Low-Swelling Adhesive Hydrogel with Rapid Hemostasis and Potent Anti-Inflammatory Capability for Full-Thickness Oral Mucosal Defect Repair

Porous gradient hydrogel promotes skin regeneration by angiogenesis

The skin has a multilayered structure, and deep-seated injuries are exposed to external microbial invasion and in vivo microenvironmental destabilization. Here, a bilayer bionic skin scaffold (Bilayer SF) was developed based on methacrylated sericin protein to mimic the skin's multilayered structure and corresponding functions. The outer layer (SF@TA), which mimics the epidermal layer, was endowed with the function of resisting external bacterial and microbial invasion using a small pore structure and bio-crosslinking with tannic acid (TA). The inner layer (SF@DA@Gel), which mimics the dermal layer, was used to promote cellular growth using a large pore structure and introducing dopamine (DA) to regulate the wound microenvironment. This Bilayer SF showed good mechanical properties and structural stability, satisfactory antioxidant and promote cell proliferation and migration abilities. In vitro studies confirmed the antimicrobial properties of the outer layer and the pro-angiogenic ability of the inner layer. In vivo animal studies demonstrated that the bilayer scaffolds promoted collagen deposition, neovascularization, and marginal hair follicle formation, which might be a promising new bionic skin scaffold.

A Bilayer Polyurethane Patch with Sustained Growth Factor Release and Antibacteria for Re-epithelization of Large-Scale Oral Mucosal Defects

In the field of oral and maxillofacial surgery, extensive oral soft-tissue injuries occur repeatedly in clinical practice; however, effective restorative materials are lacking. In this study, a biodegradable waterborne polyurethane patch featuring a mucosa bionic bilayer structure is presented. This patch consists of a porous scaffold layer that faces the lesion, incorporating a polydopamine coating to achieve sustained release of epidermal growth factors (EGFs) for mucosal defect reconstruction. Additionally, there is a dense barrier layer toward the oral cavity loaded with silver nanoparticles, which prevents bacteria from entering the wound and simultaneously acts as a physical barrier. This patch can sustainably release EGF in vitro for 2 weeks, thereby facilitating the proliferation and migration of HaCaT and L929 cells, while effectively killing common oral cavity bacteria. In a rabbit buccal mucosal full-thickness defect model, the patch demonstrates better efficacy than the clinical benchmark, decellularized extracellular matrix (dECM). It effectively reduces wound inflammation and significantly upregulates gene expression associated with epithelialization by activating the EGF/epidermal growth factor receptor (EGFR) pathway. These mechanisms promote the proliferation, differentiation, and migration of epithelial/keratinocyte cells, ultimately expediting mucosal defect healing and wound closure.

Multifunctional Hydrogels Based on γ-Polyglutamic Acid/Polyethyleneimine for Hemostasis and Wound Healing

Current hemostatic materials have many shortcomings, such as biotoxicity or poor degradability, and do not effectively promote wound healing after hemostasis. To address these limitations, a hemostasis-promoting wound-healing hydrogel, polyglutamic acid/polyethyleneimine/montmorillonite (PPM), comprising polyglutamic acid, 3,4-dihydroxybenzaldehyde-modified polyethyleneimine, and amino-modified montmorillonite (montmorillonite-NH2) was constructed in this study. Due to the excellent water absorption abilities of γ-polyglutamic acid, the PPM and polyglutamic acid/polyethyleneimine hydrogels could rapidly absorb the blood and tissue fluid exuded from the wound to keep the wound clean and accelerate the blood coagulation. The homogeneous distribution of montmorillonite-NH2 enhanced not only the mechanical properties of the hydrogel but also its hemostatic properties. In addition, the modification of polyethylenimine with 3,4-dihydroxybenzaldehyde provided anti-inflammatory effects and endorsed the wound healing. Cellular and blood safety experiments demonstrated the biocompatibility of the PPM hydrogel, and animal studies demonstrated that the PPM hydrogel effectively stopped bleeding and promoted wound healing. The concept design of clay-based hydrogel may create diverse opportunities for constructing hemostasis and wound-healing dressings.

Adhesive Nanoparticle-in-Microgel System with ROS Scavenging Capability and Hemostatic Activity for Postoperative Adhesion Prevention

Postoperative adhesion is a noteworthy clinical complication in abdominal surgery due to the existing physical barriers are unsatisfactory and inefficient in preventing its occurrence. In this work, an elaborate nanoparticle-in-microgel system (nMGel) is presented for postoperative adhesion prevention. nMGel is facilely formed by crosslinking manganese dioxide (MnO2) nanoparticles-loaded gelatin microspheres with polydopamine using a modified emulsification-chemical crosslinking method, generating a nano-micron spherical hydrogel. After drying, powdery nMGel with sprayability can perfectly cover irregular wounds and maintains robust tissue adhesiveness even in a wet environment. Additionally, nMGel possesses prominent antioxidant and free radical scavenging activity, which protects cell viability and preserves cell biological functions in an oxidative microenvironment. Furthermore, nMGel displays superior hemostatic property as demonstrated in mouse tail amputation models and liver trauma models. Importantly, nMGel can be conveniently administrated in a mouse cecal defect model to prevent adhesion between the injured cecum and the peritoneum by reducing inflammation, oxidative stress, collagen synthesis, and angiogenesis. Thus, the bioactive nMGel offers a practical and efficient approach for ameliorating postsurgical adhesion.

All-in-one polysaccharide hydrogel with resistant vascular burst pressure and cooperative wound microenvironment regulation for fatal arterial hemorrhage and diabetic wound healing

Fatal massive hemorrhage and diabetic wound healing are world widely challenging in surgical managements, and uncontrolled bleeding, chronic inflammation and damaged remodeling heavily hinder the whole healing processes. Considering hemostasis, inflammation and wound microenvironment cooperatively affect the healing progression, we design all-in-one beta-glucan (BG) hybrid hydrogels reinforced with laponite nanoclay that demonstrate tunable tissue adhesion, resistant vascular burst pressure and cooperative wound microenvironment regulation for arterial hemostasis and diabetic wound prohealing. Those hydrogels had honeycomb-like porous microstructure with average pore size of 7-19 μm, tissue adhesion strength of 18-46 kPa, and vascular burst pressure of 58-174 mmHg to achieve superior hemostasis in rat liver and femoral artery models. They could effectively scavenge reactive oxygen species, transform macrophages from proinflammatory M1 into prohealing M2, and shorten the inflammation duration via synergistic actions of BG and nitric oxide (NO). Single treatment of NO-releasing BG hybrid hydrogels attained complete closure of diabetic wounds within 14 days, orchestrated to accelerate the epithelization and dermis growth, and restored normal vascularization, achieving high performance healing with optimal collagen deposition and hair follicle regeneration. Consequently, this work opens up a new avenue to design all-in-one polysaccharide hydrogels for applications in massive bleeding hemostats and diabetic wound dressings.

Reversibly Adhesive, Anti-Swelling, and Antibacterial Hydrogels for Tooth-Extraction Wound Healing

Oral wound treatment faces challenges due to the complex oral environment, thus, sealing the wound quickly becomes necessary. Although some materials have achieved adhesion and sterilization, how to effectively solve the contradiction between strong adhesion and on-demand removal remains a challenge. Herein, a reversibly adhesive hydrogel is designed by free radical copolymerization of cationic monomer [2-(acryloyloxy) ethyl] trimethylammonium chloride (ATAC), hydrophobic monomer ethylene glycol phenyl ether acrylate (PEA) and N-isopropylacrylamide (NIPAAm). The cationic quaternary ammonium salts provide electrostatic interactions, the hydrophobic groups provide hydrophobic interactions, and the PNIPAAm chain segments provide hydrogen bonding, leading to strong adhesion. Therefore, the hydrogel obtains an adhesion strength of 18.67 KPa to oral mucosa and can seal wounds fast within 10 s. Furthermore, unlike pure PNIPAAm, the hydrogel has a lower critical solution temperature of 40.3 °C due to the contribution of ATAC and PEA, enabling rapid removal with 40 °C water after treatment. In addition, the hydrogel realizes excellent anti-swelling ratio (≈80%) and antibacterial efficiency (over 90%). Animal experiments prove that the hydrogel effectively reduces inflammation infiltration, promotes collagen deposition and vascular regeneration. Thus, hydrogel as a multi-functional dressing has great application prospects in oral wound management.

From Short Circuit to Completed Circuit: Conductive Hydrogel Facilitating Oral Wound Healing

The primary challenges posed by oral mucosal diseases are their high incidence and the difficulty in managing symptoms. Inspired by the ability of bioelectricity to activate cells, accelerate metabolism, and enhance immunity, a conductive polyacrylamide/sodium alginate crosslinked hydrogel composite containing reduced graphene oxide (PAA-SA@rGO) is developed. This composite possesses antibacterial, anti-inflammatory, and antioxidant properties, serving as a bridge to turn the "short circuit" of the injured site into a "completed circuit," thereby prompting fibroblasts in proximity to the wound site to secrete growth factors and expedite tissue regeneration. Simultaneously, the PAA-SA@rGO hydrogel effectively seals wounds to form a barrier, exhibits antibacterial and anti-inflammatory properties, and prevents foreign bacterial invasion. As the electric field of the wound is rebuilt and repaired by the PAA-SA@rGO hydrogel, a 5 × 5 mm2 wound in the full-thickness buccal mucosa of rats can be expeditiously mended within mere 7 days. The theoretical calculations indicate that the PAA-SA@rGO hydrogel can aggregate and express SOX2, PITX1, and PITX2 at the wound site, which has a promoting effect on rapid wound healing. Importantly, this PAA-SA@rGO hydrogel has a fast curative effect and only needs to be applied for the first three days, which significantly improves patient satisfaction during treatment.

Composite Aerogel Scaffolds Containing Flexible Silica Nanofiber and Tricalcium Phosphate Enable Skin Regeneration

Poor hemostatic ability and less vascularization at the injury site could hinder wound healing as well as adversely affect the quality of life (QOL). An ideal wound dressing should exhibit certain characteristics: (a) good hemostatic ability, (b) rapid wound healing, and (c) skin appendage formation. This necessitates the advent of innovative dressings to facilitate skin regeneration. Therapeutic ions, such as silicon ions (Si4+) and calcium ions (Ca2+), have been shown to assist in wound repair. The Si4+ released from silica (SiO2) can upregulate the expression of proteins, including the vascular endothelial growth factor (VEGF) and alpha smooth muscle actin (α-SMA), which is conducive to vascularization; Ca2+ released from tricalcium phosphate (TCP) can promote the coagulation alongside upregulating the expression of cell migration and cell differentiation related proteins, thereby facilitating the wound repair. The overarching objective of this study was to exploit short SiO2 nanofibers along with the TCP to prepare TCPx@SSF aerogels and assess their wound healing ability. Short SiO2 nanofibers were prepared by electrospinning and blended with varying proportions of TCP to afford TCPx@SSF aerogel scaffolds. The TCPx@SSF aerogels exhibited good cytocompatibility in a subcutaneous implantation model and manifested a rapid hemostatic effect (hemostatic time 75 s) in a liver trauma model in the rabbit. These aerogel scaffolds also promoted skin regeneration and exhibited rapid wound closure, epithelial tissue regeneration, and collagen deposition. Taken together, TCPx@SSF aerogels may be valuable for wound healing.

Preparation and Application of Hemostatic Hydrogels

Hemorrhage remains a critical challenge in various medical settings, necessitating the development of advanced hemostatic materials. Hemostatic hydrogels have emerged as promising solutions to address uncontrolled bleeding due to their unique properties, including biocompatibility, tunable physical characteristics, and exceptional hemostatic capabilities. In this review, a comprehensive overview of the preparation and biomedical applications of hemostatic hydrogels is provided. Particularly, hemostatic hydrogels with various materials and forms are introduced. Additionally, the applications of hemostatic hydrogels in trauma management, surgical procedures, wound care, etc. are summarized. Finally, the limitations and future prospects of hemostatic hydrogels are discussed and evaluated. This review aims to highlight the biomedical applications of hydrogels in hemorrhage management and offer insights into the development of clinically relevant hemostatic materials.

Tannic Acid-Modified Decellularized Tendon Scaffold with Antioxidant and Anti-Inflammatory Activities for Tendon Regeneration

Tendon regeneration is greatly influenced by the oxidant and the inflammatory microenvironment. Persistent inflammation during the tendon repair can cause matrix degradation, tendon adhesion, and excessive accumulation of reactive oxygen species (ROS), while excessive ROS affect extracellular matrix remodeling and tendon integration. Herein, we used tannic acid (TA) to modify a decellularized tendon slice (DTS) to fabricate a functional scaffold (DTS-TA) with antioxidant and anti-inflammatory properties for tendon repair. The characterizations and cytocompatibility of the scaffolds were examined in vitro. The antioxidant and anti-inflammatory activities of the scaffold were evaluated in vitro and further studied in vivo using a subcutaneous implantation model. It was found that the modified DTS combined with TA via hydrogen bonds and covalent bonds, and the hydrophilicity, thermal stability, biodegradability, and mechanical characteristics of the scaffold were significantly improved. Afterward, the results demonstrated that DTS-TA could effectively reduce inflammation by increasing the M2/M1 macrophage ratio and interleukin-4 (IL-4) expression, decreasing the secretion of interleukin-6 (IL-6) and interleukin-1β (IL-1β), as well as scavenging excessive ROS in vitro and in vivo. In summary, DTS modified with TA provides a potential versatile scaffold for tendon regeneration.

Emerging polymeric materials for treatment of oral diseases: design strategy towards a unique oral environment

Oral diseases are prevalent but challenging diseases owing to the highly movable and wet, microbial and inflammatory environment. Polymeric materials are regarded as one of the most promising biomaterials due to their good compatibility, facile preparation, and flexible design to obtain multifunctionality. Therefore, a variety of strategies have been employed to develop materials with improved therapeutic efficacy by overcoming physicobiological barriers in oral diseases. In this review, we summarize the design strategies of polymeric biomaterials for the treatment of oral diseases. First, we present the unique oral environment including highly movable and wet, microbial and inflammatory environment, which hinders the effective treatment of oral diseases. Second, a series of strategies for designing polymeric materials towards such a unique oral environment are highlighted. For example, multifunctional polymeric materials are armed with wet-adhesive, antimicrobial, and anti-inflammatory functions through advanced chemistry and nanotechnology to effectively treat oral diseases. These are achieved by designing wet-adhesive polymers modified with hydroxy, amine, quinone, and aldehyde groups to provide strong wet-adhesion through hydrogen and covalent bonding, and electrostatic and hydrophobic interactions, by developing antimicrobial polymers including cationic polymers, antimicrobial peptides, and antibiotic-conjugated polymers, and by synthesizing anti-inflammatory polymers with phenolic hydroxy and cysteine groups that function as immunomodulators and electron donors to reactive oxygen species to reduce inflammation. Third, various delivery systems with strong wet-adhesion and enhanced mucosa and biofilm penetration capabilities, such as nanoparticles, hydrogels, patches, and microneedles, are constructed for delivery of antibiotics, immunomodulators, and antioxidants to achieve therapeutic efficacy. Finally, we provide insights into challenges and future development of polymeric materials for oral diseases with promise for clinical translation.

A mussel inspired polyvinyl alcohol/collagen/tannic acid bioadhesive for wet adhesion and hemostasis

Bioadhesives are useful in surgery for hemostasis, tissue sealing and wound healing. However, most bioadhesives have limitations such as weak adhesion in wet conditions, insufficient sealing and poor clotting performance. Inspired by the adhesion mechanism of marine mussels, a novel bioadhesive (PCT) was developed by simply combining polyvinyl alcohol (PVA), collagen (COL) and tannic acid (TA) together. The results showed that the adhesion, sealing and blood coagulation properties boosted with the increase of tannic acid content in PCT. The wet shear adhesion strength of PCT-5 (the weight ratio of PVA:COL:TA=1:1:5) was 60.8 ± 0.6 kPa, the burst pressure was 213.7 ± 0.7 mmHg, and the blood clotting index was 39.3% ± 0.6%, respectively. In rat heart hemostasis tests, PCT-5 stopped bleeding in 23.7 ± 3.2 s and reduced bleeding loss to 83.0 ± 19.1 mg, which outperformed the benchmarks of commercial gauze (53.3 ± 8.7 s and 483.0 ± 15.0 mg) and 3 M adhesive (Type No.1469SB, 35.3 ± 5.0 s and 264.0 ± 14.2 mg). The as-prepared bioadhesive could provide significant benefits for tissue sealing and hemorrhage control along its low cost and facile preparation process.

Biosafe Polydopamine-Decorated MnO2 Nanoparticles with Hemostasis and Antioxidative Properties for Postoperative Adhesion Prevention

Surgical bleeding and cumulative oxidative stress are significant factors in the development of postoperative adhesions, which are always associated with adverse patient outcomes. However, effective strategies for adhesion prevention are currently lacking in clinical practice. In this study, we propose a solution using polydopamine-decorated manganese dioxide nanoparticles (MnO2@PDA) with rapid hemostasis and remarkable antioxidant properties to prevent postsurgical adhesion. The PDA modification provides MnO2@PDA with enhanced tissue adhesiveness and hemocompatibility with negligible hemolysis. Furthermore, MnO2@PDA exhibits impressive antioxidant and free radical scavenging properties, protecting cells from the negative effects of oxidative stress. The hemostatic activity of MnO2@PDA is evaluated in a mouse truncated tail model and a liver injury model, with results demonstrating reduced bleeding time and volume. The in vivo test on a mouse cecal abrasion model shows that MnO2@PDA exhibits excellent antiadhesion properties coupled with alleviated inflammation around the damaged tissue. Therefore, MnO2@PDA, which exhibits high biosafety, rapid hemostasis, and beneficial antioxidant capacity, displays exceptional antiadhesion performance, holding great potential for clinical applications to prevent postoperative adhesion.

Periodontium-Mimicking, Multifunctional Biomass-Based Hydrogel Promotes Full-Course Socket Healing

Preserving stable tooth-periodontal tissue integration is vital for maintaining alveolar bone stability under physiological conditions. However, tooth extraction compromises this integration and impedes socket healing. Therefore, it becomes crucial to provide early stage coverage of the socket to promote optimal healing. Drawing inspiration from the periodontium, we have developed a quaternized methacryloyl chitosan/dopamine-grafted oxidized sodium alginate hydrogel, termed the quaternized methacryloyl chitosan/dopamine-grafted oxidized sodium alginate hydrogel (QDL hydrogel). Through blue-light-induced cross-linking, the QDL hydrogel serves as a comprehensive wound dressing for socket healing. The QDL hydrogel exhibits remarkable efficacy in closing irregular tooth extraction wounds. Its favorable mechanical properties, flexible formability, and strong adhesion are achieved through modifications of chitosan and sodium alginate derived from biomass sources. Moreover, the QDL hydrogel demonstrates a superior hemostatic ability, facilitating swift blood clot formation. Additionally, the inherent antibacterial properties of the QDL hydrogel effectively inhibit oral microorganisms. Furthermore, the QDL hydrogel promotes angiogenesis, which facilitates the nutrient supply for subsequent tissue regeneration. Notably, the hydrogel accelerates socket healing by upregulating the expression of genes associated with wound healing. In conclusion, the periodontium-mimicking multifunctional hydrogel exhibits significant potential as a clinical tooth extraction wound dressing.

Multifunctional chitosan-based gel sponge with efficient antibacterial, hemostasis and strong adhesion

Developing wound dressings with solid adhesive properties that enable efficient, painless hemostasis and prevent wound infection remain a huge challenge. Herein, the tris(hydroxymethyl) methyl glycine-modified chitosan derivative (CTMG) was prepared and freeze-dried after simply adjusting the concentration of CTMG to obtain the chitosan-based gel sponge with desired multi-hollow structure, special antibacterial and biocompatibility. The adhesion strength on porcine skin was impressive up to 113 KPa, much higher than fibrin glue. It can withstand the pressure that far exceeds blood pressure. CTMG exhibits bacteriostatic abilities as demonstrated in a bacteriostatic assay, and alongside biocompatibility, as shown in cytotoxicity and hemolytic assays. Moreover, CTMG gel sponge showed hemostatic properties in both in vivo and in vitro hemostasis experiments. During an experiment on liver hemorrhage in rats, CTMG gel sponge proved to be more effective in controlling bleeding than other hemostatic sponges available on the market, indicating its promising hemostatic properties. CTMG gel sponge possesses the potential to function as a wound dressing and hemostatic material, making it suitable for various clinical applications.

Tailored chitosan/glycerol micropatterned composite dressings by 3D printing for improved wound healing

Wound infection control is a primary clinical concern nowadays. Various innovative solutions have been developed to fabricate adaptable wound dressings with better control of infected wound healing. This work presents a facile approach by leveraging 3D printing to fabricate chitosan/glycerol into composite dressings with tailored micropatterns to improve wound healing. The bioinks of chitosan/glycerol were investigated as suitable for 3D printing. Then, three tailored micropatterns (i.e., sheet, strip, and mesh) with precise geometry control were 3D printed onto a commercial dressing to fabricate the micropatterned composite dressings. In vitro and in vivo studies indicate that these micropatterned dressings could speed up wound healing due to their increased water uptake capacity (up to ca. 16-fold@2 min), benign cytotoxicity (76.7 % to 90.4 % of cell viability), minor hemolytic activity (<1 %), faster blood coagulation effects (within 76.3 s), low blood coagulation index (14.5 % to 18.7 % @ 6 min), enhanced antibacterial properties (81.0 % to 86.1 % against S. aureus, 83.7 % to 96.5 % against E. coli), and effective inhibition of wound inflammation factors of IL-1β and TNF-α. Such tailored micropatterned composite dressing is facile to obtain, highly reproducible, and cost-efficient, making it a promising implication for improved and personalized contaminated wound healing.

Laponite nanoparticle-crosslinked carboxymethyl cellulose-based injectable hydrogels with efficient underwater-specific adhesion for rapid hemostasis

Tissue adhesives have attracted intense and increasing interest due to their multiple biomedical applications. Despite the rapid development of adhesive hydrogels, huge challenges remain for materials that can ensure strong adhesion and seal hemostasis in aqueous and blood environments. To address this issue, we have developed an innovative design of PAA-based coacervate hydrogel with strong wet adhesion capability through a simple mixture of PAA copolymers with oxidized-carboxymethylcellulose (OCMC), and tannic acid (TA) as the main components, and structurally enhanced with natural clays (Laponite XLG). The absorbed TA provides solid adhesion to dry and wet substrates via multiple interactions, which endows the XLG-enhanced coacervate with the desired underwater adhesive strength. More importantly, the dielectric constant is introduced to evaluate the polarity of the tested samples, which may be used as guidance for the design of mussel-inspired adhesives with even better underwater adhesive properties. In vivo hemorrhage experiments further confirmed that the hydrogel adhesive dramatically shortened the hemostatic time to tens of seconds. Overall, the persistent adhesion and acceptable cytocompatibility of the hydrogel nanocomposite make it a promising alternative suture-free approach for rapid hemostasis at different length scales and is expected to be extended to clinical application for other organ injuries.

Body temperature-induced adhesive hyaluronate/gelatin-based hybrid hydrogel dressing for promoting skin regeneration

Skin wound management faces significant clinical challenges, including continuous bacterial infection and inflammation. Therefore, developing removable hydrogel dressings with intrinsic multifunctional properties is highly desirable. In this study, a body temperature-induced adhesive and removable hydrogel was designed to treat skin defect wounds. The HA/Gel-R-Ag hybrid gel was prepared by incorporating a silver ion-crosslinked sulfhydryl hyaluronate/gelatin-based polymeric gel network into a supramolecular rhein gel network, thereby significantly enhancing its mechanical properties. Temperature-responsive gelatin chains give the hybrid gel reversible tissue adhesiveness and detachment, thus avoiding secondary injury to wounds when changing the hydrogels. The hybrid gel exhibited excellent bactericidal ability owing to the antibacterial capacity of the silver ions and rhein. Moreover, both HA and rhein endowed the hybrid gel with immunoregulatory effects by promoting macrophage polarization from pro-inflammatory M1 phenotype to anti-inflammatory M2 phenotype. In a full-thickness skin defect mouse mode, this porous, degradable, and biocompatible HA/Gel-R-Ag hybrid gel boosted skin regeneration by inhibiting inflammation and promoting collagen deposition and angiogenesis. It is thus a simple method for widening the application range of mechanically weak rhein gels and providing a promising wound dressing material with multiple intrinsic functions for treating skin wounds.

Progress and future prospects of hemostatic materials based on nanostructured clay minerals

The occurrence of uncontrolled hemorrhage is a significant threat to human life and health. Although hemostatic materials have made remarkable advances in the biomaterials field, it remains a challenge to develop safe and effective hemostatic materials for global medical use. Natural clay minerals (CMs) have long been used as traditional inorganic hemostatic agents due to their good hemostatic capability, biocompatibility and easy availability. With the advancement of science, technology and ideology, CM-based hemostatic materials have undergone continuous innovations by integrating new inspirations with conventional concepts. This review systematically summarizes the hemostatic mechanisms of different natural CMs based on their nanostructures. Moreover, it also comprehensively reviews the latest research progress for CM-based hemostatic hybrid and nanocomposite materials, and discusses the challenges and developments in this field.

Double-Cross-Linked Hydrogel with Long-Lasting Underwater Adhesion: Enhancement of Maxillofacial In Situ and Onlay Bone Retention

Bone retention is a usual clinical problem existing in a lot of maxillofacial surgeries involving bone reconstruction and bone transplantation, which puts forward the requirements for bone adhesives that are stable, durable, biosafe, and biodegradable in wet environment. To relieve the suffering of patients during maxillofacial surgery with one-step operation and satisfying repair, herein, we developed a double-cross-linked A-O hydrogel named by its two components: [(3-Aminopropyl) methacrylamide]-co-{[Tris(hydroxymethyl) methyl] acrylamide} and oxidated methylcellulose. With excellent bone adhesion ability, it can maintain long-lasting stable underwater bone adhesion for over 14 days, holding a maximum adhesion strength of 2.32 MPa. Schiff-base reaction and high-density hydrogen bonds endow the hydrogel with strong cohesion and adhesion performance as well as maneuverable properties such as easy formation and injectability. A-O hydrogel not only presents rarely reported long-lasting underwater adhesion of hard tissue but also owns inherent biocompatibility and biodegradation properties with a porous structure that facilitates the survival of bone graft. Compared to the commercial cyanoacrylate adhesive (3 M Vetbond Tissue Adhesive), the A-O hydrogel is confirmed to be safer, more stable, and more effective in calvarial in situ bone retention model and onlay bone retention model of rat, providing a practical solution for the everyday scenario of clinical bone retention.

Hydrogel Bioelectronics for Health Monitoring

Hydrogels are considered an ideal platform for personalized healthcare due to their unique characteristics, such as their outstanding softness, appealing biocompatibility, excellent mechanical properties, etc. Owing to the high similarity between hydrogels and biological tissues, hydrogels have emerged as a promising material candidate for next generation bioelectronic interfaces. In this review, we discuss (i) the introduction of hydrogel and its traditional applications, (ii) the work principles of hydrogel in bioelectronics, (iii) the recent advances in hydrogel bioelectronics for health monitoring, and (iv) the outlook for future hydrogel bioelectronics' development.

Fabrication and Characterization of π-π Stacking Peptide-Contained Double Network Hydrogels

Since the physical properties are similar to native extracellular matrices, double network (DN) hydrogels have been studied extensively in the tissue engineering. However, the double chemical crosslinked DN hydrogel is limited by poor fatigue resistance. π-π stacking is a non-covalent bonding interaction, which is essential to maintain and self-assemble the three-dimensional structure of biological proteins and nucleic acids. In this study, a robust polyethylene glycol diacrylate (PEGDA)/FFK hybrid DN hydrogel was prepared by Michael addition and π-π stacking. The hybrid DN hydrogels with π-π stacking interactions have excellent mechanical strength and fatigue resistance. The DN FFK/PEGDA hydrogels reveal great biocompatibility and hemocompatibility. The DN hydrogels containing π-π stacking have the potential to fabricate robust hybrid DN hydrogels in drug release and tissue engineering.

Recent advances in adhesive materials used in the biomedical field: adhesive properties, mechanism, and applications

Adhesive materials are natural or synthetic polymers with the ability to adhere to the surface of luminal mucus or epithelial cells. They are widely used in the biomedical field due to their unique adhesion, biocompatibility, and excellent surface properties. When used in the human body, they can adhere to an accessible target and remain at the focal site for a longer period, improving the therapeutic effect on local disease. An adhesive material with bacteriostatic properties can play an antibacterial role at the focal site and the adhesive properties of the material can prevent the focal site from being infected by bacteria for a period. In addition, some adhesive materials can promote cell growth and tissue repair. In this review, the properties and mechanism of natural adhesive materials, organic adhesive materials, composite adhesive materials, and underwater adhesive materials have been introduced systematically. The applications of these adhesive materials in drug delivery, antibacterials, tissue repair, and other applications are described in detail. Finally, we have discussed the prospects and challenges of using adhesive materials in the field of biomedicine.

Advances of Mussel-Inspired Nanocomposite Hydrogels in Biomedical Applications

Hydrogels, with 3D hydrophilic polymer networks and excellent biocompatibilities, have emerged as promising biomaterial candidates to mimic the structure and properties of biological tissues. The incorporation of nanomaterials into a hydrogel matrix can tailor the functions of the nanocomposite hydrogels to meet the requirements for different biomedical applications. However, most nanomaterials show poor dispersion in water, which limits their integration into the hydrophilic hydrogel network. Mussel-inspired chemistry provides a mild and biocompatible approach in material surface engineering due to the high reactivity and universal adhesive property of catechol groups. In order to attract more attention to mussel-inspired nanocomposite hydrogels, and to promote the research work on mussel-inspired nanocomposite hydrogels, we have reviewed the recent advances in the preparation of mussel-inspired nanocomposite hydrogels using a variety of nanomaterials with different forms (nanoparticles, nanorods, nanofibers, nanosheets). We give an overview of each nanomaterial modified or hybridized by catechol or polyphenol groups based on mussel-inspired chemistry, and the performances of the nanocomposite hydrogel after the nanomaterial's incorporation. We also highlight the use of each nanocomposite hydrogel for various biomedical applications, including drug delivery, bioelectronics, wearable/implantable biosensors, tumor therapy, and tissue repair. Finally, the challenges and future research direction in designing mussel-inspired nanocomposite hydrogels are discussed.