Tailoring the Swelling-Shrinkable Behavior of Hydrogels for Biomedical Applications

Biomimetic nanostructural materials based on placental amniotic membrane-derived nanofibers for self-healing and anti-adhesion during cesarean section

Cesarean section (CS) is highly prevalent surgery among females. However, current absorbable anti-adhesion membranes used clinically can partially prevent postoperative adhesions but show limited efficacy in tissue regeneration, leaving post-cesarean women at risk for severe complications including cesarean scar pregnancy, placenta previa, and uterine rupture. Herein, we designed a fully amniotic membrane (AM)-derived biomimetic nanostructural materials (AM-BNMs) as an anti-adhesion barrier, and validated its therapeutic efficacy in a rat CS model. The biomaterial consisted of AM-extracellular matrix (ECM) nanofibers, enriched with hemostatic proteins (collagen, S100A8, S100A9, etc.), carrying AM mesenchymal stem cells (MSCs)-secretome that exhibited significantly elevated levels of pro-regenerative factors (miR-302a-3p, angiogenin, VEGF, etc.) compared to endogenous secretion. The reconstituted AM-BNMs demonstrated synergistic effects at CS wounds, effectively preventing adhesion formation while promoting hemostasis and tissue regeneration. In summary, this readily accessible human-derived biomaterial shows promising potential in preventing adhesion-related complications and enhancing uterine wound healing, thereby promoting female reproductive health.

Mechanically robust non-swelling cold water fish gelatin hydrogels for 3D bioprinting

Three-dimensional (3D) bioprinting of hydrogels allows embedded cells to be patterned and hosted in an extracellular matrix (ECM)-mimicking environment. This method shows great promise for the engineering of complex tissues on account of the facile spatial control over materials and cells within the printed constructs. Hydrogels, which represent extensively explored and employed biomaterials for 3D bioprinting, are characterized by both their high water content and swelling behavior. Post-printing swelling inevitably alters the geometrical and mechanical properties of printed features, thus causing a deviation from the original design and affecting both cellular function and tissue structure. Despite substantial effort being dedicated to the development of non-swelling hydrogels, their application in 3D encapsulation and bioprinting of living cells is yet to be realized, owing to limitations imposed by their often tedious material syntheses and complex network structures. Herein, we describe a new type of non-swelling hydrogel based fully on cold water fish gelatin (cfGel-Hydrogel) consisting of only a single network formed via thiol-ene "click" chemistry. We show that such cfGel-Hydrogels enable 3D patterning of living cells in a shape-retaining and mechanically robust matrix. These cfGel-Hydrogels show negligible swelling (<2 %) under physiologically relevant conditions (simulated by 37 °C PBS buffer), while also being able to withstand large cyclic deformations (80 % compressive strain) by dissipating around 40 % of the imposed loading energy. Human dermal fibroblast (HDF)-laden cfGel-Hydrogels could be fabricated via extrusion-based 3D printing, allowing for the in vitro culturing of cells in shape-retaining constructs, thus offering new opportunities for hydrogel-based applications in tissue engineering and regenerative medicine.

Imine Crosslinked, Injectable, and Self-Healing Fucoidan Hydrogel with Immunomodulatory Properties

Biomaterials with inherent anti-inflammatory properties and the ability to foster a pro-regenerative environment hold significant promise for enhancing cell transplantation and tissue regeneration. Fucoidan, a sulfated polysaccharide with well-documented immune-regulatory and antioxidant capabilities, offers strong potential for creating such biomaterials. Yet, there is a lack of engineered fucoidan hydrogels that are injectable and provide tunable physicochemical properties. In this study, the ability of fucoidan to undergo periodate-mediated oxidation is leveraged to introduce aldehydes into backbone (oxidized fucoidan, OFu), enabling the formation of reversible, imine-crosslinks with amine-containing molecules such as gelatin. The imine-crosslinked OFu-gelatin hydrogel provided excellent control over gelation rate and mechanical properties. Counter-intuitively, OFu-gelatin hydrogel exhibited excellent long-term stability (≥28 days), even though imine crosslinks are known to be relatively less stable. Moreover, the OFu-gelatin hydrogels are self-healing, injectable, and biocompatible, supporting cell culture and encapsulation. Furthermore, fucoidan hydrogels displayed immune-modulatory properties both in vitro and in vivo. This innovative injectable fucoidan hydrogel presents a versatile platform for applications in tissue engineering and regenerative medicine.

Novel tragacanth gum-collagen-polyurethane hydrogels: Super-swelling, antibacterial, and fibrillogenesis-enhancing properties for efficient wound healing

Tragacanth gum, a biodegradable polymer from Astragalus sap, offers a promising platform for advanced biomaterials due to its thickening, emulsifying, and stabilizing properties. This study synthesized novel tragacanth gum-collagen-polyurethane hydrogels with 20-60 wt% polysaccharide content. Semi-interpenetration of gum chains within the collagen-polyurethane matrix generated hybrid fibrillar-granular surfaces, with granular content increasing with gum concentration. Hydrogels with 40 wt% gum achieved 42 % collagen crosslinking, showing superabsorbent behavior with swelling capacities over 2600 %. Higher gum content improved viscoelastic stability, enhancing resistance to degradation at skin-relevant (pH 5.0) and physiological (pH 7.4) conditions while increasing susceptibility to alkaline (pH 8.5) and collagenase-rich environments. Granular regions efficiently encapsulated methylene blue, achieving 68 % release at skin pH and demonstrating antibacterial activity against E. coli (62 %) and S. aureus (50 %). The hydrogels exhibited excellent biocompatibility, promoting monocyte and fibroblast proliferation without hemolytic or cytotoxic effects. Notably, the 40 wt% gum hydrogel modulated immune responses by enhancing anti-inflammatory (TGF-β) release without increasing pro-inflammatory (CCL-2) cytokines. Additional features include self-healing capacity, fatigue resistance, and strong adhesiveness, highlighting the hydrogel's multifunctional potential for advanced wound healing applications.

Physicochemical Properties of Freeze-Dried Bigel-Based Materials Composed of Sodium Alginate/Whey Protein Isolate Hydrogel and Ethylcellulose/Sunflower Oil Oleogel

Freeze-drying bigels is a novel technique for developing functional materials for dermatological and cosmetic use, leveraging the benefits of two structured phases. This study optimized freeze-dried bigels composed of whey protein isolate (WPI)/sodium alginate/glycerin hydrogel and ethylcellulose (EC)/Span 80/sunflower oil oleogel at varying hydrogel/oleogel ratios. The materials showed swelling ratios from 50% to 255%, with higher values for a lower oleogel content and higher polymer concentration. The higher oleogel content extended the degradation from a few hours to 7 days. The polymer concentrations and hydrogel/oleogel ratios influenced Young's modulus (1.25-3.7 MPa). Porosity varied from 35% to 58%, and density varied from 100 to 200 mg/mL. The residual moisture content (5% to 20%) increased with EC content and decreased with WPI and oleogel content. These findings underscore the role of polymer concentrations and phase ratios in tuning the physicochemical properties of freeze-dried gels, positioning them as promising biomaterials for skincare and cosmetic applications.

Adhesive and Antioxidant Hydrogel with Glucose/ROS Dual-Responsive Drug Release for Diabetic Oral Mucosal Wound Healing

Diabetes mellitus is a global health threat, with chronic wounds, including oral mucosal wounds, being a severe complication. These wounds are characterized by delayed healing and increased inflammation due to hyperglycemia, affecting patients' quality of life. Current treatments for oral mucosal wounds cannot offer sustained management of these injuries in diabetic patients. Here, a glucose/ROS dual-responsive hydrogel incorporating sitagliptin was developed for the treatment of diabetic oral mucosal wounds. After chemical modification of tetra-armed poly(ethylene glycol) succinimidyl glutarate (tetra-PEG-SG) by dopamine (DA) and tetra-armed poly(ethylene glycol) amine (tetra-PEG-NH2) by phenylboronic acid (PBA), the resulting hydrogel was capable of rapid gelation, robust tissue adhesion, self-healing, antioxidant capacity, and dual response to glucose and reactive oxygen species (ROS), enabling the feasible injection and stable adherence in the moist oral environment while ensuring sustained therapeutic sitagliptin release. In vivo experiments on oral mucosal defects in diabetic mice revealed that the sitagliptin-loaded hydrogel could effectively reduce inflammation and promote wound healing. Collectively, this finding identifies a potential wound dressing as a therapeutic strategy for diabetic oral mucosal wounds.

Luffa cylindrica-inspired powerless micropump: long-term, high-flow operation and energy-generation application

Powerless micropumps are in increasing demand for applications requiring portability, simplicity, and long-term operation. However, several existing passive pumps have limitations such as sustained high flow rates and extended operational periods. Inspired by the unique structural characteristics of Luffa cylindrica, this study aims to develop a biomimetic micropump capable of long-term and high-flow operation. By examining the water transport mechanisms in a hierarchical porous structure, we designed and fabricated micropumps that replicate these mechanisms. A key aspect of this design is the integration of flow resistors, which enables precise control over the absorption rates and extend the pumping duration. The cone-shaped agarose aerogel (AAG) micropump operates for over 930 min with an average flow rate of 5.6 μl min-1, demonstrating significant longevity. The agarose superabsorbent polymer aerogel (ASAG) micropump, while having a shorter operational duration of approximately 620 min, exhibited a significantly higher average pumping rate of 13.2 μl min-1. This study highlights the potential of bio-inspired designs for advancing efficient and powerless pumping systems. The proposed micropump shows promise for applications in microfluidic devices and reverse electrodialysis systems, where continuous and sustainable fluid transport is essential.

Catalyst-Free Synthesis of a Mechanically Tailorable, Nitric-Oxide-Releasing Organohydrogel and Its Derived Underwater Superoleophobic Coatings

Organohydrogels are an emerging class of soft materials that mimick the mechanical durability and organic solvent affinity of organogels and the biocompatibility and water swelling ability characteristics of hydrogels for prospective biomedical applications. This work introduces a facile, catalyst-free one-step chemical approach to develop an organohydrogel with impeccable antibiofouling properties following the epoxy-amine ring-opening reaction under ambient conditions. The mechanical properties of the as-fabricated organohydrogel can be tailored depending on the concentration of the epoxy-based cross-linker, from 0.10 to 1.12 MPa (compressive modulus). The affinity of the as-developed organohydrogel to both organic solvents and water was exploited to incorporate the antimicrobial nitric oxide donor (NO) molecule, S-nitroso-N-acetylpenicillamine (SNAP) from ethanol, and subsequently, the water-sensitive NO-releasing behavior of the organohydrogels was analyzed. The SNAP-incorporated organohydrogels release physiologically active levels of NO with 3.13 ± 0.27 × 10-10 and 0.36 ± 0.14 × 10-10 mol cm-2 min-1 flux of NO release observed at 0 and 24 h, respectively. The as-reported organohydrogel demonstrated excellent antibacterial activity against Escherichia coli and Staphylococcus aureus with >99% and >87% reduction, respectively, without eliciting any cytotoxicity concerns. Moreover, the organohydrogel with remarkable water uptake capacity was extended as a coating on different medically relevant polymers to demonstrate transparent underwater superoleophobicity. Thus, the facile synthesis of the reported organohydrogel and its derived underwater antifouling coating can open avenues for utility in biomedical, energy, and environmental applications.

Polypyrrole-modified gelatin-based hydrogel: A dressing for intestinal perforation treatment with enhanced wound healing and anti-adhesion properties

Intestinal perforation is a serious medical emergency, and traditional surgery often causes adhesion and other complications. Innovative hydrogels improve postoperative care and rehabilitation with their anti-adhesion, antibacterial, and hemostatic properties. We have developed an advanced anti-adhesion hydrogel, AA-A30, composed of polypyrrole-modified gelatin (PPy-GelMA), carboxymethyl chitosan (CMCS), and NHS-functionalized polyethylene glycol (PEG-NHS). This hydrogel is specifically tailored for intestinal perforations. Upon hydrolysis, PEG-NHS forms a protective barrier that effectively prevents adhesion to surrounding normal tissues. Furthermore, the integration of PPy-GelMA significantly extends the degradation duration of the hydrogel, from 24 to 48 h. In a mouse model of intestinal perforation, the AA-A30 hydrogel demonstrated remarkable efficacy in inhibiting inflammation and preventing tissue adhesion by modulating the expression of both inflammatory and tissue adhesion-related factors, such as IL-1β, TNF-α, and the ratio of tPA to PAI-1. These findings underscore the considerable potential of AA-A30 for the therapeutic management of intestinal perforations.

Thioether-Functionalized Cellulose for the Fabrication of Oxidation-Responsive Biomaterial Coatings and Films

Biomaterial coatings and films can prevent premature failure and enhance the performance of chronically implanted medical devices. However, current hydrophilic polymer coatings and films have significant drawbacks, including swelling and delamination. To address these issues, hydroxyethyl cellulose is modified with thioether groups to generate an oxidation-responsive polymer, HECMTP. HECMTP readily dissolves in green solvents and can be fabricated as coatings or films with tunable thicknesses. HECMTP coatings effectively scavenge hydrogen peroxide, resulting in the conversion of thioether groups to sulfoxide groups on the polymer chain. Oxidation-driven, hydrophobic-to-hydrophilic transitions that are isolated to the surface of HECMTP coatings under physiologically relevant conditions increase wettability, decrease stiffness, and reduce protein adsorption to generate a non-fouling interface with minimal coating delamination or swelling. HECMTP can be used in diverse optical applications and permits oxidation-responsive, controlled drug release. HECMTP films are non-resorbable in vivo and evoke minimal foreign body responses. These results highlight the versatility of HECMTP and support its incorporation into chronically implanted medical devices.

Strontium alginate hydrogel containing psoralen has superior mechanical properties and immunomodulatory functions to alleviate intervertebral disc degeneration

Changes in mechanical properties, inflammation, and oxidative stress are key factors in the progression of intervertebral disc degeneration, while phytoestrogens have shown promising therapeutic potential. In this study, we propose the synthesis of a hydrogel using psoralen that can mimic the mechanical properties of human intervertebral disc nucleus pulposus tissue. This hydrogel exhibits anti-inflammatory and antioxidant properties, aiming to alleviate intervertebral disc degeneration. Firstly, we synthesized a strontium alginate hydrogel containing psoralen (SA@Sr/PSO). The material was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), drug release testing, and mechanical property assessment. The optimal drug loading concentration was determined through CCK-8 assay and live/dead staining. The biological functions were assessed using enzyme-linked immunosorbent assay (ELISA), quantitative real-time PCR, and immunofluorescence staining. The results showed that the synthesized SA@Sr/PSO exhibited a porous structure and favorable water absorption, with excellent elasticity and mechanical properties. Cell experiments demonstrated that SA@Sr/PSO promoted cell proliferation, downregulated the expression of IL-1β, IL-6, iNOS, and NO, and upregulated the expression of IL-10, Arg-1, and CD206. The DPPH assay confirmed that the hydrogel can inhibit oxidative stress. The successful synthesis of SA@Sr/PSO, with its excellent mechanical properties and biological functions, improves intervertebral disc degeneration.

Hydration Induces Dehydration: Creating Negative Swelling Gel by a Paradox

Swelling positively in water is a common behavior of hydrogels, which, however, can lead to reduced mechanical performance and stability. Enabling negative swelling represents a promising way to address those issues but is extremely challenging to realize. Here, real negative swelling hydrogels are successfully prepared for the first time through a unique molecular architecture. Specifically designed interpenetrating transformable-rigid polymer network undergoes self-assembly and collapses upon hydration, which in turn dehydrates itself. This paradoxical hydration-induced-dehydration process brings about revolutionary outcomes. Gels can now lose up to 35% weight underwater and exhibit water-strengthened mechanical properties, enhanced structural responsiveness, underwater repair ability, resistance to deformation, and swelling turn-off effect. Those unique properties allow future material development and applications to be carried out in much broader dimensions.

Nature-inspired surface modification strategies for implantable devices

Medical and implantable devices are essential instruments in contemporary healthcare, improving patient quality of life and meeting diverse clinical requirements. However, ongoing problems such as bacterial colonization, biofilm development, foreign body responses, and insufficient device-tissue adhesion hinder the long-term effectiveness and stability of these devices. Traditional methods to alleviate these issues frequently prove inadequate, necessitating the investigation of nature-inspired alternatives. Biomimetic surfaces, inspired by the chemical and physical principles found in biological systems, present potential opportunities to address these challenges. Recent breakthroughs in manufacturing techniques, including lithography, vapor deposition, self-assembly, and three-dimensional printing, now permit precise control of surface properties at the micro- and nanoscale. Biomimetic coatings can diminish inflammation, prevent bacterial adherence, and enhance stable tissue integration by replicating the antifouling, antibacterial, and adhesive properties observed in creatures such as geckos, mussels, and biological membranes. This review emphasizes the cutting-edge advancements in biomimetic surfaces for medical and implantable devices, outlining their design methodologies, functional results, and prospective clinical applications. Biomimetic coatings, by integrating biological inspiration with advanced surface engineering, have the potential to revolutionize implantable medical devices, providing safer, more lasting, and more effective interfaces for prolonged patient benefit.

Anti-inflammatory and antibacterial hydrogel based on a polymerizable ionic liquid

In the present era, the treatment of skin-infected wounds and their associated inflammation constitutes a significant challenge. These infections have the potential to impede the healing process and become a life-threatening pathology, particularly due to the rise of bacterial resistance. Hydrogels could successfully address this issue due to their unique capabilities and versatility. Among them, natural polymer-based hydrogels are especially advantageous as they resemble the extracellular matrix (ECM) and mechanical properties of natural tissues. In this study, we propose a dual-action hydrogel composed of methacrylated gelatin as a matrix and a salicylate (Sal) anion-exchanged polymerizable ionic liquid (PIL) to achieve anti-inflammatory and antibacterial activities. This material facilitated cell attachment and colonization with mouse endothelial fibroblasts. A flow cytometry assay was conducted to evaluate the anti-inflammatory effect, and demonstrated the differentiation of mouse macrophages to an M2 (reparative) phenotype. Therefore, the levels of TNF-α, interleukin-6 (IL-6), and interleukin (IL-10) were quantified to further evaluate this effect, demonstrating an inhibition on the pro-inflammatory ones. The inherent antibacterial capacity of the PIL was demonstrated against Staphylococcus aureus and Escherichia coli, thereby corroborating its potential as a wound dressing. To the best of our knowledge, this is the first reported hydrogel incorporating an anion-exchanged polymerizable ionic liquid that is capable of promoting macrophage differentiation into a reparative phenotype, of reducing pro-inflammatory cytokines, and of simultaneously retaining antibacterial activity. These features open the gate to the potential application of this hydrogel as a wound dressing. STATEMENT OF SIGNIFICANCE: Bacterial wound infections may lead to severe problems due to their associate tissue inflammation and the emergence of bacterial resistance. In this sense, local therapies such as hydrogels have gathered much attention as alternative therapies for these pathologies. In this work, we have developed a natural polymer-based hydrogel copolymerized with a polymerizable ionic liquid containing salicylate as an anion. The hydrogel was shown to be biocompatible, and promoted macrophage differentiation to a reparative phenotype, while reducing the levels of pro-inflammatory cytokines. Finally, the high antibacterial capability against both gram-positive and gram-negative bacteria makes it a promising candidate for use in wound dressings.

The mussel-inspired GelMA/dopamine/hyaluronic acid composite hydrogel dressing for wet surface adhesion

Tissue adhesives have attracted wide attention as alternatives to sutures. Further developments in adhesives with excellent adhesion and biocompatibility for wet tissue surfaces are still required. This study provides a new solution for the development of bioadhesives for use on tissue surfaces under wet conditions. In this study, a novel adhesive composite hydrogel (GDHA) consisting of methacrylated gelatin (GelMA), hyaluronic acid (HA) and dopamine (DA) is developed by Schiff base reaction and photo-crosslinking. A series of experiments including material characterization, mechanical tests, biocompatibility test and experiments in mice have been done to evaluate the proposed dressing. The results show that GDHA composite hydrogel dressing retains the photo-crosslinking properties of GelMA, which makes it easier to be prepared. In addition, the dressing overcomes the easy oxidation disadvantages of existing mussel-inspired adhesives by grafting DA onto HA, which makes it adhere more stable, especially for wet surfaces. Besides, the GDHA hydrogel exhibits excellent biocompatibility and it could promote wound healing by reducing inflammatory cells and accelerating collagen deposition in a full-layer skin wound mode of mice. These results suggest that the GDHA hydrogel with stable adhesion and great biocompatibility is an alternative for wet surface, presenting potential clinical applications.

Swelling-Shrinking Behavior of a Hydrogel with a CO2-Switchable Volume Phase Transition Temperature

Macromolecules exhibit rich phase behavior that may be exploited for advanced material design. In particular, the volume phase transition in certain crosslinked hydrogels is a key property controlling the transition between a collapsed/dehydrated and a swollen/hydrated state, thereby regulating the release and absorption of water via a temperature change. In this work, a simple and tunable system exhibiting a carbon dioxide (CO2)-switchable volume phase transition is introduced, which displays isothermal swelling-shrinking behavior that is activated by addition and removal of CO2, respectively. Through systematic compositional studies, shifts in phase transition temperatures of up to 8.6 °C are measured upon CO2 exposure, which enables pronounced isothermal swelling in response to CO2, reaching up to a fivefold increase in mass. The shift in transition temperature and the extent of swelling are controlled by the hydrogel composition, thus enabling the transition temperature and swelling degree to be tuned a priori for a particular application. Controlled release experiments from these gels upon a CO2-induced phase transition suggest viability for drug delivery applications. It is anticipated that this work will motivate and expand efforts to exploit phase behavior for smart material development.

Hierarchical Porous Aerogel-Hydrogel Interlocking Bioelectronic Interface for Arrhythmia Management

Carbon aerogels with exceptional electrical properties are considered promising materials for bioelectronics in signal detection and electrical stimulation. To address the mechanical incompatibilities of carbon aerogels with bio-interfaces, particularly for dynamic tissues and organs, the incorporation of hydrogels is an effective strategy. However, achieving excellent electrical performance in carbon aerogel-hydrogel hybrids remains a significant challenge. Two key factors contribute to this difficulty: 1) unrestricted hydrogel infiltration during preparation can lead to complete encapsulation of the conductive aerogel, and 2) the high swelling behavior of hydrogels can cause disconnection of the aerogel. Herein, a stretchable, highly conductive bioelectronic interface is achieved by forming an interlocking network between hierarchical porous carbon aerogel (PA) with polyvinyl alcohol (PVA) hydrogel. Partial exposure of the PA due to confined infiltration of PVA into the porous structure maintains the electrical performance, while the non-swellable PVA ensures mechanical stretchability and stability. The hybrid demonstrates excellent conductivity (370 S·m-1), high charge storage capacity (1.66 mC cm-2), remarkable stretchability (250%), and long-term stability over three months, enabling effective signal recording and electrical stimulation. For the first time, carbon aerogel-hydrogel hybrids enable cardiac pacing both ex vivo and in vivo in rat heart models. Compared to conventional platinum electrodes, the PA-PVA electrodes require lower pacing voltages, suggesting potential advantages in power efficiency and reduced tissue damage. The electrodes can be integrated with a wireless implantable device for in vivo synchronous electrocardiogram monitoring and cardiac pacing, underscoring their potential for arrhythmia management.

A novel core-shell microsphere with hydrophobic and gel chromatography functions enhances protein purification

The spatial configuration and bonding conditions of polysaccharide microspheres make it difficult to distinguish molecules with similar hydrophobic properties in practical applications. Fortunately, medium modification offers more flexible chromatography conditions and higher selectivity, providing new solutions for complex purification environments. We synthesized hydrophobic composite core-shell agarose microspheres equipped with hydrophobic ligands and investigated the effects of hydrophobic ligand coupling on the morphology, particle size, pressure resistance, functional group change and protein adsorption capacity of microspheres. On this basis, the protein adsorption kinetics indicated that the best coupling temperature and time of phenyl and butyl were 40 °C, 8 h and 20 °C, 16 h, respectively. When the concentration of (NH4)2SO4 salt in the mobile phase is 2 M, and the pH is 7.0, the dynamic adsorption capacity of the medium for BSA reaches 12.6 mg/mL. The separation, purification efficiency, and resolution of these microspheres in a crude enzyme solution containing flavin monooxygenase improved significantly, demonstrating the practical implications and potential applications of this research. Overall, our findings reveal that this natural polysaccharide core-shell medium increases the modifiable sites of ligands, and can modify ligands in both the inner and outer layers, exhibiting its potential application in biomolecular separation.

Enhanced gelatin methacryloyl nanohydroxyapatite hydrogel for high-fidelity 3D printing of bone tissue engineering scaffolds

Patients suffering from large bone defects are in urgent need of suitable bone replacements. Besides biocompatibility, such replacements need to mimic the 3D architecture of bone and match chemical, mechanical and biological properties, ideally promoting ossification. As natural bone mainly contains collagen type I and carbonate hydroxyapatite, a 3D-printable biomaterial consisting of methacrylated gelatin (GelMA) and nanohydroxyapatite (nHAp) would be beneficial to mimic the composition and shape of natural bone. So far, such nanocomposite hydrogels (NCH) suffered from unsatisfactory rheological properties making them unsuitable for extrusion-based 3D printing with high structural fidelity. In this study, we introduce a novel GelMA/nHAp NCH composition, incorporating the rheological modifier carbomer to improve rheological properties and addressing the challenge of calcium cations released from nHAp that hinder GelMA gelation. Leveraging its shear-thinning and self-healing properties, the NCH ink retains its shape and forms cohesive structures after deposition, which can be permanently stabilized by subsequent UV crosslinking. Consequently, the NCH enables the printing of 3D structures with high shape fidelity in all dimensions, including thez-direction, allowing the fabrication of highly macroporous constructs. Both the uncured and the UV crosslinked NCH behave like a viscoelastic solid, withG'>G″ at deformations up to 100-200 %. After UV crosslinking, the NCH can, depending on the GelMA concentration, reach storage moduli of approximately 10 to over 100 kPa and a mean Young's Modulus of about 70 kPa. The printed scaffolds permit not only cell survival but also osteogenic differentiation, highlighting their potential for bone tissue engineering.

Alginate/bacterial cellulose/GelMA scaffolds with aligned nanopatterns and hollow channel networks for vascularized bone repair

Designed macropores and nanopatterned surfaces are important architectural cues in three-dimensional (3D) scaffolds for promoting vascularization and bone regeneration. However, the fabrication of 3D scaffolds with both controlled nanopatterned surfaces and designed macropores remains a challenge, especially for hydrogel-based scaffolds. Herein, alginate (Alg)/bacterial cellulose (BC)/ Gelatin Methacryloyl (GelMA) composite scaffold with fully interconnected Hollow Channel Networks And An Aligned Nanopatterned Surface (HCAS) is fabricated using 3D printing, surface crosslinking, and prestretching/drying-induced orientation. The highly aligned nanofibrous structures significantly enhance the mechanical properties, as well as the structural stability of the hydrogel scaffold. In vitro experiments prove that the HCAS scaffold exhibits apparently enhanced angiogenic and osteogenic properties compared to the control groups since the aligned nanopatterns and hollow channels can activate the cyclic AMP-dependent Ras-related protein 1 (cAMP-RAP1) and mitogen-activated protein kinase (MAPK) pathways, respectively, and jointly promote the downstream phosphoinositide 3-kinase/hypoxia-inducible factor-1 (PI3K/HIF-1) pathway. In vivo experiments also show that HCAS scaffold significantly promotes vascularization and bone regeneration, further verifying the joint effect of the aligned nanopatterned surface and fully interconnected hollow channels in promoting vascularization and osteogenesis. Thus, the HCAS scaffold demonstrates that a cell- and growth factor-free approach can also promote satisfactory vascularization and bone regeneration, simply by creating nanopatterned surfaces and designed hollow channels within hydrogel scaffolds.

Hydrogel adhesives for tissue recovery

Hydrogel adhesives (HAs) are promising and rewarding tools for improving tissue therapy management. Such HAs had excellent properties and potential applications in biological tissues, such as suture replacement, long-term administration, and hemostatic sealing. In this review, the common designs and the latest progress of HAs based on various methodologies are systematically concluded. Thereafter, how to deal with interfacial water to form a robust wet adhesion and how to balance the adhesion and non-adhesion are underlined. This review also provides a brief description of gelation strategies and raw materials. Finally, the potentials of wound healing, hemostatic sealing, controlled drug delivery, and the current applications in dermal, dental, ocular, cardiac, stomach, and bone tissues are discussed. The comprehensive insight in this review will inspire more novel and practical HAs in the future.

Eco-Friendly Conductive Hydrogels: Towards Green Wearable Electronics

The rapid advancement of wearable electronics has catalyzed the development of flexible, lightweight, and highly conductive materials. Among these, conductive hydrogels have emerged as promising candidates due to their tissue-like properties, which can minimize the mechanical mismatch between flexible devices and biological tissues and excellent electrical conductivity, stretchability and biocompatibility. However, the environmental impact of synthetic components and production processes in conventional conductive hydrogels poses significant challenges to their sustainable application. This review explores recent advances in eco-friendly conductive hydrogels used in healthcare, focusing on their design, fabrication, and applications in green wearable electronics. Emphasis is placed on the use of natural polymers, bio-based crosslinkers, and green synthesis methods to improve sustainability while maintaining high performance. We discuss the incorporation of conductive polymers and carbon-based nanomaterials into environmentally benign matrices. Additionally, the article highlights strategies for improving the biodegradability, recyclability, and energy efficiency of these materials. By addressing current limitations and future opportunities, this review aims to provide a comprehensive understanding of environmentally friendly conductive hydrogels as a basis for the next generation of sustainable wearable technologies.

Bioderived Green Algae Metabolite as a Latent Cross-Linking Agent for Protein-Based Hydrogels with High Potential for Skin Repair Applications

Despite advances in wound treatment through tissue engineering, the rapid colonization of biomaterials by host cells remains a crucial step toward complete wound healing. Thanks to their excellent biocompatibility, biodegradability, low antigenicity and cost-effectiveness, cross-linked hydrogels have attracted much attention as a viable solution for wound treatment. In this work, we have developed an inovative cross-linking method for gelatin-based hydrogels inspired by the wound closure mechanism of the green algae Caulerpa taxifolia. Caulerpenyne (CYN), a metabolite extracted from the algae, was used as a latent cross-linking agent for gelatin. The covalent cross-linking process is triggered by an in situ and on-demand deacetylation of the enol acetate functionalities of CYN in oxytoxin 2 (OXY) containing 1,4-dialdehyde, which immediately reacts with the lysine residue in gelatin. The content of ε-amino groups in gelatin was monitored as a function of CYN concentration. Swelling and gel content were analyzed as a function of CYN concentration. Morphology, rheological and biological properties were evaluated by in vitro and in vivo tests. Cell adhesion and viability tests performed with OXY-cross-linked hydrogels and compared with non-cross-linked and genipin-cross-linked gelatin showed excellent performance. Their use in whole skin wounds in pigs showed that CYN-cross-linked hydrogels promoted complete skin regeneration without any cytotoxicity, making them extremely promising matrices in the field of regenerative medicine.

Functionalization of Polycaprolactone 3D Scaffolds with Hyaluronic Acid Glycine-Peptide Conjugates and Endothelial Cell Adhesion

This study enhances the bioactivity of polycaprolactone (PCL) scaffolds for tissue engineering by functionalizing them with oxidized hyaluronic acid glycine-peptide conjugates to improve endothelial cell adhesion and growth. Hyaluronic acid was conjugated with a glycine-peptide to create a bioactive interface on PCL (static water contact angle, SCA(H2O): 98°). The scaffolds were fabricated using a melt extrusion 3D printing technique. The HA-glycine peptide conjugates were oxidized and immobilized on aminolyzed PCL via Schiff-base chemistry, introducing hydrophilicity (SCA(H2O): 21°), multiple functional groups, and a negative zeta potential (-12.04 mV at pH 7.4). A quartz crystal microbalance confirmed chemical conjugation and quantified the mass (8.5-10.3 mg m-2) of oxidized HA-glycine on PCL. The functionalized scaffolds showed enhanced swelling, improved mechanical properties (2-fold increase in strength, from 26 to 51 MPa), and maintained integrity during degradation. In-vitro experiments demonstrated improved endothelial cell adhesion, proliferation and viability, suggesting the potential for vascularized tissue constructs.

Calcium-ion-driving assembly of polysaccharide deriving from Zizyphus jujuba to hemostatic hydrogel for treating diabetic wound

Due to good biocompatibility and biodegradable, natural polysaccharide-based hydrogels have received worldwide attentions, where polysaccharide polymers were usually chemically modified to meet the specific elastic requirements. However, it remained highly challenging to develop polysaccharide-based hydrogels with desired mechanical properties and biological functions devoid of any structural modifications. Herein, with the coordination of Ca2+ (15.0 mM), the jujuba polysaccharide (JPS, 1 %) was facilely fabricated to a hydrogel (JPS-gel) within 1 min at pH 10, where the residual proteins also played crucial roles on the assembly. The JPS-gel showed outstanding stability and mechanical properties, which were tunable by adjusting the content of Ca2+/JPS. The JPS-gel also revealed excellent biocompatibility, and could expedite the migration and proliferation of healing-related cells, angiogenesis and alleviate inflammation response. More interestingly, the JPS-gel had hemostatic capacity, where the hemostatic time and blood loss in liver incision model were 13 ± 3 s and 6.3 ± 1.6 mg after 120 s treatment with JPS-gel, respectively. All these superiorities endowed JPS-gel high performance healing in diabetic wounds (10 days). Specially, the expressions of inflammation-related genes were downregulated, but gene expressions associated with cell migration and proliferation, and angiogenesis were upregulated, thus uncovering the action mechanism of JPS-gel on accelerating wound contraction.

Facile synthesis of ultratough conductive gels with swelling and freezing resistance for flexible sensor applications

The application of flexible hydrogel sensors in extreme environments, such as low temperatures, underwater, or significant mechanical deformations, poses considerable challenges. Here, we present a simple one-pot method to fabricate ultra-tough, swelling- and freezing-resistant conductive organohydrogels without external conductive and freeze-resistant fillers. During gelation, by-products (C6H15NHCl, KCl) provide both conductivity and antifreeze properties, thus eliminating compatibility issues and dispersion challenges associated with external fillers. The resulting gel exhibits super toughness, with tensile strength reaching 10.2 MPa and stretchability up to 800% in the dry state. Following covalent crosslinking, the gel demonstrates excellent anti-swelling properties, with a swelling ratio of only 15.4% after 24 h of water immersion, while maintaining a tensile strength of 5.8 MPa and an elongation of up to 1000%. When fabricated into flexible sensors, these gels display stable electrical responsiveness and desired Gauge Factor (0.58-2.25), effectively detecting limb movements. Furthermore, the gel's superior resistance to freezing and swelling ensures reliable signal stability under both - 20 °C and underwater conditions. These combined properties render the conductive gel a promising candidate for flexible sensing components in robotic and bionic applications.

An active shrinkage and antioxidative hydrogel with biomimetic mechanics functions modulates inflammation and fibrosis to promote skin regeneration

Achieving scar-free skin regeneration in clinical settings presents significant challenges. Key issues such as the imbalance in macrophage phenotype transition, delayed re-epithelialization, and excessive proliferation and differentiation of fibroblasts hinder wound healing and lead to fibrotic repair. To these, we developed an active shrinkage and antioxidative hydrogel with biomimetic mechanical functions (P&G@LMs) to reshape the healing microenvironment and effectively promote skin regeneration. The hydrogel's immediate hemostatic effect initiated sequential remodeling, the active shrinkage property sealed and contracted the wound at body temperature, and the antioxidative function eliminated ROS, promoting re-epithelialization. The spatiotemporal release of LMs (ACEI) during the inflammation phase regulated macrophage polarization towards the anti-inflammatory M2 phenotype, promoting progression to the proliferation phase. However, the profibrotic niche of macrophages induced a highly contractile α-SMA positive state in myofibroblasts, whereas the sustained LMs release could regulate this niche to control fibrosis and promote the correct biomechanical orientation of collagen. Notably, the biomimetic mechanics of the hydrogel mimicked the contraction characteristics of myofibroblasts, and the skin-like elastic modulus could accommodate the skin dynamic changes and restore the mechanical integrity of wound defect, partially substituting myofibroblasts' mechanical role in tissue repair. This study presents an innovative strategy for skin regeneration.

Gellan-amino acid hydrogel-based bioreactor for optimizing the production of yeast metabolites

Hydrogels mimic natural environments due to their hydrated, polymeric networks which are beneficial for microorganism growth. The substantial water content maintains a consistently moist environment, and porous structure of hydrogel promotes efficient nutrient transfer and cell distribution, offering advantages over traditional liquid bioreactors. While their application in cell immobilization for bioconversion is well-known, their use as a solid-state fermentation matrix remains unexplored. This study is the first attempt to integrate gellan and amino acids to develop an innovative hydrogel bioreactor. The performance of this system was determined by cultivating Rhodosporidium sp. (MTCC 9733) as a model organism and evaluating its metabolite production. Further, gellan and amino acids concentration was optimized using one-factor-at-a-time and D-optimal response surface methodologies to produce β-carotene, lipid, and protein. Additionally, a comparison of productivity, yield, and process economics suggested that novel solid-state hydrogel fermentation approach outperformed classical submerged fermentation in YMB liquid media. Moreover, rheological properties of optimized hydrogel, conducted before and after yeast cultivation, revealed that this system possesses significant mechanical strength and structural integrity. Such attributes render the hydrogel suitable for utilization across multiple fermentation cycles. Hence, this study illustrates the potential of gellan-amino acid hydrogels as sustainable, efficient alternatives to conventional fermentation methods.

Lauric acid-loaded biomimetic, biocompatible, and antioxidant jelly fig (Ficus awkeotsang Makino) pectin hydrogel accelerates wound healing in diabetic rats

Herein, we have presented a lauric acid (LA)-loaded jelly fig pectin (JFP)-based biocompatible hydrogel, which possesses strong antioxidant and antibacterial properties to treat diabetic wounds. The antioxidant and antibacterial activity of the JFP + LA hydrogels were beneficial in eliminating the reactive oxygen species (ROS) and bacterial infection in the wound bed, thereby protecting the wound surface and accelerating the tissue repair process. The in vivo diabetic wound healing studies demonstrated that applying JFP + LA hydrogels improved the rate of wound contraction and reduced the epithelialization time significantly. The epithelialization period of the control, JFP, JFP + LA 0.5 %, and JFP + LA 1 % hydrogels were 28 ± 1.5 days, 24 ± 1 days, 18.5 ± 1 days, and 19 ± 1 days, respectively. JFP also enhanced the neovascularization and collagen synthesis during wound healing. The incorporation of LA reduced the inflammation and helped recruit macrophages to proceed to other phases of wound healing in rats treated with JFP + LA hydrogels. The results presented provide insight into the clinical management of infected diabetic wounds. Overall, the results demonstrated that the JFP + LA hydrogels were an inexpensive dressing material that accelerated the healing of diabetic wounds.

Integrating microfluidics, hydrogels, and 3D bioprinting for personalized vessel-on-a-chip platforms

Thrombosis, a major cause of morbidity and mortality worldwide, presents a complex challenge in cardiovascular medicine due to the intricacy of clotting mechanisms in living organisms. Traditional research approaches, including clinical studies and animal models, often yield conflicting results due to the inability to control variables in these complex systems, highlighting the need for more precise investigative tools. This review explores the evolution of in vitro thrombosis models, from conventional polydimethylsiloxane (PDMS)-based microfluidic devices to advanced hydrogel-based systems and cutting-edge 3D bioprinted vascular constructs. We discuss how these emerging technologies, particularly vessel-on-a-chip platforms, are enabling researchers to control previously unmanageable factors, thereby offering unprecedented opportunities to pinpoint specific clotting mechanisms. While PDMS-based devices offer optical transparency and fabrication ease, their inherent limitations, including non-physiological rigidity and surface properties, have driven the development of hydrogel-based systems that better mimic the extracellular matrix of blood vessels. The integration of microfluidics with biomimetic materials and tissue engineering approaches has led to the development of sophisticated models capable of simulating patient-specific vascular geometries, flow dynamics, and cellular interactions under highly controlled conditions. The advent of 3D bioprinting further enables the creation of complex, multi-layered vascular structures with precise spatial control over geometry and cellular composition. Despite significant progress, challenges remain in achieving long-term stability, incorporating immune components, and translating these models to clinical applications. By providing a comprehensive overview of current advancements and future prospects, this review aims to stimulate further innovation in thrombosis research and accelerate the development of more effective, personalized approaches to thrombosis prevention and treatment.

Reversible Swell-Shrink Hydrogel Microspheres for High-Selectivity Digital SERS Analysis of Nonvolatile Fentanyl in Simulated Breath Aerosols

In clinical diagnostics, human breath presents an alternative and more convenient sample than biofluids for detecting the ingestion of nonvolatile drugs. Surface-enhanced Raman spectroscopy (SERS) is a powerful vibrational spectroscopy technique with high sensitivity based on molecular fingerprinting. However, the low affinity of traditional SERS substrates for aerosols and the stochastic fluctuation of the SERS signal at low concentrations limit their application in breath aerosol analysis. In this study, we synthesized hydrogel microsphere SERS substrates with highly reversible swelling/shrinking properties that enhance target analyte accumulation in breath aerosols and promote plasmonic nanoparticle aggregation for intense Raman hotspot formation. Furthermore, these hydrogel microsphere SERS substrates function as a three-in-one system, enabling multilevel selectivity based on size, charge, and hydrophilicity for target molecules simultaneously without pretreatment. Notably, by "digitizing" the SERS signal of each individual hydrogel microsphere and calculating the proportion of positive microspheres, the hydrogel microspheres can serve as a digital SERS platform that circumvents the low stability issues resulting from fluctuations in SERS signal intensity. Consequently, the digital SERS platform achieved a detection limit of 0.5 ppm for fentanyl in simulated breath aerosols. This innovative sensing strategy not only demonstrates a promising approach for screening nonvolatile drugs but also simplifies the sampling process, holding great potential for clinical diagnosis of breath aerosols.

Schiff Base-Crosslinked Tetra-PEG-BSA Hydrogel: Design, Properties, and Multifunctional Functions

Hydrogel network structures play a crucial role in determining mechanical properties and have broad applications in biomedical and industrial fields. Therefore, their rational design is essential. Herein, we developed a Schiff base-crosslinked hydrogel through the reaction of Tetra-armed polyethylene glycol with aldehyde end groups (Tetra-PEG-CHO) and bovine serum albumin (BSA) under alkaline conditions. In addition, the Tetra-PEG-BSA hydrogel showed a rapid gelation time of around 11 s, much faster than that of the GLU-BSA, HT-BSA, and GDL-BSA hydrogels. It had high optical transmittance (92.92% at 600 nm) and swelling ratios superior to the other gels in different solutions, maintaining structural integrity even in denaturing environments such as guanidine hydrochloride and SDS. Mechanical tests showed superior strain at break (84.12 ± 0.76%), rupture stress (28.64 ± 1.21 kPa), and energy dissipation ability (468.0 ± 34.9 kJ·m-3), surpassing all control group hydrogels. MTT cytotoxicity assays indicated that cell viability remained >80% at lower concentrations, confirming excellent biocompatibility. These findings suggest that Tetra-PEG-BSA hydrogels may serve as effective materials for drug delivery, tissue engineering, and 3D printing.

Cellulose-based biodegradable superabsorbent hydrogel: A sustainable approach for water conservation and plant growth in agriculture

Innovative deficit irrigation technologies are imperative to overcome challenges posed to crop growth/yield and agriculture sustainability due to water scarcity in arid and semiarid regions. In the current study, superabsorbent biodegradable hydrogel based on carboxymethylcellulose sodium salt (NaCMC) and hydroxy ethyl cellulose (HEC) has been developed using citric acid (CA) as a crosslinker. The hydrogel has demonstrated excellent water absorption, retention, and release properties. Moreover, hydrogel (2 %) modified soil (HMS) has depicted increased porosity (57 %) and reduced soil density (1.06 g/cm3), compared to unmodified soil (UMS) with porosity of 53 % and density of 1.16 g/cm3, as well as, the water use efficiency of the plants (25.25 %-45.52 % over UMS) grown in HMS, which is vital for comprehending soil properties and their impact on water retention and aeration. The plant growth study in HMS concerning critical growth parameters such as germination rate, Seedling Vigour Index (SVI), Root Shoot Ratio (RSR), crop growth ratio (CGR), and chlorophyll content of three plants, i.e., one summer-grown plant-cucumber and two winter-grown plants- tomato and mung bean, has manifested promising results. Decisive parameters such as seedling viability (4.51 %), plant growth rate (3.77 %), and photosynthetic ability (16.74 %) were increased for chosen plants grown in HMS as compared to UMS. Improved growth parameters and photosynthetic ability of plants in HMS have suggested ameliorated nutrient and water absorption rates, increased resource utilization, and improved response to extrinsic resource allotment caused by hydrogel modification. Statistical analyses supported the trends in plant growth. Thus, hydrogel modification of the soil can effectively mitigate water use by retaining moisture efficiently and positively facilitating growth.

Advanced alginate/58S bioactive glass inks with enhanced printability, mechanical strength, and cytocompatibility for soft tissue engineering

Alginate-based hydrogels are promising biomaterials for extrusion-based bioprinting; however, their poor mechanical properties, printability, and shape integrity limit their utility in mimicking complex tissues and organs. In this study, a novel sodium alginate (Alg)/58S bioactive glass (BG)-based ink was developed for soft tissue engineering applications. The inks were characterised for shear-thinning, flowability, and shape integrity by printing various structures, including single filaments (0° and 90° nozzle movement), scaffolds, and rings. The ABG10 ink (10 wt% 58S BG in Alg) exhibited superior printability, achieving a printing accuracy of over 90 %, compared to a printing accuracy of 30-40 % for pure Alg. Fourier transform infrared spectroscopy revealed interactions between 58S BG and the Alg matrix, while scanning electron microscopy characterised the 58S BG morphology within the matrix. The storage modulus increased from 767 (pure Alg) to 13,604 Pa (ABG10), while compressive strength rose from 23 ± 3 to 43 ± 4 kPa (58 % enhancement). The cytocompatibility of the inks was assessed using an MTT assay (with SH-SY5Y cells), which confirmed that ABG10 ink supports cell viability. Overall, ABG10 hydrogel-based inks exhibited enhanced shear-thinning behaviour, printability, mechanical strength, and cytocompatibility, which could help to develop patient-specific soft tissues.

Food-Derived Tripeptide-Copper Self-Healing Hydrogel for Infected Wound Healing

The field of infected wound management continues to face challenges, and traditional methods used to cope with wounds include debridement, gauze coverage, medication, and others. Currently, synthetic and natural biomaterials are readily available today, enabling the creation of new wound dressings that substantially enhance wound healing. Considerable attention is being paid to hydrogels based on natural materials, which have good biocompatibility and degradability properties, while exhibiting higher similarity to natural extracellular matrix as compared to synthetic materials. In this study, we extracted the active ingredients of oxidized konjac glucomannan (OKGM) and fresh egg white (EW) from 2 foods, konjac, and egg, respectively, and formed a self-repairing hydrogel based on the cross-linking of a Schiff base. Subsequently, a natural active peptide, glycyl-l-histidyl-l-lysine-Cu (GHK-Cu), was loaded, and an all-natural composite hydrogel dressing, EW/OKGM@GHK-Cu (GEK), was developed. The GEK hydrogel, exhibiting both antibacterial and anti-inflammatory properties, plays a hemostatic role by adhering to tissues and promoting neovascularization and serves as an optimal dressing for skin regeneration. Taken together, GEK hydrogel dressings derived from natural food sources therefore constitute an efficient and cost-effective strategy for managing infected wound healing and have significant potential for clinical application and transformation.

Biomaterials for Corneal Regeneration

Corneal blindness is a significant reason for visual impairment globally. Researchers have been investigating several methods for corneal regeneration in order to cure these patients. Biomaterials are favored due to their biocompatibility and capacity to promote cell adhesion. A variety of natural and synthetic biomaterials, along with decellularized cornea, have been employed in corneal wound healing. Commonly utilized natural biomaterials encompass proteins such as collagen, gelatin, and silk fibroin (SF), as well as polysaccharides including alginate, chitosan (CS), hyaluronic acid (HA), and cellulose. Synthetic biomaterials primarily consist of polyvinyl alcohol (PVA), poly(ε-caprolactone) (PCL), and poly (lactic-co-glycolic acid) (PLGA). Bio-based materials and their composites are primarily utilized as hydrogels, films, scaffolds, patches, nanocapsules, and other formats for the treatment of blinding ocular conditions, including corneal wounds, corneal ulcers, corneal endothelium, and stromal defects. This review attempts to summarize in vitro, preclinical, and clinical trial studies relevant to corneal regeneration using biomaterials within the last five years, and expect that these experiences and outcomes will inspire and provide practical strategies for the future development of biomaterials for corneal regeneration. Furthermore, potential improvements and difficulties for these biomaterials are discussed.

Environmental and Wastewater Treatment Applications of Stimulus-Responsive Hydrogels

Stimulus-responsive hydrogels have emerged as versatile materials for environmental and wastewater treatment applications due to their ability to adapt to changing environmental conditions. This review highlights recent advances in the design, synthesis, and functionalization of such hydrogels, focusing on their environmental applications. Various synthesis techniques, including radical polymerization, grafting, and copolymerization, enable the development of hydrogels with tailored properties such as enhanced adsorption capacity, selectivity, and reusability. The incorporation of nanoparticles and bio-based polymers further improves their structural integrity and pollutant removal efficiency. Key mechanisms such as adsorption, ion exchange, and photodegradation are discussed, emphasizing their roles in removing heavy metals, dyes, and organic pollutants from wastewater. Additionally, this review presents the potential of hydrogels for oil-water separation, pathogen control, and future sustainability through integration into circular economy frameworks. The adaptability, cost-effectiveness, and eco-friendliness of these hydrogels make them promising candidates for large-scale environmental remediation.

Alopecia Management Potential of Rosemary-Based Nanoemulgel Loaded with Metformin: Approach Combining Active Essential Oil and Repurposed Drug

Introduction

Androgenetic alopecia (AGA) is a multifactorial and age-related dermatological disease that affects both males and females, usually at older ages. Traditional hair repair drugs exemplified by minoxidil have limitations such as skin irritation and hypertrichosis. Thus, attention has been shifted to the use of repurposing drugs. Metformin is an anti-diabetic drug, that can promote hair follicle regeneration via upregulation of the hair-inductive capability. Hence, the current study aims to fabricate a safe and effective nanoemulsion to improve metformin efficacy in targeting AGA.

Methods

Rosemary oil was selected as the oily phase due to its ability to increase blood flow and hair growth. Rosemary-based nanoemulsions were statistically optimized by Box-Behnken experimental design, loaded with metformin, and incorporated into a hydrogel to form a nanoemulgel. Metformin-loaded nanoemulsions were assessed for their diametric size, uniformity, zeta potential, and metformin characteristics within the formulated nanosystem. The nanoemulgel was then evaluated in terms of its pH, percentage drug content, and in-vitro release performance. In-vivo study assessed the nanoemulgel's ability to augment hair growth in rats.

Results

The experimental design displayed that using 50%w/w, 20%w/w, and 10%w/w of Cremophor®, Labrafil®, and deionized water, respectively, resulted in nanoemulsion formulation with the smallest globule size (125.01 ± 0.534 nm), unimodal size distribution (PDI=0.103), negative surface charge (-19.9 ± 2.01 mV) with a spherical morphological structure. Rosemary-based nanoemulgel displayed acceptable physicochemical characterizations namely; a neutral pH value of 6.7±0.15, high drug content (92.9± 2.3%), and controlled metformin in-vitro release. Besides, the formulated nanoemulgel significantly increased the number of hair follicles in the animal model compared with other controls and tested groups.

Conclusion

The designed nanoemulgel is a promising approach for treating androgenic alopecia.

Development of Amniotic Epithelial Stem Cells Secretome-Loaded In Situ Inverse Electron Demand Diels-Alder-Cross-Linked Hydrogel as a Potential Immunomodulatory Therapeutical Tool

Amniotic epithelial stem cells (AEC) hold potential for tissue regeneration, especially through their conditioned medium (AEC-CM) due to their immunomodulatory and regenerative effects. Nevertheless, advanced drug delivery systems such as hydrogels are needed to enable clinical applications. Herein, an in situ gellable hyaluronic acid and polyethylene glycol-based iEDDA-cross-linked hydrogel was developed for the encapsulation and controlled release of AEC-CM. The developed system was formed by norbornene-modified hyaluronic acid and tetrazine-modified polyethylene glycol functionalized with heparin. The hydrogel was formed by mixing both precursor polymers, displaying fast cross-linking kinetics and showcasing a highly porous inner structure and low swelling properties. Moreover, the heparin-functionalized system allowed the sustained release of predominant growth factors from AEC-CM over 14 days. In vitro studies in peripheral blood mononuclear cells (PBMCs) showed an enhanced suppression efficacy and a significant shift toward the M2 macrophage phenotype in comparison with nonencapsulated AEC-CM. Therefore, this work provides a suitable alternative for the encapsulation of AEC-CM in a hydrogel formulation, highlighting its potential as an alternative immunomodulatory therapeutic tool for tissue regeneration.

Pectin-chitosan hydrogels with modified properties for the encapsulation of strawberry phenolic compounds

Pectin-chitosan hydrogels with blends of low (50-190 kDa) and medium (310-395 KDa) molecular weight (MW) chitosan (LC and MC, respectively) were developed, and their characteristics were investigated before and after the encapsulation of an aqueous strawberry extract. The pectin to total chitosan mass ratio, the composition of the strawberry extract and the MW of chitosan greatly affected the interactions between pectin and chitosan at different pH values. More specifically, blends of low and medium MW chitosan improved the stability of the strawberry-gels in acidic conditions compared to their corresponding MC-gels, showed better flow and texture profiles, as well as slower release of phenolic compounds during in vitro digestion compared to the only stable LC-gel. Therefore, by manipulating the length range of chitosan chains would allow the formation of pectin-chitosan hydrogels with improved properties for the development of functional food products.

Enhanced Tunability of Photo-Cross-Linkable Silk Sericins from Bombyx mori

Over the past decade, silk sericin has emerged as a promising material for biomedical applications, especially in tissue engineering, where fine-tuning the physicochemical properties is crucial. However, previous studies, including those on the methacrylation of sericin (yielding SS-MA), showed limited tunability. Here, we developed a photo-cross-linkable sericin-based material modified with 2-aminoethyl methacrylate (AEMA) using two synthesis routes: sequential modification of SS-MA with AEMA (SS-MA-AEMA) and an efficient one-pot synthesis (SS-AEMA). The one-pot synthesis yielded materials containing only methacrylate groups, unlike the sequential modification that yielded a combination of methacrylamides and methacrylates. Our approach resulted in superior physicochemical properties. The resulting materials, including the previously described SS-MA, exhibited a broad range of properties, such as cross-linking kinetics (0.9-64.0 s), swelling behavior (311-3775%), and mechanical properties (10-140 kPa). These properties support applications across various tissues, from dermis to fibrous tissue. The materials also demonstrated fibroblast cytocompatibility with cell viabilities exceeding 96%.

Research progress on non covalent interaction dissolution characterization of insoluble wheat protein based on swelling

The non covalent interactions of proteins are usually characterized by solubility, which is based on the principle that specific solvents can disrupt non covalent interactions and promote protein dissolution. However, this method is generally applicable to highly soluble protein materials. The solubility of wheat protein is poor. When using this method to characterize non covalent interactions, there is always a portion of protein aggregates that can only reach a swollen state and cannot be completely dissolved. At present, there are no research reports on the role of non covalent interactions in swelling. In view of this, this article first reviews the swelling and dissolution processes of insoluble proteins such as wheat protein in solvents, focusing on the characterization mechanisms and influencing factors of three non covalent interactions using solubility characterization. At the same time, this article also explores the potential of swelling in characterizing non covalent interactions, aiming to improve the characterization methods of non covalent interactions between wheat proteins and provide methodological support for analyzing processing differences from the hierarchical analysis of wheat protein interactions in the future.

Advancements in GelMA bioactive hydrogels: Strategies for infection control and bone tissue regeneration

Infectious bone defects present a significant clinical challenge, characterized by infection, inflammation, and subsequent bone tissue destruction. Traditional treatments, including antibiotic therapy, surgical debridement, and bone grafting, often fail to address these defects effectively. However, recent advancements in biomaterials research have introduced innovative solutions for managing infectious bone defects. GelMA, a three-dimensional network of hydrophilic polymers that can absorb and retain substantial amounts of water, has attracted considerable attention in the fields of materials science and biomedical engineering. Its distinctive properties, such as biocompatibility, responsiveness to stimuli, and customisable mechanical characteristics make GelMA an exemplary scaffold material for bone tissue engineering. This review aims to thoroughly explore the current literature on antibacterial and osteogenic strategies using GelMA hydrogels for the restoration of infected bones. It discusses their fabrication methods, biocompatibility, antibacterial effectiveness, and bioactivity. We conclude by discussing the existing challenges and future research directions in this field, with the hope of inspiring further innovations in the synthesis, modification, and application of GelMA-based hydrogels for infection control and bone tissue regeneration.

Fabrication of In Situ-Cross-Linked N-Succinyl Chitosan/Oxidized Alginate Hydrogel-Loaded Ascorbic Acid and Biphasic Calcium Phosphate for Bone Tissue Engineering

Bone tissue engineering is a promising technology being studied globally to become an effective and sustainable method to treat the problems of damaged or diseased bones. In this work, we developed an in situ cross-linking hydrogel system that combined N-succinyl chitosan (NSC) and oxidized alginate (OA) at varying mixing ratios through Schiff base cross-linking. The hydrogel system also contains biphasic calcium phosphate (BCP) and ascorbic acid (AA), which could enhance biological characteristics and accelerate bone repair. The hydrogels' properties were examined through physicochemical tests such as scanning electron microscopy (SEM), energy-dispersive x-ray spectroscopy (EDS), Fourier transform infrared spectroscopy (FT-IR), x-ray diffraction (XRD), pore size and porosity measurement, swelling ratio, degradation rate, AA release study, as well as cytocompatibility, including live/dead and cytotoxicity assays. The results revealed that the supplementation of AA and BCP components can affect the physico-mechanical properties of the hydrogel system. However, they exhibited noncytotoxic properties. Overall, the results demonstrated that the hydrogel composed of 3% (w/v) NSC and 3% (w/v) OA (NSC: OA volume ratio is 8:2) loaded with 40% (w/w) BCP and 0.3 mg/mL AA has the potential for bone regeneration.

Multi-responsive shape memory and self-healing hydrogels with gold and silver nanoparticles

Nanocomposite smart gels (Nc-x) with self-healing and shape memory properties were designed in different types and size nano particles with temperature or light stimuli. Nc-x networks were prepared by bulk polymerization of stearyl methacrylate (SM) and vinyl pyrrolidone (VP) in the presence of gold and silver nanoparticles. The structure, which does not contain any chemical cross-linkers, is held together by hydrophobic interactions while consisting of dipole-dipole bonds of the VP units and long alkyl groups in the side chains of the SM. Thanks to their crystalline regions, shape memory gels can self-heal with the presence of long hydrophobic chains, and furthermore, the nanoparticles (NPs) incorporated into the structure facilitate the controlled tuning of hydrophilic and hydrophobic properties. Nc-x gels have the ability to self-heal by repairing mechanical damage independently or in the presence of a stimulus, as well as transforming from a temporary form to a permanent form. In vitro experiments on human skin fibroblast cells revealed that cell viability was over 100% after 48 hours and almost complete recovery was observed in scratch experiments at the end of this period. Based on the results obtained, Nc-x gels have been shown to have the potential to be used as a non-invasive wound dressing material alternative to traditional wound closure methods.

Chitosan-Alginate Hydrogel Enriched with Hypericum perforatum Callus Extract for Improved Wound Healing and Scar Inhibition

Hypericum perforatum callus contains pluripotent stem cells, and its extract (HPCE) is a natural compound that includes various biologically active components, such as phenolic acids, flavonoids, and naphthodiantrons like hypericin and hyperforin. These components give HPCE significant antibacterial and antioxidant properties, making it a valuable option for wound healing. Unlike traditional wound dressings that may leave a residue or necessitate invasive procedures like phototherapy, HPCE is a promising alternative. This study presents a hydrogel wound dressing made from a chitosan/alginate scaffold loaded with HPCE (CA/HPCE). This system displayed remarkable mechanical properties coupled with a high swelling capacity. Moreover, it demonstrated potent antibacterial, antioxidant, and anti-inflammatory activities, promoting a favorable environment for wound healing. In vitro studies confirmed that our wound dressings effectively inhibited Escherichia coli (E. coli) and drug-resistant bacteria like Klebsiella pneumoniae (K. pneumoniae), methicillin-resistant Staphylococcus aureus (MRSA), and methicillin-resistant coagulase-negative Staphylococcus (MR-CoNS). Additionally, CA/HPCE had the potential to significantly augment fibroblast migration. Moreover, in vivo investigations confirmed that this system accelerated re-epithelialization, neovascularization, and collagen deposition while reducing inflammation. Immunohistochemistry (IHC) analysis of α-smooth muscle actin (α-SMA) indicated the absence of hypertrophic scar formation postdressing. These findings suggest that CA/HPCE is a highly effective and innovative solution for advanced wound care.

Quantum Sensing Unravels Antioxidant Efficacy Within PCL/Matrigel Skin Equivalents

Skin equivalents (SE) that recapitulate biological and mechanical characteristics of the native tissue are promising platforms for assessing cosmetics and studying fundamental biological processes. Methods to achieve SEs with well-organized structure, and ideal biological and mechanical properties are limited. Here, the combination of melt electrowritten PCL scaffolds and cell-laden Matrigel to fabricate SE is described. The PCL scaffold provides ideal structural and mechanical properties, preventing deformation of the model. The model consists of a top layer for seeding keratinocytes to mimic the epidermis, and a bottom layer of Matrigel-based dermal compartment with fibroblasts. The compressive modulus and the biological properties after 3-day coculture indicate a close resemblance with the native skin. Using the SE, a testing system to study the damage caused by UVA irradiation and evaluate antioxidant efficacy is established. The effectiveness of Tea polyphenols (TPs) and L-ascorbic acid (Laa) is compared based on free radical generation. TPs are demonstrated to be more effective in downregulating free radical generation. Further, T1 relaxometry is used to detect the generation of free radicals at a single-cell level, which allows tracking of the same cell before and after UVA treatment.

Multifunctional poloxamer-based thermo-responsive hydrogel loaded with human lactoferricin niosomes: In vitro study on anti-bacterial activity, accelerate wound healing, and anti-inflammation

Chronic wound infections are attributed to delayed tissue repair, which remains a major clinical challenge in long-term health care. Particularly, infections with antibiotic resistance have more serious effects on health, often resulting in unsuccessful treatments. Thus, antimicrobial peptide (AMP)-based therapy holds promise as a potential therapeutic approach to overcoming drug resistance. Conventional wound dressing is a passive strategy for wound care that is not capable of eradicating pathogens and promoting tissue repair. In this study, we aim to construct an advanced wound dressing; a thermo-responsive hydrogel incorporated with lactoferricin (Lfcin) niosome (Lfcin-Nio/hydrogel) for bacterial pathogen treatment. The Lfcin-loaded niosome (Lfcin-Nio) has a particle size of 396.91 ± 20.96 nm, 0.38 ± 0.01 of PdI, -10.5 ± 0.3 mV of ζ potential, and 72.30 ± 7.05 % Lfcin entrapment efficiency. Lfcin-Nio exhibited broad antibacterial activity on both drug-susceptible and drug-resistant strains, and also on bacteria residing in the biofilm matrix. The Lfcin-Nio/hydrogel was fabricated from 0.5 % w/v poloxamer 188-20 % w/v poloxamer 407, and supplemented with Lfcin-Nio and epidermal growth factor (EGF). The physical properties of Lfcin-Nio/hydrogels showed elasticity, swelling ability, and strong injectability with responsiveness to 33-37 °C temperatures. The biological properties of Lfcin-Nio/hydrogels exhibited a bactericidal effect against drug-resistant strains of S. aureus and P. aeruginosa, and showed less toxicity to the human skin fibroblast. It also promoted the healing of scratches by 55 % within 6 h, compared to the wound closure rate of 20 % in the cell control. The inflammatory response of the Lfcin-Nio/hydrogel-treated cells was reduced via suppression of IL-1β and COX-2 mRNA expressions. From this study, Lfcin-Nio/hydrogels can be suggested as a modern wound dressing that possesses multifunctional and beneficial properties for the management of chronic wound infections.

Release and Transport of Nanomaterials from Hydrogels Controlled by Temperature

Understanding the transport of nanoparticles from and within hydrogels is a key issue for the design of nanocomposite hydrogels for drug delivery systems and tissue engineering. To investigate the translocation of nanocarriers from and within hydrogel networks triggered by changes of temperature, ultrasmall (8 nm) and small (80 nm) silica nanocapsules are embedded in temperature-responsive hydrogels and non-responsive hydrogels. The ultrasmall silica nanocapsules are released from temperature-responsive hydrogels to water or transported to other hydrogels upon direct activation by heating or indirect activation by Joule heating; while, they are not released from non-responsive hydrogel. Programmable transport of nanocarriers from and in hydrogels provides insights for the development of complex biomedical devices and soft robotics.

Multifunctional hydrogel based on polyvinyl alcohol/chitosan/metal polyphenols for facilitating acute and infected wound healing

Bacterial-infected wounds could cause delayed wound healing due to increased inflammation, especially wounds infected by drug-resistant bacteria remain a major clinical problem. However, traditional treatment strategies were gradually losing efficacy, such as the abuse of antibiotics leading to enhanced bacterial resistance. Therefore, there was an urgent need to develop an antibiotic-free multifunctional dressing for bacterially infected wound healing. This study demonstrated the preparation of a multifunctional injectable hydrogel and evaluated its efficacy in treating acute and infected wounds. The hydrogel was prepared by a one-step mixing method, and cross-linked by natural deep eutectic solvent (DES), polyvinyl alcohol (PVA), chitosan (CS), tannic acid (TA), and Cu2+ through non-covalent interactions (hydrogen bonds and metal coordination bonds). PVA/CS/DES/CuTA500 hydrogel has multiple functional properties, including injectability, tissue adhesion, biocompatibility, hemostasis, broad-spectrum antibacterial, anti-inflammatory, and angiogenesis. Most importantly, in the MRSA-infected skin wound model, PVA/CS/DES/CuTA500 hydrogel could ultimately accelerate infected wound healing by killing bacteria, activating M2 polarization, inhibiting inflammation, and promoting angiogenesis. In summary, the PVA/CS/DES/CuTA500 hydrogel showed great potential as a wound dressing for bacterial infected wounds treatment in the clinic.