extract on Honey Gummy Jelly Properties: Optimization Using D-Optimal Mixture Design
by Kultida Kaewpetch, Saowapa Yolsuriyan, Terd Disayathanoowat, Patcharin Phokasem, Taruedee Jannu, Gerry Renaldi and Rajnibhas Sukeaw Samakradhamrongthai
Gels 2024, 10(4), 282; https://doi.org/10.3390/gels10040282 - 21 Apr 2024
Cited by 1 | Viewed by 2047
Abstract
Gelatin is commonly used as a gelling agent in gummy candy. Honey and bee products are valuable and rich sources of biologically active substances. In this study, the influence of gelatin and propolis extract on honey gummy jelly (HGJ) properties was investigated. Honey [...] Read more.
Gelatin is commonly used as a gelling agent in gummy candy. Honey and bee products are valuable and rich sources of biologically active substances. In this study, the influence of gelatin and propolis extract on honey gummy jelly (HGJ) properties was investigated. Honey (28–32%), xylitol (13–17%), and gelatin (6–10%) were utilized to develop HGJ products by mixture design methodology. Subsequently, the optimized formulation of HGJ was fortified with 1% and 2% propolis extract to enhance its phytochemicals and antimicrobial activities. The variation in the ingredients significantly affected the physicochemical, textural, and sensory properties of the HGJ. The optimized HGJ formulation consisted of honey (32%), xylitol (14%), and gelatin (7%) and exhibited 13.35 × 103 g.force of hardness, −0.56 × 103 g.sec of adhesiveness, 11.96 × 103 N.mm of gumminess, 0.58 of resilience, and a moderate acceptance score (6.7–7.5). The fortification of HGJ with propolis extract significantly increased its phytochemical properties. Furthermore, the incorporation of propolis extract (2%) into the HGJ was able to significantly inhibit the growth of Gram-positive (Streptococcus mutans and Staphylococcus aureus) and Gram-negative (Escherichia coli) bacteria. The mixture of gelatin, xylitol, honey, and propolis extract can be utilized to develop a healthy gummy product with acceptable physicochemical, textural, and sensory qualities. Full article
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17 pages, 4049 KiB  
Article
Active Fish Gelatin/Chitosan Blend Film Incorporated with Guava Leaf Powder Carbon Dots: Properties, Release and Antioxidant Activity
by Gokulprasanth Murugan, Krisana Nilsuwan, Thummanoon Prodpran, Arunachalasivamani Ponnusamy, Jong-Whan Rhim, Jun Tae Kim and Soottawat Benjakul
Gels 2024, 10(4), 281; https://doi.org/10.3390/gels10040281 - 21 Apr 2024
Cited by 6 | Viewed by 2500
Abstract
Active packaging is an innovative approach to prolonge the shelf-life of food products while ensuring their quality and safety. Carbon dots (CDs) from biomass as active fillers for biopolymer films have been introduced to improve their bioactivities as well as properties. Gelatin/chitosan (G/C) [...] Read more.
Active packaging is an innovative approach to prolonge the shelf-life of food products while ensuring their quality and safety. Carbon dots (CDs) from biomass as active fillers for biopolymer films have been introduced to improve their bioactivities as well as properties. Gelatin/chitosan (G/C) blend films containing active guava leaf powder carbon dots (GL-CDs) at various levels (0–3%, w/w) were prepared by the solvent casting method and characterized. Thickness of the control increased from 0.033 to 0.041 mm when 3% GL-CDs were added (G/C-CD-3%). Young’s modulus of the resulting films increased (485.67–759.00 MPa), whereas the tensile strength (26.92–17.77 MPa) and elongation at break decreased (14.89–5.48%) as the GL-CDs’ level upsurged (p < 0.05). Water vapor barrier property and water contact angle of the film were enhanced when incorporated with GL-CDs (p < 0.05). GL-CDs had a negligible impact on film microstructure, while GL-CDs interacted with gelatin or chitosan, as determined by FTIR. The release of GL-CDs from blend films was more pronounced in water than in alcoholic solutions (10–95% ethanol). The addition of GL-CDs improved the UV light barrier properties and antioxidant activities of the resultant films in a dose-dependent manner. Thus, GL-CD-added gelatin/chitosan blend films with antioxidant activities could be employed as potential active packaging for the food industry. Full article
(This article belongs to the Special Issue Marine Biopolymers-Based Hydrogels, Xerogels and Aerogels: Preparation and Applications)
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26 pages, 8628 KiB  
Article
Novel Injectable Hydrogel Formulations and Gas Chromatography Analysis of the Residual Crosslinker in Formulations Intended for Pharmaceutical and Cosmetic Applications
by Fatimah Rashid, Paul Carter and Stephen Childs
Gels 2024, 10(4), 280; https://doi.org/10.3390/gels10040280 - 21 Apr 2024
Cited by 1 | Viewed by 1630
Abstract
Novel hyaluronic acid (HA) crosslinked with pentaerythritol tetra-acrylate (PT) injectable hydrogels was invented. These injectable hydrogel/dermal filler formulations were synthesised using HA and the acrylate PT as a crosslinker under basic pH conditions using thermal crosslinking methods (oven heating), which provides a simple, [...] Read more.
Novel hyaluronic acid (HA) crosslinked with pentaerythritol tetra-acrylate (PT) injectable hydrogels was invented. These injectable hydrogel/dermal filler formulations were synthesised using HA and the acrylate PT as a crosslinker under basic pH conditions using thermal crosslinking methods (oven heating), which provides a simple, safe, and eco-friendly method for crosslinking in 4 h under 45 °C. Fourier-transform infrared spectroscopy (FTIR) and scanning electron microscopy (SEM) analyses were conducted to represent the difference between the formulations in terms of peak formation and pore size, respectively. The crosslinking was partial as is considered to be typical for dermal injectable fillers. The rheological properties of these formulations showed that these novel dermal injectables are highly promising, and the newly developed fillers could be used with better results for dermal anti-wrinkle corrections, shaping, and volumising reasons. Furthermore, crosslinker (PT) residual analysis was carried out to state the formulations that are valid and acceptable for intradermal usage. The results from the GC method validation revealed it was a suitable method for this study. The GC analysis of all five injectable hydrogel/filler formulations demonstrated the formulations HA-PT 1, 2, 3 and 4 were formulated using (0.05–0.1)% w/w PT containing residual PT monomers within the safe limits that were determined to be below (0.008% w/w). This work has shown the development of a novel injectable hydrogel/filler formulation for pharmaceutical and cosmetic applications can be prepared in a more sustainable and simple way using pentaerythritol tetra-acrylate as a crosslinker agent, which holds great promise for the industry’s future advancement. Full article
(This article belongs to the Special Issue Hydrogels: Synthesis, Characterization and Applications (2nd Edition))
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16 pages, 6761 KiB  
Article
Polyhedral Oligomeric Sesquioxane Cross-Linked Chitosan-Based Multi-Effective Aerogel Preparation and Its Water-Driven Recovery Mechanism
by Yang Liu, Mingjian Ma, Yuan Shen, Zhengdong Zhao, Xuefei Wang, Jiaqi Wang, Jiangbo Pan, Di Wang, Chengyu Wang and Jian Li
Gels 2024, 10(4), 279; https://doi.org/10.3390/gels10040279 - 20 Apr 2024
Cited by 1 | Viewed by 1515
Abstract
The use of environmentally friendly and non-toxic biomass-based interfacial solar water evaporators has been widely reported as a method for water purification in recent years. However, the poor stability of the water transport layer made from biomass materials and its susceptibility to deformation [...] Read more.
The use of environmentally friendly and non-toxic biomass-based interfacial solar water evaporators has been widely reported as a method for water purification in recent years. However, the poor stability of the water transport layer made from biomass materials and its susceptibility to deformation when exposed to harsh environments limit its practical application. To address this issue, water-driven recovery aerogel (PCS) was prepared by cross-linking epoxy-based polyhedral oligomeric silsesquioxane (EP-POSS) epoxy groups with chitosan (CS) amino groups. The results demonstrate that PCS exhibits excellent water-driven recovery performance, regaining its original volume within a very short time (1.9 s) after strong compression (ε > 80%). Moreover, PCS has a water absorption rate of 2.67 mm s−1 and exhibits an excellent water absorption capacity of 22.09 g g−1 even after ten cycles of absorption-removal. Furthermore, a photothermal evaporator (PCH) was prepared by loading the top layer with hydrothermally reacted tannins (HAs) and Zn2+ complexes. The results indicate that PCH achieves an impressive evaporation rate of 1.89 kg m−2 h−1 under one sun illumination. Additionally, due to the antimicrobial properties of Zn2+, PCH shows inhibitory effects against Staphylococcus aureus and Escherichia coli, thereby extending the application of solar water evaporators to include antimicrobial purification in natural waters. Full article
(This article belongs to the Special Issue Gels for Removal and Adsorption (2nd Edition))
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14 pages, 7285 KiB  
Article
In Vitro Antibacterial and Anti-Inflammatory Properties of Imidazolium Poly(ionic liquids) Microspheres Loaded in GelMA-PEG Hydrogels
by Chao Zhou, Mengdi Sun, Danni Wang, Mingmei Yang, Jia Ling Celestine Loh, Yawen Xu and Ruzhi Zhang
Gels 2024, 10(4), 278; https://doi.org/10.3390/gels10040278 - 20 Apr 2024
Viewed by 1948
Abstract
Repairing damaged tissue caused by bacterial infection poses a significant challenge. Traditional antibacterial hydrogels typically incorporate various components such as metal antimicrobials, inorganic antimicrobials, organic antimicrobials, and more. However, drawbacks such as the emergence of multi-drug resistance to antibiotics, the low antibacterial efficacy [...] Read more.
Repairing damaged tissue caused by bacterial infection poses a significant challenge. Traditional antibacterial hydrogels typically incorporate various components such as metal antimicrobials, inorganic antimicrobials, organic antimicrobials, and more. However, drawbacks such as the emergence of multi-drug resistance to antibiotics, the low antibacterial efficacy of natural agents, and the potential cytotoxicity associated with metal antibacterial nanoparticles in hydrogels hindered their broader clinical application. In this study, we successfully developed imidazolium poly(ionic liquids) (PILs) polymer microspheres (APMs) through emulsion polymerization. These APMs exhibited notable antibacterial effectiveness and demonstrated minimal cell toxicity. Subsequently, we integrated the APMs into a gelatin methacryloyl (GelMA)—polyethylene glycol (PEG) hydrogel. This composite hydrogel not only showcased strong antibacterial and anti-inflammatory properties but also facilitated the migration of human skin fibroblasts (HSF) and human umbilical vein endothelial cells (HUVECs) and promoted osteogenic differentiation in vitro. Full article
(This article belongs to the Special Issue Hydrogel and Membrane Dressings for Antibacterial Applications)
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15 pages, 2639 KiB  
Article
Determination of Density of Starch Hydrogel Microspheres from Sedimentation Experiments Using Non-Stokes Drag Coefficient
by Margherita Cretella, Mina Fazilati, Nedim Krcic, Ivan Argatov and Vitaly Kocherbitov
Gels 2024, 10(4), 277; https://doi.org/10.3390/gels10040277 - 19 Apr 2024
Cited by 2 | Viewed by 1651
Abstract
Sedimentation is an important property of colloidal systems that should be considered when designing pharmaceutical formulations. In pharmaceutical applications, sedimentation is normally described using Stokes’ law, which assumes laminar flow of fluid. In this work we studied swelling and hydration of spherical cross-linked [...] Read more.
Sedimentation is an important property of colloidal systems that should be considered when designing pharmaceutical formulations. In pharmaceutical applications, sedimentation is normally described using Stokes’ law, which assumes laminar flow of fluid. In this work we studied swelling and hydration of spherical cross-linked amorphous starch microspheres in pure water, solutions of sodium chloride, and in pH-adjusted aqueous solutions. We demonstrated that Reynolds numbers obtained in these experiments correspond to the transition regime between the laminar flow and the turbulent flow and, hence, expressions based on the non-Stokes drag coefficient should be used for calculations of sedimentation velocity from known density or for assessment of density from observed sedimentation velocity. The density of starch microparticles hydrated in water was about 1050 kg/m3, while densities obtained from experiment with other liquids were dependent on the liquids’ densities. The data indicate that the swelling of the cross-linked starch microparticles as characterized by their densities is not sensitive to pH and salt concentration in the studied range of these parameters. Full article
(This article belongs to the Section Gel Analysis and Characterization)
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25 pages, 7411 KiB  
Article
Comprehensive Evaluation of Injectability Attributes in OxiFree™ Dermal Fillers: MaiLi® Product Variants and Clinical Case Reports
by Patrick Micheels, Alexandre Porcello, Thierry Bezzola, Daniel Perrenoud, Marie-Odile Christen, Lee Ann Applegate and Alexis Laurent
Gels 2024, 10(4), 276; https://doi.org/10.3390/gels10040276 - 19 Apr 2024
Viewed by 1560
Abstract
Dermal filler injectability is a critical factor for commercial product adoption by medical aesthetic professionals and for successful clinical administration. We have previously reported (in vitro and ex vivo) cross-linked hyaluronic acid (HA)-based dermal filler benchmarking in terms of manual and automated injectability [...] Read more.
Dermal filler injectability is a critical factor for commercial product adoption by medical aesthetic professionals and for successful clinical administration. We have previously reported (in vitro and ex vivo) cross-linked hyaluronic acid (HA)-based dermal filler benchmarking in terms of manual and automated injectability requirements. To further enhance the function-oriented product characterization workflows and the clinical relevance of dermal filler injectability assessments, the aim of this study was to perform in vivo evaluations. Therefore, several variants of the MaiLi® product range (OxiFree™ technology) were characterized in vitro and in vivo in terms of injectability attributes, with a focus on hydrogel system homogeneity and ease of injection. Firstly, standardized in vitro assays were performed in SimSkin® cutaneous equivalents, with variations of the clinical injector, injection site, and injection technique. Then, automated injections in SimSkin® cutaneous equivalents were comparatively performed in a texture analysis setup to obtain fine-granulometry injection force profile results. Finally, five female participants were recruited for the in vivo arm of the study (case reports), with variations of the clinical injector, injection site, and injection technique. Generally, the obtained quantitative force values and injection force profiles were critically appraised from a translational viewpoint, based on discussions around the OxiFree™ manufacturing technology and on in-use specialized clinician feedback. Overall, the present study outlined a notable level of homogeneity across the MaiLi® product range in terms of injectability attributes, as well as consistently high ease of administration by medical aesthetic clinicians. Full article
(This article belongs to the Special Issue Current Directions and Prospects of Hydrogels for Biomedical Applications)
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9 pages, 3420 KiB  
Communication
Dried Porous Biomaterials from Mealworm Protein Gels: Proof of Concept and Impact of Drying Method on Structural Properties and Zinc Retention
by Martina Klost, Claudia Keil and Pavel Gurikov
Gels 2024, 10(4), 275; https://doi.org/10.3390/gels10040275 - 18 Apr 2024
Viewed by 1077
Abstract
Dried porous materials can be found in a wide range of applications. So far, they are mostly prepared from inorganic or indigestible raw materials. The aim of the presented study was to provide a proof of concept for (a) the suitability of mealworm [...] Read more.
Dried porous materials can be found in a wide range of applications. So far, they are mostly prepared from inorganic or indigestible raw materials. The aim of the presented study was to provide a proof of concept for (a) the suitability of mealworm protein gels to be turned into dried porous biomaterials by either a combination of solvent exchange and supercritical drying to obtain aerogels or by lyophilization to obtain lyophilized hydrogels and (b) the suitability of either drying method to retain trace elements such as zinc in the gels throughout the drying process. Hydrogels were prepared from mealworm protein, subsequently dried using either method, and characterized via FT-IR, BET volume, and high-resolution scanning electron microscopy. Retention of zinc was evaluated via energy-dispersive X-ray spectroscopy. Results showed that both drying methods were suitable for obtaining dried porous biomaterials and that the drying method mainly influenced the overall surface area and pore hydrophobicity but not the secondary structure of the proteins in the gels or their zinc content after drying. Therefore, a first proof of concept for utilizing mealworm protein hydrogels as a base for dried porous biomaterials was successful and elucidated the potential of these materials as future sustainable alternatives to more conventional dried porous materials. Full article
(This article belongs to the Special Issue International Perspectives on Aerogels)
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14 pages, 3814 KiB  
Article
Optimized Synthesis of Poly(Lactic Acid) Nanoparticles for the Encapsulation of Flutamide
by Duarte Almeida, Mariana Dias, Beatriz Teixeira, Carolina Frazão, Mónica Almeida, Gil Gonçalves, Miguel Oliveira and Ricardo J. B. Pinto
Gels 2024, 10(4), 274; https://doi.org/10.3390/gels10040274 - 18 Apr 2024
Viewed by 1818
Abstract
Biopolymeric nanoparticles (NPs) have gained significant attention in several areas as an alternative to synthetic polymeric NPs due to growing environmental and immunological concerns. Among the most promising biopolymers is poly(lactic acid) (PLA), with a reported high degree of biocompatibility and biodegradability. In [...] Read more.
Biopolymeric nanoparticles (NPs) have gained significant attention in several areas as an alternative to synthetic polymeric NPs due to growing environmental and immunological concerns. Among the most promising biopolymers is poly(lactic acid) (PLA), with a reported high degree of biocompatibility and biodegradability. In this work, PLA NPs were synthesized according to a controlled gelation process using a combination of single-emulsion and nanoprecipitation methods. This study evaluated the influence of several experimental parameters for accurate control of the PLA NPs’ size distribution and aggregation. Tip sonication (as the stirring method), a PLA concentration of 10 mg/mL, a PVA concentration of 2.5 mg/mL, and low-molecular-weight PLA (Mw = 5000) were established as the best experimental conditions to obtain monodisperse PLA NPs. After gelification process optimization, flutamide (FLU) was used as a model drug to evaluate the encapsulation capability of the PLA NPs. The results showed an encapsulation efficiency of 44% for this cytostatic compound. Furthermore, preliminary cell viability tests showed that the FLU@PLA NPs allowed cell viabilities above 90% up to a concentration of 20 mg/L. The comprehensive findings showcase that the PLA NPs fabricated using this straightforward gelification method hold promise for encapsulating cytostatic compounds, offering a novel avenue for precise drug delivery in cancer therapy. Full article
(This article belongs to the Special Issue Advanced Hydrogels for Tissue Engineering and Drug Delivery)
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21 pages, 4120 KiB  
Article
Effect of Callus Cell Immobilization on the Textural and Rheological Properties, Loading, and Releasing of Grape Seed Extract from Pectin Hydrogels
by Elena Günter, Oxana Popeyko, Fedor Vityazev and Sergey Popov
Gels 2024, 10(4), 273; https://doi.org/10.3390/gels10040273 - 17 Apr 2024
Cited by 1 | Viewed by 1244
Abstract
The purpose of the present study was to prepare pectin hydrogels with immobilized Lemna minor callus cells and to identify the effect of cell immobilization on the textural, rheological, and swelling properties; loading; and releasing of grape seed extract (GSE) from the hydrogels. [...] Read more.
The purpose of the present study was to prepare pectin hydrogels with immobilized Lemna minor callus cells and to identify the effect of cell immobilization on the textural, rheological, and swelling properties; loading; and releasing of grape seed extract (GSE) from the hydrogels. Hardness, adhesiveness, elasticity, the strength of linkage, and complex viscosity decreased with increasing cell content in the hydrogels based on pectin with a degree of methyl esterification (DM) of 5.7% (TVC) and during incubation in gastrointestinal fluids. An increase in the rheological properties and fragility of pectin/callus hydrogels based on pectin with a DM of 33.0% (CP) was observed at a cell content of 0.4 g/mL. TVC-based pectin/callus beads increased their swelling in gastrointestinal fluids as cell content increased. TVC-based beads released GSE very slowly into simulated gastric and intestinal fluids, indicating controlled release. The GSE release rate in colonic fluid decreased with increasing cell content, which was associated with the accumulation of GSE in cells. CP-based beads released GSE completely in the intestinal fluid due to weak textural characteristics and rapid degradation within 10 min. Pectin/callus hydrogels have the ability to preserve GSE for a long time and may have great potential for the development of proanthocyanidin delivery systems due to their novel beneficial physicochemical and textural properties. Full article
(This article belongs to the Special Issue Recent Developments in Food Gels (2nd Edition))
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16 pages, 6743 KiB  
Article
Cytotoxicity and Degradation Resistance of Cryo- and Hydrogels Based on Carboxyethylchitosan at Different pH Values
by Elena Blinova, Anastasia Korel, Ekaterina Zemlyakova, Alexander Pestov, Alexander Samokhin, Maxim Zelikman, Vadim Tkachenko, Viktoria Bets, Elena Arzhanova and Ekaterina Litvinova
Gels 2024, 10(4), 272; https://doi.org/10.3390/gels10040272 - 17 Apr 2024
Viewed by 1438
Abstract
Background: The use of chitosan-based gels is still limited due to their restricted solubility in acid solutions, where the molecules have a positive charge. The functionalization of chitosan makes it possible to significantly expand the possibilities of using both the polymer itself and [...] Read more.
Background: The use of chitosan-based gels is still limited due to their restricted solubility in acid solutions, where the molecules have a positive charge. The functionalization of chitosan makes it possible to significantly expand the possibilities of using both the polymer itself and hydrogels based on its derivatives. Objective: To evaluate the effect of the conditions for the production of cryo- and hydrogels based on carboxyethylchitosan (CEC) crosslinked with glutaraldehyde on gel swelling and its resistance to degradation depending on pH and cytotoxic effects and to test the hypothesis that the amount of crosslinking agent during synthesis may affect the cytotoxicity of the gel. Methods: Gels’ swelling values and degradation resistance were determined using the gravimetric method. The cytotoxic effect was evaluated during the co-cultivation of gels in the presence of human fibroblasts using light optical microscopy and flow cytometry. Results: All CEC-based cryogels had a higher equilibrium swelling value and degradation time than the CEC hydrogel in the pH range from 4.6 to 8.0. This demonstrates the superiority of cryogels relative to CEC-based hydrogels in terms of swelling potential and degradation resistance, while an increase in the number of crosslinks with glutaraldehyde contributes to longer swelling of the cryogel. The positive control (intact fibroblasts) and all gel samples were statistically identical in the number of viable cells. On the third day, the viability of the fibroblast cells was consistently high (above 95%) and did not differ between all tested CEC-based gels. And in general, the cell morphology analysis results corresponded with the results obtained in the flow cytometry-based cytotoxicity test. We also did not find proof in our experiment to support our hypothesis that the amount of crosslinking agent during synthesis may affect the cytotoxicity of the material. Full article
(This article belongs to the Special Issue Polysaccharide Gels and Beyond: From the Synthesis to Application)
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18 pages, 3877 KiB  
Article
Exploring the Model of Cefazolin Released from Jellyfish Gelatin-Based Hydrogels as Affected by Glutaraldehyde
by Wiriya Charoenchokpanich, Pratchaya Muangrod, Sittiruk Roytrakul, Vilai Rungsardthong, Benjamaporn Wonganu, Sawanya Charoenlappanit, Federico Casanova and Benjawan Thumthanaruk
Gels 2024, 10(4), 271; https://doi.org/10.3390/gels10040271 - 17 Apr 2024
Cited by 1 | Viewed by 1653
Abstract
Due to its excellent biocompatibility and ease of biodegradation, jellyfish gelatin has gained attention as a hydrogel. However, hydrogel produced from jellyfish gelatin has not yet been sufficiently characterized. Therefore, this research aims to produce a jellyfish gelatin-based hydrogel. The gelatin produced from [...] Read more.
Due to its excellent biocompatibility and ease of biodegradation, jellyfish gelatin has gained attention as a hydrogel. However, hydrogel produced from jellyfish gelatin has not yet been sufficiently characterized. Therefore, this research aims to produce a jellyfish gelatin-based hydrogel. The gelatin produced from desalted jellyfish by-products varied with the part of the specimen and extraction time. Hydrogels with gelatin: glutaraldehyde ratios of 10:0.25, 10:0.50, and 10:1.00 (v/v) were characterized, and their cefazolin release ability was determined. The optimal conditions for gelatin extraction and chosen for the development of jellyfish hydrogels (JGel) included the use of the umbrella part of desalted jellyfish by-products extracted for 24 h (WU24), which yielded the highest gel strength (460.02 g), viscosity (24.45 cP), gelling temperature (12.70 °C), and melting temperature (22.48 °C). The quantities of collagen alpha−1(XXVIII) chain A, collagen alpha−1(XXI) chain, and collagen alpha−2(IX) chain in WU24 may influence its gel properties. Increasing the glutaraldehyde content in JGel increased the gel fraction by decreasing the space between the protein chains and gel swelling, as glutaraldehyde binds with lateral amino acid residues and produces a stronger network. At 8 h, more than 80% of the cefazolin in JGel (10:0.25) was released, which was higher than that released from bovine hydrogel (52.81%) and fish hydrogel (54.04%). This research is the first report focused on the production of JGel using glutaraldehyde as a cross-linking agent. Full article
(This article belongs to the Special Issue Gels in Medicine and Pharmacological Therapies (2nd Edition))
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21 pages, 5015 KiB  
Review
Shape Memory Hydrogels for Biomedical Applications
by Aleeza Farrukh and Sana Nayab
Gels 2024, 10(4), 270; https://doi.org/10.3390/gels10040270 - 17 Apr 2024
Cited by 2 | Viewed by 2453
Abstract
The ability of shape memory polymers to change shape upon external stimulation makes them exceedingly useful in various areas, from biomedical engineering to soft robotics. Especially, shape memory hydrogels (SMHs) are well-suited for biomedical applications due to their inherent biocompatibility, excellent shape morphing [...] Read more.
The ability of shape memory polymers to change shape upon external stimulation makes them exceedingly useful in various areas, from biomedical engineering to soft robotics. Especially, shape memory hydrogels (SMHs) are well-suited for biomedical applications due to their inherent biocompatibility, excellent shape morphing performance, tunable physiochemical properties, and responsiveness to a wide range of stimuli (e.g., thermal, chemical, electrical, light). This review provides an overview of the unique features of smart SMHs from their fundamental working mechanisms to types of SMHs classified on the basis of applied stimuli and highlights notable clinical applications. Moreover, the potential of SMHs for surgical, biomedical, and tissue engineering applications is discussed. Finally, this review summarizes the current challenges in synthesizing and fabricating reconfigurable hydrogel-based interfaces and outlines future directions for their potential in personalized medicine and clinical applications. Full article
(This article belongs to the Special Issue Properties and Applications of Biomaterials Related to Gels (2nd Edition))
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11 pages, 1541 KiB  
Article
The Injection of Gels Through an Intact Annulus Maintains Biomechanical Performance without Extrusion Risk
by Hans-Joachim Wilke, Holger Fuchs, Karin Benz, Juergen Mollenhauer, Christoph Gaissmaier, Frank Heuer and Cornelia Neidlinger-Wilke
Gels 2024, 10(4), 269; https://doi.org/10.3390/gels10040269 - 17 Apr 2024
Cited by 3 | Viewed by 1315
Abstract
For autologous-disc-derived chondrocyte transplantation (ADCT) a transglutaminase crosslinked gelatine gel and an albumin hyaluronic acid gel, crosslinked with bis-thio-polyethylene glycol, were injected through a syringe into a degenerated intervertebral disc, where they solidified in situ. This biomechanical in vitro study with lumbar bovine [...] Read more.
For autologous-disc-derived chondrocyte transplantation (ADCT) a transglutaminase crosslinked gelatine gel and an albumin hyaluronic acid gel, crosslinked with bis-thio-polyethylene glycol, were injected through a syringe into a degenerated intervertebral disc, where they solidified in situ. This biomechanical in vitro study with lumbar bovine motion segments evaluated disc height changes, motion characteristics in a quasi-static spine loading simulators, and the potential extrusion risk of these biomaterials in a complex dynamic multi-axial loading set-up with 100,000 loading cycles. After the injection and formation of the gel in the center of the nucleus, the disc height increase was about 0.3 mm. During cyclic testing, a gradual decrease in height could be detected due to viscoelastic effects and fluid loss. No gel extrusion could be observed for all specimens during the entire test procedure. A macroscopic inspection after dissections showed an accumulation of the solidified gel in the center of the nucleus. The results demonstrate that the injection of in situ solidifying gels through the intact annulus allows for the stable maintenance of the injected gel at the target location, with high potential for use as a suitable scaffold to anchor therapeutically applied cells for disc regeneration within the treated nucleus pulposus. Full article
(This article belongs to the Special Issue Hydrogels for the Regeneration of Joints of the Musculoskeletal System in Orthopedics)
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18 pages, 5122 KiB  
Article
Enhancing the Topical Antibacterial Activity of Fusidic Acid via Embedding into Cinnamon Oil Nano-Lipid Carrier
by Heba S. Elsewedy, Tamer M. Shehata, Shaymaa M. Genedy, Khuzama M. Siddiq, Bushra Y. Asiri, Rehab A. Alshammari, Sarah I. Bukhari, Adeola T. Kola-Mustapha, Heba A. Ramadan and Wafaa E. Soliman
Gels 2024, 10(4), 268; https://doi.org/10.3390/gels10040268 - 16 Apr 2024
Cited by 4 | Viewed by 1663
Abstract
Presently, antimicrobial resistance is of great risk to remarkable improvements in health conditions and infection management. Resistance to various antibiotics has been considered a great obstacle in their usage, necessitating alternative strategies for enhancing the antibacterial effect. Combination therapy has been recognized as [...] Read more.
Presently, antimicrobial resistance is of great risk to remarkable improvements in health conditions and infection management. Resistance to various antibiotics has been considered a great obstacle in their usage, necessitating alternative strategies for enhancing the antibacterial effect. Combination therapy has been recognized as a considerable strategy that could improve the therapeutic influence of antibacterial agents. Therefore, the aim of this study was to combine the antibacterial action of compounds of natural origin like fusidic acid (FA) and cinnamon essential oil (CEO) for synergistic effects. A distinctive nanoemulsion (NE) was developed using cinnamon oil loaded with FA. Applying the Box–Behnken design (BBD) approach, one optimized formula was selected and integrated into a gel base to provide an FA-NE-hydrogel for optimal topical application. The FA-NE-hydrogel was examined physically, studied for in vitro release, and investigated for stability upon storage at different conditions, at room (25 °C) and refrigerator (4 °C) temperatures, for up to 3 months. Ultimately, the NE-hydrogel preparation was inspected for its antibacterial behavior using multidrug-resistant bacteria and checked by scanning electron microscopy. The FA-NE-hydrogel formulation demonstrated a pH (6.32), viscosity (12,680 cP), and spreadability (56.7 mm) that are acceptable for topical application. The in vitro release could be extended for 6 h, providing 52.0%. The formulation was stable under both test conditions for up to 3 months of storage. Finally, the FA-NE-hydrogel was found to inhibit the bacterial growth of not only Gram-positive but also Gram-negative bacteria. The inhibition was further elucidated by a scanning electron micrograph, indicating the efficiency of CEO in enhancing the antibacterial influence of FA when combined in an NE system. Full article
(This article belongs to the Special Issue Designing Gels for Antibacterial and Antiviral Agents)
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22 pages, 7639 KiB  
Article
Development and Characterization of Thermosensitive and Bioadhesive Ophthalmic Formulations Containing Flurbiprofen Solid Dispersions
by Pınar Adısanoğlu and Işık Özgüney
Gels 2024, 10(4), 267; https://doi.org/10.3390/gels10040267 - 15 Apr 2024
Viewed by 1285
Abstract
In this study, we aimed to develop thermosensitive and bioadhesive in situ gelling systems containing solid dispersions of flurbiprofen (FB-SDs) using poloxamer 407 (P407) and 188 (P188) for ophthalmic delivery. FB-SDs were prepared with the melt method using P407, characterized by solubility, stability, [...] Read more.
In this study, we aimed to develop thermosensitive and bioadhesive in situ gelling systems containing solid dispersions of flurbiprofen (FB-SDs) using poloxamer 407 (P407) and 188 (P188) for ophthalmic delivery. FB-SDs were prepared with the melt method using P407, characterized by solubility, stability, SEM, DSC, TGA, and XRD analyses. Various formulations of poloxamer mixtures and FB-SDs were prepared using the cold method and P407/P188 (15/26.5%), which gels between 32 and 35 °C, was selected to develop an ophthalmic in situ gelling system. Bioadhesive polymers Carbopol 934P (CP) or carboxymethyl cellulose (CMC) were added in three concentrations (0.2, 0.4, and 0.6% (w/w)). Gelation temperature and time, mechanical properties, flow properties, and viscosity values were determined. The in vitro release rate, release kinetics, and the release mechanism of flurbiprofen (FB) from the ophthalmic formulations were analyzed. The results showed that FB-SDs’ solubility in water increased 332-fold compared with FB. The oscillation study results indicated that increasing bioadhesive polymer concentrations decreased gelation temperature and time, and formulations containing CP gel at lower temperatures and in a shorter time. All formulations except F3 and F4 showed Newtonion flow under non-physiological conditions, while all formulations exhibited non-Newtonion pseudoplastic flow under physiological conditions. Viscosity values increased with an increase in bioadhesive polymer concertation at physiological conditions. Texture profile analysis (TPA) showed that CP-containing formulations had higher hardness, compressibility, and adhesiveness, and the gel structure of formulation F4, containing 0.6% CP, exhibited the greatest hardness, compressibility, and adhesiveness. In vitro drug release studies indicated that CP and CMC had no effect below 0.6% concentration. Kinetic evaluation favored first-order and Hixson–Crowell kinetic models. Release mechanism analysis showed that the n values of the formulations were greater than 1 except for formulation F5, suggesting that FB might be released from the ophthalmic formulations by super case II type diffusion. When all the results of this study are evaluated, the in situ gelling formulations prepared with FB-SDs that contained P407/P188 (15/26.5%) and 0.2% CP or 0.2% CMC or 0.4 CMC% (F2, F5, and F6, respectively) could be promising formulations to prolong precorneal residence time and improve ocular bioavailability of FB. Full article
(This article belongs to the Special Issue Antibacterial Gels)
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13 pages, 11949 KiB  
Article
Hydrophobic Silk Fibroin–Agarose Composite Aerogel Fibers with Elasticity for Thermal Insulation Applications
by Yuxiang Du, Pengjie Jiang, Xin Yang, Rui Fu, Lipeng Liu, Changqing Miao, Yaxiong Wang and Huazheng Sai
Gels 2024, 10(4), 266; https://doi.org/10.3390/gels10040266 - 15 Apr 2024
Cited by 2 | Viewed by 1506
Abstract
Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers [...] Read more.
Aerogel fibers, characterized by their ultra-low density and ultra-low thermal conductivity, are an ideal candidate for personal thermal management as they hold the potential to effectively reduce the energy consumption of room heating and significantly contribute to energy conservation. However, most aerogel fibers have weak mechanical properties or require complex manufacturing processes. In this study, simple continuous silk fibroin–agarose composite aerogel fibers (SCAFs) were prepared by mixing agarose with silk fibroin through wet spinning and rapid gelation, followed by solvent replacement and supercritical carbon dioxide treatment. Among them, the rapid gelation of the SCAFs was achieved using agarose physical methods with heat-reversible gel properties, simplifying the preparation process. Hydrophobic silk fibroin–agarose composite aerogel fibers (HSCAFs) were prepared using a simple chemical vapor deposition (CVD) method. After CVD, the HSCAFs’ gel skeletons were uniformly coated with a silica layer containing methyl groups, endowing them with outstanding radial elasticity. Moreover, the HSCAFs exhibited low density (≤0.153 g/cm3), a large specific surface area (≥254.0 m2/g), high porosity (91.1–94.7%), and excellent hydrophobicity (a water contact angle of 136.8°). More importantly, they showed excellent thermal insulation performance in low-temperature (−60 °C) or high-temperature (140 °C) environments. The designed HSCAFs may provide a new approach for the preparation of high-performance aerogel fibers for personal thermal management. Full article
(This article belongs to the Special Issue Recent Advances in Aerogel-Based Composites)
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16 pages, 1549 KiB  
Article
Hypromellose-, Gelatin- and Gellan Gum-Based Gel Films with Chlorhexidine for Potential Application in Oral Inflammatory Diseases
by Monika Wojtyłko, Anna Froelich and Barbara Jadach
Gels 2024, 10(4), 265; https://doi.org/10.3390/gels10040265 - 15 Apr 2024
Cited by 3 | Viewed by 1828
Abstract
The oral cavity is constantly exposed to contact with an external environment. Pathogens can easily access and colonize it, causing a number of medical conditions that are usually accompanied by inflammation, which in turn require medical intervention and cause the deterioration of wellbeing. [...] Read more.
The oral cavity is constantly exposed to contact with an external environment. Pathogens can easily access and colonize it, causing a number of medical conditions that are usually accompanied by inflammation, which in turn require medical intervention and cause the deterioration of wellbeing. The aim of this study was to obtain polymer films that could be a carrier for chlorhexidine, an active substance used in the treatment of inflammation in the oral cavity, and at the same time act as a dressing for the application on the mucous membrane. Combinations of three biocompatible and biodegradable polymers were used to prepare the films. The obtained samples were characterized by assessing their water loss after drying, swelling ability, hygroscopicity and tensile strength. It was shown that the mixture of HPMC and gellan gum or gelatin could be used to prepare transparent, flexible polymer films with chlorhexidine. All tested films showed high hygroscopicity and swelling ability. However, it was observed that the composition containing gellan gum was more suitable for obtaining films with prolonged stay at the site of administration, which predisposes it to the role of a local dressing. Full article
(This article belongs to the Special Issue Advances in Gel Films)
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17 pages, 5735 KiB  
Article
Coated Microneedle System for Delivery of Clotrimazole in Deep-Skin Mycoses
by Barbara Jadach, Agata Nowak, Jolanta Długaszewska, Oliwia Kordyl, Irena Budnik and Tomasz Osmałek
Gels 2024, 10(4), 264; https://doi.org/10.3390/gels10040264 - 15 Apr 2024
Cited by 2 | Viewed by 2337
Abstract
Mycoses of the skin are infectious diseases caused by fungal microorganisms that are generally treated with topical agents. However, such therapy is often ineffective and has to be supported by oral use of active substances, which, in turn, can cause many side effects. [...] Read more.
Mycoses of the skin are infectious diseases caused by fungal microorganisms that are generally treated with topical agents. However, such therapy is often ineffective and has to be supported by oral use of active substances, which, in turn, can cause many side effects. A good alternative for the treatment of deep-skin mycoses seems to be microneedles (MNs). The aim of this research was to fabricate and evaluate the properties of innovative MNs coated with a hydrogel as potential carriers for clotrimazole (CLO) in the treatment of deep fungal skin infections. A 3D printing technique using a photo-curable resin was employed to produce MNs, which were coated with hydrogels using a dip-coating method. Hydrogels were prepared with carbopol EZ-3 Polymer (Lubrizol) in addition to glycerol and triisopropanolamine. Clotrimazole was introduced into the gel as the solution in ethanol or was suspended. In the first step of the investigation, a texture analysis of hydrogels was prepared with a texture analyzer, and the drug release studies were conducted with the use of automatic Franz diffusion cells. Next, the release profiles of CLO for coated MNs were checked. The last part of the investigation was the evaluation of the antifungal activity of the prepared systems, and the inhibition of the growth of Candida albicans was checked with the diffusion and suspended-plate methods. The texture profile analysis (TPA) for the tested hydrogels showed that the addition of ethanol significantly affects the following studied parameters: hardness, adhesiveness and gumminess, causing a decrease in their values. On the other hand, for the gels with suspended CLO, better spreadability was seen compared to gels with dissolved CLO. The presence of the active substance did not significantly affect the values of the tested parameters. In the dissolution study, the results showed that higher amounts of CLO were released for MNs coated with a hydrogel containing dissolved CLO. Also, microbiological tests proved its efficacy against fungal cultures. Qualitative tests carried out using the diffusion method showed that circular zones of inhibition of fungal growth on the plate were obtained, confirming the hypothesis of effectiveness. The suspension-plate technique confirmed the inhibitory effect of applied CLO on the growth of Candida albicans. From the analysis of the data, the MNs coated with CLO dissolved in hydrogel showed better antifungal activity. All received results seem to be helpful in developing further studies for MNs as carriers of antifungal substances. Full article
(This article belongs to the Special Issue Hydrogel for Tissue Engineering and Biomedical Therapeutics)
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19 pages, 7053 KiB  
Article
Stereochemical Behavior of Pyrrolo-Pyrazole Peptidomimetics Promoting Phase-Selective Supramolecular Organogels
by Enrica Chiesa, Francesco Anastasi, Francesca Clerici, Edoardo Mario Lumina, Ida Genta, Sara Pellegrino and Maria Luisa Gelmi
Gels 2024, 10(4), 263; https://doi.org/10.3390/gels10040263 - 14 Apr 2024
Viewed by 1180
Abstract
Supramolecular gels were developed by taking advantage of an assembly of small dipeptides containing pyrrolo-pyrazole scaffolds. The dipeptides were prepared through a robust and ecofriendly synthetic approach from the commercially available starting materials of diazoalkanes and maleimides. By playing with the functionalization of [...] Read more.
Supramolecular gels were developed by taking advantage of an assembly of small dipeptides containing pyrrolo-pyrazole scaffolds. The dipeptides were prepared through a robust and ecofriendly synthetic approach from the commercially available starting materials of diazoalkanes and maleimides. By playing with the functionalization of the scaffold, the choice of the natural amino acid, and the stereochemistry, we were able to obtain phase-selective gels. In particular, one peptidomimetic showed gelation ability and thermoreversibility in aromatic solvents at very low concentrations. Rheology tests showed a typical viscoelastic solid profile, indicating the formation of strong gels that were stable under high mechanical deformation. NMR studies were performed, allowing us to determine the conformational and stereochemical features at the base of the supramolecular interactions. Full article
(This article belongs to the Special Issue State-of-the-Art Gel Research in Italy (2nd Edition))
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27 pages, 2660 KiB  
Review
Advances in Hydrogel-Based Drug Delivery Systems
by Boya Liu and Kuo Chen
Gels 2024, 10(4), 262; https://doi.org/10.3390/gels10040262 - 13 Apr 2024
Cited by 20 | Viewed by 6205
Abstract
Hydrogels, with their distinctive three-dimensional networks of hydrophilic polymers, drive innovations across various biomedical applications. The ability of hydrogels to absorb and retain significant volumes of water, coupled with their structural integrity and responsiveness to environmental stimuli, renders them ideal for drug delivery, [...] Read more.
Hydrogels, with their distinctive three-dimensional networks of hydrophilic polymers, drive innovations across various biomedical applications. The ability of hydrogels to absorb and retain significant volumes of water, coupled with their structural integrity and responsiveness to environmental stimuli, renders them ideal for drug delivery, tissue engineering, and wound healing. This review delves into the classification of hydrogels based on cross-linking methods, providing insights into their synthesis, properties, and applications. We further discuss the recent advancements in hydrogel-based drug delivery systems, including oral, injectable, topical, and ocular approaches, highlighting their significance in enhancing therapeutic outcomes. Additionally, we address the challenges faced in the clinical translation of hydrogels and propose future directions for leveraging their potential in personalized medicine and regenerative healthcare solutions. Full article
(This article belongs to the Special Issue Advanced Hydrogels for Regenerative Medicine and Tissue Engineering (2nd Edition))
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14 pages, 4631 KiB  
Article
Time Dependence of Gel Formation in Lyotropic Nematic Liquid Crystals: From Hours to Weeks
by Max Dombrowski, Michael Herbst, Natalie Preisig, Frank Giesselmann and Cosima Stubenrauch
Gels 2024, 10(4), 261; https://doi.org/10.3390/gels10040261 - 13 Apr 2024
Viewed by 1272
Abstract
The combination of lyotropic liquid crystals (LLCs) and low-molecular-weight gelators (LMWGs) for the formation of lyotropic liquid crystal gels (LLC gels) leads to a versatile and complex material combining properties of both parent systems. We gelled the calamitic nematic NC phases of [...] Read more.
The combination of lyotropic liquid crystals (LLCs) and low-molecular-weight gelators (LMWGs) for the formation of lyotropic liquid crystal gels (LLC gels) leads to a versatile and complex material combining properties of both parent systems. We gelled the calamitic nematic NC phases of a binary and ternary system using the LMWG 3,5-bis-(5-hexylcarbamoyl-pentoxy)-benzoic acid hexyl ester (BHPB-6). This binary system consists of the surfactant N,N-dimethyl-N-ethyl-1-hexadecylammonium bromide (CDEAB) and water, whereas the ternary system consists of the surfactant N,N,N-trimethyl-N-tetradecylammonium bromide (C14TAB), the cosurfactant n-decanol, and water. Though containing similar surfactants, the gelled NC phases of the binary and ternary systems show differences in their visual and gel properties. The gelled NC phase of the binary system remains clear for several days after preparation, whereas the gelled NC phase of the ternary system turns turbid within 24 h. We investigated the time evolution of the gel strength with oscillation rheology measurements (a) within the first 24 h and (b) up to two weeks after gel formation. The shape of the fibers was investigated over different time scales with freeze fracture electron microscopy (FFEM). We demonstrate that despite their similarities, the two LLC gels also have distinct differences. Full article
(This article belongs to the Section Gel Chemistry and Physics)
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28 pages, 6758 KiB  
Review
Recent Insights into Glucose-Responsive Concanavalin A-Based Smart Hydrogels for Controlled Insulin Delivery
by Maria Bercea and Alexandra Lupu
Gels 2024, 10(4), 260; https://doi.org/10.3390/gels10040260 - 11 Apr 2024
Cited by 4 | Viewed by 2764
Abstract
Many efforts are continuously undertaken to develop glucose-sensitive biomaterials able of controlling glucose levels in the body and self-regulating insulin delivery. Hydrogels that swell or shrink as a function of the environmental free glucose content are suitable systems for monitoring blood glucose, delivering [...] Read more.
Many efforts are continuously undertaken to develop glucose-sensitive biomaterials able of controlling glucose levels in the body and self-regulating insulin delivery. Hydrogels that swell or shrink as a function of the environmental free glucose content are suitable systems for monitoring blood glucose, delivering insulin doses adapted to the glucose concentration. In this context, the development of sensors based on reversible binding to glucose molecules represents a continuous challenge. Concanavalin A (Con A) is a bioactive protein isolated from sword bean plants (Canavalia ensiformis) and contains four sugar-binding sites. The high affinity for reversibly and specifically binding glucose and mannose makes Con A as a suitable natural receptor for the development of smart glucose-responsive materials. During the last few years, Con A was used to develop smart materials, such as hydrogels, microgels, nanoparticles and films, for producing glucose biosensors or drug delivery devices. This review is focused on Con A-based materials suitable in the diagnosis and therapeutics of diabetes. A brief outlook on glucose-derived theranostics of cancer is also presented. Full article
(This article belongs to the Special Issue Recent Advances in Protein Gels)
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18 pages, 5826 KiB  
Article
Heavy Metal Removal from Wastewater Using Poly(Gamma-Glutamic Acid)-Based Hydrogel
by Fujie Chen, Yanbin Zhao, Hang Zhao, Xuan Zhou and Xiuying Liu
Gels 2024, 10(4), 259; https://doi.org/10.3390/gels10040259 - 11 Apr 2024
Cited by 1 | Viewed by 1583
Abstract
The removal of toxic heavy metal ions from wastewater is of great significance in the protection of the environment and human health. Poly(gamma-glutamic acid) (PGA) is a non-toxic, biodegradable, and highly water-soluble polymer possessing carboxyl and imino functional groups. Herein, water-insoluble PGA-based hydrogels [...] Read more.
The removal of toxic heavy metal ions from wastewater is of great significance in the protection of the environment and human health. Poly(gamma-glutamic acid) (PGA) is a non-toxic, biodegradable, and highly water-soluble polymer possessing carboxyl and imino functional groups. Herein, water-insoluble PGA-based hydrogels were prepared, characterized, and investigated as heavy metal adsorbents. The prepared hydrogels were recyclable and exhibited good adsorption effects on heavy metal ions including Cu2+, Cr6+, and Zn2+. The effects of adsorption parameters including temperature, solution pH, initial concentration of metal ions, and contact time on the adsorption capacity of the hydrogel for Cu2+ were investigated. The adsorption was a spontaneous and exothermic process. The process followed the pseudo-first-order kinetic model and Langmuir isotherm model, implying a physical and monolayer adsorption. The adsorption mechanisms investigation exhibited that Cu2+ adsorbed on the hydrogel via electrostatic interactions with anionic carboxylate groups of PGA in addition to the coordination interactions with the –NH groups. Importantly, the PGA hydrogel exhibited good reusability and the adsorption capability for Cu2+ remained high after five consecutive cycles. The properties of PGA hydrogel make it a potential candidate material for heavy metal ion removal in wastewater treatment. Full article
(This article belongs to the Special Issue Functionalized Gels for Environmental Applications (2nd Edition))
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13 pages, 3180 KiB  
Article
A High-Stretching, Rapid-Self-Healing, and Printable Composite Hydrogel Based on Poly(Vinyl Alcohol), Nanocellulose, and Sodium Alginate
by Mingyang Li, Yanen Wang, Qinghua Wei, Juan Zhang, Xiaohu Chen and Yalong An
Gels 2024, 10(4), 258; https://doi.org/10.3390/gels10040258 - 11 Apr 2024
Cited by 1 | Viewed by 1916
Abstract
Hydrogels with excellent flexibility, conductivity, and controllable mechanical properties are the current research hotspots in the field of biomaterial sensors. However, it is difficult for hydrogel sensors to regain their original function after being damaged, which limits their practical applications. Herein, a composite [...] Read more.
Hydrogels with excellent flexibility, conductivity, and controllable mechanical properties are the current research hotspots in the field of biomaterial sensors. However, it is difficult for hydrogel sensors to regain their original function after being damaged, which limits their practical applications. Herein, a composite hydrogel (named SPBC) of poly(vinyl alcohol) (PVA)/sodium alginate (SA)/cellulose nanofibers (CNFs)/sodium borate tetrahydrate was synthesized, which has good self-healing, electrical conductivity, and excellent mechanical properties. The SPBC0.3 hydrogel demonstrates rapid self-healing (<30 s) and achieves mechanical properties of 33.92 kPa. Additionally, it exhibits high tensile strain performance (4000%). The abundant internal ions and functional groups of SPBC hydrogels provide support for the good electrical conductivity (0.62 S/cm) and electrical response properties. In addition, the SPBC hydrogel can be attached to surfaces such as fingers and wrists to monitor human movements in real time, and its good rheological property supports three-dimensional (3D) printing molding methods. In summary, this study successfully prepared a self-healing, conductive, printable, and mechanically superior SPBC hydrogel. Its suitability for 3D-printing personalized fabrication and outstanding sensor properties makes it a useful reference for hydrogels in wearable devices and human motion monitoring. Full article
(This article belongs to the Special Issue Multifunctional Polymer Nano-, Micro- and Hydro- Gels: Synthesis, Properties and Applications)
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23 pages, 14529 KiB  
Article
A Gellan Gum, Polyethylene Glycol, Hydroxyapatite Composite Scaffold with the Addition of Ginseng Derived Compound K with Possible Applications in Bone Regeneration
by Muthukumar Thangavelu, Pil-Yun Kim, Hunhwi Cho, Jeong-Eun Song, Sunjae Park, Alessio Bucciarelli and Gilson Khang
Gels 2024, 10(4), 257; https://doi.org/10.3390/gels10040257 - 10 Apr 2024
Viewed by 1435
Abstract
Engineered bone scaffolds should mimic the natural material to promote cell adhesion and regeneration. For this reason, natural biopolymers are becoming a gold standard in scaffold production. In this study, we proposed a hybrid scaffold produced using gellan gum, hydroxyapatite, and Poly (ethylene [...] Read more.
Engineered bone scaffolds should mimic the natural material to promote cell adhesion and regeneration. For this reason, natural biopolymers are becoming a gold standard in scaffold production. In this study, we proposed a hybrid scaffold produced using gellan gum, hydroxyapatite, and Poly (ethylene glycol) within the addition of the ginseng compound K (CK) as a candidate for bone regeneration. The fabricated scaffold was physiochemically characterized. The morphology studied by scanning electron microscopy (SEM) and image analysis revealed a pore distribution suitable for cells growth. The addition of CK further improved the biological activity of the hybrid scaffold as demonstrated by the MTT assay. The addition of CK influenced the scaffold morphology, decreasing the mean pore diameter. These findings can potentially help the development of a new generation of hybrid scaffolds to best mimic the natural tissue. Full article
(This article belongs to the Special Issue Hydrogels for the Regeneration of Joints of the Musculoskeletal System in Orthopedics)
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14 pages, 2589 KiB  
Article
Effect of Tannic Acid Concentrations on Temperature-Sensitive Sol–Gel Transition and Stability of Tannic Acid/Pluronic F127 Composite Hydrogels
by Jeong Yun Lee, Hyun Ho Shin, Chungyeon Cho and Ji Hyun Ryu
Gels 2024, 10(4), 256; https://doi.org/10.3390/gels10040256 - 10 Apr 2024
Viewed by 2120
Abstract
Recently, interest in polyphenol-containing composite adhesives for various biomedical applications has been growing. Tannic acid (TA) is a polyphenolic compound with advantageous properties, including antioxidant and antimicrobial properties. Additionally, TA contains multiple hydroxyl groups that exhibit biological activity by forming hydrogen bonds with [...] Read more.
Recently, interest in polyphenol-containing composite adhesives for various biomedical applications has been growing. Tannic acid (TA) is a polyphenolic compound with advantageous properties, including antioxidant and antimicrobial properties. Additionally, TA contains multiple hydroxyl groups that exhibit biological activity by forming hydrogen bonds with proteins and biomacromolecules. Furthermore, TA-containing polymer composites exhibit excellent tissue adhesion properties. In this study, the gelation behavior and adhesion forces of TA/Pluronic F127 (TA/PluF) composite hydrogels were investigated by varying the TA and PluF concentrations. PluF (above 16 wt%) alone showed temperature-responsive gelation behavior because of the closely packed micelle aggregates. After the addition of a small amount of TA, the TA/PluF hydrogels showed thermosensitive behavior similar to that of PluF hydrogels. However, the TA/PluF hydrogels containing more than 10 wt% TA completely suppressed the thermo-responsive gelation kinetics of PluF, which may have been due to the hydrogen bonds between TA and PluF. In addition, TA/PluF hydrogels with 40 wt% TA showed excellent tissue adhesion properties and bursting pressure in porcine intestinal tissues. These results are expected to aid in understanding the use of mixtures of TA and thermosensitive block copolymers to fabricate adhesive hydrogels for versatile biomedical applications. Full article
(This article belongs to the Special Issue Advanced Hydrogels for Regenerative Medicine and Tissue Engineering (2nd Edition))
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14 pages, 2771 KiB  
Article
Improving the Decay Resistance of Wood through the Fixation of Different Nanoparticles Using Silica Aerogel
by Miklós Bak, Zsófia Plesér and Róbert Németh
Gels 2024, 10(4), 255; https://doi.org/10.3390/gels10040255 - 10 Apr 2024
Viewed by 1410
Abstract
Nowadays, the protection of wood is becoming more important with the increasing demand for durable wood, in addition to its limited accessibility. One possible way to increase the durability is the use of nanoparticles, which can be effective even with a low intake [...] Read more.
Nowadays, the protection of wood is becoming more important with the increasing demand for durable wood, in addition to its limited accessibility. One possible way to increase the durability is the use of nanoparticles, which can be effective even with a low intake of active ingredients. However, avoiding their leaching is a challenge. A possible solution to leaching is the use of silica aerogel as a fixative. This study investigated the use of mesoporous silica aerogel against the leaching of different nanoparticles under laboratory conditions. Tests were performed involving beech (Fagus sylvatica) and Scots pine (Pinus sylvestris) sapwood, using Trametes versicolor as a white rot and Coniophora puteana as a brown rot fungus. The results show that the subsequent treatment of the wood with mesoporous silica aerogel effectively fixed the nanoparticles in wood. The durability of the samples without aerogel significantly decreased as a result of leaching, whereas the resistance of the samples treated with aerogel decreased only slightly. However, the silica aerogel modification itself caused the leaching of silver nanoparticles, which is a limitation in the use of this method for the fixation of nanoparticles. Full article
(This article belongs to the Special Issue Advances in Xerogels: From Design to Applications (2nd Edition))
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