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Gels, Volume 8, Issue 6 (June 2022) – 64 articles

Cover Story (view full-size image): Three-dimensional (3D) printing is an incredibly powerful approach to engineer tissues and organs. The success of such techniques is critically dependent on the printing ink. However, 3D printing fine anatomic structures such as microvascular beds remains notoriously difficult. In this work, therefore, capillary alginate hydrogel (Capgel) biomaterial scaffolds were transformed into a new family of microstructured biomaterial 3D printing inks. The Capgel biomaterial inks extruded as sheared slurries of entangled microgels that each retained the anisotropic array of densely packed parallel capillary microchannels. These novel inks were stackable, and formulations with poly-L-lysine supported human cells and self-adhered through shear-induced fragmentation polyelectrolyte bonding (SIFPeB). View this paper
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17 pages, 2859 KiB  
Article
Unravelling the Supramolecular Driving Forces in the Formation of CO2-Responsive Pseudopeptidic Low-Molecular-Weight Hydrogelators
by Ferran Esteve, Alexis Villanueva-Antolí, Belén Altava, Eduardo García-Verdugo and Santiago V. Luis
Gels 2022, 8(6), 390; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060390 - 20 Jun 2022
Viewed by 1398
Abstract
A new family of C2-symmetric pseudopeptides with a high functional density for supramolecular interactions has been synthetized through the attachment of four amino acid subunits to a diamino aliphatic spacer. The resulting open-chain compounds present remarkable properties as low-molecular-weight hydrogelators. The [...] Read more.
A new family of C2-symmetric pseudopeptides with a high functional density for supramolecular interactions has been synthetized through the attachment of four amino acid subunits to a diamino aliphatic spacer. The resulting open-chain compounds present remarkable properties as low-molecular-weight hydrogelators. The self-assembled 3D networks were characterized by SEM analyses, observing regular nanofibres with 80–100 nm diameters. Spectroscopic and molecular modelling experiments revealed the presence of strong synergic effects between the H-bonding and π–π interactions, with the best results obtained for the homoleptic tetra-pseudopeptide derived from l-Phe. In addition, these bioinspired hydrogels possessed pH- and CO2-responsive sol–gel transitions. The formation of ammonium carbamate derivatives in the presence of carbon dioxide led to a detrimental change in its adequate self-assembly. CO2 desorption temperatures of ca. 70 °C were assigned to the thermodynamically favoured recovery of the supramolecular gel. Full article
(This article belongs to the Special Issue Advances in Stimuli-Responsive Polymer Gels)
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15 pages, 2210 KiB  
Review
Advances of Stimulus-Responsive Hydrogels for Bone Defects Repair in Tissue Engineering
by Shuai Chang, Shaobo Wang, Zhongjun Liu and Xing Wang
Gels 2022, 8(6), 389; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060389 - 20 Jun 2022
Cited by 24 | Viewed by 2844
Abstract
Bone defects, as one of the most urgent problems in the orthopedic clinic, have attracted much attention from the biomedical community and society. Hydrogels have been widely used in the biomedical field for tissue engineering research because of their excellent hydrophilicity, biocompatibility, and [...] Read more.
Bone defects, as one of the most urgent problems in the orthopedic clinic, have attracted much attention from the biomedical community and society. Hydrogels have been widely used in the biomedical field for tissue engineering research because of their excellent hydrophilicity, biocompatibility, and degradability. Stimulus-responsive hydrogels, as a new type of smart biomaterial, have more advantages in sensing external physical (light, temperature, pressure, electric field, magnetic field, etc.), chemical (pH, redox reaction, ions, etc.), biochemical (glucose, enzymes, etc.) and other different stimuli. They can respond to stimuli such as the characteristics of the 3D shape and solid–liquid phase state, and exhibit special properties (injection ability, self-repair, shape memory, etc.), thus becoming an ideal material to provide cell adhesion, proliferation, and differentiation, and achieve precise bone defect repair. This review is focused on the classification, design concepts, and research progress of stimulus-responsive hydrogels based on different types of external environmental stimuli, aiming at introducing new ideas and methods for repairing complex bone defects. Full article
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14 pages, 3542 KiB  
Article
Imidazolium Ionic Liquids as Designer Solvents Confined in Silica Nanopores
by Ana-Maria Putz, Adél Len, László Trif, Zsolt Endre Horváth and László Almásy
Gels 2022, 8(6), 388; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060388 - 19 Jun 2022
Cited by 1 | Viewed by 1807
Abstract
Composite silica xerogels were prepared via acid catalysed sol–gel route using tetraethoxysilan (TEOS) as silica precursor, and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium chloride [BMIM][Cl] ionic liquids, used simultaneously as co-solvents, catalysts and pore templates, at various IL-to-silica ratios. Morphology of the [...] Read more.
Composite silica xerogels were prepared via acid catalysed sol–gel route using tetraethoxysilan (TEOS) as silica precursor, and 1-butyl-3-methylimidazolium tetrafluoroborate [BMIM][BF4] or 1-butyl-3-methylimidazolium chloride [BMIM][Cl] ionic liquids, used simultaneously as co-solvents, catalysts and pore templates, at various IL-to-silica ratios. Morphology of the xerogels prepared using the different IL templating agents were investigated using scanning electron microscopy (SEM), nitrogen sorption and small angle neutron scattering (SANS). The thermal behavior of the composites was analyzed by thermal gravimetry, whereas the compositions were checked by infrared spectroscopy and EDX. The differences in the morphology and thermal behavior of the composites due to the different IL additives were revealed. Full article
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13 pages, 2548 KiB  
Article
Tuning Myogenesis by Controlling Gelatin Hydrogel Properties through Hydrogen Peroxide-Mediated Cross-Linking and Degradation
by Wildan Mubarok, Kelum Chamara Manoj Lakmal Elvitigala and Shinji Sakai
Gels 2022, 8(6), 387; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060387 - 17 Jun 2022
Cited by 8 | Viewed by 2230
Abstract
Engineering skeletal muscle tissue in vitro is important to study the mechanism of myogenesis, which is crucial for regenerating muscle cells. The physicochemical properties of the cellular microenvironment are known to govern various cell behaviours. Yet, most studies utilised synthetic materials to model [...] Read more.
Engineering skeletal muscle tissue in vitro is important to study the mechanism of myogenesis, which is crucial for regenerating muscle cells. The physicochemical properties of the cellular microenvironment are known to govern various cell behaviours. Yet, most studies utilised synthetic materials to model the extracellular matrix that suffers from cytotoxicity to the cells. We have previously reported that the physicochemical property of hydrogels obtained from horseradish peroxidase (HRP)-catalysed cross-linking could be controlled by a simple adjustment to the exposure time to air containing H2O2. In this study, we evaluated the influence of physicochemical properties dynamics in the gelatin possessing phenol groups (Gelatin-Ph) hydrogel to regulate the myogenesis in vitro. We controlled the Young’s modulus of the Gelatin-Ph hydrogel by tuning the air containing 16 ppm H2O2 exposure time for 15–60 min. Additionally, prolonged exposure to air containing H2O2 also induced Gelatin-Ph degradation. Myoblasts showed higher adhesion and myotube formation on stiff hydrogel (3.53 kPa) fabricated through 30 min of exposure to air containing H2O2 compared to those on softer hydrogel (0.77–2.79 kPa) fabricated through 15, 45, and 60 min of the exposure. These results demonstrate that the myogenesis can be tuned by changes in the physicochemical properties of Gelatin-Ph hydrogel mediated by H2O2. Full article
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22 pages, 8408 KiB  
Review
Types and Performances of Polymer Gels for Oil-Gas Drilling and Production: A Review
by Shaofei Lei, Jinsheng Sun, Kaihe Lv, Qitao Zhang and Jingbin Yang
Gels 2022, 8(6), 386; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060386 - 17 Jun 2022
Cited by 20 | Viewed by 3373
Abstract
Polymer gels with suitable viscoelasticity and deformability have been widely used for formation plugging and lost circulation control, profile control, and water shutoff. This article systematically reviews the research progress on the preparation principle, temperature resistance, salt resistance, and mechanical properties of the [...] Read more.
Polymer gels with suitable viscoelasticity and deformability have been widely used for formation plugging and lost circulation control, profile control, and water shutoff. This article systematically reviews the research progress on the preparation principle, temperature resistance, salt resistance, and mechanical properties of the ground and in situ crosslinked polymer gels for oil-gas drilling and production engineering. Then, it comparatively analyzes the applicable conditions of the two types of polymer gel. To expand the application range of polymer gels in response to the harsh formation environments (e.g., high temperature and high salinity), we reviewed strategies for increasing the high temperature resistance, high salt resistance, and rheological/mechanical strengths of polymer gels. This article provides theoretical and technical references for developing and optimizing polymer gels suitable for oil-gas drilling and production. Full article
(This article belongs to the Special Issue Gels for Oil Drilling and Enhanced Recovery)
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16 pages, 4418 KiB  
Article
Design and Development of Neomycin Sulfate Gel Loaded with Solid Lipid Nanoparticles for Buccal Mucosal Wound Healing
by Khaled M. Hosny, N. Raghavendra Naveen, Mallesh Kurakula, Amal M. Sindi, Fahad Y. Sabei, Adel Al Fatease, Abdulmajeed M. Jali, Waleed S. Alharbi, Rayan Y. Mushtaq, Majed Felemban, Hossam H. Tayeb, Eman Alfayez and Waleed Y. Rizg
Gels 2022, 8(6), 385; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060385 - 16 Jun 2022
Cited by 16 | Viewed by 2456
Abstract
Drug administration to the wound site is a potential method for wound healing. The drug retention duration should be extended, and drug permeability through the buccal mucosal layer should be regulated. Oral wounds can be caused by inflammation, ulcers, trauma, or pathological lesions; [...] Read more.
Drug administration to the wound site is a potential method for wound healing. The drug retention duration should be extended, and drug permeability through the buccal mucosal layer should be regulated. Oral wounds can be caused by inflammation, ulcers, trauma, or pathological lesions; if these wounds are not treated properly, they can lead to pain, infection, and subsequent undesirable scarring. This study aimed to develop Kolliphor-407 P-based gel containing neomycin sulfate (NES) loaded in solid lipid nanoparticles (SLNs) and enhance the antimicrobial activity. By considering lipid concentrations and achieving the lowest particle size (Y1) and maximum entrapment (EE-Y2) effectiveness, the formulation of NES-SLN was optimized using the Box–Behnken design. For the selected responses, 17 runs were formulated (as anticipated by the Design-Expert software) and evaluated accordingly. The optimized formulation could achieve a particle size of 196.25 and EE of 89.27% and was further utilized to prepare the gel formulation. The NES-SLN-G formula was discovered to have a smooth, homogeneous structure and good mechanical and rheological properties. After 24 h of treatment, NES-SLN-G showed a regulated in vitro drug release pattern, excellent ex vivo permeability, and increased in vitro antibacterial activity. These findings indicate the potential application of NES-SLN-loaded gels as a promising formulation for buccal mucosal wound healing. Full article
(This article belongs to the Special Issue Recent Research Trends in New Generation Polymer Gels)
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11 pages, 1660 KiB  
Article
Formulation Development and Ex-Vivo Permeability of Curcumin Hydrogels under the Influence of Natural Chemical Enhancers
by Asif Nawaz, Arshad Farid, Muhammad Safdar, Muhammad Shahid Latif, Shakira Ghazanfar, Nosheen Akhtar, Soad K. Al Jaouni, Samy Selim and Muhammad Waseem Khan
Gels 2022, 8(6), 384; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060384 - 16 Jun 2022
Cited by 11 | Viewed by 2047
Abstract
Background: The aim of the present research was to formulate and evaluate curcumin hydrogel and to investigate the potential of natural essential oils as permeation enhancers. Methods: Curcumin 2% w/w hydrogel containing various concentrations of eucalyptus oil, aloe vera oil and [...] Read more.
Background: The aim of the present research was to formulate and evaluate curcumin hydrogel and to investigate the potential of natural essential oils as permeation enhancers. Methods: Curcumin 2% w/w hydrogel containing various concentrations of eucalyptus oil, aloe vera oil and clove oil was developed using carboxy methyl cellulose (CMC) as a gelling agent. Differential scanning calorimetry and Fourier Transform infrared spectroscopy were used to evaluate the compatibility between the drug and the excipients. In order to assess the efficacy of the formulation; rheological properties, skin irritation studies, in vitro release, ex vivo permeation and retention studies were conducted. Results: DSC and FTIR suggest no in-compatibility between curcumin and excipients. Studies proved that addition of suitable natural permeation enhancers to the hydrogels improved the in vitro release and ex vivo permeation and retention of curcumin. From the various natural essential oils, the aloe vera oil at a concentration of 3% w/w had the greatest effect on the permeability rate and skin retention of the Curcumin and produces the highest enhancement ratio amongst all the concentrations of essential oils examined. Conclusion: Aloe vera oil enhances the permeation of curcumin across the skin by altering the complex structure of the stratum corneum without itself undergoing any change. The developed curcumin hydrogels along with natural essential oils may present an effective choice regarding skin infection/wound healing. Full article
(This article belongs to the Special Issue Advanced Hydrogels for Controlled Drug Delivery)
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9 pages, 7110 KiB  
Article
Use of Carbotrace 480 as a Probe for Cellulose and Hydrogel Formation from Defibrillated Microalgae
by Frederik L. Zitzmann, Ewan Ward and Avtar S. Matharu
Gels 2022, 8(6), 383; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060383 - 16 Jun 2022
Cited by 2 | Viewed by 1886
Abstract
Carbotrace 480 is a commercially available fluorescent optotracer that specifically binds to cellulose’s glycosidic linkages. Herein, the use of Carbotrace 480 is reported as an analytical tool for linking cellulose content to hydrogel formation capability in defibrillated celluloses obtained from proprietary microalgae. Defibrillated [...] Read more.
Carbotrace 480 is a commercially available fluorescent optotracer that specifically binds to cellulose’s glycosidic linkages. Herein, the use of Carbotrace 480 is reported as an analytical tool for linking cellulose content to hydrogel formation capability in defibrillated celluloses obtained from proprietary microalgae. Defibrillated celluloses obtained from acid-free hydrothermal microwave processing at low temperature (160 °C) showed poor hydrogel formation attributed to a low cellulose concentration as evidenced through the lack of Carbotrace fluorescence. High temperature (220 °C) processing afforded reasonable gels commensurate with a higher cellulose loading and stronger response to Carbotrace. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels)
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17 pages, 2268 KiB  
Article
RGD-Functionalized Hydrogel Supports the Chondrogenic Commitment of Adipose Mesenchymal Stromal Cells
by Cristina Manferdini, Diego Trucco, Yasmin Saleh, Elena Gabusi, Paolo Dolzani, Enrico Lenzi, Lorenzo Vannozzi, Leonardo Ricotti and Gina Lisignoli
Gels 2022, 8(6), 382; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060382 - 15 Jun 2022
Cited by 9 | Viewed by 6413
Abstract
Articular cartilage is known to have limited intrinsic self-healing capacity when a defect or a degeneration process occurs. Hydrogels represent promising biomaterials for cell encapsulation and injection in cartilage defects by creating an environment that mimics the cartilage extracellular matrix. The aim of [...] Read more.
Articular cartilage is known to have limited intrinsic self-healing capacity when a defect or a degeneration process occurs. Hydrogels represent promising biomaterials for cell encapsulation and injection in cartilage defects by creating an environment that mimics the cartilage extracellular matrix. The aim of this study is the analysis of two different concentrations (1:1 and 1:2) of VitroGel® (VG) hydrogels without (VG-3D) and with arginine-glycine-aspartic acid (RGD) motifs, (VG-RGD), verifying their ability to support chondrogenic differentiation of encapsulated human adipose mesenchymal stromal cells (hASCs). We analyzed the hydrogel properties in terms of rheometric measurements, cell viability, cytotoxicity, and the expression of chondrogenic markers using gene expression, histology, and immunohistochemical tests. We highlighted a shear-thinning behavior of both hydrogels, which showed good injectability. We demonstrated a good morphology and high viability of hASCs in both hydrogels. VG-RGD 1:2 hydrogels were the most effective, both at the gene and protein levels, to support the expression of the typical chondrogenic markers, including collagen type 2, SOX9, aggrecan, glycosaminoglycan, and cartilage oligomeric matrix protein and to decrease the proliferation marker MKI67 and the fibrotic marker collagen type 1. This study demonstrated that both hydrogels, at different concentrations, and the presence of RGD motifs, significantly contributed to the chondrogenic commitment of the laden hASCs. Full article
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17 pages, 4155 KiB  
Article
Photopolymerizable Ionogel with Healable Properties Based on Dioxaborolane Vitrimer Chemistry
by Fengdi Li, Giao T. M. Nguyen, Cédric Vancaeyzeele, Frédéric Vidal and Cédric Plesse
Gels 2022, 8(6), 381; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060381 - 15 Jun 2022
Cited by 5 | Viewed by 2378
Abstract
Ionogels are solid polymer gel networks loaded with ionic liquid (IL) percolating throughout each other, giving rise to ionically conducting solid electrolytes. They combine the mechanical properties of polymer networks with the ionic conductivity, non-volatility, and non-flammability of ILs. In the frame of [...] Read more.
Ionogels are solid polymer gel networks loaded with ionic liquid (IL) percolating throughout each other, giving rise to ionically conducting solid electrolytes. They combine the mechanical properties of polymer networks with the ionic conductivity, non-volatility, and non-flammability of ILs. In the frame of their applications in electrochemical-based flexible electronics, ionogels are usually subjected to repeated deformation, making them susceptible to damage. It appears critical to devise a simple and effective strategy to improve their durability and lifespan by imparting them with healing ability through vitrimer chemistry. In this work, we report the original in situ synthesis of polythioether (PTE)-based vitrimer ionogels using fast photopolymerization through thiol-acrylate Michael addition. PTE-based vitrimer was prepared with a constant amount of the trithiol crosslinker and varied proportions of static dithiol spacers and dynamic chain extender BDB containing dynamic exchangeable boronic ester groups. The dynamic ionogels were prepared using 50 wt% of either 1-Ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl) imide or 1-Ethyl-3-methylimidazolium trifluoromethanesulfonate, both of which were selected for their high ionic conductivity. They are completely amorphous (Tg below −30 °C), suggesting they can be used at low temperatures. They are stretchable with an elongation at break around 60%, soft with Young’s modulus between 0.4 and 0.6 MPa, and they have high ionic conductivities for solid state electrolytes in the order of 10−4 S·cm−1 at room temperature. They display dynamic properties typical of the vitrimer network, such as stress relaxation and healing, retained despite the large quantity of IL. The design concept illustrated in this work further enlarges the library of vitrimer ionogels and could potentially open a new path for the development of more sustainable, flexible electrochemical-based electronics with extended service life through repair or reprocessing. Full article
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11 pages, 3057 KiB  
Article
A Facile Method for Fabricating a Monolithic Mullite Fiber-Reinforced Alumina Aerogel with Excellent Mechanical and Thermal Properties
by Lin Liu, Xiaodong Wang, Ze Zhang, Yixin Shi, Yicheng Zhao, Shiqi Shen, Xiandong Yao and Jun Shen
Gels 2022, 8(6), 380; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060380 - 15 Jun 2022
Cited by 4 | Viewed by 1665
Abstract
Alumina aerogels are considered to have good application prospects in the high-temperature field. In this study, monolithic mullite fiber-reinforced alumina aerogels with excellent mechanical and thermal properties were synthesized via a facile method without the use of any chelating agents. This method successfully [...] Read more.
Alumina aerogels are considered to have good application prospects in the high-temperature field. In this study, monolithic mullite fiber-reinforced alumina aerogels with excellent mechanical and thermal properties were synthesized via a facile method without the use of any chelating agents. This method successfully avoids the introduction of impurities during the use of catalysts and chelating agents while greatly reducing gelation time, and thus helps mullite fibers to uniformly disperse in the sol. The compressive stress at 80% strain of the obtained mullite fiber-reinforced alumina aerogels was as high as 16.04 MPa—426% higher than that of the alumina aerogel without the addition of mullite fibers. Regarding thermal properties, the shrinkage of the mullite fiber-reinforced alumina aerogels (AM) samples was less than 1% after heat treatment at 1300 °C for 2 h. Furthermore, the rear-surface temperature of the AM samples burned by a butane blow torch was only 68 °C. These outstanding properties make AM samples promising for application in thermal insulation materials in high-temperature fields such as aerospace and industrial thermal protection in the future. Full article
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25 pages, 2866 KiB  
Systematic Review
Advances of Engineered Hydrogel Organoids within the Stem Cell Field: A Systematic Review
by Zheng Li, Muxin Yue, Yunsong Liu, Ping Zhang, Jia Qing, Hao Liu and Yongsheng Zhou
Gels 2022, 8(6), 379; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060379 - 15 Jun 2022
Cited by 13 | Viewed by 3377
Abstract
Organoids are novel in vitro cell culture models that enable stem cells (including pluripotent stem cells and adult stem cells) to grow and undergo self-organization within a three-dimensional microenvironment during the process of differentiation into target tissues. Such miniature structures not only recapitulate [...] Read more.
Organoids are novel in vitro cell culture models that enable stem cells (including pluripotent stem cells and adult stem cells) to grow and undergo self-organization within a three-dimensional microenvironment during the process of differentiation into target tissues. Such miniature structures not only recapitulate the histological and genetic characteristics of organs in vivo, but also form tissues with the capacity for self-renewal and further differentiation. Recent advances in biomaterial technology, particularly hydrogels, have provided opportunities to improve organoid cultures; by closely integrating the mechanical and chemical properties of the extracellular matrix microenvironment, with novel synthetic materials and stem cell biology. This systematic review critically examines recent advances in various strategies and techniques utilized for stem-cell-derived organoid culture, with particular emphasis on the application potential of hydrogel technology in organoid culture. We hope this will give a better understanding of organoid cultures for modelling diseases and tissue engineering applications. Full article
(This article belongs to the Collection Hydrogel in Tissue Engineering and Regenerative Medicine)
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18 pages, 3827 KiB  
Article
The Study of Amidoxime-Functionalized Cellulose Separate Th(IV) from Aqueous Solution
by Yiling Zhi, Guojian Duan, Zhiwei Lei, Hui Chen, Haobo Zhang, Huining Tian and Tonghuan Liu
Gels 2022, 8(6), 378; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060378 - 15 Jun 2022
Cited by 5 | Viewed by 1747
Abstract
Selective extraction of low-concentration thorium (Th(IV)) from wastewater is a very important research topic. In this paper, amidoxime cellulose was synthesized, and its composition and structure were characterized by FT-IR, SEM, XPS, and elemental analysis. The adsorption experiment results showed that the adsorption [...] Read more.
Selective extraction of low-concentration thorium (Th(IV)) from wastewater is a very important research topic. In this paper, amidoxime cellulose was synthesized, and its composition and structure were characterized by FT-IR, SEM, XPS, and elemental analysis. The adsorption experiment results showed that the adsorption reaction was a spontaneous exothermic process. When the solid–liquid ratio was 0.12 g/L and the pH value was 3.5, the adsorption percentage of the Th(IV) in water onto amidoxime-functionalized cellulose (AO-CELL) could reach over 80%. The maximum adsorption capacity can reach to 450 mg/g. At the same time, the adsorption selectivity, desorption process and reusability of the material were also studied. The results showed that the AO-CELL had a good selectivity for Th(IV) in the system with Sr2+, Cu2+, Mg2+, Zn2+, Pb2+, Ni2+, and Co2+ as co-ions. In the nitric acid concentration of 0.06 mol/L system, the AO-CELL desorption rate of Th(IV) can reach 95%, and the adsorption rate of Th(IV) in aqueous solution of AO-CELL is still above 60% when the AO-CELL is reused four times. The above results show that the amidoxime cellulose adsorption material synthesized by our research group has good selective adsorption performance for Th(IV) of a low concentration in an aqueous solution and has a good practical application value. Full article
(This article belongs to the Special Issue Recent Research Trends in New Generation Polymer Gels)
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17 pages, 4709 KiB  
Article
Emulsion Gels as Precursors for Porous Silicones and All-Polymer Composites—A Proof of Concept Based on Siloxane Stabilizers
by Carmen Racles, Adrian Bele, Ana-Lavinia Vasiliu and Liviu Sacarescu
Gels 2022, 8(6), 377; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060377 - 14 Jun 2022
Cited by 3 | Viewed by 1671
Abstract
In spite of its versatility, the emulsion templating method is rather uncommon for the preparation of porous silicones. In this contribution, two siloxane-containing stabilizers, designed to be soluble in polar (water) and non-polar (toluene) solvents, respectively, were used in low concentrations to produce [...] Read more.
In spite of its versatility, the emulsion templating method is rather uncommon for the preparation of porous silicones. In this contribution, two siloxane-containing stabilizers, designed to be soluble in polar (water) and non-polar (toluene) solvents, respectively, were used in low concentrations to produce stable emulsions, wherein polysiloxane gels were obtained by UV-photoinitiated thiol-ene click cross-linking. The stabilizers exhibited negative interfacial tension, as measured by Wilhelmy plate tensiometry. The emulsion gels evolved into porous silicones (xerogels), with tunable morphology and properties. According to TEM and SEM investigations, the emulsion template was preserved in the final materials. Several parameters (e.g., the structure of the polysiloxane precursors, composition of the emulsion gels, nature of the continuous phase, cross-linking conditions, or additives) can be varied in order to obtain porous elastic materials with desired properties, such as Janus membranes, absorbent monoliths, all-polymer porous composites, or silicone-swollen gels. The feasibility of these types of materials was tested, and exemplary porous silicones were briefly characterized by contact angle measurements, mechanical testing, and absorption tests. The proposed method is simple, fast, and economic, uses very little amounts of stabilizers, and can be adjusted as a green technique. In this contribution, all the silicon-based materials with a convenient design were prepared in house. Full article
(This article belongs to the Special Issue Dynamics of Gels and Its Applications)
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15 pages, 3162 KiB  
Article
Transforming Capillary Alginate Gel (Capgel) into New 3D-Printing Biomaterial Inks
by Andrew Philip Panarello, Corey Edward Seavey, Mona Doshi, Andrew K. Dickerson, Thomas J. Kean and Bradley Jay Willenberg
Gels 2022, 8(6), 376; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060376 - 14 Jun 2022
Cited by 4 | Viewed by 2768
Abstract
Three-dimensional (3D) printing has great potential for creating tissues and organs to meet shortfalls in transplant supply, and biomaterial inks are key components of many such approaches. There is a need for biomaterial inks that facilitate integration, infiltration, and vascularization of targeted 3D-printed [...] Read more.
Three-dimensional (3D) printing has great potential for creating tissues and organs to meet shortfalls in transplant supply, and biomaterial inks are key components of many such approaches. There is a need for biomaterial inks that facilitate integration, infiltration, and vascularization of targeted 3D-printed structures. This study is therefore focused on creating new biomaterial inks from self-assembled capillary alginate gel (Capgel), which possesses a unique microstructure of uniform tubular channels with tunable diameters and densities. First, extrusions of Capgel through needles (0.1–0.8 mm inner diameter) were investigated. It was found that Capgel ink extrudes as slurries of fractured and entangled particles, each retaining capillary microstructures, and that extruded line widths W and particle sizes A were both functions of needle inner diameter D, specifically power-law relationships of W~D0.42 and A~D1.52, respectively. Next, various structures were successfully 3D-printed with Capgel ink, thus demonstrating that this biomaterial ink is stackable and self-supporting. To increase ink self-adherence, Capgel was coated with poly-L-lysine (PLL) to create a cationic “skin” prior to extrusion. It was hypothesized that, during extrusion of Capgel-PLL, the sheared particles fracture and thereby expose cryptic sites of negatively-charged biomaterial capable of forming new polyelectrolyte bonds with areas of the positively-charged PLL skin on neighboring entangled particles. This novel approach resulted in continuous, self-adherent extrusions that remained intact in solution. Human lung fibroblasts (HLFs) were then cultured on this ink to investigate biocompatibility. HLFs readily colonized Capgel-PLL ink and were strongly oriented by the capillary microstructures. This is the first description of successful 3D-printing with Capgel biomaterial ink as well as the first demonstration of the concept and formulation of a self-adherent Capgel-PLL biomaterial ink. Full article
(This article belongs to the Special Issue Functional Transformations in Polymer Gels)
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17 pages, 7296 KiB  
Article
A Novel Numerical Model of Gelant Inaccessible Pore Volume for In Situ Gel Treatment
by Jianqiao Leng, Xindi Sun, Mingzhen Wei and Baojun Bai
Gels 2022, 8(6), 375; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060375 - 13 Jun 2022
Cited by 2 | Viewed by 1337
Abstract
Inaccessible pore volume (IAPV) can have an important impact on the placement of gelant during in situ gel treatment for conformance control. Previously, IAPV was considered to be a constant factor in simulators, yet it lacked dynamic characterization. This paper proposes a numerical [...] Read more.
Inaccessible pore volume (IAPV) can have an important impact on the placement of gelant during in situ gel treatment for conformance control. Previously, IAPV was considered to be a constant factor in simulators, yet it lacked dynamic characterization. This paper proposes a numerical simulation model of IAPV. The model was derived based on the theoretical hydrodynamic model of gelant molecules. The model considers both static features, such as gelant and formation properties, and dynamic features, such as gelant rheology and retention. To validate our model, we collected IAPV from 64 experiments and the results showed that our model fit moderately into these lab results, which proved the robustness of our model. The results of the sensitivity test showed that, considering rheology and retention, IAPV in the matrix dramatically increased when flow velocity and gelant concentration increased, but IAPV in the fracture maintained a low value. Finally, the results of the penetration degree showed that the high IAPV in the matrix greatly benefited gelant placement near the wellbore situation with a high flow velocity and gelant concentration. By considering dynamic features, this new numerical model can be applied in future integral reservoir simulators to better predict the gelant placement of in situ gel treatment for conformance control. Full article
(This article belongs to the Special Issue Gels for Oil Drilling and Enhanced Recovery)
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11 pages, 7825 KiB  
Article
Smart Antifreeze Hydrogels with Abundant Hydrogen Bonding for Conductive Flexible Sensors
by Bailin Dai, Ting Cui, Yue Xu, Shaoji Wu, Youwei Li, Wu Wang, Sihua Liu, Jianxin Tang and Li Tang
Gels 2022, 8(6), 374; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060374 - 13 Jun 2022
Cited by 11 | Viewed by 2413
Abstract
Recently, flexible sensors based on conductive hydrogels have been widely used in human health monitoring, human movement detection and soft robotics due to their excellent flexibility, high water content, good biocompatibility. However, traditional conductive hydrogels tend to freeze and lose their flexibility at [...] Read more.
Recently, flexible sensors based on conductive hydrogels have been widely used in human health monitoring, human movement detection and soft robotics due to their excellent flexibility, high water content, good biocompatibility. However, traditional conductive hydrogels tend to freeze and lose their flexibility at low temperature, which greatly limits their application in a low temperature environment. Herein, according to the mechanism that multi−hydrogen bonds can inhibit ice crystal formation by forming hydrogen bonds with water molecules, we used butanediol (BD) and N−hydroxyethyl acrylamide (HEAA) monomer with a multi−hydrogen bond structure to construct LiCl/p(HEAA−co−BD) conductive hydrogel with antifreeze property. The results indicated that the prepared LiCl/p(HEAA−co−BD) conductive hydrogel showed excellent antifreeze property with a low freeze point of −85.6 °C. Therefore, even at −40 °C, the hydrogel can still stretch up to 400% with a tensile stress of ~450 KPa. Moreover, the hydrogel exhibited repeatable adhesion property (~30 KPa), which was attributed to the existence of multiple hydrogen bonds. Furthermore, a simple flexible sensor was fabricated by using LiCl/p(HEAA−co−BD) conductive hydrogel to detect compression and stretching responses. The sensor had excellent sensitivity and could monitor human body movement. Full article
(This article belongs to the Special Issue Advances in Smart and Tough Hydrogels)
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19 pages, 9579 KiB  
Article
Identification of Gas Channeling and Construction of a Gel-Enhanced Foam Plugging System for Oxygen-Reduced Air Flooding in the Changqing Oilfield
by Tengfei Wang, Liangliang Wang, Haoliang Qin, Cong Zhao, Zongxian Bai and Xingbang Meng
Gels 2022, 8(6), 373; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060373 - 13 Jun 2022
Cited by 5 | Viewed by 1731
Abstract
The accurate identification of gas channeling channels during foam-assisted oxygen-reduced air flooding (FAORAF) and the analysis of the main controlling factors are essential to propose reasonable and effective countermeasures to enhance oil recovery (EOR). However, there are few comprehensive studies on identifying gas [...] Read more.
The accurate identification of gas channeling channels during foam-assisted oxygen-reduced air flooding (FAORAF) and the analysis of the main controlling factors are essential to propose reasonable and effective countermeasures to enhance oil recovery (EOR). However, there are few comprehensive studies on identifying gas channeling channels, the influencing factors, and the corresponding plugging EOR systems in FAORAF. The channeling channels of the injection and production wells of the Changqing Oilfield, China, under varying development schemes are identified utilizing fuzzy membership function theory in this work to obtain their primary distribution. The characteristics and influence factors of gas channeling channels are analyzed by numerical simulation using CMG. The recovery performance of each foam blocking system is evaluated by twin-tube sand pack models. As well, based on the features of reservoir fractures, a new gel-enhanced foam plugging system is developed. The results show that channeling channels chiefly develop along NE 60–70° and that foam could reduce gas channeling. Natural and artificial fractures are the principal factors causing gas channeling, followed by the injection method and gas injection rate. Under the premise of the injection and migration efficiency, the optimal gel system is a 0.1% HPAM + 0.1% organic chromium crosslinking agent. The addition of gel increases the viscosity of the liquid phase and strengthens the mechanical strength of the foam liquid film. At a permeability ratio of 12, the recovery factors of the binary plugging systems composed of microspheres, PEG, and gel combined with foam are 40.89%, 45.85%, and 53.33%, respectively. The movable gel foam system has a short breaking time (only 18 days) and a recovery factor of about 40% at a permeability ratio of 20. To be suitable for oil reservoirs with microfractures, an improved ternary gel foam system—0.1% HPAM + 0.1% chromium crosslinking agent + 0.05–0.1% nano-SiO2—is developed. Compared with the binary gel foam system, the recovery rate of the new nano-SiO2 gel foam system after 15 days of ageing using the core splitting test is 25.24% during the FAORAF process, increasing by 12.38%. Full article
(This article belongs to the Special Issue Gels for Oil Drilling and Enhanced Recovery)
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9 pages, 2122 KiB  
Article
Polyaniline Functionalized Peptide Self-Assembled Conductive Hydrogel for 3D Cell Culture
by Jieling Li, Yan Xue, Anhe Wang, Shaonan Tian, Qi Li and Shuo Bai
Gels 2022, 8(6), 372; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060372 - 13 Jun 2022
Cited by 5 | Viewed by 2326
Abstract
The functionalization of self-assembled peptide hydrogel is of great importance to broaden its applications in the field of biomedicine. In this work, conductive hydrogel is fabricated by introducing conductive polymer polyaniline into peptide self-assembled hydrogel. Compared with pure peptide formed hydrogel, the conductive [...] Read more.
The functionalization of self-assembled peptide hydrogel is of great importance to broaden its applications in the field of biomedicine. In this work, conductive hydrogel is fabricated by introducing conductive polymer polyaniline into peptide self-assembled hydrogel. Compared with pure peptide formed hydrogel, the conductive hydrogel exhibits enhanced conductivity, mechanical property and stability. In addition, the hydrogel is tested to be of great injectability and 3D bio-printability and could support the viability of encapsulated cells that are sensitive to electrical signals. It should have great application prospects in the preparation of tissue engineering scaffolds. Full article
(This article belongs to the Special Issue Advance in Supramolecular Gels)
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21 pages, 6955 KiB  
Article
Enhanced Oil Recovery Mechanism and Technical Boundary of Gel Foam Profile Control System for Heterogeneous Reservoirs in Changqing
by Liang-Liang Wang, Teng-Fei Wang, Jie-Xiang Wang, Hai-Tong Tian, Yi Chen and Wei Song
Gels 2022, 8(6), 371; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060371 - 12 Jun 2022
Cited by 13 | Viewed by 1786
Abstract
The gel plugging and flooding system has a long history of being researched and applied, but the Changqing reservoir geological characteristics are complex, and the synergistic performance of the composite gel foam plugging system is not fully understood, resulting in poor field application. [...] Read more.
The gel plugging and flooding system has a long history of being researched and applied, but the Changqing reservoir geological characteristics are complex, and the synergistic performance of the composite gel foam plugging system is not fully understood, resulting in poor field application. Additionally, the technique boundary chart of the heterogeneous reservoir plugging system has hardly appeared. In this work, reservoir models of porous, fracture, and pore-fracture were constructed, a composite gel foam plugging system was developed, and its static injection and dynamic profile control and oil displacement performance were evaluated. Finally, combined with the experimental studies, a technical boundary chart of plugging systems for heterogeneous reservoirs is proposed. The research results show that the adsorption effect of microspheres (WQ-100) on the surface of elastic gel particles-1 (PEG-1) is more potent than that of pre-crosslinked particle gel (PPG) and the deposition is mainly on the surface of PPG. The adsorption effect of PEG-1 on the surface of PPG is not apparent, primarily manifested as deposition stacking. The gel was synthesized with 0.2% hydrolyzed polyacrylamide (HPAM) + 0.2% organic chromium cross-linking agent, and the strength of enhanced gel with WQ-100 was higher than that of PEG-1 and PPG. The comprehensive value of WQ-100 reinforced foam is greater than that of PEG-1, and PPG reinforced foam, and the enhanced foam with gel has a thick liquid film and poor foaming effect. For the heterogeneous porous reservoir with the permeability of 5/100 mD, the enhanced foam with WQ-100 shows better performance in plugging control and flooding, and the recovery factor increases by 28.05%. The improved foam with gel enhances the fluid flow diversion ability and the recovery factor of fractured reservoirs with fracture widths of 50 μm and 180 μm increases by 29.41% and 24.39%, respectively. For pore-fractured reservoirs with a permeability of 52/167 mD, the PEG + WQ-100 microsphere and enhanced foam with WQ-100 systems show better plugging and recovering performance, and the recovery factor increases are 20.52% and 17.08%, 24.44%, and 21.43%, respectively. The smaller the particle size of the prefabricated gel, the more uniform the adsorption on the foam liquid film and the stronger the stability of the foam system. The plugging performance of the composite gel system is stronger than that of the enhanced gel with foam, but the oil displacement performance of the gel-enhanced foam is better than that of the composite gel system due to the “plug-flooding-integrated” feature of the foam. Combined with the plugging and flooding performance of each plugging system, a technique boundary chart for the plugging system was established for the coexisting porous, fracture, and pore-fracture heterogeneous reservoirs in Changqing Oilfield. Full article
(This article belongs to the Special Issue Gels for Oil and Gas Industry Applications)
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22 pages, 48757 KiB  
Article
Gel Polymer Electrolytes with Mixture of Triazolium Ionic Liquids and Propylene Carbonate
by Aneta Lewandowska, Piotr Gajewski, Katarzyna Szcześniak and Agnieszka Marcinkowska
Gels 2022, 8(6), 370; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060370 - 12 Jun 2022
Viewed by 2098
Abstract
This study is focused on the structural influence of 1,2,4-triazolium ionic liquid (IL), that is, the effect of the length of the substituent and the type of substitution (1-methyl-4-alkyl or 1-alkyl-4-methyl) used in the mixture with propylene carbonate (PC) on the properties of [...] Read more.
This study is focused on the structural influence of 1,2,4-triazolium ionic liquid (IL), that is, the effect of the length of the substituent and the type of substitution (1-methyl-4-alkyl or 1-alkyl-4-methyl) used in the mixture with propylene carbonate (PC) on the properties of thiol–ene polymer ionogels and on the preparation of an ionogel with satisfactory mechanical and conductive properties. PC allows for higher conductivity but also causes electrolyte leakage from the gel. When using triazolium IL (instead of the imidazolium one), because of the stronger interactions between components of the system, the ionogels do not leak. In this study, 1,4-dialkyl-1,2,4-triazolium ILs were successfully synthesized by the alkylation of 1,2,4-triazole. Subsequently, gel polymer electrolytes were obtained by one-pot thiol–ene photopolymerization reactions of tetrafunctional thiols with different chemical structures: pentaerythritol tetra(3-mercaptopropionate) (PETMP) or pentaerythritol tetra(3-mercaptobutyrate) (PETMB) and trifunctional ene (TATT) in the presence of a mixture of 1,4-dialkyl-1,2,4-triazolium IL with PC. Measurements made by electrochemical impedance spectroscopy showed that all ionogels with TATT+PETMB as a polymer matrix presented smaller relative ionic conductivity compared to ionogels containing TATT+PETMP. The puncture resistance and elongation at puncture, measured by the puncture resistance method, were higher for ionogels with poly(TATT+PETMB) than for those with poly(TATT+PETMP). Moreover, ILs containing a methyl group in position N1 of the 1,2,4-triazole ring presented lower puncture resistance than ionogels with ILs containing a methyl group in position N4, especially for shorter alkyl chains. Additionally, the photo-differential scanning calorimetry method was employed to characterize the course of photopolymerization. The compositions and their constituents were characterized by UV and IR spectroscopy. Full article
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14 pages, 1799 KiB  
Article
Development of β-Cyclodextrin/Konjac-Based Emulsion Gel for a Pork Backfat Substitute in Emulsion-Type Sausage
by Yea-Ji Kim, Dong-Min Shin, Jong-Hyeok Yune, Hyun-Su Jung, Hyuk-Cheol Kwon, Kyung-Woo Lee, Jae-Wook Oh, Beob-Gyun Kim and Sung-Gu Han
Gels 2022, 8(6), 369; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060369 - 11 Jun 2022
Cited by 8 | Viewed by 2247
Abstract
Emulsion gel has been used to replace animal fats in meat products. Konjac is a widely used gelling agent; however, its low emulsion stability limits its use in meat products. This study aimed to examine the quality characteristics of β-cyclodextrin (CD)-supplemented konjac-based emulsion [...] Read more.
Emulsion gel has been used to replace animal fats in meat products. Konjac is a widely used gelling agent; however, its low emulsion stability limits its use in meat products. This study aimed to examine the quality characteristics of β-cyclodextrin (CD)-supplemented konjac-based emulsion gel (KEG) (CD-KEG) and its application as a fat substitute in emulsion-type sausages. The supplementation of CD increased hydrogen bonds and hydrophobic interactions with konjac and oil in the gels, respectively. Additionally, CD increased the structural complexity and strength of KEG. Since adding more than 6% of CD to KEG did not increase the gel strength, 6% CD-added KEG was adopted to substitute for pork backfat in manufacturing low-fat emulsion-type sausages. The following formulations of the sausages were prepared: pork backfat 20% (PF20); pork backfat 10% + KEG 10% (KEG10); KEG 20% (KEG20); pork backfat 10% + CD-KEG 10% (CD-KEG10); CD-KEG 20% (CD-KEG20); and pork backfat 5% (PF5). The CD-KEG20 formulation exhibited higher viscosity and viscoelasticity than KEG20, which suggested that CD improves the rheological properties and the thermal stability of meat batter. Additionally, CD-KEG20 showed similar emulsion stability, cooking yield and texture parameters compared with PF20. Therefore, 6% CD-added KEG is a suitable fat substitute for preparing low-fat emulsion-type sausages. Full article
(This article belongs to the Special Issue Novel Gels for Food Product Development)
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17 pages, 5528 KiB  
Article
Solidification of Gelatine Hydrogels by Using a Cryoplatform and Its Validation through CFD Approaches
by Yasir Beeran Pottathara, Miha Jordan, Timi Gomboc, Blaž Kamenik, Boštjan Vihar, Vanja Kokol and Matej Zadravec
Gels 2022, 8(6), 368; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060368 - 10 Jun 2022
Cited by 2 | Viewed by 1915
Abstract
In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to [...] Read more.
In this work, we developed a numerical approach based on an experimental platform to determine the working conditions on a cryoplatform and to predict and evaluate the cryogenic printing of hydrogels. Although hydrogels have good biocompatibility, their material properties make it difficult to print them with high precision and shape fidelity. To overcome these problems, a cryogenic cooling platform was introduced to accelerate the physical stabilisation of each deposited layer during the printing process. By precisely controlling solidification (crystallisation), each printed material can withstand its own weight to maintain shape fidelity, and the porosity of the scaffolds can also be controlled more selectively. The thermophysical properties of gelatine hydrogels were investigated to gain a better understanding of the phase change upon freezing. The corresponding material properties and experimental observations of gelatine solidification served as the basis for developing a computational fluid model (CFD) to mimic the solidification of gelatine hydrogels using a cryoplatform at different process conditions and extruder speeds. The goal was to develop a tool simple enough to predict acceptable process conditions for printing gelatine hydrogels using a cryoplatform. Full article
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20 pages, 5101 KiB  
Article
Facile Fabrication of Transparent and Opaque Albumin Methacryloyl Gels with Highly Improved Mechanical Properties and Controlled Pore Structures
by Mengdie Xu, Nabila Mehwish and Bae Hoon Lee
Gels 2022, 8(6), 367; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060367 - 10 Jun 2022
Cited by 9 | Viewed by 2167
Abstract
For porous protein scaffolds to be employed in tissue-engineered structures, the development of cost-effective, macroporous, and mechanically improved protein-based hydrogels, without compromising the original properties of native protein, is crucial. Here, we introduced a facile method of albumin methacryloyl transparent hydrogels and opaque [...] Read more.
For porous protein scaffolds to be employed in tissue-engineered structures, the development of cost-effective, macroporous, and mechanically improved protein-based hydrogels, without compromising the original properties of native protein, is crucial. Here, we introduced a facile method of albumin methacryloyl transparent hydrogels and opaque cryogels with adjustable porosity and improved mechanical characteristics via controlling polymerization temperatures (room temperature and −80 °C). The structural, morphological, mechanical, and physical characteristics of both porous albumin methacryloyl biomaterials were investigated using FTIR, CD, SEM, XRD, compression tests, TGA, and swelling behavior. The biodegradation and biocompatibility of the various gels were also carefully examined. Albumin methacryloyl opaque cryogels outperformed their counterpart transparent hydrogels in terms of mechanical characteristics and interconnecting macropores. Both materials demonstrated high mineralization potential as well as good cell compatibility. The solvation and phase separation owing to ice crystal formation during polymerization are attributed to the transparency of hydrogels and opacity of cryogels, respectively, suggesting that two fully protein-based hydrogels could be used as visible detectors/sensors in medical devices or bone regeneration scaffolds in the future. Full article
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14 pages, 4668 KiB  
Article
Synthesis and Hydrogelation of Star-Shaped Graft Copolypetides with Asymmetric Topology
by Thi Ha My Phan, Yu-Hsun Yang, Yi-Jen Tsai, Fang-Yu Chung, Tooru Ooya, Shiho Kawasaki and Jeng-Shiung Jan
Gels 2022, 8(6), 366; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060366 - 09 Jun 2022
Cited by 1 | Viewed by 1795
Abstract
To study the self-assembly and hydrogel formation of the star-shaped graft copolypeptides with asymmetric topology, star-shaped poly(L-lysine) with various arm numbers were synthesized by using asymmetric polyglycerol dendrimers (PGDs) as the initiators and 1,1,3,3-tetramethylguanidine (TMG) as an activator for OH groups, [...] Read more.
To study the self-assembly and hydrogel formation of the star-shaped graft copolypeptides with asymmetric topology, star-shaped poly(L-lysine) with various arm numbers were synthesized by using asymmetric polyglycerol dendrimers (PGDs) as the initiators and 1,1,3,3-tetramethylguanidine (TMG) as an activator for OH groups, followed by deprotection and grafting with indole or phenyl group on the side chain. The packing of the grafting moiety via non-covalent interactions not only facilitated the polypeptide segments to adopt more ordered conformations but also triggered the spontaneous hydrogelation. The hydrogelation ability was found to be correlated with polypeptide composition and topology. The star-shaped polypeptides with asymmetric topology exhibited poorer hydrogelation ability than those with symmetric topology due to the less efficient packing of the grafted moiety. The star-shaped polypeptides grafted with indole group on the side chain exhibited better hydrogelation ability than those grafted with phenyl group with the same arm number. This report demonstrated that the grafted moiety and polypeptide topology possessed the potential ability to modulate the polypeptide hydrogelation and hydrogel characteristics. Full article
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18 pages, 3981 KiB  
Article
Gelatin Nanoparticles for Targeted Dual Drug Release out of Alginate-di-Aldehyde-Gelatin Gels
by Sophie Schrade, Lucas Ritschl, Regine Süss, Pia Schilling and Michael Seidenstuecker
Gels 2022, 8(6), 365; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060365 - 08 Jun 2022
Cited by 6 | Viewed by 2189
Abstract
The aim of the present work was to develop a dual staged drug release of an antibiotic (clindamycin) and a growth factor: bone morphogenetic protein-2 (BMP-2) from a biodegradable system consisting of hydrogel and gelatin nanoparticles (GNP). Two-step de-solvation allowed us to prepare [...] Read more.
The aim of the present work was to develop a dual staged drug release of an antibiotic (clindamycin) and a growth factor: bone morphogenetic protein-2 (BMP-2) from a biodegradable system consisting of hydrogel and gelatin nanoparticles (GNP). Two-step de-solvation allowed us to prepare GNPs (~100 nm) as drug carriers. Fluorescein isothiocyanate (FITC)-conjugated protein A was used as a model substance for BMP-2. A 28-day release experiment was performed to determine the release kinetics from GNP for both FITC-protein A and BMP-2, and for clindamycin (CLI) from the hydrogel. The size, structure, and overall morphology of GNP samples (empty, loaded with FITC-protein A and BMP-2) were examined using an environmental scanning electron microscope (ESEM). Cell culture assays (Live/dead; cell proliferation; cytotoxicity) were performed with MG-63 cells and BMP-2-loaded GNPs. Drug release experiments using clindamycin-loaded alginate-di-aldehyde (ADA) gelatin gels containing the drug-loaded GNPs were performed for 28 days. The resulting GNPs showed an empty size of 117 ± 29 nm, 176 ± 15 nm and 216 ± 36 nm when containing 2% FITC-protein A and 1% BMP-2, respectively. No negative effects of BMP-2-loaded GNPs on MG-63 cells were observed in live/dead staining. In the proliferation assay, an increase in cell proliferation was observed for both GNPs (GNP + BMP-2 and controls). The cytotoxicity assay continuously showed very low cytotoxicity for GNPs (empty; loaded). Clindamycin release showed a concentration of 25-fold higher than the minimum inhibitory concentration (MIC) against Staphylococcus aureus throughout the 28 day period. BMP-2 showed a reduced burst release and a steady release (~2 µg/mL) over a 28 day period. Full article
(This article belongs to the Special Issue Bioceramics, Bioglasses and Gels for Tissue Engineering)
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29 pages, 5239 KiB  
Review
Advances in Cellulose-Based Hydrogels for Biomedical Engineering: A Review Summary
by Pengfei Zou, Jiaxin Yao, Ya-Nan Cui, Te Zhao, Junwei Che, Meiyan Yang, Zhiping Li and Chunsheng Gao
Gels 2022, 8(6), 364; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060364 - 08 Jun 2022
Cited by 23 | Viewed by 3979
Abstract
In recent years, hydrogel-based research in biomedical engineering has attracted more attention. Cellulose-based hydrogels have become a research hotspot in the field of functional materials because of their outstanding characteristics such as excellent flexibility, stimulus-response, biocompatibility, and degradability. In addition, cellulose-based hydrogel materials [...] Read more.
In recent years, hydrogel-based research in biomedical engineering has attracted more attention. Cellulose-based hydrogels have become a research hotspot in the field of functional materials because of their outstanding characteristics such as excellent flexibility, stimulus-response, biocompatibility, and degradability. In addition, cellulose-based hydrogel materials exhibit excellent mechanical properties and designable functions through different preparation methods and structure designs, demonstrating huge development potential. In this review, we have systematically summarized sources and types of cellulose and the formation mechanism of the hydrogel. We have reviewed and discussed the recent progress in the development of cellulose-based hydrogels and introduced their applications such as ionic conduction, thermal insulation, and drug delivery. Also, we analyzed and highlighted the trends and opportunities for the further development of cellulose-based hydrogels as emerging materials in the future. Full article
(This article belongs to the Special Issue Advances in Cellulose-Based Hydrogels)
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24 pages, 5835 KiB  
Article
Plasticizers and Salt Concentrations Effects on Polymer Gel Electrolytes Based on Poly (Methyl Methacrylate) for Electrochemical Applications
by Carmen Rizzuto, Dale C. Teeters, Riccardo C. Barberi and Marco Castriota
Gels 2022, 8(6), 363; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060363 - 08 Jun 2022
Cited by 10 | Viewed by 2305
Abstract
This work describes the electrochemical properties of a type of PMMA-based gel polymer electrolytes (GPEs). The gel polymer electrolyte systems at a concentration of (20:80) % w/w were prepared from poly (methyl methacrylate), lithium perchlorate LiClO4 and single plasticizer propylene [...] Read more.
This work describes the electrochemical properties of a type of PMMA-based gel polymer electrolytes (GPEs). The gel polymer electrolyte systems at a concentration of (20:80) % w/w were prepared from poly (methyl methacrylate), lithium perchlorate LiClO4 and single plasticizer propylene carbonate (PMMA-Li-PC) and a mixture of plasticizers made by propylene carbonate and ethylene carbonate in molar ratio 1:1, (PMMA-Li-PC-EC). Different salt concentrations (0.1 M, 0.5 M, 1 M, 2 M) were studied. The effect of different plasticizers (single and mixed) on the properties of gel polymer electrolytes were considered. The variation of conductivity versus salt concentration, thermal properties using DSC and TGA, anodic stability and FTIR spectroscopy were used in this study. The maximum ionic conductivity of σ = 0.031 S/cm were obtained for PMMA-Li-PC-EC with a salt concentration equal to 1 M. Ion-pairing phenomena and all ion associations were observed between lithium cations, plasticizers and host polymers through FTIR spectroscopy. The anodic stability of the PMMA-based gel polymer electrolytes was recorded up to 4 V. The glass temperatures of these electrolytes were estimated. We found they were dependent on the plasticization effect of plasticizers on the polymer chains and the increase of the salt concentration. Unexpectedly, it was determined that an unreacted PMMA monomer was present in the system, which appears to enhance ion conduction. The presence and possibly the addition of a monomer may be a technique for increasing ion conduction in other gel systems that warrants further study. Full article
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15 pages, 7099 KiB  
Article
New Insights and Experimental Investigation of High-Temperature Gel Reinforced by Nano-SiO2
by Hongbin Guo, Jijiang Ge, Longjie Li, Guoliang Zhang, Ziwei Li, Wenhui Wang and Mingjia Liu
Gels 2022, 8(6), 362; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060362 - 08 Jun 2022
Cited by 4 | Viewed by 1581
Abstract
The properties of a reinforced gel with partially hydrolyzed polyacrylamide (HPAM) as the main agent, water-soluble phenolic resin (WSPR) as the crosslinker, and nano-SiO2 as the stabilizer were evaluated in terms of gelation time, gel strength and thermal stability under the conditions [...] Read more.
The properties of a reinforced gel with partially hydrolyzed polyacrylamide (HPAM) as the main agent, water-soluble phenolic resin (WSPR) as the crosslinker, and nano-SiO2 as the stabilizer were evaluated in terms of gelation time, gel strength and thermal stability under the conditions of 110 °C and 12.124 g/L salinity in water. The results showed that the gelation time of the gel with high strength was adjustable from 3 to 23 h, remaining stable for more than 180 days under stratigraphic conditions, although with a certain degree of early dehydration in the gel. Cryo-scanning electron microscopy (cryo-SEM) and dynamic light scattering (DLS) analysis revealed that nano-SiO2 improves the dispersion of the polymer in water, resulting in a more homogeneous structure of the formed gel and thus improving the strength of the gels. In addition, rheological tests and cryo-SEM showed that the interaction between nano-SiO2 and the polymer could inhibit the degradation of polymer to a certain extent and improve the thermal stability of the gel. However, the oxidative degradation of the gel is still the main cause of early dehydration of water-soluble phenolic resin gel, and the addition of a small amount of hydroquinone to the gelants can significantly improve the antioxidative degradation properties of phenolic resin gel. Full article
(This article belongs to the Special Issue Colorful Gels)
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17 pages, 4167 KiB  
Review
Recent Studies on Hydrogels Based on H2O2-Responsive Moieties: Mechanism, Preparation and Application
by Weihua Song, Jipeng You, Yuangong Zhang, Qi Yang, Jin Jiao and Hailei Zhang
Gels 2022, 8(6), 361; https://0-doi-org.brum.beds.ac.uk/10.3390/gels8060361 - 08 Jun 2022
Cited by 7 | Viewed by 2325
Abstract
H2O2 is essential for cellular processes and plays a vital role in the regulation of cell signaling pathways, which can be viewed as a warning signal for many kinds of disease including cancer, cardiovascular disease, reproductive abnormalities, diabetes, and renal [...] Read more.
H2O2 is essential for cellular processes and plays a vital role in the regulation of cell signaling pathways, which can be viewed as a warning signal for many kinds of disease including cancer, cardiovascular disease, reproductive abnormalities, diabetes, and renal failure. A H2O2-responsive hydrogel (H2O2-Gel) is a promising candidate for biomedical applications because of its good biocompatibility, similarity to soft biological tissues, ease of preparation, and its ability to respond to H2O2. In this study, the H2O2-responsive moieties used to fabricate H2O2-Gels were reviewed, including thioethers, disulfide bonds, selenides, diselenium bonds, diketones, boronic, and others. Next, the preparation method of H2O2-Gel was divided into two major categories according to their reaction mechanisms: either self-crosslinking or mechanisms entailing the addition of difunctional crosslinkers. Last, the applications of H2O2-Gels were emphasized, which have been viewed as desirable candidates in the fields of drug delivery, the detection of H2O2, glucose-responsive systems, ROS scavengers, tissue engineering, and cell-encapsulation. Full article
(This article belongs to the Special Issue Advances in Stimuli-Responsive Polymer Gels)
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