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Gels, Volume 9, Issue 3 (March 2023) – 92 articles

Cover Story (view full-size image): Monolithic silica aerogel is a promising material for innovative glazing systems. The long-term performance of aerogel is crucial since glazing systems are exposed to deteriorating agents during building service life. After fabrication and hydrophobicity, porosity, optical, acoustic, and color rendering tests, the samples were artificially aged by combining temperature and solar radiation effects. A natural service life of 12 years was achieved in about 4 months, and the samples’ properties were retested. Contact angle tests showed loss of hydrophobicity after aging. Visible transmittance values in the 0.67–0.37 range were obtained for hydrophilic and hydrophobic samples, reduced by 0.02–0.05 after aging, and a slight loss in acoustic performance was observed. The presence of aerogel, regardless of hydrophobicity, results in a deterioration in light green and azure tones. View this paper
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17 pages, 3734 KiB  
Article
Injectable Chitosan-Based Hydrogels for Trans-Cinnamaldehyde Delivery in the Treatment of Diabetic Foot Ulcer Infections
by Henry Chijcheapaza-Flores, Nicolas Tabary, Feng Chai, Mickaël Maton, Jean-Noel Staelens, Frédéric Cazaux, Christel Neut, Bernard Martel, Nicolas Blanchemain and Maria José Garcia-Fernandez
Gels 2023, 9(3), 262; https://doi.org/10.3390/gels9030262 - 22 Mar 2023
Cited by 7 | Viewed by 2527
Abstract
Diabetic foot ulcers (DFU) are among the most common complications in diabetic patients and affect 6.8% of people worldwide. Challenges in the management of this disease are decreased blood diffusion, sclerotic tissues, infection, and antibiotic resistance. Hydrogels are now being used as a [...] Read more.
Diabetic foot ulcers (DFU) are among the most common complications in diabetic patients and affect 6.8% of people worldwide. Challenges in the management of this disease are decreased blood diffusion, sclerotic tissues, infection, and antibiotic resistance. Hydrogels are now being used as a new treatment option since they can be used for drug delivery and to improve wound healing. This project aims to combine the properties of hydrogels based on chitosan (CHT) and the polymer of β cyclodextrin (PCD) for local delivery of cinnamaldehyde (CN) in diabetic foot ulcers. This work consisted of the development and characterisation of the hydrogel, the evaluation of the CN release kinetics and cell viability (on a MC3T3 pre-osteoblast cell line), and the evaluation of the antimicrobial and antibiofilm activity (S. aureus and P. aeruginosa). The results demonstrated the successful development of a cytocompatible (ISO 10993-5) injectable hydrogel with antibacterial (99.99% bacterial reduction) and antibiofilm activity. Furthermore, a partial active molecule release and an increase in hydrogel elasticity were observed in the presence of CN. This leads us to hypothesise that a reaction between CHT and CN (a Schiff base) can occur and that CN could act as a physical crosslinker, thus improving the viscoelastic properties of the hydrogel and limiting CN release. Full article
(This article belongs to the Special Issue Recent Developments in Chitosan Hydrogels)
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15 pages, 5974 KiB  
Article
Amidoamine Oxide Surfactants as Low-Molecular-Weight Hydrogelators: Effect of Methylene Chain Length on Aggregate Structure and Rheological Behavior
by Rie Kakehashi, Naoji Tokai, Makoto Nakagawa, Kazunori Kawasaki, Shin Horiuchi and Atsushi Yamamoto
Gels 2023, 9(3), 261; https://doi.org/10.3390/gels9030261 - 22 Mar 2023
Viewed by 1238
Abstract
Rheology control is an important issue in many industrial products such as cosmetics and paints. Recently, low-molecular-weight compounds have attracted considerable attention as thickeners/gelators for various solvents; however, there is still a significant need for molecular design guidelines for industrial applications. Amidoamine oxides [...] Read more.
Rheology control is an important issue in many industrial products such as cosmetics and paints. Recently, low-molecular-weight compounds have attracted considerable attention as thickeners/gelators for various solvents; however, there is still a significant need for molecular design guidelines for industrial applications. Amidoamine oxides (AAOs), which are long-chain alkylamine oxides with three amide groups, are surfactants that act as hydrogelators. Here, we show the relationship between the length of methylene chains at four different locations of AAOs, the aggregate structure, the gelation temperature Tgel, and the viscoelasticity of the formed hydrogels. As seen from the results of electron microscopic observations, the aggregate structure (ribbon-like or rod-like) can be controlled by changing the length of methylene chain in the hydrophobic part, the length of methylene chain between the amide and amine oxide groups, and the lengths of methylene chains between amide groups. Furthermore, hydrogels consisting of rod-like aggregates showed significantly higher viscoelasticity than those consisting of ribbon-like aggregates. In other words, it was shown that the gel viscoelasticity could be controlled by changing the methylene chain lengths at four different locations of the AAO. Full article
(This article belongs to the Special Issue Hydrogels, Microgels, and Nanogels: From Fundamentals to Applications)
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28 pages, 5203 KiB  
Review
Hydrogels—A Promising Materials for 3D Printing Technology
by Gobi Saravanan Kaliaraj, Dilip Kumar Shanmugam, Arish Dasan and Kamalan Kirubaharan Amirtharaj Mosas
Gels 2023, 9(3), 260; https://doi.org/10.3390/gels9030260 - 22 Mar 2023
Cited by 16 | Viewed by 6608
Abstract
Hydrogels are a promising material for a variety of applications after appropriate functional and structural design, which alters the physicochemical properties and cell signaling pathways of the hydrogels. Over the past few decades, considerable scientific research has made breakthroughs in a variety of [...] Read more.
Hydrogels are a promising material for a variety of applications after appropriate functional and structural design, which alters the physicochemical properties and cell signaling pathways of the hydrogels. Over the past few decades, considerable scientific research has made breakthroughs in a variety of applications such as pharmaceuticals, biotechnology, agriculture, biosensors, bioseparation, defense, and cosmetics. In the present review, different classifications of hydrogels and their limitations have been discussed. In addition, techniques involved in improving the physical, mechanical, and biological properties of hydrogels by admixing various organic and inorganic materials are explored. Future 3D printing technology will substantially advance the ability to pattern molecules, cells, and organs. With significant potential for producing living tissue structures or organs, hydrogels can successfully print mammalian cells and retain their functionalities. Furthermore, recent advances in functional hydrogels such as photo- and pH-responsive hydrogels and drug-delivery hydrogels are discussed in detail for biomedical applications. Full article
(This article belongs to the Special Issue 3D Printing of Gel-Based Materials)
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15 pages, 2180 KiB  
Article
Modeling the Phase Transition in Hydrophobic Weak Polyelectrolyte Gels under Compression
by Alexander D. Kazakov, Varvara M. Prokacheva, Oleg V. Rud, Lucie Nová and Filip Uhlík
Gels 2023, 9(3), 259; https://doi.org/10.3390/gels9030259 - 22 Mar 2023
Cited by 1 | Viewed by 1071
Abstract
One of the emerging water desalination techniques relies on the compression of a polyelectrolyte gel. The pressures needed reach tens of bars, which are too high for many applications, damage the gel and prevent its reuse. Here, we study the process by means [...] Read more.
One of the emerging water desalination techniques relies on the compression of a polyelectrolyte gel. The pressures needed reach tens of bars, which are too high for many applications, damage the gel and prevent its reuse. Here, we study the process by means of coarse-grained simulations of hydrophobic weak polyelectrolyte gels and show that the necessary pressures can be lowered to only a few bars. We show that the dependence of applied pressure on the gel density contains a plateau indicating a phase separation. The phase separation was also confirmed by an analytical mean-field theory. The results of our study show that changes in the pH or salinity can induce the phase transition in the gel. We also found that ionization of the gel enhances its ion capacity, whereas increasing the gel hydrophobicity lowers the pressure required for gel compression. Therefore, combining both strategies enables the optimization of polyelectrolyte gel compression for water desalination purposes. Full article
(This article belongs to the Special Issue New Era in the Volume Phase Transition of Gels II)
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12 pages, 3848 KiB  
Article
Consolidation and Forced Elasticity in Double-Network Hydrogels
by S. Shams Es-haghi and R. A. Weiss
Gels 2023, 9(3), 258; https://doi.org/10.3390/gels9030258 - 22 Mar 2023
Cited by 1 | Viewed by 1372
Abstract
This paper discusses two observations that are unique with respect to the mechanics of double network (DN) hydrogels, forced elasticity driven by water diffusion and consolidation, which are analogous to the so-called Gough–Joule effects in rubbers. A series of DN hydrogels were synthesized [...] Read more.
This paper discusses two observations that are unique with respect to the mechanics of double network (DN) hydrogels, forced elasticity driven by water diffusion and consolidation, which are analogous to the so-called Gough–Joule effects in rubbers. A series of DN hydrogels were synthesized from 2-acrylamido-2-methylpropane sulfuric acid (AMPS), 3-sulfopropyl acrylate potassium salt (SAPS) and acrylamide (AAm). Drying of AMPS/AAm DN hydrogels was monitored by extending the gel specimens to different stretch ratios and holding them until all the water evaporated. At high extension ratios, the gels underwent plastic deformation. Water diffusion measurements performed on AMPS/AAm DN hydrogels that were dried at different stretch ratios indicated that the diffusion mechanism deviated from Fickian behavior at extension ratios greater than two. Study of the mechanical behavior of AMPS/AAm and SAPS/AAm DN hydrogels during tensile and confined compression tests showed that despite their large water content, DN hydrogels can retain water during large-strain tensile or compression deformations. Full article
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28 pages, 5139 KiB  
Review
Recent Development of Self-Powered Tactile Sensors Based on Ionic Hydrogels
by Zhen Zhao, Yong-Peng Hu, Kai-Yang Liu, Wei Yu, Guo-Xian Li, Chui-Zhou Meng and Shi-Jie Guo
Gels 2023, 9(3), 257; https://doi.org/10.3390/gels9030257 - 22 Mar 2023
Cited by 7 | Viewed by 3040
Abstract
Hydrogels are three-dimensional polymer networks with excellent flexibility. In recent years, ionic hydrogels have attracted extensive attention in the development of tactile sensors owing to their unique properties, such as ionic conductivity and mechanical properties. These features enable ionic hydrogel-based tactile sensors with [...] Read more.
Hydrogels are three-dimensional polymer networks with excellent flexibility. In recent years, ionic hydrogels have attracted extensive attention in the development of tactile sensors owing to their unique properties, such as ionic conductivity and mechanical properties. These features enable ionic hydrogel-based tactile sensors with exceptional performance in detecting human body movement and identifying external stimuli. Currently, there is a pressing demand for the development of self-powered tactile sensors that integrate ionic conductors and portable power sources into a single device for practical applications. In this paper, we introduce the basic properties of ionic hydrogels and highlight their application in self-powered sensors working in triboelectric, piezoionic, ionic diode, battery, and thermoelectric modes. We also summarize the current difficulty and prospect the future development of ionic hydrogel self-powered sensors. Full article
(This article belongs to the Special Issue Advances in Conductive Polymers and Hydrogels)
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17 pages, 5291 KiB  
Article
Ca-Alginate Hydrogel with Immobilized Callus Cells as a New Delivery System of Grape Seed Extract
by Elena Günter, Oxana Popeyko and Sergey Popov
Gels 2023, 9(3), 256; https://doi.org/10.3390/gels9030256 - 22 Mar 2023
Cited by 1 | Viewed by 1288
Abstract
The development of new delivery systems for polyphenols is necessary to maintain their antioxidant activity and targeted delivery. The purpose of this investigation was to obtain alginate hydrogels with immobilized callus cells, in order to study the interaction between the physicochemical properties of [...] Read more.
The development of new delivery systems for polyphenols is necessary to maintain their antioxidant activity and targeted delivery. The purpose of this investigation was to obtain alginate hydrogels with immobilized callus cells, in order to study the interaction between the physicochemical properties of hydrogels, texture, swelling behaviour, and grape seed extract (GSE) release in vitro. The inclusion of duckweed (LMC) and campion (SVC) callus cells in hydrogels led to a decrease in their porosity, gel strength, adhesiveness, and thermal stability, and an increase in the encapsulation efficiency compared with alginate hydrogel. The incorporation of LMC cells (0.17 g/mL), which were smaller, resulted in the formation of a stronger gel. The Fourier transform infrared analyses indicated the entrapment of GSE in the alginate hydrogel. Alginate/callus hydrogels had reduced swelling and GSE release in the simulated intestinal (SIF) and colonic (SCF) fluids due to their less porous structure and the retention of GSE in cells. Alginate/callus hydrogels gradually released GSE in SIF and SCF. The faster GSE release in SIF and SCF was associated with reduced gel strength and increased swelling of the hydrogels. LMC-1.0Alginate hydrogels with lower swelling, higher initial gel strength, and thermal stability released GSE more slowly in SIF and SCF. The GSE release was dependent on the content of SVC cells in 1.0% alginate hydrogels. The data obtained show that the addition of callus cells to the hydrogel provides them with physicochemical and textural properties that are useful for the development of drug delivery systems in the colon. Full article
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15 pages, 4959 KiB  
Article
Microencapsulation of a Pickering Oil/Water Emulsion Loaded with Vitamin D3
by Alessandro Candiani, Giada Diana, Manuel Martoccia, Fabiano Travaglia, Lorella Giovannelli, Jean Daniel Coïsson and Lorena Segale
Gels 2023, 9(3), 255; https://doi.org/10.3390/gels9030255 - 22 Mar 2023
Viewed by 1570
Abstract
The ionotropic gelation technique was chosen to produce vitamin D3-loaded microparticles starting from oil-in-water (O/W) Pickering emulsion stabilized by flaxseed flour: the hydrophobic phase was a solution of vitamin D3 in a blend of vegetable oils (ω6:ω3, 4:1) composed of extra virgin olive [...] Read more.
The ionotropic gelation technique was chosen to produce vitamin D3-loaded microparticles starting from oil-in-water (O/W) Pickering emulsion stabilized by flaxseed flour: the hydrophobic phase was a solution of vitamin D3 in a blend of vegetable oils (ω6:ω3, 4:1) composed of extra virgin olive oil (90%) and hemp oil (10%); the hydrophilic phase was a sodium alginate aqueous solution. The most adequate emulsion was selected carrying out a preliminary study on five placebo formulations which differed in the qualitative and quantitative polymeric composition (concentration and type of alginate selected). Vitamin D3-loaded microparticles in the dried state had a particle size of about 1 mm, 6% of residual water content and excellent flowability thanks to their rounded shape and smooth surface. The polymeric structure of microparticles demonstrated to preserve the vegetable oil blend from oxidation and the integrity of vitamin D3, confirming this product as an innovative ingredient for pharmaceutical and food/nutraceutical purposes. Full article
(This article belongs to the Special Issue Functional Gels Applied in Drug Delivery)
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11 pages, 2878 KiB  
Article
Optimization of the Extraction of Chitosan and Fish Gelatin from Fishery Waste and Their Antimicrobial Potential as Active Biopolymers
by Javier Rocha-Pimienta, Bruno Navajas-Preciado, Carmen Barraso-Gil, Sara Martillanes and Jonathan Delgado-Adámez
Gels 2023, 9(3), 254; https://doi.org/10.3390/gels9030254 - 22 Mar 2023
Cited by 4 | Viewed by 1985
Abstract
Fishery residues are abundant raw materials that also provide numerous metabolites with high added value. Their classic valorization includes energy recovery, composting, animal feed, and direct deposits in landfills or oceans along with the environmental impacts that this entails. However, through extraction processes, [...] Read more.
Fishery residues are abundant raw materials that also provide numerous metabolites with high added value. Their classic valorization includes energy recovery, composting, animal feed, and direct deposits in landfills or oceans along with the environmental impacts that this entails. However, through extraction processes, they can be transformed into new compounds with high added value, offering a more sustainable solution. The aim of this study was to optimize the extraction process of chitosan and fish gelatin from fishery waste and their revalorization as active biopolymers. We successfully optimized the chitosan extraction process, achieving a yield of 20.45% and a deacetylation degree of 69.25%. For the fish gelatin extraction process, yields of 11.82% for the skin and 2.31% for the bone residues were achieved. In addition, it was demonstrated that simple purification steps using activated carbon improve the gelatin’s quality significantly. Finally, biopolymers based on fish gelatin and chitosan showed excellent bactericidal capabilities against Escherichia coli and Listeria innocua. For this reason, these active biopolymers can stop or decrease bacterial growth in their potential food packaging applications. In view of the low technological transfer and the lack of information about the revalorization of fishery waste, this work offers extraction conditions with good yields that can be easily implemented in the existing industrial fabric, reducing costs and supporting the economic development of the fish processing sector and the creation of value from its waste. Full article
(This article belongs to the Special Issue Recent Advance in Food Gels)
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15 pages, 2492 KiB  
Article
Impact of Apricot Pulp Concentration on Cylindrical Gel 3D Printing
by Carmen Molina-Montero, Adrián Matas, Marta Igual, Javier Martínez-Monzó and Purificación García-Segovia
Gels 2023, 9(3), 253; https://doi.org/10.3390/gels9030253 - 21 Mar 2023
Cited by 1 | Viewed by 1285
Abstract
The process of 3D food printing is a rapidly growing field that involves the use of specialized 3D printers to produce food items with complex shapes and textures. This technology allows the creation of customized, nutritionally balanced meals on demand. The objective of [...] Read more.
The process of 3D food printing is a rapidly growing field that involves the use of specialized 3D printers to produce food items with complex shapes and textures. This technology allows the creation of customized, nutritionally balanced meals on demand. The objective of this study was to evaluate the effect of apricot pulp content on printability. Additionally, the degradation of bioactive compounds of gels before and after printing was evaluated to analyze the effect of the process. For this proposal, physicochemical properties, extrudability, rheology, image analysis, Texture Profile Analysis (TPA), and bioactive compounds content were evaluated. The rheological parameters lead to higher mechanical strength and, thus, a decrease in elastic behavior before and after 3D printing as the pulp content increases. An increase in strength was observed when the pulp content increased; thus, sample gels with 70% apricot pulp were more rigid and presented better buildability (were more stable in their dimensions). On the other hand, a significant (p < 0.05) degradation of total carotenoid content after printing was observed in all samples. From the results obtained, it can be said that the gel with 70% apricot pulp food ink was the best sample in terms of printability and stability. Full article
(This article belongs to the Special Issue Research Progress in Food Gels)
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21 pages, 4208 KiB  
Article
Development and Evaluation of Essential Oil-Based Nanoemulgel Formulation for the Treatment of Oral Bacterial Infections
by Niamat Ullah, Adnan Amin, Arshad Farid, Samy Selim, Sheikh Abdur Rashid, Muhammad Imran Aziz, Sairah Hafeez Kamran, Muzammil Ahmad Khan, Nauman Rahim Khan, Saima Mashal and Muhammad Mohtasheemul Hasan
Gels 2023, 9(3), 252; https://doi.org/10.3390/gels9030252 - 21 Mar 2023
Cited by 6 | Viewed by 3595
Abstract
Prevalence of oral infections in diabetic patients is a health challenge due to persistent hyperglycemia. However, despite great concerns, limited treatment options are available. We therefore aimed to develop nanoemulsion gel (NEG) for oral bacterial infections based on essential oils. Clove and cinnamon [...] Read more.
Prevalence of oral infections in diabetic patients is a health challenge due to persistent hyperglycemia. However, despite great concerns, limited treatment options are available. We therefore aimed to develop nanoemulsion gel (NEG) for oral bacterial infections based on essential oils. Clove and cinnamon essential oils based nanoemulgel were prepared and characterized. Various physicochemical parameters of optimized formulation including viscosity (65311 mPa·S), spreadability (36 g·cm/s), and mucoadhesive strength 42.87 N/cm2) were within prescribed limits. The drug contents of the NEG were 94.38 ± 1.12% (cinnamaldehyde) and 92.96 ± 2.08% (clove oil). A significant concentration of clove (73.9%) and cinnamon essential oil (71.2 %) was released from a polymer matrix of the NEG till 24 h. The ex vivo goat buccal mucosa permeation profile revealed a significant (52.7–54.2%) permeation of major constituents which occurred after 24 h. When subjected to antimicrobial testing, significant inhibition was observed for several clinical strains, namely Staphylococcus aureus (19 mm), Staphylococcus epidermidis (19 mm), and Pseudomonas aeruginosa (4 mm), as well as against Bacillus chungangensis (2 mm), whereas no inhibition was detected for Bacillus paramycoides and Paenibacillus dendritiformis when NEG was utilized. Likewise promising antifungal (Candida albicans) and antiquorum sensing activities were observed. It was therefore concluded that cinnamon and clove oil-based NEG formulation presented significant antibacterial-, antifungal, and antiquorum sensing activities. Full article
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21 pages, 11512 KiB  
Article
Isolation and Staining Reveal the Presence of Extracellular DNA in Marine Gel Particles
by Aisha S. M. Al-Wahaibi, Robert C. Upstill-Goddard and J. Grant Burgess
Gels 2023, 9(3), 251; https://doi.org/10.3390/gels9030251 - 21 Mar 2023
Viewed by 1616
Abstract
Marine gel particles (MGP) are amorphous hydrogel exudates from bacteria and microalgae that are ubiquitous in the oceans, but their biochemical composition and function are poorly understood. While dynamic ecological interactions between marine microorganisms and MGPs may result in the secretion and mixing [...] Read more.
Marine gel particles (MGP) are amorphous hydrogel exudates from bacteria and microalgae that are ubiquitous in the oceans, but their biochemical composition and function are poorly understood. While dynamic ecological interactions between marine microorganisms and MGPs may result in the secretion and mixing of bacterial extracellular polymeric substances (EPS) such as nucleic acids, compositional studies currently are limited to the identification of acidic polysaccharides and proteins in transparent exopolymer particles (TEP) and Coomassie stainable particles (CSP). Previous studies targeted MGPs isolated by filtration. We developed a new way of isolating MGPs from seawater in liquid suspension and applied it to identify extracellular DNA (eDNA) in North Sea surface seawater. Seawater was filtered onto polycarbonate (PC) filters with gentle vacuum filtration, and then the filtered particles were gently resuspended in a smaller volume of sterile seawater. The resulting MGPs ranged in size from 0.4 to 100 µm in diameter. eDNA was detected by fluorescent microscopy using YOYO-1 (for eDNA), with Nile red (targeting cell membranes) as a counterstain. TOTO-3 was also used to stain eDNA, with ConA to localise glycoproteins and SYTO-9 for the live/dead staining of cells. Confocal laser scanning microscopy (CLSM) revealed the presence of proteins and polysaccharides. We found eDNA to be universally associated with MGPs. To further elucidate the role of eDNA, we established a model experimental MGP system using bacterial EPS from Pseudoalteromonas atlantica that also contained eDNA. Our results clearly demonstrate the occurrence of eDNA in MGPs, and should aid furthering our understanding of the micro-scale dynamics and fate of MGPs that underly the large-scale processes of carbon cycling and sedimentation in the ocean. Full article
(This article belongs to the Section Gel Analysis and Characterization)
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22 pages, 4065 KiB  
Review
Recent Progress in Self-Healable Hydrogel-Based Electroluminescent Devices: A Comprehensive Review
by Melkie Getnet Tadesse and Jörn Felix Lübben
Gels 2023, 9(3), 250; https://doi.org/10.3390/gels9030250 - 21 Mar 2023
Cited by 7 | Viewed by 1704
Abstract
Flexible electronics have gained significant research attention in recent years due to their potential applications as smart and functional materials. Typically, electroluminescence devices produced by hydrogel-based materials are among the most notable flexible electronics. With their excellent flexibility and their remarkable electrical, adaptable [...] Read more.
Flexible electronics have gained significant research attention in recent years due to their potential applications as smart and functional materials. Typically, electroluminescence devices produced by hydrogel-based materials are among the most notable flexible electronics. With their excellent flexibility and their remarkable electrical, adaptable mechanical and self-healing properties, functional hydrogels offer a wealth of insights and opportunities for the fabrication of electroluminescent devices that can be easily integrated into wearable electronics for various applications. Various strategies have been developed and adapted to obtain functional hydrogels, and at the same time, high-performance electroluminescent devices have been fabricated based on these functional hydrogels. This review provides a comprehensive overview of various functional hydrogels that have been used for the development of electroluminescent devices. It also highlights some challenges and future research prospects for hydrogel-based electroluminescent devices. Full article
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18 pages, 2081 KiB  
Review
Research Progress of Polysaccharide-Based Natural Polymer Hydrogels in Water Purification
by Wenxu Zhang, Yan Xu, Xuyang Mu, Sijie Li, Xiaoming Liu and Ziqiang Lei
Gels 2023, 9(3), 249; https://doi.org/10.3390/gels9030249 - 20 Mar 2023
Cited by 5 | Viewed by 2060
Abstract
The pollution and scarcity of freshwater resources are global problems that have a significant influence on human life. It is very important to remove harmful substances in the water to realize the recycling of water resources. Hydrogels have recently attracted attention due to [...] Read more.
The pollution and scarcity of freshwater resources are global problems that have a significant influence on human life. It is very important to remove harmful substances in the water to realize the recycling of water resources. Hydrogels have recently attracted attention due to their special three-dimensional network structure, large surface area, and pores, which show great potential for the removal of pollutants in water. In their preparation, natural polymers are one of the preferred materials because of their wide availability, low cost, and easy thermal degradation. However, when it is directly used for adsorption, its performance is unsatisfactory, so it usually needs to be modified in the preparation process. This paper reviews the modification and adsorption properties of polysaccharide-based natural polymer hydrogels, such as cellulose, chitosan, starch, and sodium alginate, and discusses the effects of their types and structures on performance and recent technological advances. Full article
(This article belongs to the Special Issue Synthesis and Applications of Hydrogels)
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17 pages, 9869 KiB  
Article
Synthesis of NVCL-NIPAM Hydrogels Using PEGDMA as a Chemical Crosslinker for Controlled Swelling Behaviours in Potential Shapeshifting Applications
by Billy Shu Hieng Tie, Elaine Halligan, Shuo Zhuo, Gavin Keane and Luke Geever
Gels 2023, 9(3), 248; https://doi.org/10.3390/gels9030248 - 20 Mar 2023
Cited by 2 | Viewed by 1448
Abstract
Stimuli-responsive hydrogels have recently gained interest within shapeshifting applications due to their capabilities to expand in water and their altering swelling properties when triggered by stimuli, such as pH and heat. While conventional hydrogels lose their mechanical strength during swelling, most shapeshifting applications [...] Read more.
Stimuli-responsive hydrogels have recently gained interest within shapeshifting applications due to their capabilities to expand in water and their altering swelling properties when triggered by stimuli, such as pH and heat. While conventional hydrogels lose their mechanical strength during swelling, most shapeshifting applications require materials to have mechanical strength within a satisfactory range to perform specified tasks. Thus, stronger hydrogels are needed for shapeshifting applications. Poly (N-isopropylacrylamide) (PNIPAm) and poly (N-vinyl caprolactam) (PNVCL) are the most popular thermosensitive hydrogels studied. Their close-to-physiological lower critical solution temperature (LCST) makes them superior candidates in biomedicine. In this study, copolymers made of NVCL and NIPAm and chemically crosslinked using poly (ethylene glycol) dimethacrylate (PEGDMA) were fabricated. Successful polymerisation was proven via Fourier transform infrared spectroscopy (FTIR). The effects of incorporating comonomer and crosslinker on the LCST were found minimal using cloud-point measurements, ultraviolet (UV) spectroscopy, and differential scanning calorimetry (DSC). Formulations that completed three cycles of thermo-reversing pulsatile swelling are demonstrated. Lastly, rheological analysis validated the mechanical strength of PNVCL, which was improved due to the incorporation of NIPAm and PEGDMA. This study showcases potential smart thermosensitive NVCL-based copolymers that can be applied in the biomedical shapeshifting area. Full article
(This article belongs to the Special Issue Advances in Responsive Hydrogels)
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26 pages, 6095 KiB  
Article
Advanced Polymeric Membranes as Biomaterials Based on Marine Sources Envisaging the Regeneration of Human Tissues
by Duarte Nuno Carvalho, Flávia C. M. Lobo, Luísa C. Rodrigues, Emanuel M. Fernandes, David S. Williams, Andrew Mearns-Spragg, Carmen G. Sotelo, Ricardo I. Perez-Martín, Rui L. Reis, Michael Gelinsky and Tiago H. Silva
Gels 2023, 9(3), 247; https://doi.org/10.3390/gels9030247 - 20 Mar 2023
Cited by 1 | Viewed by 1916
Abstract
The self-repair capacity of human tissue is limited, motivating the arising of tissue engineering (TE) in building temporary scaffolds that envisage the regeneration of human tissues, including articular cartilage. However, despite the large number of preclinical data available, current therapies are not yet [...] Read more.
The self-repair capacity of human tissue is limited, motivating the arising of tissue engineering (TE) in building temporary scaffolds that envisage the regeneration of human tissues, including articular cartilage. However, despite the large number of preclinical data available, current therapies are not yet capable of fully restoring the entire healthy structure and function on this tissue when significantly damaged. For this reason, new biomaterial approaches are needed, and the present work proposes the development and characterization of innovative polymeric membranes formed by blending marine origin polymers, in a chemical free cross-linking approach, as biomaterials for tissue regeneration. The results confirmed the production of polyelectrolyte complexes molded as membranes, with structural stability resulting from natural intermolecular interactions between the marine biopolymers collagen, chitosan and fucoidan. Furthermore, the polymeric membranes presented adequate swelling ability without compromising cohesiveness (between 300 and 600%), appropriate surface properties, revealing mechanical properties similar to native articular cartilage. From the different formulations studied, the ones performing better were the ones produced with 3 % shark collagen, 3% chitosan and 10% fucoidan, as well as with 5% jellyfish collagen, 3% shark collagen, 3% chitosan and 10% fucoidan. Overall, the novel marine polymeric membranes demonstrated to have promising chemical, and physical properties for tissue engineering approaches, namely as thin biomaterial that can be applied over the damaged articular cartilage aiming its regeneration. Full article
(This article belongs to the Special Issue Biosoursed and Bioinspired Gels for Biomedical Applications)
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24 pages, 5622 KiB  
Article
Study of Hydroxypropyl β-Cyclodextrin and Puerarin Inclusion Complexes Encapsulated in Sodium Alginate-Grafted 2-Acrylamido-2-Methyl-1-Propane Sulfonic Acid Hydrogels for Oral Controlled Drug Delivery
by Abid Naeem, Chengqun Yu, Weifeng Zhu, Zhenzhong Zang and Yongmei Guan
Gels 2023, 9(3), 246; https://doi.org/10.3390/gels9030246 - 20 Mar 2023
Cited by 4 | Viewed by 1816
Abstract
Puerarin has been reported to have anti-inflammatory, antioxidant, immunity enhancement, neuroprotective, cardioprotective, antitumor, and antimicrobial effects. However, due to its poor pharmacokinetic profile (low oral bioavailability, rapid systemic clearance, and short half-life) and physicochemical properties (e.g., low aqueous solubility and poor stability) its [...] Read more.
Puerarin has been reported to have anti-inflammatory, antioxidant, immunity enhancement, neuroprotective, cardioprotective, antitumor, and antimicrobial effects. However, due to its poor pharmacokinetic profile (low oral bioavailability, rapid systemic clearance, and short half-life) and physicochemical properties (e.g., low aqueous solubility and poor stability) its therapeutic efficacy is limited. The hydrophobic nature of puerarin makes it difficult to load into hydrogels. Hence, hydroxypropyl-β-cyclodextrin (HP-βCD)-puerarin inclusion complexes (PIC) were first prepared to enhance solubility and stability; then, they were incorporated into sodium alginate-grafted 2-acrylamido-2-methyl-1-propane sulfonic acid (SA-g-AMPS) hydrogels for controlled drug release in order to increase bioavailability. The puerarin inclusion complexes and hydrogels were evaluated via FTIR, TGA, SEM, XRD, and DSC. Swelling ratio and drug release were both highest at pH 1.2 (36.38% swelling ratio and 86.17% drug release) versus pH 7.4 (27.50% swelling ratio and 73.25% drug release) after 48 h. The hydrogels exhibited high porosity (85%) and biodegradability (10% in 1 week in phosphate buffer saline). In addition, the in vitro antioxidative activity (DPPH (71%), ABTS (75%), and antibacterial activity (Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa) indicated the puerarin inclusion complex-loaded hydrogels had antioxidative and antibacterial capabilities. This study provides a basis for the successful encapsulation of hydrophobic drugs inside hydrogels for controlled drug release and other purposes. Full article
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21 pages, 1303 KiB  
Review
Research Advances on Hydrogel-Based Materials for Tissue Regeneration and Remineralization in Tooth
by Zhijun Zhang, Fei Bi and Weihua Guo
Gels 2023, 9(3), 245; https://doi.org/10.3390/gels9030245 - 20 Mar 2023
Cited by 3 | Viewed by 3060
Abstract
Tissue regeneration and remineralization in teeth is a long-term and complex biological process, including the regeneration of pulp and periodontal tissue, and re-mineralization of dentin, cementum and enamel. Suitable materials are needed to provide cell scaffolds, drug carriers or mineralization in this environment. [...] Read more.
Tissue regeneration and remineralization in teeth is a long-term and complex biological process, including the regeneration of pulp and periodontal tissue, and re-mineralization of dentin, cementum and enamel. Suitable materials are needed to provide cell scaffolds, drug carriers or mineralization in this environment. These materials need to regulate the unique odontogenesis process. Hydrogel-based materials are considered good scaffolds for pulp and periodontal tissue repair in the field of tissue engineering due to their inherent biocompatibility and biodegradability, slow release of drugs, simulation of extracellular matrix, and the ability to provide a mineralized template. The excellent properties of hydrogels make them particularly attractive in the research of tissue regeneration and remineralization in teeth. This paper introduces the latest progress of hydrogel-based materials in pulp and periodontal tissue regeneration and hard tissue mineralization and puts forward prospects for their future application. Overall, this review reveals the application of hydrogel-based materials in tissue regeneration and remineralization in teeth. Full article
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20 pages, 12170 KiB  
Article
Preclinical Potential of Probiotic-Loaded Novel Gelatin–Oil Vaginal Suppositories: Efficacy, Stability, and Safety Studies
by Anchal Bassi, Garima Sharma, Parneet Kaur Deol, Ratna Sudha Madempudi and Indu Pal Kaur
Gels 2023, 9(3), 244; https://doi.org/10.3390/gels9030244 - 19 Mar 2023
Cited by 3 | Viewed by 2143
Abstract
The current study describes a suppository base composed of aqueous gelatin solution emulsifying oil globules with probiotic cells dispersed within. The favorable mechanical properties of gelatin to provide a solid gelled structure, and the tendency of its proteins to unravel into long strings [...] Read more.
The current study describes a suppository base composed of aqueous gelatin solution emulsifying oil globules with probiotic cells dispersed within. The favorable mechanical properties of gelatin to provide a solid gelled structure, and the tendency of its proteins to unravel into long strings that interlace when cooled, lead to a three-dimensional structure that can trap a lot of liquid, which was exploited herein to result in a promising suppository form. The latter maintained incorporated probiotic spores of Bacillus coagulans Unique IS-2 in a viable but non-germinating form, preventing spoilage during storage and imparting protection against the growth of any other contaminating organism (self-preserved formulation). The gelatin–oil–probiotic suppository showed uniformity in weight and probiotic content (23 ± 2.481 × 108 cfu) with favorable swelling (double) followed by erosion and complete dissolution within 6 h of administration, leading to the release of probiotic (within 45 min) from the matrix into simulated vaginal fluid. Microscopic images indicated presence of probiotics and oil globules enmeshed in the gelatin network. High viability (24.3 ± 0.46 × 108), germination upon application and a self-preserving nature were attributed to the optimum water activity (0.593 aw) of the developed composition. The retention of suppositories, germination of probiotics and their in vivo efficacy and safety in vulvovaginal candidiasis murine model are also reported. Full article
(This article belongs to the Special Issue Women’s Special Issue Series: Gels)
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24 pages, 2576 KiB  
Article
Biomanufacturing Recombinantly Expressed Cripto-1 Protein in Anchorage-Dependent Mammalian Cells Growing in Suspension Bioreactors within a Three-Dimensional Hydrogel Microcarrier
by Rachel Lev, Orit Bar-Am, Yoni Lati, Ombretta Guardiola, Gabriella Minchiotti and Dror Seliktar
Gels 2023, 9(3), 243; https://doi.org/10.3390/gels9030243 - 18 Mar 2023
Cited by 1 | Viewed by 1742
Abstract
Biotherapeutic soluble proteins that are recombinantly expressed in mammalian cells can pose a challenge when biomanufacturing in three-dimensional (3D) suspension culture systems. Herein, we tested a 3D hydrogel microcarrier for a suspension culture of HEK293 cells overexpressing recombinant Cripto-1 protein. Cripto-1 is an [...] Read more.
Biotherapeutic soluble proteins that are recombinantly expressed in mammalian cells can pose a challenge when biomanufacturing in three-dimensional (3D) suspension culture systems. Herein, we tested a 3D hydrogel microcarrier for a suspension culture of HEK293 cells overexpressing recombinant Cripto-1 protein. Cripto-1 is an extracellular protein that is involved in developmental processes and has recently been reported to have therapeutic effects in alleviating muscle injury and diseases by regulating muscle regeneration through satellite cell progression toward the myogenic lineage. Cripto-overexpressing HEK293 cell lines were cultured in microcarriers made from poly (ethylene glycol)-fibrinogen (PF) hydrogels, which provided the 3D substrate for cell growth and protein production in stirred bioreactors. The PF microcarriers were designed with sufficient strength to resist hydrodynamic deterioration and biodegradation associated with suspension culture in stirred bioreactors for up to 21 days. The yield of purified Cripto-1 obtained using the 3D PF microcarriers was significantly higher than that obtained with a two-dimensional (2D) culture system. The bioactivity of the 3D-produced Cripto-1 was equivalent to commercially available Cripto-1 in terms of an ELISA binding assay, a muscle cell proliferation assay, and a myogenic differentiation assay. Taken together, these data indicate that 3D microcarriers made from PF can be combined with mammalian cell expression systems to improve the biomanufacturing of protein-based therapeutics for muscle injuries. Full article
(This article belongs to the Special Issue Polymer Networks and Gels 2022)
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15 pages, 5391 KiB  
Article
Kneading-Dough-Inspired Quickly Dispersing of Hydrophobic Particles into Aqueous Solutions for Designing Functional Hydrogels
by Jun Huang, Youqi Wang, Ping Liu, Jinzhi Li, Min Song, Jiuyu Cui, Luxing Wei, Yonggan Yan and Jing Liu
Gels 2023, 9(3), 242; https://doi.org/10.3390/gels9030242 - 18 Mar 2023
Cited by 2 | Viewed by 3364
Abstract
Hydrogels containing hydrophobic materials have attracted great attention for their potential applications in drug delivery and biosensors. This work presents a kneading-dough-inspired method for dispersing hydrophobic particles (HPs) into water. The kneading process can quickly mix HPs with polyethyleneimine (PEI) polymer solution to [...] Read more.
Hydrogels containing hydrophobic materials have attracted great attention for their potential applications in drug delivery and biosensors. This work presents a kneading-dough-inspired method for dispersing hydrophobic particles (HPs) into water. The kneading process can quickly mix HPs with polyethyleneimine (PEI) polymer solution to form “dough”, which facilitates the formation of stable suspensions in aqueous solutions. Combining with photo or thermal curing processes, one type of HPs incorporated PEI-polyacrylamide (PEI/PAM) composite hydrogel exhibiting good self-healing ability, tunable mechanical property is synthesized. The incorporating of HPs into the gel network results in the decrease in the swelling ratio, as well as the enhancement of the compressive modulus by more than five times. Moreover, the stable mechanism of polyethyleneimine-modified particles has been investigated using surface force apparatus, where the pure repulsion during approaching contributes to the good stability of the suspension. The stabilization time of the suspension is dependent on the molecular weight of PEI: the higher the molecular weight is, the better the stability of the suspension will be. Overall, this work demonstrates a useful strategy to introduce HPs into functional hydrogel networks. Future research can be focused on understanding the strengthening mechanism of HPs in the gel networks. Full article
(This article belongs to the Special Issue Synthesis and Applications of Hydrogels)
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14 pages, 6354 KiB  
Article
Thermomechanical Performance Assessment of Sustainable Buildings’ Insulating Materials under Accelerated Ageing Conditions
by Ana Dora Rodrigues Pontinha, Johanna Mäntyneva, Paulo Santos and Luísa Durães
Gels 2023, 9(3), 241; https://doi.org/10.3390/gels9030241 - 18 Mar 2023
Cited by 8 | Viewed by 1594
Abstract
The reliable characterization of insulation materials in relevant environmental conditions is crucial, since it strongly influences the performance (e.g., thermal) of building elements. In fact, their properties may vary with the moisture content, temperature, ageing degradation, etc. Therefore, in this work, the thermomechanical [...] Read more.
The reliable characterization of insulation materials in relevant environmental conditions is crucial, since it strongly influences the performance (e.g., thermal) of building elements. In fact, their properties may vary with the moisture content, temperature, ageing degradation, etc. Therefore, in this work, the thermomechanical behaviour of different materials was compared when subjected to accelerated ageing. Insulation materials that use recycled rubber in their composition were studied, along with others for comparison: heat-pressed rubber, rubber_cork composites, aerogel_rubber composite (developed by the authors), silica aerogel, and extruded polystyrene. The ageing cycles comprised dry-heat, humid-heat, and cold conditions as the stages, during cycles of 3 and 6 weeks. The materials’ properties after ageing were compared with the initial values. Aerogel-based materials showed superinsulation behaviour and good flexibility due to their very high porosity and reinforcement with fibres. Extruded polystyrene also had a low thermal conductivity but exhibited permanent deformation under compression. In general, the ageing conditions led to a very slight increase in the thermal conductivity, which vanished after drying of the samples in an oven, and to a decrease in Young’s moduli. Full article
(This article belongs to the Special Issue Recent Advances in Aerogels)
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14 pages, 691 KiB  
Article
Sol-Gel Films Doped with Enzymes and Banana Crude Extract as Sensing Materials for Spectrophotometric Determination
by Maria A. Morosanova and Elena I. Morosanova
Gels 2023, 9(3), 240; https://doi.org/10.3390/gels9030240 - 18 Mar 2023
Cited by 4 | Viewed by 967
Abstract
Chromogenic enzymatic reactions are very convenient for the determination of various biochemically active compounds. Sol-gel films are a promising platform for biosensor development. The creation of sol-gel films with immobilized enzymes deserves attention as an effective way to create optical biosensors. In the [...] Read more.
Chromogenic enzymatic reactions are very convenient for the determination of various biochemically active compounds. Sol-gel films are a promising platform for biosensor development. The creation of sol-gel films with immobilized enzymes deserves attention as an effective way to create optical biosensors. In the present work, the conditions are selected to obtain sol-gel films doped with horseradish peroxidase (HRP), mushroom tyrosinase (MT) and crude banana extract (BE), inside the polystyrene spectrophotometric cuvettes. Two procedures are proposed: the use of tetraethoxysilane-phenyltriethoxysilane (TEOS-PhTEOS) mixture as precursor, as well as the use of silicon polyethylene glycol (SPG).In both types of films, the enzymatic activity of HRP, MT, and BE is preserved. Based on the kinetics study of enzymatic reactions catalyzed by sol-gel films doped with HRP, MT, and BE, we found that encapsulation in the TEOS-PhTEOS films affects the enzymatic activity to a lesser extent compared to encapsulation in SPG films. Immobilization affects BE significantly less than MT and HRP. The Michaelis constant for BE encapsulated in TEOS-PhTEOS films almost does not differ from the Michaelis constant for a non-immobilized BE. The proposed sol-gel films allow determining hydrogen peroxide in the range of 0.2–3.5 mM (HRP containing film in the presence of TMB), and caffeic acid in the ranges of 0.5–10.0 mM and 2.0–10.0 mM (MT- and BE-containing films, respectively). BE-containing films have been used to determine the total polyphenol content of coffee in caffeic acid equivalents; the results of the analysis are in good agreement with the results obtained using an independent method of determination. These films are highly stable and can be stored without the loss of activity for 2 months at +4 °C and 2 weeks at +25 °C. Full article
(This article belongs to the Special Issue Advances in Xerogels: From Design to Applications)
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18 pages, 3804 KiB  
Review
Polymeric DNA Hydrogels and Their Applications in Drug Delivery for Cancer Therapy
by Jing Li, Wenzhe Song and Feng Li
Gels 2023, 9(3), 239; https://doi.org/10.3390/gels9030239 - 18 Mar 2023
Cited by 9 | Viewed by 2175
Abstract
The biomolecule deoxyribonucleic acid (DNA), which acts as the carrier of genetic information, is also regarded as a block copolymer for the construction of biomaterials. DNA hydrogels, composed of three-dimensional networks of DNA chains, have received considerable attention as a promising biomaterial due [...] Read more.
The biomolecule deoxyribonucleic acid (DNA), which acts as the carrier of genetic information, is also regarded as a block copolymer for the construction of biomaterials. DNA hydrogels, composed of three-dimensional networks of DNA chains, have received considerable attention as a promising biomaterial due to their good biocompatibility and biodegradability. DNA hydrogels with specific functions can be prepared via assembly of various functional sequences containing DNA modules. In recent years, DNA hydrogels have been widely used for drug delivery, particularly in cancer therapy. Benefiting from the sequence programmability and molecular recognition ability of DNA molecules, DNA hydrogels prepared using functional DNA modules can achieve efficient loading of anti-cancer drugs and integration of specific DNA sequences with cancer therapeutic effects, thus achieving targeted drug delivery and controlled drug release, which are conducive to cancer therapy. In this review, we summarized the assembly strategies for the preparation of DNA hydrogels on the basis of branched DNA modules, hybrid chain reaction (HCR)-synthesized DNA networks and rolling circle amplification (RCA)-produced DNA chains, respectively. The application of DNA hydrogels as drug delivery carriers in cancer therapy has been discussed. Finally, the future development directions of DNA hydrogels in cancer therapy are prospected. Full article
(This article belongs to the Special Issue Preparation and Application of DNA Hydrogel)
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18 pages, 11671 KiB  
Article
Molten Salts Approach of Poly(vinyl alcohol)-Derived Bimetallic Nickel–Iron Sheets Supported on Porous Carbon Nanosheet as an Effective and Durable Electrocatalyst for Methanol Oxidation
by Badr M. Thamer, Meera Moydeen Abdul Hameed and Mohamed H. El-Newehy
Gels 2023, 9(3), 238; https://doi.org/10.3390/gels9030238 - 17 Mar 2023
Cited by 2 | Viewed by 1269
Abstract
The preparation of metallic nanostructures supported on porous carbon materials that are facile, green, efficient, and low-cost is desirable to reduce the cost of electrocatalysts, as well as reduce environmental pollutants. In this study, a series of bimetallic nickel–iron sheets supported on porous [...] Read more.
The preparation of metallic nanostructures supported on porous carbon materials that are facile, green, efficient, and low-cost is desirable to reduce the cost of electrocatalysts, as well as reduce environmental pollutants. In this study, a series of bimetallic nickel–iron sheets supported on porous carbon nanosheet (NiFe@PCNs) electrocatalysts were synthesized by molten salt synthesis without using any organic solvent or surfactant through controlled metal precursors. The as-prepared NiFe@PCNs were characterized by scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction, and photoelectron spectroscopy (XRD and XPS). The TEM results indicated the growth of NiFe sheets on porous carbon nanosheets. The XRD analysis confirmed that the Ni1−xFex alloy had a face-centered polycrystalline (fcc) structure with particle sizes ranging from 15.5 to 30.6 nm. The electrochemical tests showed that the catalytic activity and stability were highly dependent on the iron content. The electrocatalytic activity of catalysts for methanol oxidation demonstrated a nonlinear relationship with the iron ratio. The catalyst doped with 10% iron showed a higher activity compared to the pure nickel catalyst. The maximum current density of Ni0.9Fe0.1@PCNs (Ni/Fe ratio 9:1) was 190 mA/cm2 at 1.0 M of methanol. In addition to the high electroactivity, the Ni0.9Fe0.1@PCNs showed great improvement in stability over 1000 s at 0.5 V with a retained activity of 97%. This method can be used to prepare various bimetallic sheets supported on porous carbon nanosheet electrocatalysts. Full article
(This article belongs to the Special Issue Gel Electro-Catalysts)
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17 pages, 3693 KiB  
Article
Study on the Interaction of Plasma-Polymerized Hydrogel Coatings with Aqueous Solutions of Different pH
by Monique Levien, Zahra Nasri, Klaus-Dieter Weltmann and Katja Fricke
Gels 2023, 9(3), 237; https://doi.org/10.3390/gels9030237 - 17 Mar 2023
Cited by 2 | Viewed by 1105
Abstract
Amphiphilic hydrogels from mixtures of 2-hydroxyethyl methacrylate and 2-(diethylamino)ethyl methacrylate p(HEMA-co-DEAEMA) with specific pH sensitivity and hydrophilic/hydrophobic structures were designed and polymerized via plasma polymerization. The behavior of plasma-polymerized (pp) hydrogels containing different ratios of pH-sensitive DEAEMA segments was investigated concerning possible applications [...] Read more.
Amphiphilic hydrogels from mixtures of 2-hydroxyethyl methacrylate and 2-(diethylamino)ethyl methacrylate p(HEMA-co-DEAEMA) with specific pH sensitivity and hydrophilic/hydrophobic structures were designed and polymerized via plasma polymerization. The behavior of plasma-polymerized (pp) hydrogels containing different ratios of pH-sensitive DEAEMA segments was investigated concerning possible applications in bioanalytics. In this regard, the morphological changes, permeability, and stability of the hydrogels immersed in solutions of different pHs were studied. The physico-chemical properties of the pp hydrogel coatings were analyzed using X-ray photoelectron spectroscopy, surface free energy measurements, and atomic force microscopy. Wettability measurements showed an increased hydrophilicity of the pp hydrogels when stored in acidic buffers and a slightly hydrophobic behavior after immersion in alkaline solutions, indicating a pH-dependent behavior. Furthermore, the pp (p(HEMA-co-DEAEMA) (ppHD) hydrogels were deposited on gold electrodes and studied electrochemically to investigate the pH sensitivity of the hydrogels. The hydrogel coatings with a higher ratio of DEAEMA segments showed excellent pH responsiveness at the studied pHs (pH 4, 7, and 10), demonstrating the importance of the DEAEMA ratio in the functionality of pp hydrogel films. Due to their stability and pH-responsive properties, pp (p(HEMA-co-DEAEMA) hydrogels are conceivable candidates for functional and immobilization layers for biosensors. Full article
(This article belongs to the Special Issue Advances in Responsive Hydrogels)
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12 pages, 3007 KiB  
Article
Thermo-Responsive Injectable Hydrogels Formed by Self-Assembly of Alginate-Based Heterograft Copolymers
by Konstantinos Safakas, Sofia-Falia Saravanou, Zacharoula Iatridi and Constantinos Tsitsilianis
Gels 2023, 9(3), 236; https://doi.org/10.3390/gels9030236 - 17 Mar 2023
Cited by 7 | Viewed by 1511
Abstract
Polysaccharide-based graft copolymers bearing thermo-responsive grafting chains, exhibiting LCST, have been designed to afford thermo-responsive injectable hydrogels. The good performance of the hydrogel requires control of the critical gelation temperature, Tgel. In the present article, we wish to show an alternative [...] Read more.
Polysaccharide-based graft copolymers bearing thermo-responsive grafting chains, exhibiting LCST, have been designed to afford thermo-responsive injectable hydrogels. The good performance of the hydrogel requires control of the critical gelation temperature, Tgel. In the present article, we wish to show an alternative method to tune Tgel using an alginate-based thermo-responsive gelator bearing two kinds of grafting chains (heterograft copolymer topology) of P(NIPAM86-co-NtBAM14) random copolymers and pure PNIPAM, differing in their lower critical solution temperature (LCST) about 10 °C. Interestingly, the Tgel of the heterograft copolymer is controlled from the overall hydrophobic content, NtBAM, of both grafts, implying the formation of blended side chains in the crosslinked nanodomains of the formed network. Rheological investigation of the hydrogel showed excellent responsiveness to temperature and shear. Thus, a combination of shear-thinning and thermo-thickening effects provides the hydrogel with injectability and self-healing properties, making it a good candidate for biomedical applications. Full article
(This article belongs to the Special Issue Structured Gels: Mechanics, Responsivity and Applications)
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15 pages, 2456 KiB  
Article
Chain-Extendable Crosslinked Hydrogels Using Branching RAFT Modification
by Stephen Rimmer, Paul Spencer, Davide Nocita, John Sweeney, Marcus Harrison and Thomas Swift
Gels 2023, 9(3), 235; https://doi.org/10.3390/gels9030235 - 17 Mar 2023
Cited by 1 | Viewed by 1626
Abstract
Functional crosslinked hydrogels were prepared from 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA). The acid monomer was incorporated both via copolymerization and chain extension of a branching, reversible addition–fragmentation chain-transfer agent incorporated into the crosslinked polymer gel. The hydrogels were intolerant to high [...] Read more.
Functional crosslinked hydrogels were prepared from 2-hydroxyethyl methacrylate (HEMA) and acrylic acid (AA). The acid monomer was incorporated both via copolymerization and chain extension of a branching, reversible addition–fragmentation chain-transfer agent incorporated into the crosslinked polymer gel. The hydrogels were intolerant to high levels of acidic copolymerization as the acrylic acid weakened the ethylene glycol dimethacrylate (EGDMA) crosslinked network. Hydrogels made from HEMA, EGDMA and a branching RAFT agent provide the network with loose-chain end functionality that can be retained for subsequent chain extension. Traditional methods of surface functionalization have the downside of potentially creating a high volume of homopolymerization in the solution. Branching RAFT comonomers act as versatile anchor sites by which additional polymerization chain extension reactions can be carried out. Acrylic acid grafted onto HEMA–EGDMA hydrogels showed higher mechanical strength than the equivalent statistical copolymer networks and was shown to have functionality as an electrostatic binder of cationic flocculants. Full article
(This article belongs to the Special Issue Preparation, Properties and Applications of Functional Hydrogels)
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21 pages, 3873 KiB  
Article
Anti-Inflammatory Effect and Toxicological Profile of Pulp Residue from the Caryocar Brasiliense, a Sustainable Raw Material
by Julia Amanda Rodrigues Fracasso, Mariana Bittencourt Ibe, Luísa Taynara Silvério da Costa, Lucas Pires Guarnier, Amanda Martins Viel, Gustavo Reis de Brito, Mariana Conti Parron, Anderson Espírito do Santo Pereira, Giovana Sant’Ana Pegorin Brasil, Valdecir Farias Ximenes, Leonardo Fernandes Fraceto, Cassia Roberta Malacrida Mayer, João Tadeu Ribeiro-Paes, Fernando Yutaka de Ferreira, Natália Alves Zoppe and Lucinéia dos Santos
Gels 2023, 9(3), 234; https://doi.org/10.3390/gels9030234 - 16 Mar 2023
Cited by 3 | Viewed by 1908
Abstract
Caryocar brasiliense Cambess is a plant species typical of the Cerrado, a Brazilian biome. The fruit of this species is popularly known as pequi, and its oil is used in traditional medicine. However, an important factor hindering the use of pequi oil is [...] Read more.
Caryocar brasiliense Cambess is a plant species typical of the Cerrado, a Brazilian biome. The fruit of this species is popularly known as pequi, and its oil is used in traditional medicine. However, an important factor hindering the use of pequi oil is its low yield when extracted from the pulp of this fruit. Therefore, in this study, with aim of developing a new herbal medicine, we an-alyzed the toxicity and anti-inflammatory activity of an extract of pequi pulp residue (EPPR), fol-lowing the mechanical extraction of the oil from its pulp. For this purpose, EPPR was prepared and encapsulated in chitosan. The nanoparticles were analyzed, and the cytotoxicity of the encapsu-lated EPPR was evaluated in vitro. After confirming the cytotoxicity of the encapsulated EPPR, the following evaluations were performed with non-encapsulated EPPR: in vitro anti-inflammatory activity, quantification of cytokines, and acute toxicity in vivo. Once the anti-inflammatory activity and absence of toxicity of EPPR were verified, a gel formulation of EPPR was developed for topical use and analyzed for its in vivo anti-inflammatory potential, ocular toxicity, and previous stability assessment. EPPR and the gel containing EPPR showed effective anti-inflammatory activity and lack of toxicity. The formulation was stable. Thus, a new herbal medicine with anti-inflammatory activity can be developed from discarded pequi residue. Full article
(This article belongs to the Special Issue Gels in Medicine and Pharmacological Therapies)
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15 pages, 2410 KiB  
Article
The Effect of Sage (Salvia sclarea) Essential Oil on the Physiochemical and Antioxidant Properties of Sodium Alginate and Casein-Based Composite Edible Films
by Saurabh Bhatia, Ahmed Al-Harrasi, Yasir Abbas Shah, Muhammad Jawad, Mohammed Said Al-Azri, Sana Ullah, Md Khalid Anwer, Mohammed F. Aldawsari, Esra Koca and Levent Yurdaer Aydemir
Gels 2023, 9(3), 233; https://doi.org/10.3390/gels9030233 - 16 Mar 2023
Cited by 13 | Viewed by 2079
Abstract
The aim of this study was to examine the effect of Sage (Salvia sclarea) essential oil (SEO) on the physiochemical and antioxidant properties of sodium alginate (SA) and casein (CA) based films. Thermal, mechanical, optical, structural, chemical, crystalline, and barrier properties [...] Read more.
The aim of this study was to examine the effect of Sage (Salvia sclarea) essential oil (SEO) on the physiochemical and antioxidant properties of sodium alginate (SA) and casein (CA) based films. Thermal, mechanical, optical, structural, chemical, crystalline, and barrier properties were examined using TGA, texture analyzer, colorimeter, SEM, FTIR, and XRD. Chemical compounds of the SEO were identified via GC–MS, the most important of which were linalyl acetate (43.32%) and linalool (28.51%). The results showed that incorporating SEO caused a significant decrease in tensile strength (1.022–0.140 Mpa), elongation at break (28.2–14.6%), moisture content (25.04–14.7%) and transparency (86.1–56.2%); however, WVP (0.427–0.667 × 10−12 g·cm/cm2·s·Pa) increased. SEM analysis showed that the incorporation of SEO increased the homogeneousness of films. TGA analysis showed that SEO-loaded films showed better thermal stability than others. FTIR analysis revealed the compatibility between the components of the films. Furthermore, increasing the concentration of SEO increased the antioxidant activity of the films. Thus, the present film shows a potential application in the food packaging industry. Full article
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