A Mechanically Resilient and Tissue-Conformable Hydrogel with Hemostatic and Antibacterial Capabilities for Wound Care

Wet tissue adhesive polymeric powder hydrogels for skeletal muscle regeneration

Volumetric muscle loss (VML) frequently results from traumatic incidents and can lead to severe functional disabilities. Hydrogels have been widely employed for VML tissue regeneration, which are unfortunately ineffective because of the lack of intimate contact with injured tissue for structural and mechanical support. Adhesive hydrogels allow for strong tissue connections for wound closure. Nevertheless, conventional adhesive hydrogels exhibit poor tissue adhesion in moist, bleeding wounds due to the hydration layer at the tissue-hydrogel interfaces, resulting in insufficient performance. In this study, we developed a novel, biocompatible, wet tissue adhesive powder hydrogel consisting of dextran-aldehyde (dex-ald) and gelatin for the regeneration of VML. This powder absorbs the interfacial tissue fluid and buffer solution on the tissue, spontaneously forms a hydrogel, and strongly adheres to the tissue via various molecular interactions, including the Schiff base reaction. In particular, the powder composition with a 1:4 ratio of dex-ald to gelatin exhibited optimal characteristics with an appropriate gelation time (258 s), strong tissue adhesion (14.5 kPa), and stability. Dex-ald/gelatin powder hydrogels presented strong adhesion to various organs and excellent hemostasis compared to other wet hydrogels and fibrin glue. A mouse VML injury model revealed that the dex-ald/gelatin powder hydrogel significantly improved muscle regeneration, reduced fibrosis, enhanced vascularization, and decreased inflammation. Consequently, our wet-adhesive powder hydrogel can serve as an effective platform for repairing various tissues, including the heart, muscle, and nerve tissues.

Spatial Confinement Engineered Gel Composite Evaporators for Efficient Solar Steam Generation

Recently, solar-driven interfacial evaporation (SDIE) has been developed quickly for low-cost and sustainable seawater desalination, but addressing the conflict between a high evaporation rate and salt rejection during SDIE is still challenging. Here, a spatial confinement strategy is proposed to prepare the gel composite solar evaporator (SCE) by loading one thin hydrogel layer onto the skeleton of a carbon aerogel. The SCE retains the hierarchically porous structure of carbon aerogels with an optimized water supply induced by dual-driven forces (capillary effects and osmotic pressure) and takes advantage of both aerogels and hydrogels, which can gain energy from air and reduce water enthalpy. The SCE has a high evaporation rate (up to 4.23 kg m-2 h-1 under one sun) and excellent salt rejection performance and can maintain structural integrity after long-term evaporation even at high salinities. The SDIE behavior, including heat distribution, water transport, and salt ion distribution, is investigated by combining theoretical simulations and experimental results. This work provides new inspiration and a theoretical basis for the development of high-performance interfacial evaporators.

Smart responsive staple for dynamic promotion of anastomotic stoma healing

The precise combination of conflicting biological properties through sophisticated structural and functional design to meet all the requirements of anastomotic healing is of great demand but remains challenging. Here, we develop a smart responsive anastomotic staple (Ti-OH-MC) by integrating porous titanium anastomotic staple with multifunctional polytannic acid/tannic acid coating. This design achieves dynamic sequential regulation of antibacterial, anti-inflammatory, and cell proliferation properties. During the inflammatory phase of the anastomotic stoma, our Ti-OH-MC can release tannic acid to provide antibacterial and anti-inflammatory properties, together with immune microenvironment regulation function. At the same time, as the healing progresses, the multifunctional coating gradually falls off to expose the porous structure of the titanium anastomotic staple, which promotes cell adhesion and proliferation during the later proliferative and remodeling phases. As a result, our Ti-OH-MC exceeds the properties of clinically used titanium anastomotic staple, and can effectively promote the healing. The staple's preparation strategy is simple and biocompatible, promising for industrialisation and clinical application. This work provides an effective anastomotic staple for anastomotic stoma healing and serve as a reference for the functional design and preparation of other types of titanium-based tissue repair materials.

Antibacterial Hydrogels for Wound Dressing Applications: Current Status, Progress, Challenges, and Trends

Bacterial infection treatment for chronic wounds has posed a major medical threat and challenge. Bacteria at the wounded sites can compete with the immune system and subsequently invade live tissues, leading to more severe tissue damage. Therefore, there is an urgent demand for wound dressings with antibacterial and anti-inflammatory properties. Considering the concept of moist healing, hydrogels with a three-dimensional (3D) network structure are widely used as wound dressings due to their excellent hydrophilicity, water retention properties, and biocompatibility. Developing antibacterial hydrogels for the treatment of infected wounds has been receiving extensive attention recently. This article categorizes antibacterial hydrogels according to their materials and antibacterial modes, and introduces the recent findings and progress regarding their status. More importantly, with the development of emerging technologies, new therapies are utilized to prepare antibacterial hydrogels such as nanoenzymes, photothermal therapy (PTT), photodynamic therapy (PDT), metal-organic frameworks (MOFs), and other external stimuli-responsive methods. Therefore, this review also examines their progress, challenges, and future trends as wound dressings. In the following studies, there will still be a focus on antibacterial hydrogels that have a high performance, multi-functions, and intelligence, especially biocompatibility, a high and long-lasting antibacterial property, responsiveness, and on-demand therapeutic ability.

A comprehensive exploration of hydrogel applications in multi-stage skin wound healing

Hydrogels, as an emerging biomaterial, have found extensive use in the healing of wounds due to their distinctive physicochemical structure and functional properties. Moreover, hydrogels can be made to match a range of therapeutic requirements for materials used in wound healing through specific functional modifications. This review provides a step-by-step explanation of the processes involved in cutaneous wound healing, including hemostasis, inflammation, proliferation, and reconstitution, along with an investigation of the factors that impact these processes. Furthermore, a thorough analysis is conducted on the various stages of the wound healing process at which functional hydrogels are implemented, including hemostasis, anti-infection measures, encouraging regeneration, scar reduction, and wound monitoring. Next, the latest progress of multifunctional hydrogels for wound healing and the methods to achieve these functions are discussed in depth and categorized for elucidation. Finally, perspectives and challenges associated with the clinical applications of multifunctional hydrogels are discussed.

Modulus-tunable multifunctional hydrogel ink with nanofillers for 3D-Printed soft electronics

Seamless integration and conformal contact of soft electronics with tissue surfaces have emerged as major challenges in realizing accurate monitoring of biological signals. However, the mechanical mismatch between the electronics and biological tissues impedes the conformal interfacing between them. Attempts have been made to utilize soft hydrogels as the bioelectronic materials to realize tissue-comfortable bioelectronics. However, hydrogels have several limitations in terms of their electrical and mechanical properties. In this study, we present the development of a 3D-printable modulus-tunable hydrogel with multiple functionalities. The hydrogel has a cross-linked double network, which greatly improves its mechanical properties. Functional fillers such as XLG or functionalized carbon nanotubes (fCNT) can be incorporated into the hydrogel to provide tunable mechanics (Young's modulus of 10-300 kPa) and electrical conductivity (electrical conductivity of ∼20 S/m). The developed hydrogel exhibits stretchability (∼1000% strain), self-healing ability (within 5 min), toughness (400-731 kJ/m3) viscoelasticity, tissue conformability, and biocompatibility. Upon examining the rheological properties in the modulated region, hydrogels can be 3D printed to customize the shape and design of the bioelectronics. These hydrogels can be fabricated into ring-shaped strain sensors for wearable sensor applications.

Nature-Inspired Gelatin-Based Adhesive Hydrogel: A Rapid and User-Friendly Solution for Hemostatic Applications

Conventional hemostatic agents face challenges in achieving rapid hemostasis and effective tissue repair due to limited hemostatic scenarios, suboptimal efficacy, and inadequate adhesion to wet tissues. Drawing inspiration from nature-sourced materials, a gelatin-based adhesive hydrogel (AOT)  is designed, easily prepared and quick to form, driven by Schiff base and multiple hydrogen bonds for applications in arterial and liver bleeding models. AOT exhibits exceptional adhesion to wet tissues (48.67 ± 0.16 kPa) and displays superior hemostatic properties with reduced blood loss and hemostatic time compared to other hydrogels and conventional hemostatic materials. Moreover, AOT exhibits good biocompatibility and biodegradability. In summary, this easily prepared adhesive hydrogel has the potential to supplant traditional hemostatic agents, offering a novel approach to achieve swift sealing of hemostasis and facilitate wound healing and repair in broader application scenarios, owing to its unique advantages.

Silk fibroin-based hemostatic powders with instant and robust adhesion performance for sutureless sealing of gastrointestinal defects

Powder-based hemostatic technology has offered unprecedented opportunities in surgical sealing and repair of irregularly shaped and noncompressible wounds. Despite their routine use, existing clinical hemostatic powders are challenged either by poor mechanical properties or inadequate adhesion to bleeding tissues in biological environments. Here, inspired by the mussel foot proteins' fusion assembly strategy, a novel silk fibroin-based hemostatic powder (named as SF/PEG/TA) with instant and robust adhesion performance is developed. Upon absorbing interfacial liquids, the SF/PEG/TA powders rapidly swell into micro-gels and subsequently contact with each other to transform into a macroscopically homogeneous hydrogel in situ, strengthening its interfacial bonding with various substrates in fluidic environments. The in vitro and in vivo results show that the SF/PEG/TA powder possesses ease of use, good biocompatibility, strong antibacterial activities, and effective blood clotting abilities. The superior hemostatic sealing capability of the SF/PEG/TA powder is demonstrated in the rat liver, heart, and gastrointestinal injury models. Moreover, in vivo investigation of rat skin incision and gastrointestinal perforation models validates that the SF/PEG/TA powder promotes wound healing and tissue regeneration. Taken together, compared to existing clinical hemostatic powders, the proposed SF/PEG/TA powder with superior wound treatment capabilities has high potential for clinical hemostasis and emergency rescue.

Micro-environment triple-responsive hyaluronic acid hydrogel dressings to promote antibacterial activity, collagen deposition, and angiogenesis for diabetic wound healing

The clinical treatment of chronic diabetic wounds is a long-standing thorny issue. Strategies targeting the diabetic micro-environment have been developed to promote wound healing. However, it remains challenging to reverse the adverse conditions and re-activate tissue regeneration and angiogenesis. In this work, we develop injectable hydrogels that are responsive to acidic conditions, reactive oxygen species (ROS), and high glucose levels in a diabetic wound micro-environment to sustainably deliver tannic acid (TA) to augment antibacterial, anti-inflammatory, and anti-oxidative activities. This triple-responsive mechanism is designed by introducing dynamic acylhydrazone and phenylboronic ester bonds to crosslink modified hyaluronic acid (HA) chains. At a diabetic wound, the acylhydrazone bonds may be hydrolyzed at low pH. Meanwhile, glucose may compete with TA, and ROS may oxidize the C-B bond to release TA. Thus, sustained release of TA is triggered by the diabetic micro-environment. The released TA effectively scavenges ROS and kills bacteria. In vivo experiments on diabetic mice demonstrate that the hydrogel dressing highly promotes angiogenesis and extracellular matrix (ECM) deposition, leading to eventual full healing of diabetic skin wounds. This micro-environment-triggered triple-responsive drug release provides a promising method for chronic diabetic wound healing.

Multifunctional antibacterial hydrogels for chronic wound management

Chronic wounds have gradually evolved into a global health challenge, comprising long-term non-healing wounds, local tissue necrosis, and even amputation in severe cases. Accordingly, chronic wounds place a considerable psychological and economic burden on patients and society. Chronic wounds have multifaceted pathogenesis involving excessive inflammation, insufficient angiogenesis, and elevated reactive oxygen species levels, with bacterial infection playing a crucial role. Hydrogels, renowned for their excellent biocompatibility, moisture retention, swelling properties, and oxygen permeability, have emerged as promising wound repair dressings. However, hydrogels with singular functions fall short of addressing the complex requirements associated with chronic wound healing. Hence, current research emphasises the development of multifunctional antibacterial hydrogels. This article reviews chronic wound characteristics and the properties and classification of antibacterial hydrogels, as well as their potential application in chronic wound management.

Enhanced physiochemical, antibacterial, and hemostatic performance of collagen-quaternized chitosan-graphene oxide sponges for promoting infectious wound healing

Bacteria-infected wound healing has attracted widespread attention in biomedical engineering. Wound dressing is a potential strategy for repairing infectious wounds. However, the development of wound dressing with appropriate physiochemical, antibacterial, and hemostatic properties, remains challenging. Hence, there is a motivation to develop new synthetic dressings to improve bacteria-infected wound healing. Here, we fabricate a biocompatible sponge through the covalent crosslinking of collagen (Col), quaternized chitosan (QCS), and graphene oxide (GO). The resulting Col-QCS-GO sponge shows an elastic modulus of 1.93-fold higher than Col sponge due to enhanced crosslinking degree by GO incorporation. Moreover, the fabricated Col-QCS-GO sponge shows favorable porosity (84.30 ± 3.12 %), water absorption / retention (2658.0 ± 113.4 % / 1114.0 ± 65.7 %), and hemostasis capacities (blood loss <50.0 mg). Furthermore, the antibacterial property of the Col-QCS-GO sponge under near-infrared (NIR) irradiation is significantly enhanced (the inhibition rates are 99.9 % for S. aureus and 99.9 % for E. coli) due to the inherent antibacterial properties of QCS and the photothermal antibacterial capabilities of GO. Finally, the Col-QCS-GO+NIR sponge exhibits the lowest percentage of wound area (9.05 ± 1.42 %) at day 14 compared to the control group (31.61 ± 1.76 %). This study provides new insights for developing innovative sponges for bacteria-infected wound healing.

Double-Network Hydrogel with Strengthened Mechanical Property for Controllable Release of Antibacterial Peptide

Developing double-network (DN) hydrogels with high mechanical properties and antibacterial efficacy to combat multidrug-resistant bacterial infections and serve as scaffolds for cell culture still remains an ongoing challenge. In this study, an ion-responsive antibacterial peptide (AMP) (C16-WIIIKKK, termed as IK7) was synergistically combined with a photoresponsive gelatin methacryloyl (GelMA) polymer to fabricate a biocompatible DN hydrogel. The GelMA-IK7 DN hydrogel showed enhanced mechanical properties in contrast to the individual IK7 and GelMA hydrogels and demonstrated substantial antibacterial efficacy. Further investigations revealed that the DN hydrogel effectively inhibited bacterial growth by the controlled and sustained release of the IK7 peptide. In addition, the formation of the DN hydrogel was also found to protect AMP IK7 from rapid degradation by proteinase K. Our findings suggested that the developed GelMA-IK7 DN hydrogel holds great potential for next-generation antibacterial hydrogels for three-dimensional cell culture and tissue regeneration.

[Research progress of antibacterial hydrogel in treatment of infected wounds]

Objective

To review the research progress of new antibacterial hydrogels in the treatment of infected wounds in the field of biomedicine, in order to provide new methods and ideas for clinical treatment of infected wounds.

Methods

The research literature on antibacterial hydrogels at home and abroad was extensively reviewed in recent years, and the antibacterial hydrogels for the treatment of infected wounds were classified and summarized.

Results

Antibacterial hydrogels can be divided into three categories: inherent antibacterial hydrogels, antibacterial agent release hydrogels, and environmental response antibacterial hydrogels. The advantages and disadvantages of antibacterial materials, antibacterial mechanism, antibacterial ability, and biocompatibility were discussed respectively. Inherent antibacterial hydrogels have the characteristics of wide source, low cost, and simple preparation, but their antibacterial ability is relatively weak. New antimicrobial substances are added to antibacterial agent release hydrogels, such as antimicrobial peptides, metal ions, graphene materials, etc., providing a new therapeutic strategy for alternative antibiotic therapy. On the basis of the antibacterial material, environmental promoting factors such as photothermal effect, pH value, and magnetic force are added to the environmental response antibacterial hydrogels, which synergically enhances the antibacterial ability of the hydrogel, improves the precise regulation function and bionic effect of the hydrogel.

Conclusion

The selection of a variety of materials, the addition of a variety of antibacterial agents, and the effect of various promoting factors make composite hydrogels show multiple characteristics. The development of antibacterial hydrogels that can effectively address practical clinical applications remains a significant challenge. In the future, expanding the application range of antibacterial hydrogels, constructing drug-loaded hydrogels, and developing intelligent hydrogels are still new areas that need to be explored and studied.

Progress in injectable hydrogels for the treatment of incompressible bleeding: an update

Uncontrollable haemorrhage from deep, noncompressible wounds remains a persistent and intractable challenge, accounting for a very high proportion of deaths in both war and disaster situations. Recently, injectable hydrogels have been increasingly studied as potential haemostatic materials, highlighting their enormous potential for the management of noncompressible haemorrhages. In this review, we summarize haemostatic mechanisms, commonly used clinical haemostatic methods, and the research progress on injectable haemostatic hydrogels. We emphasize the current status of injectable hydrogels as haemostatic materials, including their physical and chemical properties, design strategy, haemostatic mechanisms, and application in various types of wounds. We discuss the advantages and disadvantages of injectable hydrogels as haemostatic materials, as well as the opportunities and challenges involved. Finally, we propose cutting-edge research avenues to address these challenges and opportunities, including the combination of injectable hydrogels with advanced materials and innovative strategies to increase their biocompatibility and tune their degradation profile. Surface modifications for promoting cell adhesion and proliferation, as well as the delivery of growth factors or other biologics for optimal wound healing, are also suggested. We believe that this paper will inform researchers about the current status of the use of injectable haemostatic hydrogels for noncompressible haemorrhage and spark new ideas for those striving to propel this field forward.