Gels

28 pages, 4433 KB

Open AccessArticle

Injectable Arnebia Euchroma Polysaccharide-Based Hydrogel as CpG Oligonucleotide Delivery System with Dual Immunomodulatory Activities

by Chenxiang Xiao, Man Zhang, Mu Dan, Yaru Hu, Peng Zhao, Sarangowa Ochir, Wenming Bai and Surina Bo

Gels 2026, 12(8), 703; https://doi.org/10.3390/gels12080703 - 5 Aug 2026

Abstract

This study developed novel immunostimulatory hydrogels composed of aldehyde-modified Arnebia euchroma polysaccharide (oxidized ARP, O-ARP) and gelatin (GE) for oligonucleotide delivery. Structural characterization of three O-ARP derivatives with varying degrees of oxidation confirmed reduced molecular weight, a preserved yet altered molar ratio of [...] Read more.

This study developed novel immunostimulatory hydrogels composed of aldehyde-modified Arnebia euchroma polysaccharide (oxidized ARP, O-ARP) and gelatin (GE) for oligonucleotide delivery. Structural characterization of three O-ARP derivatives with varying degrees of oxidation confirmed reduced molecular weight, a preserved yet altered molar ratio of monosaccharide composition, and triple-helical conformation. Hydrogels (GE-O1, GE-O2, GE-O3) were formed via a Schiff base reaction between aldehyde and amino groups. Molecular dynamics simulations showed that O-ARP and gelatin can form a stable three-dimensional (3D) network via hydrogen bonding and van der Waals interactions. In vitro studies demonstrated that both the O1-ARP derivative and GE-O1 hydrogel significantly improved RAW 264.7 macrophage viability, phagocytosis, NO production, and pro-inflammatory cytokine secretion, including IL-6, IL-1β, and TNF-α. The cationic GE-O1 hydrogel efficiently loaded anionic CpG oligonucleotides (CpG-ODN 1862) via electrostatic interaction, forming GE-O1-CpG complexes and promoting cellular uptake. Importantly, the GE-O1-CpG complex exhibited superior immunomodulatory effects compared with either GE-O1 or CpG alone, indicating a synergistic dual immunostimulatory response. In vivo studies confirmed the biosafety of GE-O1-CpG. Using OVA as a model antigen, GE-O1-CpG/OVA enhanced both humoral and cellular immune responses. These findings support GE-O1-CpG hydrogels as potential system for combined immunomodulation and nucleotide delivery. Full article

(This article belongs to the Section Gel Applications)

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31 pages, 13810 KB

Open AccessArticle

Preparation and Performance Evaluation of a Lost-Circulation-Control Gel for Fractured Formations

by Yundong Zheng, Xiaojiang Qiu, Zhaocai Yu, Fan Xiao, Tianan Deng, Peng Xu, Lei Pu and Jingwei Liu

Gels 2026, 12(8), 702; https://doi.org/10.3390/gels12080702 - 5 Aug 2026

Abstract

To address the dual challenges of severe lost circulation and wellbore instability in fractured formations, an acrylamide-based lost-circulation-control gel (DF-PG) was synthesized via aqueous-solution free radical polymerization using acrylamide (AM) and sodium acrylate (SA) as monomers, N,N′-methylenebisacrylamide (MBA) as a crosslinker, and ammonium [...] Read more.

To address the dual challenges of severe lost circulation and wellbore instability in fractured formations, an acrylamide-based lost-circulation-control gel (DF-PG) was synthesized via aqueous-solution free radical polymerization using acrylamide (AM) and sodium acrylate (SA) as monomers, N,N′-methylenebisacrylamide (MBA) as a crosslinker, and ammonium persulfate (APS) as an initiator. The optimal formulation was determined as 6.8% AM, 1.7% SA (mass ratio 4:1), 0.09% MBA, and 0.18% APS, reacted at 60 °C for 4 h. The gel achieves a 276% equilibrium swelling ratio in 20,000 mg/L simulated-formation water, with a compressive strength of 1.2 MPa and temperature resistance up to 120 °C. For fractured cores with 0.5–2.0 mm fracture widths, its sealing efficiency exceeds 95% with breakthrough pressure above 1.2 MPa, and the sealing-efficiency-retention rate remains over 85% after 72 h of scouring. DF-PG realizes the integrated functions of lost circulation control and wellbore stabilization through an “infiltration-swelling-filling“ mechanism, providing a novel technical solution for drilling operations in fractured formations. Full article

(This article belongs to the Topic Functional Materials and Interfaces for Sustainable Technology Development)

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28 pages, 1506 KB

Open AccessReview

Mechanically Active Contractile Hydrogels for Skin Wound Repair

by Shang Chen, Shengkai Yu, Jiashuo Fan and Hua Zhang

Gels 2026, 12(8), 701; https://doi.org/10.3390/gels12080701 - 5 Aug 2026

Abstract

Polymer hydrogels have been widely explored for wound repair, yet conventional designs remain passive barriers with limited mechanical intervention. Contractile hydrogels address this gap by undergoing network densification and macroscopic shrinkage, which can be converted into wound-edge traction through interfacial adhesion. This review [...] Read more.

Polymer hydrogels have been widely explored for wound repair, yet conventional designs remain passive barriers with limited mechanical intervention. Contractile hydrogels address this gap by undergoing network densification and macroscopic shrinkage, which can be converted into wound-edge traction through interfacial adhesion. This review classifies contractile hydrogels into temperature-responsive, pH-regulated, intermolecular-interaction-driven, and solvent-mediated systems according to their dominant contraction mechanisms. The transduction of contraction-derived mechanical cues into biochemical signals is discussed across tissue, cellular, and molecular scales, with emphasis on the well-supported integrin/focal adhesion kinase (FAK)-associated focal adhesion pathway and mechanosensitive ion channels. Current applications in acute full-thickness defects, infected and diabetic chronic wounds, surgical incisions, and scar control are critically surveyed. Finally, key challenges pertaining to force transmission efficiency, spatiotemporal controllability, biosafety, and clinical translatability are discussed. This review aims to provide design guidelines for the rational development of contractile hydrogel platforms for advanced wound management. Full article

(This article belongs to the Special Issue Advances in Functional Gel (4th Edition))

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21 pages, 10544 KB

Open AccessArticle

Preparation of Biomass-Based Iron-Containing Microspheres from Rice Straw: Enhancing the Water Absorption Performance of Slow-Release Fertilizer

by Chonghao Zhu, Tianhao Fang, Peiyao Na, Huiqing Li, Chenghai Liu, Xianzhe Zheng, Guoxiang Zheng and Shengming Zhang

Gels 2026, 12(8), 700; https://doi.org/10.3390/gels12080700 - 5 Aug 2026

Abstract

Reintroducing crop straw into soil boosts organic matter, but natural crop straw usually shows low nutrient content. To enhance the water absorption rate of a certain thin sheet-shaped iron-containing material, a technical approach combining ball milling, the Mannich reaction, Schiff’s base cross-linking, emulsion [...] Read more.

Reintroducing crop straw into soil boosts organic matter, but natural crop straw usually shows low nutrient content. To enhance the water absorption rate of a certain thin sheet-shaped iron-containing material, a technical approach combining ball milling, the Mannich reaction, Schiff’s base cross-linking, emulsion separation, and solid–liquid adsorption was attempted to prepare iron-containing microspheres using sodium alginate and rice straw as raw materials. This approach increased the content of the trace nutrient iron and improved the water absorption rate. The results indicated that the iron-containing microspheres exhibit a diameter ranging from approximately 15 μm, an iron content of 10.44%, and a water absorption rate of 501.76%. The release rates of iron and nitrogen in soil and water within the first day were all below 15%, while the release rates after 30 days in soil were 61.8% for iron and 44.32% for nitrogen, and the corresponding rates in water were 73.1% for iron and 63.88% for nitrogen. The water absorption capacity of the iron-containing microspheres showed a trend associated with particle size and pore structure parameters. The development of iron-containing microspheres has expanded the preparation technology for semi-interpenetrating structure type sustained-release materials, and holds the potential for further development into slow-release fertilizers. Full article

(This article belongs to the Section Gel Analysis and Characterization)

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21 pages, 12439 KB

Open AccessArticle

Soluble Chenopodin–Alginate and Chenopodin–Chitosan Nanocomplexes as Building Blocks for Food Emulsion Gels

by Tatiana Isabel Romo, Gonzalo G. Palazolo, Jorge R. Wagner, Lilian Abugoch and Cristian Tapia

Gels 2026, 12(8), 699; https://doi.org/10.3390/gels12080699 - 5 Aug 2026

Abstract

This study evaluates the network-forming and gelation capabilities of quinoa protein (QP) nanocomplexes formed with alginate (QP–Al) and chitosan (QP–C) for the development of structured food emulsion gels and their application in reduced-fat food dressings. Rheological and nanometric characterisation revealed that QP–C complexes [...] Read more.

This study evaluates the network-forming and gelation capabilities of quinoa protein (QP) nanocomplexes formed with alginate (QP–Al) and chitosan (QP–C) for the development of structured food emulsion gels and their application in reduced-fat food dressings. Rheological and nanometric characterisation revealed that QP–C complexes exhibited strong shear-thinning behaviour and particle-size instability with increasing concentration, indicating the breakdown of an organised internal network at rest. Conversely, QP–Al showed Newtonian behaviour, smaller particle sizes (~100–250 nm) and high surface charge stability. Upon oil incorporation, the chitosan-based systems underwent an abrupt, concentration-dependent transition from a liquid-like state to a solid-like gel network between 1.2% and 1.6% w/v chitosan. The EQP–C8 gel network exhibited severe structural fragility, degrading into a purely viscous fluid over 28 days. Conversely, the alginate-based system (EQP–AL8) formed a weak physical hydrogel network characterised by a progressive build-up of structure that resisted creaming and maintained structural integrity across temperature changes. EQP–AL8 was successfully used to develop a plant-based, reduced-fat dressing with high organoleptic acceptance; 98% of participants were willing to purchase the product. These findings demonstrate that QP–AL8 provides a clean-label technological path to designing tunable, highly stable food emulsion gels. Full article

(This article belongs to the Special Issue Gels in Food Systems: Ingredients for Health, Sustainability and Industrial Innovation)

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30 pages, 11499 KB

Open AccessArticle

Dynamic Perfusion and Cell Seeding Density Govern Remodeling and Mechanical Maturation of Bioprinted Collagen Constructs

by Denisa Kaňoková, Jana Matějková, Martin Otáhal, Jan Žigmond, Nina Skalová, Margit Žaloudková, Monika Šupová and Roman Matějka

Gels 2026, 12(8), 698; https://doi.org/10.3390/gels12080698 - 5 Aug 2026

Abstract

Hydrogel-based three-dimensional culture systems are widely used in tissue engineering; however, their maturation is often limited under static conditions. This study investigates the combined effects of dynamic perfusion and initial cell seeding density on remodeling behavior and mechanical properties of bioprinted collagen hydrogel [...] Read more.

Hydrogel-based three-dimensional culture systems are widely used in tissue engineering; however, their maturation is often limited under static conditions. This study investigates the combined effects of dynamic perfusion and initial cell seeding density on remodeling behavior and mechanical properties of bioprinted collagen hydrogel constructs, with additional assessment of smooth muscle cell-like (SMC) differentiation. Rectangular constructs (30 × 15 × 1.5 mm) were fabricated using high-concentration collagen (30 mg/mL) with cell densities of 10 and 20 million cells/mL. MCDB- and DMEM-based media were first compared using growth curves, leading to the selection of MCDB differentiation medium for subsequent experiments. Constructs were then cultured statically or under dynamic perfusion (20 mL/min) for up to 7 days. Remodeling was evaluated by monitoring changes in construct dimensions over time. Static constructs exhibited non-uniform deformation and rolling, whereas dynamically perfused samples retained their geometry and underwent homogeneous contraction. Mechanical testing revealed a transition from stiff and brittle to more compliant and ductile behavior, with preserved load-bearing capacity at large strains. Remodeling and mechanical outcomes were strongly influenced by cell density and culture medium, with differentiation conditions promoting more stable constructs. These changes were accompanied by increased expression of smooth muscle–related markers under dynamic culture. Overall, dynamic perfusion and cell seeding density jointly govern remodeling and mechanical maturation of bioprinted collagen constructs, highlighting their importance for functional hydrogel-based tissue development. Full article

(This article belongs to the Special Issue Hydrogel for Tissue Regeneration (2nd Edition))

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15 pages, 12650 KB

Open AccessArticle

Multiple Dynamic Covalent Bond Crosslinked Ionic Liquids-Based Hydrogel with Stretchable, Rapid Self-Healing and Antibacterial Activity Properties

by Ailing Zhang, Xuepeng Wang, Shufen Hou, Guoqing Sui, Kaoxue Li, Shuhua Cao and Panpan Sun

Gels 2026, 12(8), 697; https://doi.org/10.3390/gels12080697 - 4 Aug 2026

Abstract

The development of antibacterial hydrogel with stretchable and self-healing properties is an urgent problem in the field of biomedical engineering. Herein, a series of hydrogels with antibacterial activity was successfully fabricated using polyvinyl alcohol (PVA), borax, 4-formylphenyl-β-D-allopyranoside (HLC), 3,3′-dithiobis (propionohydrazide) (DPH) [...] Read more.

The development of antibacterial hydrogel with stretchable and self-healing properties is an urgent problem in the field of biomedical engineering. Herein, a series of hydrogels with antibacterial activity was successfully fabricated using polyvinyl alcohol (PVA), borax, 4-formylphenyl-β-D-allopyranoside (HLC), 3,3′-dithiobis (propionohydrazide) (DPH) and ionic liquid, 1-aminopropyl-3-methylimidazolium bromide (C₃MimNBr). The hydrogels were formed via in situ crosslinking through multiple dynamic covalent bonds, primarily including borate ester bonds, imine bonds and acylhydrazone bonds. A Field Emission Scanning Electron Microscope (FE-SEM) revealed that the formed hydrogels possessed a typical three-dimensional network structure. Notably, the interpenetrating network structure endowed the hydrogels with excellent stretchability and self-healing capability, as demonstrated by their ability to be molded into various shapes and stretched up to five times their original length. Furthermore, the mechanical properties of the hydrogel were affected by the amount of the ionic liquid added. Antibacterial evaluation using the colony counting method showed that the hydrogels exhibited outstanding antibacterial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli). In summary, the multifunctional hydrogels, with favorable stretchability and antibacterial activity, represent promising alternative materials for biomedical engineering applications. Full article

(This article belongs to the Special Issue Properties and Structure of Hydrogel-Related Materials (3rd Edition))

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33 pages, 1877 KB

Open AccessArticle

Amphiphilic Emulgels Loaded with Pomegranate Carbon Dots and Rosemary Oil for Metabolic pH Monitoring

by Hebat-Allah S. Tohamy and Ilaria Cacciotti

Gels 2026, 12(8), 696; https://doi.org/10.3390/gels12080696 - 4 Aug 2026

Abstract

The development of sustainable, smart food packaging materials that simultaneously provide antimicrobial protection and real-time monitoring of food quality is a critical frontier in food safety. This study reports the fabrication of a multifunctional amphiphilic emulgel designed for the detection of pathogen-induced metabolic [...] Read more.

The development of sustainable, smart food packaging materials that simultaneously provide antimicrobial protection and real-time monitoring of food quality is a critical frontier in food safety. This study reports the fabrication of a multifunctional amphiphilic emulgel designed for the detection of pathogen-induced metabolic pH changes in food systems. The system utilizes Pomegranate-derived nitrogen-doped quasi-spherical carbon dots (QS-CDs) as fluorescent nanoprobes and Rosemary Essential Oil (REO) as a natural antimicrobial agent, both encapsulated within a polyelectrolyte complex of chitosan and sugarcane bagasse-derived carboxymethyl cellulose (CMC). A low degree of substitution (DS = 0.4) was specifically engineered for the CMC to ensure an amphiphilic character, enabling nanocomposite complex stabilization of the REO droplets without synthetic surfactants. Structural characterization via Transmission Electron Microscopy (TEM) revealed well-dispersed QS-CDs (4.71–6.62 nm) and stable oil droplets (~605.49 nm) anchored within a zipped polymer network. Thermal analysis (TGA/DSC) using the Coats–Redfern model revealed a significant synergistic effect: the smart-emulgel exhibits a distinct two-stage degradation profile, with the high-temperature stage requiring an activation energy (E_a) of 95.19 kJ/mol, a substantial increase over the corresponding stage in the CD-emulgel baseline (18.69 kJ/mol). This enhanced stability is complemented by a slight increase in crystallinity (X_c from 0.11 to 0.14). While the smart-emulgel remains predominantly amorphous, this shift suggests that the integration of REO and QS-CDs into the polymer network promotes the formation of localized, more ordered domains, contributing to a more robust and structurally integrated matrix. The emulgel demonstrated a dual-mode optical response (colorimetric and fluorometric) sensitive to the metabolic byproducts (e.g., organic acids, amines, other alkaline compounds) produced by Escherichia coli and Staphylococcus aureus. These findings were corroborated by Density Functional Theory (DFT) calculations, which confirmed the thermodynamic stability and optimized electronic energy gaps for pH-responsive sensing. This research provides a green, high-performance platform for the real-time monitoring of food freshness and the prevention of foodborne illnesses. Full article

(This article belongs to the Section Gel Analysis and Characterization)

47 pages, 2334 KB

Open AccessReview

Programmable Hydrogels for Surgical Interface Control: Function-Based Design, DNA-Based Molecular Modules, and Translational Evaluation

by Hyun Jung Koh, Jin-Oh Jeong and Hoon Choi

Gels 2026, 12(8), 695; https://doi.org/10.3390/gels12080695 - 4 Aug 2026

Abstract

Surgical procedures create dynamic interfaces between tissues, fluids, gases, and applied materials. Failure to control these interfaces can cause leakage, postoperative adhesion, scar tethering, poor tissue integration, maladaptive host responses, or loss of mechanical support. Hydrogels are attractive surgical materials because their hydrated [...] Read more.

Surgical procedures create dynamic interfaces between tissues, fluids, gases, and applied materials. Failure to control these interfaces can cause leakage, postoperative adhesion, scar tethering, poor tissue integration, maladaptive host responses, or loss of mechanical support. Hydrogels are attractive surgical materials because their hydrated polymer networks can be engineered for wet-tissue conformity, adhesion, transport, degradation, mechanical compatibility, and local biological activity. However, many hydrogel systems are still evaluated by polymer chemistry, stimulus type, or isolated physicochemical properties rather than by the operative function required at a defined surgical boundary. This narrative review proposes a function-based framework for designing and evaluating programmable hydrogels in surgical-interface control. Four principal functions—sealing, separation, protection, and integration/reinforcement—are linked to dominant failure modes, design priorities, endpoints, and comparator requirements. Hemostatic and other biological activities are treated as primary clinical claims or adjunct programs when they support these interface functions. Responsiveness is distinguished from clinically meaningful programmability using five operational criteria: input relevance, encoded transition, baseline and off-target stability, interface-level output, and matched-control comparison. DNA-based hydrogels are discussed as molecular modules for recognition, assembly, crosslinking, degradation, actuation, and release, mainly within mechanically robust hybrid systems. This framework emphasizes time-resolved, function-specific evaluation under procedure-relevant conditions. Full article

(This article belongs to the Special Issue Innovations in Application of Biofunctional Hydrogels)

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21 pages, 2990 KB

Open AccessArticle

Fabrication and Performance Evaluation of Multi-Stimuli-Responsive Hydrogels Constructed from Hyperbranched Skeletons

by Xue Wang, Jun Wang, Gen Li, Yang Zhao, Zhihua Guo and Keliang Wang

Gels 2026, 12(8), 694; https://doi.org/10.3390/gels12080694 - 4 Aug 2026

Abstract

Long-lasting, high-strength plugging materials are required for deep profile control in low-permeability fractured reservoirs. In this study, a series of hyperbranched copolymer hydrogels was prepared through an aza-Michael addition-amidation-one-pot end-group coupling strategy. Linear alkylamines were used as cores to synthesize amino-terminated generation 1.0 [...] Read more.

Long-lasting, high-strength plugging materials are required for deep profile control in low-permeability fractured reservoirs. In this study, a series of hyperbranched copolymer hydrogels was prepared through an aza-Michael addition-amidation-one-pot end-group coupling strategy. Linear alkylamines were used as cores to synthesize amino-terminated generation 1.0 G broom-shaped hyperbranched macromolecular backbones via a divergent route. The resulting backbones were subsequently crosslinked with linear α,ω-diepoxy-terminated poly(ethylene glycol), affording three structurally well-defined hydrogels, denoted as C2HG, C6HG, and C8HG. Structural and physicochemical characterization showed that all hydrogels possessed interconnected three-dimensional porous networks, good thermal stability, and a lower critical solution temperature of approximately 37 °C. Rheological analysis demonstrated predominantly elastic behavior, with the storage modulus (G′) consistently exceeding the loss modulus (G″), together with pronounced shear-thinning characteristics favorable for injection into deep, low-permeability formations. By varying the alkyl-chain length of the hyperbranched backbone, the balance between environmental tolerance and plugging performance could be effectively regulated. These findings establish a structure–property relationship between backbone hydrophobicity and hydrogel performance and demonstrate that PEG-crosslinked hyperbranched copolymer hydrogels are promising candidates for deep-profile control and water shutoff in high-salinity, low-permeability fractured reservoirs. Full article

(This article belongs to the Special Issue Advances in Functional and Intelligent Hydrogels)

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12 pages, 11869 KB

Open AccessArticle

Control over the Self-Assembly of Supramolecular Hydrogels Using Hofmeister Effect

by Lai Wei, Qi Gao, Hongwang Tang, Xuhong Guo and Yiming Wang

Gels 2026, 12(8), 693; https://doi.org/10.3390/gels12080693 - 4 Aug 2026

Abstract

Supramolecular hydrogels are usually prepared in aqueous media containing diverse ions, for instance, buffer solutions, yet the influences of ions, especially the Hofmeister effect, on their self-assembly are often overlooked. Here, we systematically investigate the impacts of different anions in the Hofmeister series [...] Read more.

Supramolecular hydrogels are usually prepared in aqueous media containing diverse ions, for instance, buffer solutions, yet the influences of ions, especially the Hofmeister effect, on their self-assembly are often overlooked. Here, we systematically investigate the impacts of different anions in the Hofmeister series on the self-assembly of supramolecular hydrogels. On the basis of a hydrazone formation-mediated supramolecular gelation system, we found that the addition of kosmotropic anions can accelerate the self-assembly of gelators as determined by rheology and critical gelation concentration tests. Confocal microscopy observations and rheological measurements demonstrate that the resultant hydrogels have denser fibrous networks and higher stiffness relative to the samples without additional kosmotropic anions. In contrast, chaotropic anions effectively impede the self-assembly process. These impacts of ions on the self-assembly of supramolecular hydrogels are in line with the specific ion effect. This work suggests that the Hofmeister effect can serve as an effective approach to control the self-assembly and the properties of supramolecular hydrogels, and the effects of ions should be considered in the studies of supramolecular hydrogels. Full article

(This article belongs to the Special Issue Recent Advances in Smart and Tough Hydrogels)

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16 pages, 7903 KB

Open AccessArticle

Development of Periodontal Organoid-like Constructs Using Human Periodontal Ligament and Gingival Epithelial Cells: Comparison of Two Assembly Strategies

by Luiza de Oliveira Matos, Mariane Beatriz Sordi, Anahid Ahmadi Birjandi, Paul Thomas Sharpe and Ariadne Cristiane Cabral Cruz

Gels 2026, 12(8), 692; https://doi.org/10.3390/gels12080692 - 3 Aug 2026

Abstract

Periodontal organoid research remains underdeveloped, largely due to the lack of standardized fabrication protocols and multicellular constructs capable of reproducing epithelial–mesenchymal interactions relevant to periodontal biology. In particular, it remains unclear whether different spatial assembly strategies influence construct stability, multicellular organization, or early [...] Read more.

Periodontal organoid research remains underdeveloped, largely due to the lack of standardized fabrication protocols and multicellular constructs capable of reproducing epithelial–mesenchymal interactions relevant to periodontal biology. In particular, it remains unclear whether different spatial assembly strategies influence construct stability, multicellular organization, or early molecular behavior in periodontal three-dimensional (3D) systems. Therefore, this study aimed to develop and compare two different methods for generating dual-lineage 3D periodontal organoid-like constructs using human periodontal ligament cells (hPDL) and human gingival epithelial cells (hGEP). These strategies were selected to compare two biologically and technically distinct spatial configurations: bilayer assembly to partially mimic epithelial–connective tissue compartmentalization, and surface seeding as a simplified fabrication approach with potential advantages for reproducibility and workflow standardization. Both cell types were cultured in different media conditions (CnT-57, DMEM, and a 1:1 CnT-57/DMEM mixture) to determine compatibility for co-culture applications. Cell viability was assessed on days 1, 3, and 7 using the MTS assay. Constructs were produced in hyaluronic acid-based hydrogels using two strategies: Group 1–sequential photopolymerization of hPDL and hGEP layers to generate a bilayer construct; and Group 2—encapsulation of hPDL followed by direct seeding of hGEP onto the construct surface. Viability within constructs was evaluated on days 3 and 7 using the Live/Dead assay. Morphology was monitored using stereomicroscopy on days 0, 1, 3, and 7. Exploratory RNA sequencing was performed on day 7 to characterize transcriptomic profiles. All tested culture media maintained cellular viabilities above 70%, with no statistically significant differences among conditions (p > 0.05), indicating biocompatibility for both cell types. Group 1 exhibited viabilities of 86.54% ± 8.55% and 90.69% ± 7.88% on days 3 and 7, respectively, while Group 2 showed viabilities of 87.00% ± 9.58% and 88.08% ± 9.12%, with no significant intergroup differences (p > 0.05). Morphological analyses demonstrated preservation of construct integrity and progressive interaction between epithelial and mesenchymal compartments. Exploratory RNA sequencing revealed only subtle transcriptomic differences between assembly strategies. In conclusion, both methodologies successfully generated viable and structurally stable dual-lineage periodontal organoid-like constructs within a hyaluronic acid-based matrix. Comparison of these two assembly strategies demonstrates the feasibility of generating reproducible multicellular periodontal 3D models using distinct spatial configurations, establishing a proof-of-concept platform for future optimization toward periodontal disease modeling, regenerative studies, and advanced biofabrication applications. Full article

(This article belongs to the Special Issue Hydrogels for Tissue Repair: Innovations and Applications)

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52 pages, 16749 KB

Open AccessReview

Advances in 3D Bioprinting for Scaffold-Based and Scaffold-Free Tissue Engineering and Regenerative Medicine

by Kannan Badri Narayanan

Gels 2026, 12(8), 691; https://doi.org/10.3390/gels12080691 - 3 Aug 2026

Abstract

Three-dimensional (3D) bioprinting has emerged as a versatile biofabrication strategy that enables the precise, spatiotemporally controlled co-deposition of living cells, biomaterials, and bioactive agents, including growth factors, cytokines, and extracellular matrix (ECM) components, into geometrically defined 3D constructs. By translating digital design models [...] Read more.

Three-dimensional (3D) bioprinting has emerged as a versatile biofabrication strategy that enables the precise, spatiotemporally controlled co-deposition of living cells, biomaterials, and bioactive agents, including growth factors, cytokines, and extracellular matrix (ECM) components, into geometrically defined 3D constructs. By translating digital design models derived from computed tomography (CT), magnetic resonance imaging (MRI), or computational modeling directly into physical tissue architectures, 3D bioprinting facilitates the assembly of hierarchically organized constructs that closely recapitulate the structural, mechanical, and functional characteristics of native tissues. The principal 3D bioprinting strategies are broadly classified into scaffold-based and scaffold-free approaches. Engineered bioinks, whether formulated as cell-laden natural, synthetic, or composite polymer hydrogels, tissue-derived decellularized ECM (dECM) components, or pure cellular spheroids and organoids, constitute the cornerstone of these biofabrication platforms. Scaffold-based 3D bioprinting comprises extrusion-based, droplet-based (inkjet and drop-on-demand), light-based vat photopolymerization (stereolithography and digital light processing), and laser-assisted bioprinting based on laser-induced forward transfer (LIFT). Each of these modalities imposes distinct constraints on bioink rheology, crosslinking mechanisms, spatial resolution, throughput, and post-printing cell viability; consequently, a specific 3D bioprinting strategy is selected according to the specific requirements of the target tissue application. Scaffold-free 3D bioprinting and bioassembly techniques, including the Kenzan method, aspiration-assisted bioprinting, magnetic bioprinting, and other field-directed tissue assembly approaches, enable the fabrication of spheroid- and organoid-based constructs without the necessity for exogenous biomaterial scaffolds. Because native tissues exhibit diversity in cellular composition, ECM architecture, mechanical properties, and physiological function, no individual bioprinting platform or bioink formulation serves as a universal 3D bioprinting solution. The engineering of biomimetic tissue constructs, therefore, requires the selection of application-tailored fabrication approaches. Under this biofabrication paradigm, 3D bioprinting has been applied across a wide range of tissue engineering targets, including skin, bone, cartilage, osteochondral interfaces, cardiac and vascular tissue, neural structures, ocular, dental, and adipose tissue. This review discusses recent advances in scaffold-based and scaffold-free 3D bioprinting applications for tissue engineering and regenerative medicine across diverse tissue systems. Full article

(This article belongs to the Special Issue Designing Gels for Wound Dressing (2nd Edition))

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14 pages, 13970 KB

Open AccessArticle

High-Performance Fiber-Shaped Supercapacitors Enabled by Polyaniline @ MXene Ti₃C₂T_x Hybrid Graphene Aerogel Fiber

by Ran Jin, Qingquan Xue and Yang Zhang

Gels 2026, 12(8), 690; https://doi.org/10.3390/gels12080690 - 3 Aug 2026

Abstract

Developing fiber-shaped supercapacitors (FSCs) with high capacitance, high energy density, and exceptional rate performance is crucial for reliable, stable and high-performance wearable electronics. Here, a polyaniline (PANI) @ MXene Ti₃C₂T_x/graphene (PTG) aerogel fiber was rationally fabricated via [...] Read more.

Developing fiber-shaped supercapacitors (FSCs) with high capacitance, high energy density, and exceptional rate performance is crucial for reliable, stable and high-performance wearable electronics. Here, a polyaniline (PANI) @ MXene Ti₃C₂T_x/graphene (PTG) aerogel fiber was rationally fabricated via a confined hydrothermal method followed by freeze-drying treatment. The graphene sheets construct the skeleton of the aerogel fiber, which possesses a porous and interlinked structure, providing interconnected diffusion channels and a high specific surface area that promote electrolyte migration and abundant ion adsorption sites. Moreover, the covalent modification between PANI nanoparticles and Ti₃C₂T_x sheets can significantly improve interfacial coupling and provide abundant redox sites, resulting in a reduced energy barrier of electron transfer, good interfacial stability and superior H⁺ storage capability. As a consequence, the PTG aerogel fiber electrode delivers an excellent specific mass capacitance of 484.8 F g⁻¹, impressive rate properties (244.4 F g⁻¹ at 10 A g⁻¹) and exceptional cycle ability (85.2% after 5000 cycles). Additionally, the fabricated symmetrical FSC exhibits considerable electrochemical performance, including high capacitance and good energy density. This work depicts a novel route to prepare a graphene fiber-based electrode for high-performance FSCs in an intelligent wearable system. Full article

(This article belongs to the Special Issue Functional Fibrous Gel Materials)

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22 pages, 1178 KB

Open AccessArticle

Ghassoul-Clay- and Oil-Loading-Induced Colloidal Gelation of Lavender Essential Oil Emulsified Systems

by Barbara Bigi, Stefania Petralito, María Jesús Rodriguez-Palero, Luis Alfonso Trujillo-Cayado and Jenifer Santos

Gels 2026, 12(8), 689; https://doi.org/10.3390/gels12080689 - 3 Aug 2026

Abstract

Lavender essential oil is a promising bioactive ingredient, but its incorporation into aqueous formulations is limited by its low water solubility and high volatility. This work structured lavender oil-in-water emulsified systems through two approaches: Ghassoul clay incorporation and increased oil loading. The standard [...] Read more.

Lavender essential oil is a promising bioactive ingredient, but its incorporation into aqueous formulations is limited by its low water solubility and high volatility. This work structured lavender oil-in-water emulsified systems through two approaches: Ghassoul clay incorporation and increased oil loading. The standard formulation containing 1.25 wt.% oil showed a narrow droplet size distribution, with a Sauter mean diameter of 114 nm, respectively, and Newtonian behavior with a viscosity of 0.97 mPa·s. Ghassoul addition did not significantly modify droplet size, but induced shear-thinning and gel-like behavior. Zero-shear viscosity increased from 2 Pa·s at 5 wt.% clay to 550 Pa·s at 20 wt.%, while 15–20 wt.% Ghassoul showed the highest resistance to clay sedimentation after 30 days. Increasing lavender oil concentration promoted droplet growth and broader size distributions. The 30 wt.% oil formulation exhibited the strongest droplet-mediated structure, with G′ exceeding G″ and zero-shear viscosity reaching 156 Pa·s, whereas 40 wt.% oil weakened the network due to droplet coarsening and polydispersity. The results highlight the key role of clay-particle networking, droplet crowding, droplet-size distribution, and viscoelastic structuring in controlling gel-like behavior and physical stability, supporting the design of essential oil-based colloidal gels for topical, pharmaceutical, or cosmetic delivery applications. Full article

(This article belongs to the Special Issue Food Gels: Structure and Function (3rd Edition))

29 pages, 2066 KB

Open AccessReview

Structure–Function Engineering of Lignin-Based Hydrogels for Adsorptive Removal of Organic Dyes and Heavy Metal Ions: A Category-Oriented Review

by Jianhui Guo, Yue Hu, Yiming Sun, Chang Ma, Minghui Zhang, Yida Niu, Youming Dong and Cheng Li

Gels 2026, 12(8), 688; https://doi.org/10.3390/gels12080688 - 3 Aug 2026

Abstract

Given the widespread contamination of water bodies by diverse pollutants, particularly heavy metal ions and organic dyes, there is an urgent need to develop efficient and sustainable biomass adsorbents. Lignin is rich in active groups such as phenolic hydroxyl and carboxyl groups, making [...] Read more.

Given the widespread contamination of water bodies by diverse pollutants, particularly heavy metal ions and organic dyes, there is an urgent need to develop efficient and sustainable biomass adsorbents. Lignin is rich in active groups such as phenolic hydroxyl and carboxyl groups, making it a natural adsorbent. However, its application is still hindered by limitations, including restricted solubility and low reactivity. Converting lignin into three-dimensional porous hydrogels not only overcomes the inherent structural brittleness of lignin-based materials but also accelerates the diffusion kinetics of pollutants through well-developed pore structures, thereby fully exposing the active adsorption sites. This paper systematically reviews the latest progress in lignin-based hydrogels for water treatment and discusses in depth the underlying logic of “structure construction–micromorphology–adsorption performance.” First, this review summarizes synthesis strategies ranging from molecular-level modification to morphology regulation, including nano-reinforcement, magnetic functionalization, and interpenetrating polymer networks. It then provides a pollutant-specific analysis of the adsorption mechanisms of lignin-based adsorbents. For heavy metal ions, such as Pb²⁺ and Cr(VI), removal is mainly associated with coordination/complexation, ion exchange, and redox reactions. For typical organic dyes, adsorption is primarily driven by π–π interactions, hydrogen bonding, and electrostatic attraction. The effects of environmental factors, such as pH, are also systematically discussed. Finally, considering current challenges related to mechanical strength, regeneration performance, and practical application, this review outlines future research directions for the development of multifunctional, integrated, and stimuli-responsive lignin-based adsorbents. Full article

(This article belongs to the Special Issue Biomass-Based Gels)

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19 pages, 8534 KB

Open AccessArticle

Plasticity and the Transition from Physical Gels to Yielding Liquids

by Alexander Ya. Malkin, Svetlana R. Derkach and Vlada V. Bordiyan

Gels 2026, 12(8), 687; https://doi.org/10.3390/gels12080687 - 3 Aug 2026

Abstract

This study examines the possibility of plastic deformation in low-modulus gels and yielding liquids. The model systems were a gelatin-sodium alginate hydrogel and the same gel filled with nanoscale zinc oxide particles. The experiments involved short- and long-term observations of deformation development under [...] Read more.

This study examines the possibility of plastic deformation in low-modulus gels and yielding liquids. The model systems were a gelatin-sodium alginate hydrogel and the same gel filled with nanoscale zinc oxide particles. The experiments involved short- and long-term observations of deformation development under a prescribed shear stress, followed by stress removal and monitoring of deformation recovery. The initial hydrogel is a typical soft-matter system with an elastic modulus of 63 Pa. At low stresses, residual deformations were observed in addition to elastic deformations; these residual deformations reached up to approximately one half of the total deformation. They appeared instantaneously, depended on the applied stress, and did not change during long-term observation. This behavior is characteristic of plastic deformation. The incorporation of 5% dispersed ZnO nanoparticles converted the gel into a yielding liquid. This transition is attributed to partial disruption of the physical network, as evidenced by a sharp decrease in the elastic modulus to 18 Pa and by comparison of the FTIR spectra of the unfilled gel and the nanoparticle-modified gel. The yield stress of the yielding liquid was 7 Pa. However, at stresses below this value, while the material remained in a gel-like state, steady-state flow with a very high viscosity, at the order of 10⁵–10⁶ Pa s, was detected. After the yield point was exceeded, steady-state flow with a much lower viscosity, at the order of 3 Pa s, occurred, as is characteristic of conventional liquids containing a solid filler. Nevertheless, a small fraction of plastic deformation was still observed. Thus, the experimental results show that physical gels can behave as elastic-plastic media and that yielding liquids may flow below the yield point with very high viscosity. All existing models of the mechanical behavior of gels represent various combinations of viscous and elastic elements, to which, for yielding liquids, a slider is added that begins to slide after overcoming static friction. This element models the yield point. However, no model includes plasticity as an independent mechanical phenomenon. The phenomenon of plasticity should therefore be taken into account when developing rheological models of yielding liquids. Full article

(This article belongs to the Section Gel Analysis and Characterization)

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18 pages, 2766 KB

Open AccessFeature PaperArticle

Differential Effects of pH-Shift and Ultrasound Intervention Sequences on Physicochemical, Structural and Gelling Properties of Potato–Egg White Composite Proteins

by Jing Li, Huimin Lu, Hongxi Zhao, Qiannan Liu, Ruixuan Zhao and Honghai Hu

Gels 2026, 12(8), 686; https://doi.org/10.3390/gels12080686 - 3 Aug 2026

Abstract

Composited proteins from animal and plant sources can address the limitations of single proteins and expand their applications in food processing. In this study, potato protein and egg white protein (PP/EWP) composites were modified through pH-shift and ultrasound treatments. A systematic comparison was [...] Read more.

Composited proteins from animal and plant sources can address the limitations of single proteins and expand their applications in food processing. In this study, potato protein and egg white protein (PP/EWP) composites were modified through pH-shift and ultrasound treatments. A systematic comparison was conducted, for the first time, among three ultrasound application protocols (US-A-pH, US-P-pH, and US-B-pH, corresponding to ultrasound after, during, and before pH-shift treatment, respectively) over a range of six pH conditions (3, 4, 5, 8, 9, 10) in a composite system. It was found that PP/EWP treated with alkaline pH shifts (especially pH 9 and 10) exhibited better physicochemical, structural, and gelling properties. The complexes pretreated with US-P-pH (pH = 9) possessed higher solubility, smaller particle size, enhanced hydrophobicity, and higher number of disulfide bonds. Furthermore, this treatment yielded gels with superior hardness, chewiness, adhesion, water-holding capacity, and finer network structure. US-B-pH treatment increased the random coil content of PP/EWP, producing flexible and disordered protein states and gels with higher elasticity. In contrast, US-A-pH induced significant structural changes in the protein particles, but did not yield the required gel quality. These findings were intended to offer practical guidance for designing green and efficient protein modification strategies in food processing, with promising applications in composite gel products. Full article

(This article belongs to the Special Issue Food Gels: Structures, Properties and Applications)

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14 pages, 4526 KB

Open AccessArticle

Polyelectrolyte Microcapsules Enhance the Stability of β-Galactosidase Under Simulated Gastrointestinal Conditions

by Yuri S. Chebykin, Aleksandr L. Kim and Sergey A. Tikhonenko

Gels 2026, 12(8), 685; https://doi.org/10.3390/gels12080685 - 3 Aug 2026

Abstract

Oral enzyme replacement therapy for lactase deficiency is limited by the rapid degradation of free β-galactosidase in the gastrointestinal tract. To overcome this, β-galactosidase was encapsulated into polyelectrolyte microcapsules (PMCs) via layer-by-layer assembly using MnCO₃ sacrificial templates, with CaCO₃-based PMCs [...] Read more.

Oral enzyme replacement therapy for lactase deficiency is limited by the rapid degradation of free β-galactosidase in the gastrointestinal tract. To overcome this, β-galactosidase was encapsulated into polyelectrolyte microcapsules (PMCs) via layer-by-layer assembly using MnCO₃ sacrificial templates, with CaCO₃-based PMCs as a reference. MnCO₃-PMCs achieved 99.4% encapsulation efficiency and retained 85.8% of initial activity, significantly outperforming CaCO₃-PMCs (86.0% and 29.7%). Under simulated gastric conditions (pH 2.0, pepsin), the free enzyme and CaCO₃-PMCs were completely inactivated, whereas MnCO3-PMCs preserved ~86% activity. In simulated intestinal fluid, MnCO₃-PMCs exhibited a 4.3-fold activity increase within the first hour and maintained a 2.5-fold enhancement after 70 h, while the free enzyme progressively inactivated. Furthermore, MnCO₃-PMCs demonstrated superior storage stability, retaining 64% of initial activity after 90 days at 4 °C, compared with 25% for CaCO₃-PMCs. Although immobilization increased the Michaelis constant, the shift was smaller for MnCO₃-PMCs (8.9-fold) than for CaCO₃-PMCs (15.2-fold). In conclusion, MnCO₃-templated PMCs effectively protect β-galactosidase from gastrointestinal degradation, sustain prolonged catalytic activity, and offer excellent storage stability, highlighting their strong potential for improving oral enzyme replacement therapy in lactose intolerance. Full article

(This article belongs to the Section Gel Applications)

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