Enhanced tendon healing by a tough hydrogel with an adhesive side and high drug-loading capacity

Immunomodulatory bioadhesive technologies

Bioadhesives have found significant use in medicine and engineering, particularly for wound care, tissue engineering, and surgical applications. Compared to traditional wound closure methods such as sutures and staples, bioadhesives offer advantages, including reduced tissue damage, enhanced healing, and ease of implementation. Recent progress highlights the synergy of bioadhesives and immunoengineering strategies, leading to immunomodulatory bioadhesives capable of modulating immune responses at local sites where bioadhesives are applied. They foster favorable therapeutic outcomes such as reduced inflammation in wounds and implants or enhanced local immune responses to improve cancer therapy efficacy. The dual functionalities of bioadhesion and immunomodulation benefit wound management, tissue regeneration, implantable medical devices, and post-surgical cancer management. This review delves into the interplay between bioadhesion and immunomodulation, highlighting the mechanobiological coupling involved. Key areas of focus include the modulation of immune responses through chemical and physical strategies, as well as the application of these bioadhesives in wound healing and cancer treatment. Discussed are remaining challenges such as achieving long-term stability and effectiveness, necessitating further research to fully harness the clinical potential of immunomodulatory bioadhesives.

Janus piezoelectric adhesives regulate macrophage TRPV1/Ca2+/cAMP axis to stimulate tendon-to-bone healing by multi-omics analysis

Piezoelectric stimulation has garnered substantial interest as a promising strategy for tissue regeneration. However, studies investigating its impact on tendon-to-bone healing characterized by fibrocartilage remain scarce. Moreover, there are considerable technical challenges in achieving minimally invasive application of piezoelectric stimulation on the irregular tendon-to-bone interface. Herein, we developed Janus asymmetric piezoelectric adhesives by assembling adhesive hydrogel (GAN) and non-adhesive hydrogel (GM) on each side of piezoelectric poly (L-lactic acid) nanofiber. Piezoelectric adhesives exhibited superior anti-inflammatory effects both in vitro and ex vivo. Notably, the transient receptor potential (TRP) ion channels, a class of versatile signaling molecules, are closely associated with the regulation of inflammation. This study demonstrated that piezoelectric stimulation promoted Ca2+ influx through the activation of transient receptor potential vanilloid 1 (TRPV1), further enhancing cAMP signaling pathway in macrophages by RNA sequencing. Additionally, in vivo proteomic analysis revealed Arachidonic acid metabolism and TNF-α signaling pathway downregulation and VEGF signaling pathway upregulation in a rat rotator cuff repair model. Piezoelectric adhesives ultimately achieved inflammation alleviation, angiogenesis enhancement, and fibrocartilage regeneration promotion, improving the biomechanical strength of the enthesis. This study elucidated the mechanism by which piezoelectric stimulation regulated tendon-to-bone healing through multi-omics analysis. The piezoelectric adhesives hold promise as a convenient and effective strategy for enhancing tendon-to-bone healing in clinical practice.

Advanced Postsynthetic Modification of COF: Elevating Hydrophilicity for Efficient Doxorubicin Delivery

Covalent organic frameworks (COFs) show great potential as drug delivery systems (DDSs) due to their customizable structures, stability, and capacity for pore surface functionalization. However, their natural hydrophobicity limits their dispersion in water, posing challenges for biological applications. We address this issue by initially reducing a COF (Az-COF) to an amine-linked form (Az-AL-COF) and subsequently sulfonating it to obtain Az-AL-SO3H-COF, a water-dispersible derivative. Water contact angle (WCA) analysis confirmed increased hydrophilicity across the series of 84.5, 61.2, and 54.7° for Az-COF, Az-AL-COF, and Az-AL-SO3H-COF, respectively. Using doxorubicin (Dox) as a model drug, the modified COFs exhibited pH-sensitive drug release, with greater release at acidic pH (5.6) compared to neutral pH (7.4). Cytotoxicity assays revealed that Az-AL-SO3H-COF was biocompatible with normal cells (MCF-10) while effectively suppressing the growth of cancer cells (MDA-MB-231). The Dox-loaded sulfonated COF (Dox@Az-AL-SO3H-COF) showed selective cytotoxicity against cancer cells, highlighting its potential as a pH-responsive, biocompatible DDS for cancer treatment.

Polylactic acid electrospun membranes coated with chiral hierarchical-structured hydroxyapatite nanoplates promote tendon healing based on a macrophage-homeostatic modulation strategy

Tendon injury is a common and challenging problem in the motor system that lacks an effective treatment, affecting daily activities and lowering the quality of life. Limited tendon regenerative capability and immune microenvironment dyshomeostasis are considered the leading causes hindering tendon repair. The chirality of biomaterials was proved to dictate immune microenvironment and dramatically affect tissue repair. Herein, chiral hierarchical structure hydroxylapatite (CHAP) nanoplates are innovatively synthesized for immunomodulatory purposes and further coated onto polylactic acid electrospinning membranes to achieve long-term release for tendon regeneration adaption. Notably, levorotatory-chiral HAP (L-CHAP) nanoplates rather than dextral-chiral or racemic-chiral exhibit good biocompatibility and bioactivity. In vitro experiments demonstrate that L-CHAP induces macrophage M2 polarization by enhancing macrophage efferocytosis, which alleviates inflammatory damage to tendon stem cells (TDSCs) through downregulated IL-17-NF-κB signaling. Meanwhile, L-CHAP-mediated macrophage efferocytosis also promotes TDSCs proliferation and tenogenic differentiation. By establishing a rat model of Achilles tendon injury, L-CHAP was demonstrated to comprehensively promoting tendon repair by enhancing macrophage efferocytosis and M2 polarization in vivo, finally leading to improvement of tendon ultrastructural and mechanical properties and motor function. This novel strategy highlights the role of L-CHAP in tendon repair and thus provides a promising therapeutic strategy for tendon injury.

Lessons Learned and Challenges Ahead in the Translation of Implantable Microscale Sensors and Actuators

Microscale sensors and actuators have been widely explored by the scientific community to augment the functionality of conventional medical implants. However, despite the many innovative concepts proposed, a negligible fraction has successfully made the leap from concept to clinical translation. This shortfall is primarily due to the considerable disparity between academic research prototypes and market-ready products. As such, it is critically important to examine the lessons learned in successful commercialization efforts to inform early-stage translational research efforts. Here, we review the regulatory prerequisites for market approval and provide a comprehensive analysis of commercially available microimplants from a device design perspective. Our objective is to illuminate both the technological advances underlying successfully commercialized devices and the key takeaways from the commercialization process, thereby facilitating a smoother pathway from academic research to clinical impact.

Strong and Tough Tendon-Mimetic Silk Fibroin for Tissue Regeneration

Tendons exhibit outstanding mechanical performance due to their hierarchical and anisotropic structures. Despite notable progress in mimicking anisotropy, developing biomaterials that simultaneously exhibit high strength, and excellent biocompatibility remains a significant challenge. In this study, a novel strategy is proposed to fabricate multiscale, tendon-mimetic regenerated silk fibroin (RSF) scaffold with a preferentially aligned microstructure and superior mechanical properties. This strategy integrates ethanol-annealing to induce β-sheet crystallization (nanoscale), freeze-casting to create aligned microstructures (microscale), and densification to enhance interfacial bonding (macroscale). The synergistic effect of these multiscale structures effectively resists crack propagation, yielding impressive mechanical properties: a tensile strength of 7.8 MPa, elongation at break of 206%, and toughness of 14.52 MJ m-3. Notably, the scaffold is fabricated through a purely physical process, free of chemical modifications or additives, preserving its biocompatibility and suggesting promising clinical potential. This biomimetic RSF scaffold promotes tendon cell adhesion, directional migration, and upregulated expression of tendon-specific proteins. After 8 weeks of implantation in a rabbit full-thickness Achilles tendon defect model, the scaffold effectively promoted realignment of the newly formed collagen fibers, resulting in a regenerated tendon structure that closely resembles native tendon architecture. This study provides insights into the design and manufacturing of high-performance biomaterials.

Conductive Hydrogels with Topographical Geometry and Mechanical Robustness for Enhanced Peripheral Nerve Regeneration

Nerve guidance conduits (NGCs) emerge as a promising solution for nerve regeneration; however, conventional NGCs fail to fulfill the requirements for peripheral nerve regeneration, which are subjected to periodical yet vigorous stretching, bending, and compression. Here, we developed a fatigue-resistant conductive hydrogel-based NGC by integrating topographical geometry, enhanced electroactivity, and superior fatigue resistance within one unit. The hydrogel, consisting of a PVA matrix with PEDOT:PSS as a conductive filler, features a topographical alignment that promotes axonal growth and achieves a fatigue threshold over 500 J/m2, making it well-suited for sciatic nerve repairing. Phase segregation of PEDOT chains enhances its electrical conductivity (>500 S/m) and mitigates the interfacial impedance mismatch, allowing for high-efficiency bioelectrical signal transmission. In vivo studies on a rat sciatic nerve injury model corroborate the accelerated peripheral nerve regeneration through improved motor function recovery and efficient electrophysiological signal transmission. These findings establish our hydrogel-based NGCs as a promising solution for high-efficiency nerve regeneration through the synergy of topographical, mechanical, and electrical engineering.

Versatile Solid-State Medical Superglue Precursors of α-Lipoic Acid

α-Lipoic acid (αLA) is an attractive building block for medical adhesives. However, due to poor water solubility of αLA and high hydrophobicity of poly(αLA), elevated temperatures, organic solvents, or complex preparations are typically required to obtain and deliver αLA-based adhesives to biological tissue. Here, we report αLA-based powder and low-viscosity liquid superglues that polymerize and bond rapidly upon contact with wet tissue. A monomeric mixture of αLA, sodium lipoate, and an activated ester of lipoic acid was used to formulate the versatile adhesives. Stress-strain measurements of the wet adhesives confirmed the high flexibility of the adhesive. Moreover, a small molecule regenerative drug was successfully incorporated into and released from the adhesive without altering the physical and adhesive properties. In vitro and in vivo studies of the developed adhesives confirmed their cell and tissue compatibility, biodegradability, and potential for sustained drug delivery. Moreover, due to the inherent ionic nature of the adhesives, they demonstrated high electric conductivity and sensitivity to deformation, allowing for the development of a tissue-adherent strain sensor.

A Microphase Separation-Driven Supramolecular Tissue Adhesive with Instantaneous Dry/Wet Adhesion, Alcohol-Triggered Debonding, and Antibacterial Hemostasis

Tissue adhesives are promising materials for expeditious hemorrhage control, while it remains a grand challenge to engineer a superior formulation with instantaneous adhesion, on-demand debonding, and the integration of multiple desirable properties such as antibacterial and hemostatic capabilities. Herein, a multifunctional supramolecular tissue adhesive based on guanidinium-modified polydimethylsiloxane (PDMS) is introduced, driven by a reversible microphase separation mechanism. By optimizing the content of guanidinium ions, precise control over cohesive strength, adhesion, and wettability is achieved, resulting in strong instantaneous adhesion under both dry and wet conditions. Notably, the supramolecular nature of the adhesive allows for convenient on-demand removal using medical-grade alcohol, offering a critical advantage for easy debonding. Additionally, the adhesive exhibits remarkable antimicrobial properties while maintaining excellent biocompatibility and hemocompatibility. Its underwater injectability supports minimally invasive surgical procedures. Furthermore, the adhesive's ability to incorporate solid particles enhances its versatility, particularly for the development of drug-embedded bioadhesives. This work addresses key challenges in tissue adhesive design via a microphase separation-driven working principle, thereby opening promising new avenues for the development of advanced bioadhesives with tailored properties and enhanced surgical and wound care outcomes.

Robust Janus Hydrogel with Wet-Tissue Adhesive Properties for Wound Dressing and Anti-Postoperative Adhesion

Although adhesive hydrogels have advanced rapidly in recent years, conventional double-sided adhesives still face challenges in achieving effective adhesion to wet tissues and preventing postoperative tissue adhesion. In this study, a novel Janus hydrogel wet adhesive was successfully designed by precisely regulating the distribution of free hydroxyl and phenolic hydroxyl groups on the two surfaces of the hydrogel. The resulting Janus hydrogel exhibits significantly different adhesive and nonadhesive properties on its upper and lower surfaces. Specifically, through a simple boric acid (BA) solution immersion process, BA cross-linked with poly(vinyl alcohol) (PVA) and tannic acid (TA), effectively suppressing the exposure of hydroxyl groups on the upper surface, leading to low adhesion. In contrast, the lower surface retains strong adhesion to various wet tissues, even underwater. Adhesion simulations with pig skin validated the robust adhesion of the hydrogel's bottom surface to wet tissues, while the low-adhesion upper surface effectively prevented tissue adhesion. Furthermore, cytocompatibility, hemolysis, and coagulation tests demonstrated that the PVA/TA/BA hydrogel possesses excellent biocompatibility and notable hemostatic properties. This simple and efficient preparation strategy offers a practical approach for developing novel Janus hydrogels, laying a solid theoretical and practical foundation for their application in wet tissue repair and postoperative antiadhesion treatments.

A Dual-Layer Hydrogel Barrier Integrating Bio-Adhesive and Anti-Adhesive Properties Prevents Postoperative Abdominal Adhesions

Postoperative abdominal adhesions are a common and painful complication after surgery, leading to high healthcare costs and diminished quality of life. This report presents a novel bilayer hydrogel barrier featuring an inner adhesive layer and an outer antiadhesive layer. The inner adhesive layer hydrogel (PT) is prepared by mixing polyethyleneimine (PEI) and thioctic acid (TA). The outer layer (HP) hydrogel is fabricated by the conjugation reaction of thermoresponsive zwitterionic hyaluronic acid, phenylboronic acid, and epigallocatechin gallate complex and polyvinyl alcohol based on dynamic boronic ester bond. The PEI/TA layer enhances attachment to moist tissue surfaces in vivo, and the anti-adhesive layer HP hydrogel promotes biocompatibility and anti-inflammation while minimizing protein adsorption and improving mechanical stability. The bilayer hydrogel (HPPT) exhibited rapid gelation, robust adhesion in dynamic and moist environments, superior viscoelastic properties and cellular biocompatibility. A mouse-cecum abdominal wall adhesion model is utilized to evaluate efficacy, and the HPPT hydrogel shows local retention, anti-inflammatory effect, and inhibits fibrin deposition while minimizing adhesion formation. These findings highlight the innovative structural and functional properties of the HPPT hydrogel, positioning it as a promising therapeutic barrier in peritoneal surgery aimed at reducing postoperative adhesions and enhancing surgical outcomes.

One-Step Formed Janus Hydrogel with Time-Space Regulating Properties for Suture-Free and High-Quality Tendon Healing

Janus hydrogels have promising applications in tendon healing and anti-peritendinous adhesions. However, their complicated preparation methods, weak mechanical properties, and unstable adhesion interfaces have severely limited their application in suture-free and high-quality tendon healing. In this work, by controlling the interfacial distribution of free -COOH groups and cationic-π structures on both sides of the hydrogels, a series of PZBA-EGCG-ALC Janus hydrogels with varying degrees of asymmetric properties are successfully prepared using a simple and efficient one-step synthesis method. The tensile strength and elongation at the break of the Janus hydrogel are as high as 0.51 ± 0.04 MPa and 922.89 ± 28.59%. In addition, the Janus hydrogel can achieve a high difference in adhesion strength (nearly 20-fold) while maintaining a strong adhesion strength on their bottom sides (up to 524.8 ± 33.1 J m-2). In the spatial dimension, its excellent mechanical compliance and one-sided adhesion behavior can provide effective mechanical support and physical barriers for the injured Achilles tendons. More importantly, the Janus hydrogel can also minimize early inflammation generation in the time dimension via its ROS-responsive PZBA-EGCG prodrug macromolecules. This study provided a more effective and convenient suture-free strategy for constructing Janus hydrogels to promote high-quality tendon healing.

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.

Biomimetic Microstructured Scaffold with Release of Re-Modified Teriparatide for Osteoporotic Tendon-to-Bone Regeneration via Balancing Bone Homeostasis

Osteoporotic tendon-to-bone interface healing is challenging, with a high surgical repair failure rate of up to 68%. Conventional tissue engineering approaches have primarily focused on promoting interface healing by stimulating regeneration in either the tendon or bone. However, these methods often fall short of achieving optimal therapeutic outcomes due to their neglect of balancing bone homeostasis and remodeling the microstructure at the osteoporotic tendon-to-bone interface. Herein, a series of site-specific functional modifications are carried out on teriparatide to develop recombinant human parathyroid hormone (R-PTH). A biomimetic microstructured reconstruction scaffold (BMRP) is constructed using a decalcified mussel shell scaffold, pre-gel, and R-PTH. The BMRP mimics the microstructures of the native tendon-to-bone interface and restores the original structure of the interface tissue by repairing injured cells, balancing bone homeostasis, and remodeling the microstructure of the osteoporotic tendon-to-bone interface. In an osteoporotic rotator cuff tear model, BMRP is in situ implanted at the injured site, resulting in structural reconstruction and functional recovery. The BMRP demonstrates excellent repair effects, representing a novel therapeutical alternative for treating osteoporotic tendon-to-bone injury potential for clinical application.

Long-lasting comfort ocular surface drug delivery by in situ formation of an adhesive lubricative Janus nanocoating

Topical drug delivery on ocular surface always suffers from frequent administration and low bioavailability due to short drug residence. Despite advances of different adhesive ophthalmic drugs in extending release, cornea and eyelid nonselective adhesion inevitably causes ocular discomfort and even damage. Here, we describe in situ formation of an adhesive lubricative Janus nanocoating (ALJN) to enable long-lasting comfort drug delivery. By iron complexation, an asymmetric ALJN is formed on ocular surface via facile sequential instillation. The adhesive polyphenol inner layer binding with ocular surface enables drug loading and sustained release, while the lubricative zwitterionic polymer outer layer prevents eyelid adhesion to ensure comfort. Following instillation, ALJN retains on ocular surface over 24 hours and reduces blinking frequency to normal level. Moreover, ALJN demonstrates remarkable therapeutic potential in mouse and rabbit models of corneal contusion and alkali burn. This work proposes a comfortable long-lasting topical delivery platform for treating various ocular diseases.

Bioinspired hierarchical porous tough adhesive to promote sealing of high-pressure bleeding

Timely and stable sealing of uncontrolled high-pressure hemorrhage in emergency situations outside surgical units remains a major clinical challenge, contributing to the high mortality rate associated with trauma. The currently widely used hemostatic bioadhesives are ineffective for hemorrhage from major arteries and the heart due to the absence of biologically compatible flexible structures capable of simultaneously ensuring conformal tough adhesion and biomechanical support. Here, inspired by the principle of chromatin assembly, we present a tissue-conformable tough matrix for robust sealing of severe bleeding. This hierarchical matrix is fabricated through a phase separation process, which involves the in-situ formation of nanoporous aggregates within a microporous double-network (DN) matrix. The dispersed aggregates disrupt the rigid physical crosslinking of the original DN matrix and function as a dissipative component, enabling the aggregate-based DN (aggDN) matrix to efficiently dissipate energy during stress and achieve improved conformal attachment to soft tissues. Subsequently, pre-activated bridging polymers facilitate rapid interfacial bonding between the matrix and tissue surfaces. They synergistically withstand considerable hydraulic pressure of approximately 700 mmHg and demonstrate exceptional tissue adhesion and sealing in rat cardiac and canine aortic hemorrhages, outperforming the commercially available bioadhesives. Our findings present a promising biomimetic strategy for engineering biomechanically compatible and tough adhesive hydrogels, facilitating prompt and effective treatment of hemorrhagic wounds.

Implantable wireless suture sensor for in situ tendon and ligament strain monitoring

Tendon and ligament ruptures are prevalent, and severe sports injuries require surgical repair. In clinical practice, monitoring of tissue strain is critical to alert severe postoperative complications such as graft reinjury and loosening. Here, we present a sensor system that integrates a strain sensor and communication coil onto surgical silk sutures, enabling in situ monitoring and wireless readout of tissue strains via surgical implantation. The flexible sensor shows excellent adaptability to soft tissues, providing a strain monitoring range of 0 to 10% with a minimum detection threshold of 0.25% and maintaining stability more than 300,000 stretching cycles. The wireless sensor could be integrated with complex structures in surgical scenarios involving lateral collateral ligament injury and anterior cruciate ligament reconstruction, enabling distinct responses to graft stretching, reinjury, and loosening. Animal experiments demonstrate that the sensor can acquire real-time, clinical-grade strain data while exhibiting high biocompatibility. The sensor system shows considerable potential in evaluating preclinical implant performance and monitoring implant-related surgical complications.

Hypoxia-Mimicking Microenvironment Scaffold for Enhanced Tendon Regeneration

Tendon, a connective tissue structure, serves the crucial role of transmitting force between muscles and bones. However, tendon injury repair continues to pose a significant challenge in clinical settings. In this study, we utilized single-cell RNA sequencing to delve into the cell populations and signaling pathways that are integral to tendon healing. Our findings suggest that hypoxia plays a pivotal role in activating macrophages, stimulating endothelial cell migration, and fostering fibroblast proliferation. Based on these insights, we have developed a PCL scaffold coated with DFOA, which effectively mimics a hypoxic environment to enhance tendon tissue regeneration. Furthermore, the PCL-DFOA scaffolds exhibit exceptional ability in promoting macrophage polarization and angiogenesis. This research offers a therapeutic strategy that harnesses the regenerative power of hypoxia to accelerate and optimize tendon healing processes.

Erroneous Differentiation of Tendon Stem/Progenitor Cells in the Pathogenesis of Tendinopathy: Current Evidence and Future Perspectives

Tendinopathy is a condition characterized by persistent tendon pain, structural damage, and compromised functionality. Presently, the treatment for tendinopathy remains a formidable challenge, partly because of its unclear pathogenesis. Tendon stem/progenitor cells (TSPCs) are essential for tendon homeostasis, regeneration, remodeling, and repair. An innovative theory has been previously proposed, with insufficient evidence, that the erroneous differentiation of TSPCs may constitute one of the fundamental mechanisms underpinning tendinopathy. Over the past few years, there has been accumulating evidence for plausibility of this theory. In this review, we delve into alterations in the differentiation potential of TSPCs and the underlying mechanisms in the context of injury-induced tendinopathy, diabetic tendinopathy, and age-related tendinopathy to provide updated evidence on the erroneous differentiation theory. Despite certain limitations inherent in the existing body of evidence, the erroneous differentiation theory emerges as a promising and highly pertinent avenue for understanding tendinopathy. In the future, advanced methodologies will be harnessed to further deepen comprehension of this theory, paving the way for prospective developments in clinical therapies targeting TSPCs for the management of tendinopathy.

Hydrogen Bonding Polarization Strengthening the Peptide-Based Hydrogels

Peptide-based hydrogels form a kind of promising material broadly used in biomedicine and biotechnology. However, the correlation between their hydrogen bonding dynamics and mechanical properties remains uncertain. In this study, we found that the adoption of β-sheet and α-helix secondary structures by ECF-5 and GFF-5 peptides, respectively, could further form fiber networks to immobilize water molecules into hydrogels. Increasing the peptide concentrations improvethe solidity of these hydrogels, as evidenced by their higher storage modulus (G') values determined by a frequency sweep. Raman and FTIR spectroscopies probed a blue shift in the O-D stretching vibration in both ECF-5 and GFF-5 hydrogels, indicating the D-O bond contraction and stiffness gain. This finding provides valuable insight and offers an efficient means of modulating the mechanism of mechanical properties.

Compressible, anti-fatigue, extreme environment adaptable, and biocompatible supramolecular organohydrogel enabled by lignosulfonate triggered noncovalent network

Achieving a synergy of biocompatibility and extreme environmental adaptability with excellent mechanical property remains challenging in the development of synthetic materials. Herein, a "bottom-up" solution-interface-induced self-assembly strategy is adopted to develop a compressible, anti-fatigue, extreme environment adaptable, biocompatible, and recyclable organohydrogel composed of chitosan-lignosulfonate-gelatin by constructing noncovalent bonded conjoined network. The ethylene glycol/water solvent induced lignosulfonate nanoparticles function as bridge in chitosan/gelation network, forming multiple interfacial interactions that can effectively dissipate energy. The organohydrogel exhibits high compressive strength (54 MPa) and toughness (3.54 MJ/m3), 100 and 70 times higher than those of pure chitosan/gelatin hydrogel, meanwhile, excellent self-recovery and fatigue resistance properties. Even when subjected to severe compression up to a strain of 0.5 for 500,000 cycles, the organohydrogel still remains intact. This organohydrogel also demonstrates notable biocompatibility both in vivo and vitro, environment adaptability at low temperature, as well as recyclability. Such all natural organohydrogel provides a promising route towards the development of high-performance load-bearing materials.

Bioadhesive supramolecular polymer/hyaluronic acid hydrogel with sustained release of zinc ions and dexamethasone for diabetic wound healing

Diabetic patients often struggle with wound healing and are at higher risk of infections, necessitating the development of a stretchable, adhesive hydrogel dressing with antibacterial and angiogenesis-promoting properties. In this study, we synthesized a series of adhesive, antibacterial and anti-inflammatory hydrogels using free radical polymerization with materials including methacrylated hyaluronic acid (HAMA), N-[tris(hydroxymethyl)methyl]acrylamide (THMA), and 3-(bis(pyridin-2-ylmethyl)amino)propyl methacrylate (DPAMA). By leveraging the strong affinity of zinc(II)-dipicolylamine coordination complexes for the phosphorylated groups in dexamethasone sodium phosphate (DMSP), Zn2+ and DMSP were successfully incorporated into the hydrogel. The results demonstrated that the hydrogels possessed excellent adhesiveness and mechanical properties, enabling them to adhere closely to the skin while remaining easily removable without causing trauma. Antibacterial tests demonstrated significant inhibitory effects against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), attributed to the slow release of Zn2+, which effectively suppressed bacterial growth. Additionally, the slow release of DMSP provided strong anti-inflammatory effects. The DHTDZ2 hydrogel, containing 1.5 mg/mL Zn2+ and 4 mg/mL DMSP, significantly accelerated the healing of full-thickness skin wounds. In vitro angiogenesis, immunofluorescence, and immuno-histochemical results further confirmed that the DHTDZ2 hydrogel promoted angiogenesis and reduced the expression of pro-inflammatory factors. In summary, the hydrogel is an effective wound healing dressing that can reduce wound infections and inflammation.

Multifunctional Adhesive Hydrogels: From Design to Biomedical Applications

Adhesive hydrogels characterized by structural properties similar to the extracellular matrix, excellent biocompatibility, controlled degradation, and tunable mechanical properties have demonstrated significant potential in biomedical applications, including tissue engineering, biosensors, and drug delivery systems. These hydrogels exhibit remarkable adhesion to target substrates and can be rationally engineered to meet specific requirements. In recent decades, adhesive hydrogels have experienced significant advancements driven by the introduction of numerous multifunctional design strategies. This review initially summarizes the chemical bond-based design strategies for tissue adhesion, encompassing static covalent bonds, dynamic covalent bonds, and non-covalent interactions. Subsequently, the multiple functionalities imparted by these diverse design strategies, including highly stretchable and tough performances, responsiveness to microenvironments, anti-freezing/heating properties, conductivity, antibacterial activity, and hemostatic properties are discussed. In addition, recent advances in the biomedical applications of adhesive hydrogels, focusing on tissue repair, drug delivery, medical devices, and wearable sensors are reviewed. Finally, the current challenges are highlighted and future trends in this rapidly evolving field are discussed.

Ultrafast Self-Gelling, Adhesive, Anti-Bacterial Coacervate-Based Powders for Enhanced Hemostasis and Wound Healing

Uncontrolled hemorrhage, especially in non-compressible and deep wounds, remains a critical issue in emergency and surgical care. Existing hemostatic powders often lack rapid gelation, mechanical robustness, and adequate adherence, increasing the risk of rebleeding under high-pressure blood flow. To address these limitations, PQPP, a novel self-gelling hemostatic material composed of polyacrylamide/quaternized chitosan coacervates and polydopamine nanoparticles is developed. PQPP can rapidly absorb blood within 2 s, undergoes in situ gelation, and forms a robust adhesive hydrogel to effectively seal wounds. Its efficacy stems from the electrostatic adsorption and catechol functional groups of polydopamine nanoparticles. Importantly, PQPP exhibits high burst pressure resistance, excellent blood cell aggregation capability, outstanding biocompatibility, and antibacterial properties. Comprehensive in vitro and in vivo studies, including cytotoxicity and blood compatibility tests, as well as trials in mouse liver, heart, and vascular injury models, demonstrate PQPP's superior hemostatic performance under high-pressure conditions without causing inflammation. With its rapid gelation, robust adhesion, and mechanical integrity, PQPP represents a promising hemostatic material for immediate wound management in surgical and emergency applications.

Transcriptome-Optimized Hydrogel Design of a Stem Cell Niche for Enhanced Tendon Regeneration

Bioactive hydrogels have emerged as promising artificial niches for enhancing stem cell-mediated tendon repair. However, a substantial knowledge gap remains regarding the optimal combination of niche features for targeted cellular responses, which often leads to lengthy development cycles and uncontrolled healing outcomes. To address this critical gap, an innovative, data-driven materiomics strategy is developed. This approach is based on in-house RNA-seq data that integrates bioinformatics and mathematical modeling, which is a significant departure from traditional trial-and-error methods. It aims to provide both mechanistic insights and quantitative assessments and predictions of the tenogenic effects of adipose-derived stem cells induced by systematically modulated features of a tendon-mimetic hydrogel (TenoGel). The knowledge generated has enabled a rational approach for TenoGel design, addressing key considerations, such as tendon extracellular matrix concentration, uniaxial tensile loading, and in vitro pre-conditioning duration. Remarkably, our optimized TenoGel demonstrated robust tenogenesis in vitro and facilitated tendon regeneration while preventing undesired ectopic ossification in a rat tendon injury model. These findings shed light on the importance of tailoring hydrogel features for efficient tendon repair. They also highlight the tremendous potential of the innovative materiomics strategy as a powerful predictive and assessment tool in biomaterial development for regenerative medicine.

Surface enzyme-polymerization endows Janus hydrogel tough adhesion and regenerative repair in penetrating orocutaneous fistulas

Penetrating orocutaneous or oropharyngeal fistulas (POFs), severe complications following unsuccessful oral or oropharyngeal reconstruction, remain complex clinical challenges due to lack of supportive tissue, contamination with saliva and chewed food, and dynamic oral environment. Here, we present a Janus hydrogel adhesive (JHA) with asymmetric functions on opposite sides fabricated via a facile surface enzyme-initiated polymerization (SEIP) approach, which self-entraps surface water and blood within an in-situ formed hydrogel layer (RL) to effectively bridge biological tissues with a supporting hydrogel (SL), achieving superior wet-adhesion and seamless wound plugging. The tough SL hydrogel interlocked with RL dissipates energy to withstand external mechanical stimuli from continuous oral motions like chewing and swallowing, thus reducing stress-induced damage. In male New Zealand rabbit POF models, the JHA demonstrates strong adhesion and fluid-tight sealing, and maintained firm sealing for over 3 days without any decreased signs under a normal diet. After 12 days, both extraoral cutaneous and mucosal wounds achieved complete closure, with mechanical strengths comparable to normal tissues. Similar therapeutic efficacy was also confirmed in male beagle dog POF models. Thus, the proposed JHA hydrogel shows great potential for deep wound sealing and providing mechanical support to assist healing in penetrating fistulas and other injuries.

Inhibition of peritendinous adhesion through targeting JAK2-STAT3 signaling pathway: The therapeutic potential of AG490

Peritendinous adhesion is a common complication following tendon injury repair, posing a significant clinical challenge that requires urgent attention. The primary cause of peritendinous adhesion is the excessive deposition of collagen matrix due to the abnormal proliferation of fibroblasts in an inflammatory state. Janus kinase2 (JAK2) and signal transducer and activator of transcription 3 (STAT3) are key signaling molecules involved in cell proliferation and fibrosis development in various organs. However, the role of the JAK-2 and STAT3 signaling pathways in peritendinous adhesion fibrosis remains unclear. In our study, we first observed upregulation of p-JAK2 and p-STAT3 proteins in human peritendinous adhesion specimens and rat peritendinous adhesion models. In vitro, the JAK2/STAT3 pathway inhibitor AG490 effectively inhibited TGF-β1-induced fibroblast proliferation. Wound healing and transwell assays demonstrated that AG490 suppressed TGF-β1-induced fibroblast migration. Furthermore, we found that AG490 decreased the expression of pro-inflammatory factors, including IL-1β and TNF-α, as well as extracellular matrix (ECM) proteins in fibroblasts under TGF-β1 stimulation. In vivo, histological staining showed that AG490 prevented fibrous tissue formation in a rat model of tendon injury. Moreover, AG490 inhibited the overexpression of pro-inflammatory factors IL-1β and TNF-α, as well as ECM in the peritendinous adhesions. In conclusion, AG490 inhibited fibrosis and inflammation in injured tendons by targeting the JAK2-STAT3 signaling pathway, presenting a promising strategy for the prophylaxis of peritendinous adhesions.

Smart hydrogel-based trends in future tendon injury repair: A review

Despite advances in tissue engineering for tendon repair, rapid functional repair is still challenging due to its specificity and is prone to complications such as postoperative infections and tendon adhesions. Smart responsive hydrogels provide new ideas for tendon therapy with their flexibly designed three-dimensional cross-linked polymer networks that respond to specific stimuli. In recent years, a variety of smart-responsive hydrogels have been developed for the treatment of tendon disorders, showing great research promise and ability to address complex challenges. This article provides a comprehensive review of recent advances in the field of smart-responsive hydrogels for the treatment of tendon disorders, with a special focus on their response properties to different physical, chemical and biological stimuli. The multiple functional properties of these innovative materials are discussed in depth, including excellent biocompatibility and biodegradability, excellent mechanical properties, biomimetic structural design, convenient injectability, and unique self-healing capabilities. These properties enable the smart-responsive hydrogels to demonstrate significant advantages in solving difficult problems in the treatment of tendon disorders, such as precise drug delivery, tendon adhesion prevention and postoperative infection control. In addition, the article looks at the future prospects of smart-responsive hydrogels and analyses the challenges they may face in achieving widespread application.

Janus-Structured Microgel Barrier with Tissue Adhesive and Hemostatic Characteristics for Efficient Prevention of Postoperative Adhesion

Postoperative adhesion (POA) is a common and serious complication following various types of surgery. Current physical barriers either have a short residence time at the surgical site with a low tissue attachment capacity or are prone to undesired adhesion formation owing to the double-sided adhesive property, which limits the POA prevention efficacy of the barriers. In this study, Janus-structured microgels (Janus-MGs) with asymmetric tissue adhesion capabilities are fabricated using a novel bio-friendly gas-shearing microfluidic platform. The anti-adhesive side of Janus-MGs, which consists of alginate, hyaluronic acid, and derivatives, endows the material with separation, lubrication, and adhesion prevention properties. The adhesive side provided Janus-MGs with tissue attachment and retention capability through catechol-based adhesion, thereby enhancing the in situ adhesion prevention effect. In addition, Janus-MGs significantly reduced blood loss and shortened the hemostatic time in rats, further reducing adhesion formation. Three commonly used rat POA models with different tissue structures and motion patterns are established in this study, namely peritoneal adhesion, intrauterine adhesion, and peritendinous adhesion models, and the results showed that Janus-MGs effectively prevented the occurrence of POA in all the models. The fabrication of Janus-MGs offers a reliable strategy and a promising paradigm for preventing POA following diverse surgical procedures.

Dynamic hydrazone crosslinked salecan/chondroitin sulfate hydrogel platform as a promising wound healing Strategy: A comparative study on antibiotic and probiotic delivery

Natural polysaccharide-based active-ingredient carriers have been a source of great concern for a long time. In order to explore potential antibiotics and probiotics carriers, a novel injectable chondroitin sulfate/salecan (CS) hydrogel was constructed by forming dynamic hydrazone bonds. Scanning electron microscope (SEM), proton nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR), bacteriostatic test, and rheological experiments were used to investigate the chemical structure, inherent morphology, and enzymatic corruption of the hydrogel in vitro. The resulting hydrogels exhibited ideal probiotics loading capacity, drug release behavior, excellent antimicrobial activity and variable properties. Crucially, owing to its exceptional biocompatibility and reversible crosslinking network, this hydrogel can function as a three-dimensional extracellular matrix for cells, enabling cells to maintain high vitality and proliferation, and promote wound healing. The aforementioned findings indicated that this novel hydrogel can be a promising candidate as an active-ingredient carrier and scaffold material for tissue engineering.

Augmentation of Tendon and Ligament Repair with Fiber-Reinforced Hydrogel Composites

This review highlights the promise of fiber-reinforced hydrogel composites (FRHCs) for augmenting tendon and ligament repair and regeneration. Composed of reinforcing fibers embedded in a hydrogel, these scaffolds provide both mechanical strength and a conducive microenvironment for biological processes required for connective tissue regeneration. Typical properties of FRHCs are discussed, highlighting their ability to simultaneously fulfill essential mechanical and biological design criteria for a regenerative scaffold. Furthermore, features of FRHCs are described that improve specific biological aspects of tendon healing including mesenchymal progenitor cell recruitment, early polarization to a pro-regenerative immune response, tenogenic differentiation of recruited progenitor cells, and subsequent production of a mature, aligned collagenous matrix. Finally, the review offers a perspective on clinical translation of tendon FRHCs and outlines key directions for future work.

Progress in chitin/chitosan and their derivatives for biomedical applications: Where we stand

Chitin and its deacetylated form, chitosan, have demonstrated remarkable versatility in the realm of biomaterials. Their exceptional biocompatibility, antibacterial properties, pro- and anticoagulant characteristics, robust antioxidant capacity, and anti-inflammatory potential make them highly sought-after in various applications. This review delves into the mechanisms underlying chitin/chitosan's biological activity and provides a comprehensive overview of their derivatives in fields such as tissue engineering, hemostasis, wound healing, drug delivery, and hemoperfusion. However, despite the wealth of studies on chitin/chitosan, there exists a notable trend of homogeneity in research, which could hinder the comprehensive development of these biomaterials. This review, taking a clinician's perspective, identifies current research gaps and medical challenges yet to be addressed, aiming to pave the way for a more sustainable future in chitin/chitosan research and application.

An Engineered Hierarchical Hydrogel with Immune Responsiveness and Targeted Mitochondrial Transfer to Augmented Bone Regeneration

Coordinating the immune response and bioenergy metabolism in bone defect environments is essential for promoting bone regeneration. Mitochondria are important organelles that control internal balance and metabolism. Repairing dysfunctional mitochondria has been proposed as a therapeutic approach for disease intervention. Here, an engineered hierarchical hydrogel with immune responsiveness can adapt to the bone regeneration environment and mediate the targeted mitochondria transfer between cells. The continuous supply of mitochondria by macrophages can restore the mitochondrial bioenergy of bone marrow mesenchymal stem cells (BMSC). Fundamentally solving the problem of insufficient energy support of BMSCs caused by local inflammation during bone repair and regeneration. This discovery provides a new therapeutic strategy for promoting bone regeneration and repair, which has research value and practical application prospects in the treatment of various diseases caused by mitochondrial dysfunction.

Direct Metal Transfer on Swellable Hydrogel with Dehydration-Induced Physical Adhesion

Composites of hydrogels and metals are gaining interest because of each material's unique properties. However, the stable adhesion of metals on hydrogels is challenging due to the mechanical mismatch at the soft-hard interface and the liquidity of the water components in hydrogels. We propose a facile physical-adhesion method that involves the dehydration process of hydrogels to transfer metals from a glass substrate. This method is based on the hydrophobic interaction between polymer chains and metals and is stable, even in water. Continuous metal wiring was achieved on a swollen hydrogel, and electrical conduction was effective for a soft electronic device. Therefore, our method could be a versatile method for integrating hydrogels and metals.

Transcriptional regulation of living materials via extracellular electron transfer

Engineered living materials combine the advantages of biological and synthetic systems by leveraging genetic and metabolic programming to control material-wide properties. Here, we demonstrate that extracellular electron transfer (EET), a microbial respiration process, can serve as a tunable bridge between live cell metabolism and synthetic material properties. In this system, EET flux from Shewanella oneidensis to a copper catalyst controls hydrogel cross-linking via two distinct chemistries to form living synthetic polymer networks. We first demonstrate that synthetic biology-inspired design rules derived from fluorescence parameterization can be applied toward EET-based regulation of polymer network mechanics. We then program transcriptional Boolean logic gates to govern EET gene expression, which enables design of computational polymer networks that mechanically respond to combinations of molecular inputs. Finally, we control fibroblast morphology using EET as a bridge for programmed material properties. Our results demonstrate how rational genetic circuit design can emulate physiological behavior in engineered living materials.

Mechanoresponsive Drug Release from a Flexible, Tissue-Adherent, Hybrid Hydrogel Actuator

Soft robotic technologies for therapeutic biomedical applications require conformal and atraumatic tissue coupling that is amenable to dynamic loading for effective drug delivery or tissue stimulation. This intimate and sustained contact offers vast therapeutic opportunities for localized drug release. Herein, a new class of hybrid hydrogel actuator (HHA) that facilitates enhanced drug delivery is introduced. The multi-material soft actuator can elicit a tunable mechanoresponsive release of charged drug from its alginate/acrylamide hydrogel layer with temporal control. Dosing control parameters include actuation magnitude, frequency, and duration. The actuator can safely adhere to tissue via a flexible, drug-permeable adhesive bond that can withstand dynamic device actuation. Conformal adhesion of the hybrid hydrogel actuator to tissue leads to improved mechanoresponsive spatial delivery of the drug. Future integration of this hybrid hydrogel actuator with other soft robotic assistive technologies can enable a synergistic, multi-pronged treatment approach for the treatment of disease.

Engineered Janus hydrogels: biomimetic surface engineering and biomedical applications

Hydrogel bioadhesives, when applied to dysfunctional tissues substituting the epidermis or endothelium, exhibit compelling characteristics that enable revolutionary diagnostic and therapeutic procedures. Despite their demonstrated efficacy, these hydrogels as soft implants are still limited by improper symmetric surface functions, leading to postoperative complications and disorders. Janus hydrogel bioadhesives with unique asymmetric surface designs have thus been proposed as a reliable and biocompatible hydrogel interface, mimicking the structural characteristics of natural biological barriers. In this comprehensive review, we provide guidelines for the rational design of Janus hydrogel bioadhesives, covering methods for hydrogel surface chemistry and microstructure engineering. The engineering of Janus hydrogels is highlighted, specifically in tuning the basal surface to facilitate instant and robust hydrogel-tissue integration and modulating the apical surface as the anti-adhesion, anti-fouling, and anti-wear barrier. These asymmetric designs hold great potential in clinical translation, supporting applications including hemostasis/tissue sealing, chronic wound management, and regenerative medicine. By shedding light on the potential of Janus hydrogels as bioactive interfaces, this review paper aims to inspire further research and overcome current obstacles for advancing soft matter in next-generation healthcare.

A Mesoporous Silica-Loaded Multi-Functional Hydrogel Enhanced Tendon Healing via Immunomodulatory and Pro-Regenerative Effects

Tendon injuries are pervasive orthopedic injuries encountered by the general population. Nonetheless, recovery after severe injuries, such as Achilles tendon injury, is limited. Consequently, there is a pressing need to devise interventions, including biomaterials, that foster tendon healing. Regrettably, tissue engineering treatments have faced obstacles in crafting appropriate tissue scaffolds and efficacious nanomedical approaches. To surmount these hurdles, an innovative injectable hydrogel (CP@SiO2), comprising puerarin and chitosan through in situ self-assembly, is pioneered while concurrently delivering mesoporous silica nanoparticles for tendon healing. In this research, CP@SiO2 hydrogel is employed for the treatment of Achilles tendon injuries, conducting extensive in vivo and in vitro experiments to evaluate its efficacy. This reults demonstrates that CP@SiO2 hydrogel enhances the proliferation and differentiation of tendon-derived stem cells, and mitigates inflammation through the modulation of macrophage polarization. Furthermore, using histological and behavioral analyses, it is found that CP@SiO2 hydrogel can improve the histological and biomechanical properties of injured tendons. This findings indicate that this multifaceted injectable CP@SiO2 hydrogel constitutes a suitable bioactive material for tendon repair and presents a promising new strategy for the clinical management of tendon injuries.

Mechanical Regulation of Polymer Gels

The mechanical properties of polymer gels devote to emerging devices and machines in fields such as biomedical engineering, flexible bioelectronics, biomimetic actuators, and energy harvesters. Coupling network architectures and interactions has been explored to regulate supportive mechanical characteristics of polymer gels; however, systematic reviews correlating mechanics to interaction forces at the molecular and structural levels remain absent in the field. This review highlights the molecular engineering and structural engineering of polymer gel mechanics and a comprehensive mechanistic understanding of mechanical regulation. Molecular engineering alters molecular architecture and manipulates functional groups/moieties at the molecular level, introducing various interactions and permanent or reversible dynamic bonds as the dissipative energy. Molecular engineering usually uses monomers, cross-linkers, chains, and other additives. Structural engineering utilizes casting methods, solvent phase regulation, mechanochemistry, macromolecule chemical reactions, and biomanufacturing technology to construct and tailor the topological network structures, or heterogeneous modulus compositions. We envision that the perfect combination of molecular and structural engineering may provide a fresh view to extend exciting new perspectives of this burgeoning field. This review also summarizes recent representative applications of polymer gels with excellent mechanical properties. Conclusions and perspectives are also provided from five aspects of concise summary, mechanical mechanism, biofabrication methods, upgraded applications, and synergistic methodology.

Dynamic injectable tissue adhesives with strong adhesion and rapid self-healing for regeneration of large muscle injury

Wounds often necessitate the use of instructive biomaterials to facilitate effective healing. Yet, consistently filling the wound and retaining the material in place presents notable challenges. Here, we develop a new class of injectable tissue adhesives by leveraging the dynamic crosslinking chemistry of Schiff base reactions. These adhesives demonstrate outstanding mechanical properties, especially in regard to stretchability and self-healing capacity, and biodegradability. Furthermore, they also form robust adhesion to biological tissues. Their therapeutic potential was evaluated in a rodent model of volumetric muscle loss (VML). Ultrasound imaging confirmed that the adhesives remained within the wound site, effectively filled the void, and degraded at a rate comparable to the healing process. Histological analysis indicated that the adhesives facilitated muscle fiber and blood vessel formation, and induced anti-inflammatory macrophages. Notably, the injured muscles of mice treated with the adhesives displayed increased weight and higher force generation than the control groups. This approach to adhesive design paves the way for the next generation of medical adhesives in tissue repair.

Hydrogels: a promising therapeutic platform for inflammatory skin diseases treatment

Inflammatory skin diseases, such as psoriasis and atopic dermatitis, pose significant health challenges due to their long-lasting nature, potential for serious complications, and significant health risks, which requires treatments that are both effective and exhibit minimal side effects. Hydrogels offer an innovative solution due to their biocompatibility, tunability, controlled drug delivery capabilities, enhanced treatment adherence and minimized side effects risk. This review explores the mechanisms that guide the design of hydrogel therapeutic platforms from multiple perspectives, focusing on the components of hydrogels, their adjustable physical and chemical properties, and their interactions with cells and drugs to underscore their clinical potential. We also examine various therapeutic agents for psoriasis and atopic dermatitis that can be integrated into hydrogels, including traditional drugs, novel compounds targeting oxidative stress, small molecule drugs, biologics, and emerging therapies, offering insights into their mechanisms and advantages. Additionally, we review clinical trial data to evaluate the effectiveness and safety of hydrogel-based treatments in managing psoriasis and atopic dermatitis under complex disease conditions. Lastly, we discuss the current challenges and future opportunities for hydrogel therapeutics in treating psoriasis and atopic dermatitis, such as improving skin barrier penetration and developing multifunctional hydrogels, and highlight emerging opportunities to enhance long-term safety and stability.

Additive manufacturing of highly entangled polymer networks

Incorporation of polymer chain entanglements within a single network can synergistically improve stiffness and toughness, yet attaining such dense entanglements through vat photopolymerization additive manufacturing [e.g., digital light processing (DLP)] remains elusive. We report a facile strategy that combines light and dark polymerization to allow constituent polymer chains to densely entangle as they form within printed structures. This generalizable approach reaches high monomer conversion at room temperature without the need for additional stimuli, such as light or heat after printing, and enables additive manufacturing of highly entangled hydrogels and elastomers that exhibit fourfold- to sevenfold-higher extension energies in comparison to that of traditional DLP. We used this method to print high-resolution and multimaterial structures with features such as spatially programmed adhesion to wet tissues.

Engineering injectable hyaluronic acid-based adhesive hydrogels with anchored PRP to pattern the micro-environment to accelerate diabetic wound healing

Diabetic wounds remain a global challenge due to disordered wound healing led by inflammation, infection, oxidative stress, and delayed proliferation. Therefore, an ideal wound dressing for diabetic wounds not only needs tissue adhesiveness, injectability, and self-healing properties but also needs a full regulation of the microenvironment. In this work, adhesive wound dressings (HA-DA/PRP) with injectability were fabricated by combining platelet rich plasma (PRP) and dopamine-modified-hyaluronic acid (HA-DA). The engineered wound dressings exhibited tissue adhesiveness, rapid self-healing, and shape adaptability, thereby enhancing stability and adaptability to irregular wounds. The in vitro experiments demonstrated that HA-DA/PRP adhesives significantly promoted fibroblast proliferation and migration, attributed to the loaded PRP. The adhesives showed antibacterial properties against both gram-positive and negative bacteria. Moreover, in vitro experiments confirmed that HA-DA/PRP adhesives effectively mitigated oxidative stress and inflammation. Finally, HA-DA/PRP accelerated the healing of diabetic wounds by inhibiting bacterial growth, promoting granulation tissue regeneration, accelerating neovascularization, facilitating collagen deposition, and modulating inflammation through inducing M1 to M2 polarization, in an in vivo model of infected diabetic wounds. Overall, HA-DA/PRP adhesives with the ability to comprehensively regulate the microenvironment in diabetic wounds may provide a novel approach to expedite the diabetic wounds healing in clinic.

Chemically Programmed Hydrogels for Spatiotemporal Modulation of the Cardiac Pathological Microenvironment

After myocardial infarction (MI), sustained ischemic events induce pathological microenvironments characterized by ischemia-hypoxia, oxidative stress, inflammatory responses, matrix remodeling, and fibrous scarring. Conventional clinical therapies lack spatially targeted and temporally responsive modulation of the infarct microenvironment, leading to limited myocardial repair. Engineered hydrogels have a chemically programmed toolbox for minimally invasive localization of the pathological microenvironment and personalized responsive modulation over different pathological periods. Chemically programmed strategies for crosslinking interactions, interfacial binding, and topological microstructures in hydrogels enable minimally invasive implantation and in situ integration tailored to the myocardium. This enhances substance exchange and signal interactions within the infarcted microenvironment. Programmed responsive polymer networks, intelligent micro/nanoplatforms, and biological therapeutic cues contribute to the formation of microenvironment-modulated hydrogels with precise targeting, spatiotemporal control, and on-demand feedback. Therefore, this review summarizes the features of the MI microenvironment and chemically programmed schemes for hydrogels to conform, integrate, and modulate the cardiac pathological microenvironment. Chemically programmed strategies for oxygen-generating, antioxidant, anti-inflammatory, provascular, and electrointegrated hydrogels to stimulate iterative and translational cardiac tissue engineering are discussed.

Endothelial cells-derived exosomes-based hydrogel improved tendinous repair via anti-inflammatory and tissue regeneration-promoting properties

Tendon injuries are common orthopedic ailments with a challenging healing trajectory, especially in cases like the Achilles tendon afflictions. The healing trajectory of tendon injuries is often suboptimal, leading to scar formation and functional impairment due to the inherent low metabolic activity and vascularization of tendon tissue. As pressing is needed for effective interventions, efforts are made to explore biomaterials to augment tendon healing. However, tissue engineering approaches face hurdles in optimizing tissue scaffolds and nanomedical strategies. To navigate these challenges, an injectable hydrogel amalgamated with human umbilical vein endothelial cells-derived exosomes (HUVECs-Exos) was prepared and named H-Exos-gel in this study, aiming to enhance tendon repair. In our research involving a model of Achilles tendon injuries in 60 rats, we investigated the efficacy of H-Exos-gel through histological assessments performed at 2 and 4 weeks and behavioral assessments conducted at the 4-week mark revealed its ability to enhance the Achilles tendon's mechanical strength, regulate inflammation and facilitate tendon regeneration and functional recovery. Mechanically, the H-Exos-gel modulated the cellular behaviors of macrophages and tendon-derived stem cells (TDSCs) by inhibiting inflammation-related pathways and promoting proliferation-related pathways. Our findings delineate that the H-Exos-gel epitomizes a viable bioactive medium for tendon healing, heralding a promising avenue for the clinical amelioration of tendon injuries.

Water-Mediated On-Demand Detachable Solid-State Adhesive of Porous Hydroxyapatite for Internal Organ Retractions

Novel adhesives for biological tissues offer an advanced surgical approach. Here, the authors report the development and application of solid-state adhesives consisting of porous hydroxyapatite (HAp) biocompatible ceramics as novel internal organ retractors. The operational principles of the porous solid-state adhesives are experimentally established in terms of water migration from biological soft tissues into the pores of the adhesives, and their performance is evaluated on several soft tissues with different hydration states. As an example of practical medical utility, HAp adhesive devices demonstrate the holding ability of porcine livers and on-demand detachability in vivo, showing great potential as internal organ retractors in laparoscopic surgery.

Janus structure hydrogels: recent advances in synthetic strategies, biomedical microstructure and (bio)applications

Janus structure hydrogels (JSHs) are novel materials. Their primary fabrication methods and various applications have been widely reported. JSHs are primarily composed of Janus particles (JNPs) and polysaccharide components. They exhibit two distinct physical or chemical properties, generating intriguing characteristics due to their asymmetric structure. Normally, one side (adhesive interface) is predominantly constituted of polysaccharide components, primarily serving excellent adhesion. On the other side (functional surface), they integrate diverse functionalities, concurrently performing a plethora of synergistic functions. In the biomedical field, JSHs are widely applied in anti-adhesion, drug delivery, wound healing, and other areas. It also exhibits functions in seawater desalination and motion sensing. Thus, JSHs hold broad prospects for applications, and they possess significant research value in nanotechnology, environmental science, healthcare, and other fields. Additionally, this article proposes the challenges and future work facing these fields.

A low-swelling hydrogel as a multirole sealant for efficient dural defect sealing and prevention of postoperative adhesion

Dural defects and subsequent complications, including cerebrospinal fluid (CSF) leakage, are common in both spine surgery and neurosurgery, and existing clinical treatments are still unsatisfactory. In this study, a tissue-adhesive and low-swelling hydrogel sealant comprising gelatin and o-phthalaldehyde (OPA)-terminated 4-armed poly(ethylene glycol) (4aPEG-OPA) is developed via the OPA/amine condensation reaction. The hydrogel shows an adhesive strength of 79.9 ± 12.0 kPa on porcine casing and a burst pressure of 208.0 ± 38.0 cmH2O. The hydrogel exhibits a low swelling ratio at physiological conditions, avoiding nerve compression in the limited spinal and intracranial spaces. In rat and rabbit models of lumbar and cerebral dural defects, the 4aPEG-OPA/gelatin hydrogel achieves excellent performance in dural defect sealing and preventing CSF leakage. Moreover, local inflammation, epidural fibrosis and postoperative adhesion in the defect areas are markedly reduced. Thus, these findings establish the strong potential of the hydrogel sealant for the effective watertight closure of dural defects.

Lubricating Microneedles System with Multistage Sustained Drug Delivery for the Treatment of Osteoarthritis

Osteoarthritis (OA) is a typical joint degenerative disease that is prevalent worldwide and significantly affects the normal activities of patients. Traditional treatments using diclofenac (DCF) as an anti-inflammatory drug by oral administration and transdermal delivery have many inherent deficiencies. In this study, a lubricating microneedles (MNs) system for the treatment of osteoarthritis with multistage sustained drug delivery and great reduction in skin damage during MNs penetration is developed. The bilayer dissolvable MNs system, namely HA-DCF@PDMPC, is prepared by designating the composite material of hyaluronic acid (HA) and covalently conjugated drug compound (HA-DCF) as the MNs tips and then modifying the surface of MNs tips with a self-adhesive lubricating copolymer (PDMPC). The MNs system is designed to achieve sustained drug release of DCF via ester bond hydrolysis, physical diffusion from MNs tips, and breakthrough of lubrication coating. Additionally, skin damage is reduced due to the presence of the lubrication coating on the superficial surface. Therefore, the lubricating MNs with multistage sustained drug delivery show good compliance as a transdermal patch for OA treatment, which is validated from anti-inflammatory cell tests and therapeutic animal experiments, down-regulating the expression levels of pro-inflammatory factors and alleviating articular cartilage destruction.