Gold@Halloysite nanotubes-chitin composite hydrogel with antibacterial and hemostatic activity for wound healing

The Horizons of Medical Mineralogy: Structure-Bioactivity Relationship and Biomedical Applications of Halloysite Nanoclay

Medical mineralogy explores the interactions between natural minerals and living organisms such as cells, tissues, and organs and develops therapeutic and diagnostic applications in drug delivery, medical devices, and healthcare materials. Many minerals (especially clays) have been recognized for pharmacological activities and therapeutic potential. Halloysite clay (Chinese medicine name: Chishizhi), manifested as one-dimensional aluminum silicate nanotubes (halloysite nanotubes, HNTs), has gained applications in hemostasis, wound repair, gastrointestinal diseases, tissue engineering, detection and sensing, cosmetics, and daily chemicals formulations. Various biomedical applications of HNTs are derived from hollow tubular structures, high mechanical strength, good biocompatibility, bioactivity, and unique surface characteristics. This natural nanomaterial is safe, abundantly available, and may be processed with environmentally safe green chemistry methods. This review describes the structure and physicochemical properties of HNTs relative to bioactivity. We discuss surface area, porosity and surface defects, hydrophilicity, heterogeneity and charge of external and internal surfaces, as well as biosafety. The paper provides comprehensive guidance for the development of this tubule nanoclay and its advanced biomedical applications for clinical diagnosis and therapy.

Photocrosslinked carboxymethylcellulose-based hydrogels: Synthesis, characterization for curcumin delivery and wound healing

Skin could protect our body and regenerate itself to against dysfunctional and disfiguring scars when faced with external injury. As wound dressings, hydrogels are biocompatible, hydrophilic and have a 3D structure similar to the extracellular matrix (ECM). In particular, hydrogels with drug-releasing capabilities are in acute wound healing. In this paper, photocrosslinked hydrogels served as wound dressing based on sodium carboxymethylcellulose (CMC) were prepared to promote wound healing. Photocrosslinked hydrogels were prepared by grafting lysine and allyl glycidyl ether (AGE) onto CMC and encapsulating curcumin (Cur). The synthesized hydrogels had the unique 3D porous structure with a swelling ratio up to 1300 % in aqueous solution. The drug release ratios of the hydrogels were 20.8 % in acid environment, and 14.4 % in alkaline environment. Notably, the hydrogels showed good biocompatibility and antibacterial properties and also exhibited the ability to accelerate the process of skin wound healing while prevent inflammation and scar formation when applied to a mouse skin wound model. As a result, the prepared hydrogels Gel-CLA@Cur showed great potential in wound healing.

Self-Healing Conductive Hydrogels with Dynamic Dual Network Structure Accelerate Infected Wound Healing via Photothermal Antimicrobial and Regulating Inflammatory Response

Wound infections are an escalating clinical challenge with continuous inflammatory response and the threat of drug-resistant bacteria. Herein, a series of self-healing conductive hydrogels were designed based on carboxymethyl chitosan/oxidized sodium alginate/polymerized gallic acid/Fe3+ (CMC/OSA/pGA/Fe3+, COGFe) for promoting infected wound healing. The Schiff base and catechol-Fe3+ chelation in the dynamical dual network structure of the hydrogels endowed dressings with good toughness, conductivity, adhesion, and self-healing properties, thus flexibly adapting to the deformation of skin wounds. In terms of ultraviolet (UV) resistance and scavenging of reactive oxygen species (ROS), the hydrogels significantly reduced oxidative stress at the wound site. Additionally, the hydrogels with photothermal therapy (PTT) achieved a 95% bactericidal rate in 5 min of near-infrared (NIR) light radiation by disrupting the bacterial cell membrane structure through elevated temperature. Meanwhile, the inherent antimicrobial properties of GA could reduce healthy tissue damage caused by excessive heat. The composite hydrogels could effectively promote the proliferation and migration of fibroblasts and possess good biocompatibility and hemostatic effect. In full-thickness infected wound repair experiments in rats, the COGFe5 hydrogel combined with NIR effectively killed bacteria, modulated macrophage polarization (M1 to M2 phenotype) to improve the immune microenvironment of the wound, and shortened the repair time by accelerating the expression of collagen deposition (TGF-β) and vascular factors (CD31). This combined therapy might provide a prospective strategy for infectious wound treatment.

Nanomaterials for Photothermal Antimicrobial Surfaces

Microbial infection diseases are a major threat to human health and have become one of the main causes of mortality. The search for novel antimicrobial strategies is an important challenge for the scientific community, considering also the constant increase of antimicrobial resistance and the rise of new diseases. Among the new strategies to combat microbial infections, the photothermal effect seems to be one of the most promising. Hyperthermia is an effective and broad spectrum strategy for the removal of microbial infections. Among all of the strategies to reduce the diffusion of microbial infections, the preparation of antimicrobial surfaces seems of primary importance. In many cases, in fact, an infection can be diffused through surfaces just by touching them, or by inoculating microbes through an internalizable device, such as an implant, a prosthesis, or a catheter. In this review, we will summarize the recent advances in the preparation of photothermal antibacterial surfaces.

A critical overview of challenging roles of medicinal plants in improvement of wound healing technology

PURPOSE

Chronic diseases often hinder the natural healing process, making wound infections a prevalent clinical concern. In severe cases, complications can arise, potentially leading to fatal outcomes. While allopathic treatments offer numerous options for wound repair and management, the enduring popularity of herbal medications may be attributed to their perceived minimal side effects. Hence, this review aims to investigate the potential of herbal remedies in efficiently treating wounds, presenting a promising alternative for consideration.

METHODS

A literature search was done including research, reviews, systematic literature review, meta-analysis, and clinical trials considered. Search engines such as Pubmed, Google Scholar, and Scopus were used while retrieving data. Keywords like Wound healing 'Wound healing and herbal combinations', 'Herbal wound dressing', Nanotechnology and Wound dressing were used.

RESULT

This review provides valuable insights into the role of natural products and technology-based formulations in the treatment of wound infections. It evaluates the use of herbal remedies as an effective approach. Various active principles from herbs, categorized as flavonoids, glycosides, saponins, and phenolic compounds, have shown effectiveness in promoting wound closure. A multitude of herbal remedies have demonstrated significant efficacy in wound management, offering an additional avenue for care. The review encompasses a total of 72 studies, involving 127 distinct herbs (excluding any common herbs shared between studies), primarily belonging to the families Asteraceae, Fabaceae, and Apiaceae. In research, rat models were predominantly utilized to assess wound healing activities. Furthermore, advancements in herbal-based formulations using nanotechnology-based wound dressing materials, such as nanofibers, nanoemulsions, nanofiber mats, polymeric fibers, and hydrogel-based microneedles, are underway. These innovations aim to enhance targeted drug delivery and expedite recovery. Several clinical-based experimental studies have already been documented, evaluating the efficacy of various natural products for wound care and management. This signifies a promising direction in the field of wound treatment.

CONCLUSION

In recent years, scientists have increasingly utilized evidence-based medicine and advanced scientific techniques to validate the efficacy of herbal medicines and delve into the underlying mechanisms of their actions. However, there remains a critical need for further research to thoroughly understand how isolated chemicals extracted from herbs contribute to the healing process of intricate wounds, which may have life-threatening consequences. This ongoing research endeavor holds great promise in not only advancing our understanding but also in the development of innovative formulations that expedite the recovery process.

Multifunctional fish-skin collagen-based hydrogel sealant with dual-dynamic-bond cross-linked for rapid hemostasis and accelerated wound healing

Collagen (COL) is the most widespread functional protein. Designing and developing dual-dynamic-bond cross-linked COL adhesive hydrogel sealants with multifunctional is highly advantageous for achieving a superior wound closure effect and hemostasis. In this study, we developed hybrid hydrogels consisting of fish-skin COL, oxidized sodium alginate (OSA), borax and polyvinyl alcohol (PVA) to enhance full-thickness wound healing. The hydrogels were furnished with first-rate self-healing capabilities through the dual-dynamic-bond cross-linking of dynamic Schiff base bonds (COL-OSA) and diol boric acid bonds (OSA-borax) with reversible breakage and re-formation. Moreover, the incorporation of PVA stimulated the formation of hydrogen bonds in the system, bolstering the stability of the hydrogel framework. The prepared hydrogel manifests self-healing, injectability, multifunctional adhesiveness and biodegradability. In vivo assessment of the hemostatic capacity of COSP20 hydrogel was superior to gauze both in the mice liver injury model and mice tail amputation model. In addition, a full-thickness skin wound model in mice revealed that the COSP20 hydrogel facilitated faster wound closure by accelerating reepithelialization, COL deposition and angiogenesis. These findings illustrate the potential of hybrid fish-skin COL-based hydrogels to enhance wound healing and promote rapid tissue repair, and provide new possibilities for the effective utilization of marine fishery resources.

What else should hemostatic materials do beyond hemostasis: A review

Massive blood loss due to injury is the leading cause of prehospital deaths in disasters and emergencies. Hemostatic materials are used to realize rapid hemostasis and protect patients from death. Researchers have designed and developed a variety of hemostatic materials. However, in addition to their hemostatic effect, hemostatic materials must be endowed with additional functions to meet the practical application requirements in different scenarios. Here, strategies for modifications of hemostatic materials for use in different application scenarios are listed: effective positioning at the site of deep and narrow wounds to stop bleeding, resistance to high blood pressure and wound movement to maintain wound formation, rapid and easy removal from the wound without affecting further treatment after hemostasis is completed, and continued function when retained in the wound as a dressing (such as antibacterial, antiadhesion, tissue repair, etc.). The problems encountered in the practical use of hemostatic materials and the strategies and progress of researchers will be further discussed in this review. We hope to provide valuable references for the design of more comprehensive and practical hemostatic materials.

Insight into CMC-PVA-fHNTs Nanocomposite Hydrogel as an Advance Carrier for Cefadroxil Monohydrate: Fabrication and Characterization/Angiogenic Potential Analysis

Controlled drug delivery is a key strategy aimed at reducing both the frequency of therapeutic dosages and potential systemic side effects, particularly in the case of high drug concentrations. The nanocomposite hydrogel systems presented in this study were synthesized by combining carboxymethyl cellulose, polyvinyl alcohol, and (3-aminopropyl)triethoxysilane-functionalized halloysite nanotubes (fHNTs). This hydrogel system is a potential candidate for the controlled release of cefadroxil monohydrate. These hydrogels are analyzed by Fourier transform infrared spectroscopy, scanning electron microscopy, thermogravimetric analysis, and rheological measurements. Additionally, swelling properties, porosity, hydrophilicity, drug release, and in vitro and in vivo analyses were also evaluated. The observed trends in swelling and drug release demonstrated that the outcomes are dependent on the presence of fHNTs in the hydrogel matrix. Notably, fHNTs-loaded hydrogels displayed sustained drug release patterns. This innovative approach eliminates the need for traditional encapsulation and presents promising and translatable strategies for achieving more effective drug release.

Recent Advances in Topical Hemostatic Materials

Untimely or improper treatment of traumatic bleeding may cause secondary injuries and even death. The traditional hemostatic modes can no longer meet requirements of coping with complicated bleeding emergencies. With scientific and technological advancements, a variety of topical hemostatic materials have been investigated involving inorganic, biological, polysaccharide, and carbon-based hemostatic materials. These materials have their respective merits and defects. In this work, the application and mechanism of the major hemostatic materials, especially some hemostatic nanomaterials with excellent adhesion, good biocompatibility, low toxicity, and high adsorption capacity, are summarized. In the future, it is the prospect to develop multifunctional hemostatic materials with hemostasis and antibacterial and anti-inflammatory properties for promoting wound healing.

Nanoclay Hydrogel Microspheres with a Sandwich-Like Structure for Complex Tissue Infection Treatment

Addressing complex tissue infections remains a challenging task because of the lack of effective means, and the limitations of traditional bioantimicrobial materials in single-application scenarios hinder their utility for complex infection sites. Hence, the development of a bioantimicrobial material with broad applicability and potent bactericidal activity is necessary to treat such infections. In this study, a layered lithium magnesium silicate nanoclay (LMS) is used to construct a nanobactericidal platform. This platform exhibits a sandwich-like structure, which is achieved through copper ion modification using a dopamine-mediated metallophenolic network. Moreover, the nanoclay is encapsulated within gelatin methacryloyl (GelMA) hydrogel microspheres for the treatment of complex tissue infections. The results demonstrate that the sandwich-like micro- and nanobactericidal hydrogel microspheres effectively eradicated Staphylococcus aureus (S. aureus) while exhibiting excellent biocompatibility with bone marrow-derived mesenchymal stem cells (BMSCs) and human umbilical vein endothelial cells (HUVECs). Furthermore, the hydrogel microspheres upregulated the expression levels of osteogenic differentiation and angiogenesis-related genes in these cells. In vivo experiments validated the efficacy of sandwich-like micro- and nanobactericidal hydrogel microspheres when injected into deep infected tissues, effectively eliminating bacteria and promoting robust vascular regeneration and tissue repair. Therefore, these innovative sandwich-like micro- and nanobacteriostatic hydrogel microspheres show great potential for treating complex tissue infections.

Recent advances in the application of clay-containing hydrogels for hemostasis and wound healing

INTRODUCTION

Immediate control of bleeding and anti-infection play important roles in wound management. Multiple organ dysfunction syndrome and death may occur if persistent bleeding, hemodynamic instability, and hypoxemia are not addressed. The combination of clay and hydrogel provides a new outlet for wound hemostasis. In this review, the current research progress of hydrogel/clay composite hemostatic agents was reviewed.

AREAS COVERED

This paper summarizes the characteristics of several kinds of clay including kaolinite, montmorillonite, laponite, sepiolite, and palygorskite. The advantages and disadvantages of its application in hemostasis were also summarized. Future directions for the application of hydrogel/clay composite hemostatic agents are presented.

EXPERT OPINION

Clay can activate the endogenous hemostatic pathway by increasing blood cell concentration and promoting plasma absorption to accelerate the hemostasis. Clay is antimicrobial due to the slow release of metal ions and has a rich surface charge with a high affinity for proteins and cells to promote tissue repair. Hydrogels have some properties such as good biocompatibility, strong adhesion, high stretchability, and good self-healing. Despite promising advances, hydrogel/clay composite hemostasis remains a limitation. Therefore, more evidence is needed to further elucidate the risk factors and therapeutic effects of hydrogel/clay in hemostasis and wound healing.

A carboxymethyl chitosan/oxidized hyaluronic acid composite hydrogel dressing loading with stem cell exosome for chronic inflammation wounds healing

Stem cell exosomes (Exo) play an important role in the transformation of macrophages, but the rapid clearance of Exo in vivo limits their therapeutic effects for chronic inflammation wounds healing. Here, stem cell Exo was isolated and introduced to a composite hydrogel including carboxymethyl chitosan (CMCS) and oxidized hyaluronic acid (OHA) through chemical cross-linking, which formed an Exo-loaded (CMCS/OHA/Exo) hydrogel. The CMCS/OHA/Exo hydrogel exhibited a function of Exo sustained release and an Exo protection within 6 days. This CMCS/OHA/Exo hydrogel was much better than CMCS/OHA hydrogel or Exo solution in macrophage cell phagocytosis, proliferation and migration in vitro, especially, played an obviously positive role in the transformation of macrophages compared with the reference groups. For the treatment of the chronic inflammation wounds in vivo, the CMCS/OHA/Exo hydrogel had the best results at wound heal rate and inhibiting the secretion of inflammatory factors, and it was far superior to reference groups in wound re-epithelization and collagen production. CMCS/OHA/Exo hydrogels can promote Exo release based on hydrogel degradation to regulate macrophages transformation and accelerate chronic wound healing. The study offers a method for preparing Exo-loaded hydrogels that effectively promote the transformation of macrophages and accelerate chronic inflammatory wound healing.

Antimicrobial Hydrogels: Potential Materials for Medical Application

Microbial infections based on drug-resistant pathogenic organisms following surgery or trauma and uncontrolled bleeding are the main causes of increased mortality from trauma worldwide. The prevalence of drug-resistant pathogens has led to a significant increase in medical costs and poses a great threat to the normal life of people. This is an important issue in the field of biomedicine, and the emergence of new antimicrobial materials hydrogels holds great promise for solving this problem. Hydrogel is an important material with good biocompatibility, water absorption, oxygen permeability, adhesion, degradation, self-healing, corrosion resistance, and controlled release of drugs as well as structural diversity. Bacteria-disturbing hydrogels have important applications in the direction of surgical treatment, wound dressing, medical device coating, and tissue engineering. This paper reviews the classification of antimicrobial hydrogels, the current status of research, and the potential of antimicrobial hydrogels for one application in biomedicine, and analyzes the current research of hydrogels in biomedical applications from five aspects: metal-loaded hydrogels, drug-loaded hydrogels, carbon-material-loaded hydrogels, hydrogels with fixed antimicrobial activity and biological antimicrobial hydrogels, and provides an outlook on the high antimicrobial activity, biodegradability, biocompatibility, injectability, clinical applicability and future development prospects of hydrogels in this field.

Double Cross-Linked Hydrogel Dressings Based on Triblock Copolymers Bearing Antifreezing, Antidrying, and Inherent Antibacterial Properties

Bacterial infections typically invade the living tissue of wounds, thereby aggravating the inflammatory response, delaying wound healing, or causing further complications. In this paper, the antibacterial hydrogel (PNVBA) with antifreezing and antidrying properties was prepared by a two-step method using N-isopropylacrylamide (NIPAM), 1-butyl-3-vinylimidazolium bromide (VBIMBr), and 3-acrylamidophenylboronic acid (AAPBA). PNVBA hydrogels exhibited a high adsorption capacity of 280 mg·g-1 for bovine serum albumin (BSA) and can adhere to the surface of different materials through ion-dipole or hydrogen-bonding interactions. Meanwhile, the PNVBA hydrogels exhibited high viscoelasticity and good adhesion after freezing at -20 °C or heating at 70 °C for 24 h with a sterilizing rate of up to 98% against multidrug-resistant (MDR) Escherichia coli and methicillin-resistant Staphylococcus aureus (MRSA). Moreover, a survival rate of up to 90% after incubation with L929 cells over 24 h was observed. Therefore, this inherent antibacterial hydrogel can be used as an excellent alternative material for wound dressings.

Recent Advances of Halloysite Nanotubes in Biomedical Applications

Halloysite nanotubes (HNTs) have emerged as a highly regarded choice in biomedical research due to their exceptional attributes, including superior loading capacity, customizable surface characteristics, and excellent biocompatibility. HNTs feature tubular structures comprising alumina and silica layers, endowing them with a large surface area and versatile surface chemistries that facilitate selective modifications. Moreover, their substantial pore volume and wide range of pore sizes enable efficient entrapment of diverse functional molecules. This comprehensive review highlights the broad biomedical application spectrum of HNTs, shedding light on their potential as innovative and effective therapeutic agents across various diseases. It emphasizes the necessity of optimizing drug delivery techniques, developing targeted delivery systems, rigorously evaluating biocompatibility and safety through preclinical and clinical investigations, exploring combination therapies, and advancing scientific understanding. With further advancements, HNTs hold the promise to revolutionize the pharmaceutical industry, opening new avenues for the development of transformative treatments.

MXene/zinc ion embedded agar/sodium alginate hydrogel for rapid and efficient sterilization with photothermal and chemical synergetic therapy

Bacterial infections can significantly impair wound healing. Therefore, it is essential to develop wound dressings with high antimicrobial activity. Hydrogels are often used as wound dressings due to their excellent physicochemical properties. Herein, by cross linking sodium alginate (SA), agar (AG) with Ti3C2Tx MXene and Zinc ions (Zn2+), a biosafe composite hydrogel (MSG-Zn2+) was developed for fast and efficient sterilization treatment. The excellent photothermal properties of Ti3C2Tx MXene and the chemical antimicrobial activity of Zn2+ enable synergistic photothermal therapy (PTT)/chemical therapy in NIR biowindow with reduced power density and improved antimicrobial efficiency. More importantly, the incorporation of Zn2+ can enhance the effective contact between the hydrogel and bacteria, benefiting both photothermal and chemical antibacteria. In vitro antibacterial experiments showed that MSG-Zn2+ has a broad-spectrum antibacterial effect against Gram-positive Staphylococcus aureus (S. aureus) and Gram-negative Escherichia coli (E. coli). Cellular experiments showed that the hydrogel had excellent biocompatibility and the released Zn2+ stimulated cell migration. In addition, the prepared MSG-Zn2+ hydrogel has other advantages such as hydrophilic, high swelling, simple and low cost preparation, which meets the requirements of an economical wound dressing. This proposed work shows that this composite hydrogel MSG-Zn2+ has great potential for practical antimicrobial wound dressing applications.

Hydrogels based on seafood chitin: From extraction to the development

Chitin is extensively applied in vast applications due to its excellent biological properties, such as biodegradable and non-toxic. About 50 % of waste generated during seafood processing is chitin. Conventionally, chitin is extracted via chemical method. However, it has many shortcomings. Many novel extraction methods have emerged, including enzymatic hydrolysis, microbial fermentation, ultrasonic or microwave-assisted, ionic liquids, and deep eutectic solvents. Chitin and its derivatives-based hydrogels have attracted much attention due to their excellent properties. Nevertheless, they all have many limitations. Therefore, the preparation and application of chitin and its derivatives-based hydrogels are still facing great challenges. This review focuses on the challenges and prospects for sustainable chitin extraction from seafood waste and the preparation and application of chitin and its derivatives-based hydrogels. First section summarizes the mechanism and application of several methods of extracting chitin. The different extraction methods were evaluated from the aspects of yield, degree of acetylation, and protein and mineral residuals. The shortcomings of the extraction methods are also discussed. Next section summarizes the preparation and application of chitin and its derivatives-based hydrogels. Overall, we hope this mini-review can provide a practical reference for selecting chitin extraction methods from seafood and applying chitin and its derivatives-based hydrogels.

Biocompatible copper formate-based nanoparticles with strong antibacterial properties for wound healing

Copper-based antibacterial materials have emerged as a potential alternative for combating bacterial infections, which continue to pose significant health risks. Nevertheless, the use of copper-based nanoparticles as antibacterial agents has faced challenges due to their toxicity towards cells and tissues. To overcome this obstacle, we propose a new approach using a contact-active copper-based nanoparticles called polydopamine (PDA)-coated copper-amine (Cuf-TMB@PDA). The positively charged surface of Cuf-TMB@PDA enables efficient targeting of negatively charged bacteria, allowing controlled release of Cu(II) into the bacterial cell membrane. Moreover, Cuf-TMB@PDA exhibits similar ·OH signals as Cuf-TMB suspensions in previous work. In cytotoxicity assays conducted over 72 h, Cuf-TMB@PDA demonstrated an efficacy of 98.56%, while releasing lower levels of Cu(II) that were less harmful to cells, resulting in enhanced antimicrobial effects. These antimicrobial properties are attributed to the synergistic effects of charge-contact activity of PDA, controlled release of Cu(II), and free radicals. Subsequent in vivo experiments confirmed the strong antimicrobial potency of Cuf-TMB@PDA and its ability to promote wound healing.

Local Clays from China as Alternative Hemostatic Agents

In recent years, the coagulation properties of inorganic minerals such as kaolin and zeolite have been demonstrated. This study aimed to assess the hemostatic properties of three local clays from China: natural kaolin from Hainan, natural halloysite from Yunnan, and zeolite synthesized by our group. The physical and chemical properties, blood coagulation performance, and cell biocompatibility of the three materials were tested. The studied materials were characterized by using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), X-ray fluorescence spectroscopy (XRF), thermogravimetric analysis (TGA), and differential scanning calorimetry (DSC). All three clays showed different morphologies and particle size, and exhibited negative potentials between pH 6 and 8. The TGA and DSC curves for kaolin and halloysite were highly similar. Kaolin showed the highest water absorption capacity (approximately 93.8% ± 0.8%). All three clays were noncytotoxic toward L929 mouse fibroblasts. Kaolin and halloysite showed blood coagulation effects similar to that exhibited by zeolite, indicating that kaolin and halloysite are promising alternative hemostatic materials.

Application of f-FeNC@GOx cascade enzyme nanomaterials in the healing of infected wounds

AIMS

Bacterial infection is a significant factor contributing to the deterioration of wounds, and the misuse of antibiotics has exacerbated bacterial resistance. Therefore, there is an urgent need to develop a novel antibacterial strategy to replace conventional therapies. This study aims to construct a self-activated cascade reaction nanozyme, f-FeNC@GOx, which triggers a cascade reaction in the presence of glucose. This cascade reaction generates highly toxic hydroxyl radicals (OH), thereby achieving the goal of eliminating bacteria and promoting wound healing.

MATERIAL AND METHODS

In vitro antibacterial experiments, bacterial spread plate method, Live/Dead staining, and crystal violet staining were conducted to analyze the antibacterial ability and mechanism of f-FeNC@GOx. In vivo experiments, a mouse wound model was established, and H&E and Masson staining of wound tissues were performed to assess the antibacterial activity of the f-FeNC@GOx in vivo.

KEY FINDINGS

The in vivo and in vitro experiments confirmed that f-FeNC@GOx exhibited significant antibacterial effect against both Staphylococcus aureus and Escherichia coli in the presence of glucose. Furthermore, it showed optimal wound healing performance in the wound models.

SIGNIFICANCE

These findings suggested that f-FeNC@GOx was a novel and effective antibacterial nanomaterial, which provided a promising antibacterial strategy using nanoenzyme based cascade reaction.

A Review of Metal Nanoparticles Embedded in Hydrogel Scaffolds for Wound Healing In Vivo

An evolving field, nanotechnology has made its mark in the fields of nanoscience, nanoparticles, nanomaterials, and nanomedicine. Specifically, metal nanoparticles have garnered attention for their diverse use and applicability to dressings for wound healing due to their antimicrobial properties. Given their convenient integration into wound dressings, there has been increasing focus dedicated to investigating the physical, mechanical, and biological characteristics of these nanoparticles as well as their incorporation into biocomposite materials, such as hydrogel scaffolds for use in lieu of antibiotics as well as to accelerate and ameliorate healing. Though rigorously tested and applied in both medical and non-medical applications, further investigations have not been carried out to bring metal nanoparticle-hydrogel composites into clinical practice. In this review, we provide an up-to-date, comprehensive review of advancements in the field, with emphasis on implications on wound healing in in vivo experiments.

Hemostasis Strategies and Recent Advances in Nanomaterials for Hemostasis

The development of materials that effectively stop bleeding and prevent wound adhesion is essential in both military and medical fields. However, traditional hemostasis methods, such as cautery, tourniquets, and gauze, have limitations. In recent years, new nanomaterials have gained popularity in medical and health fields due to their unique microstructural advantages. Compared to traditional materials, nanomaterials offer better adhesion, versatility, and improved bioavailability of traditional medicines. Nanomaterials also possess advantages such as a high degree and stability, self-degradation, fewer side effects, and improved wound healing, which make them ideal for the development of new hemostatic materials. Our review provides an overview of the currently used hemostatic strategies and materials, followed by a review of the cutting-edge nanomaterials for hemostasis, including nanoparticles and nanocomposite hydrogels. The paper also briefly describes the challenges faced by the application of nanomaterials for hemostasis and the prospects for their future development.

A "Test-to-Treat" Pad for Real-Time Visual Monitoring of Bacterial Infection and On-Site Performing Smart Therapy Strategies

Skin infections are major threats to human health, causing ∼500 incidences per 10 000 person-year. In patients with diabetes mellitus, particularly, skin infections are often accompanied by a slow healing process, amputation, and even death. Timely diagnosis of skin infection strains and on-site therapy are vital in human health and safety. Herein, a double-layered "test-to-treat" pad is developed for the visual monitoring and selective treatment of drug-sensitive (DS)/drug-resistant (DR) bacterial infections. The inner layer (using carrageenan hydrogel as a scaffold) is loaded with bacteria indicators and an acid-responsive drug (Fe-carbenicillin frameworks) for infection detection and DS bacteria inactivation. The outer layer is a mechanoluminescence material (ML, CaZnOS:Mn²⁺) and visible-light responsive photocatalyst (Pt@TiO₂) incorporated elastic polydimethylsiloxane (PDMS). On the basis of the colorimetric sensing result (yellow for DS-bacterial infection and red for DR-bacterial infection), a suitable antibacterial strategy is guided and then performed. Two available bactericidal routes provided by double pad layers reflect the advantage. The controllable and effective killing of DR bacteria is realized by in situ generated reactive oxygen species (ROSs) from the combination of Pt@TiO₂ and ML under mechanical force, avoiding physical light sources and alleviating off-target side effects of ROS in biomedical therapy. As a proof-of-concept, the "test-to-treat" pad is applied as a wearable wound dressing for sensing and selectively dealing with DS/DR bacterial infections in vitro and in vivo. This multifunctional design effectively reduces antibiotic abuse and accelerates wound healing, providing an innovative and promising Band-Aid strategy in point-of-care diagnosis and therapy.

PHMB modified photothermally triggered nitric oxide release nanoplatform for precise synergistic therapy of wound bacterial infections

Bacterial infection has been considered as a significant obstacle for wound healing. Nitric oxide (NO), as a novel alternative for antibiotics, has emerged as a promising antibacterial agent. However, the precise spatiotemporal controlled release of NO still remains a major challenge. Herein, a near-infrared (NIR) light triggered NO release nanoplatform (designated as PB-NO@PDA-PHMB) with enhanced broad-spectrum antibacterial and anti-biofilm properties was constructed. Given that PB-NO@PDA-PHMB has strong absorption in the NIR region and exhibits excellent photothermal effect, it can rapidly trigger NO release by NIR irradiation. PB-NO@PDA-PHMB can effectively contact and capture bacteria, and then exhibit synergistic effect of photothermal and gas therapy. In vitro and in vivo experiments indicated that PB-NO@PDA-PHMB exhibited excellent biocompatibility, satisfactory synergistic antibacterial efficacy and the capability of accelerating wound healing. Under NIR irradiation (808 nm, 1 W cm^-2, 7 min), PB-NO@PDA-PHMB (80 μg mL^-1) achieved 100% bactericidal activity against both Gram-negative bacteria Escherichia coli (E. coli) and Gram-positive bacteria Staphyloccocus aureus (S. aureus), removed 58.94% of S. aureus biofilm. Therefore, this all-in-one antibacterial nanoplatform with high NIR responsiveness provides a promising antibiotic-free strategy for bacterial infection treatment.

Natural and Synthetic Clay Minerals in the Pharmaceutical and Biomedical Fields

Clay minerals are historically among the most used materials with a wide variety of applications. In pharmaceutical and biomedical fields, their healing properties have always been known and used in pelotherapy and therefore attractive for their potential. In recent decades, the research has therefore focused on the systematic investigation of these properties. This review aims to describe the most relevant and recent uses of clays in the pharmaceutical and biomedical field, especially for drug delivery and tissue engineering purposes. Clay minerals, which are biocompatible and non-toxic materials, can act as carriers for active ingredients while controlling their release and increasing their bioavailability. Moreover, the combination of clays and polymers is useful as it can improve the mechanical and thermal properties of polymers, as well as induce cell adhesion and proliferation. Different types of clays, both of natural (such as montmorillonite and halloysite) and synthetic origin (layered double hydroxides and zeolites), were considered in order to compare them and to assess their advantages and different uses.

Advances in Functional Hydrogel Wound Dressings: A Review

One of the most advanced, promising, and commercially viable research issues in the world of hydrogel dressing is gaining functionality to achieve improved therapeutic impact or even intelligent wound repair. In addition to the merits of ordinary hydrogel dressings, functional hydrogel dressings can adjust their chemical/physical properties to satisfy different wound types, carry out the corresponding reactions to actively create a healing environment conducive to wound repair, and can also control drug release to provide a long-lasting benefit. Although a lot of in-depth research has been conducted over the last few decades, very few studies have been properly summarized. In order to give researchers a basic blueprint for designing functional hydrogel dressings and to motivate them to develop ever-more intelligent wound dressings, we summarized the development of functional hydrogel dressings in recent years, as well as the current situation and future trends, in light of their preparation mechanisms and functional effects.

Photothermal/lysozyme-catalyzed hydrolysis dual-modality therapy via halloysite nanotube-based platform for effective bacterial eradication

Bacterial biofilm seriously impedes the healing of infected wound, remaining a major challenge in wound repair. Antibiotic-free antibacterial strategies based on nanotechnology are emerging as promising tools to combat bacterial infections. Here, halloysite nanotube (HNT), as a natural clay mineral, was employed to fabricate a multifunctional platform (designated as HNTs@CuS@PDA-Lys) through a layer-by-layer strategy for treating bacterial infections by utilizing synergistic lysozyme (Lys)-photothermal therapy (PTT). Specifically, amino-modified HNTs were first decorated with copper sulfide (CuS), followed by coated with a polydopamine (PDA) layer, then functionalized with antimicrobial enzyme Lys onto the surface of PDA via cation-π interactions. The as-prepared HNTs@CuS@PDA-Lys at a low dose (200 μg/mL) exhibited excellent synergistic Lys-photothermal bactericidal activity against Escherichia coli (E. coli) (100.0 ± 0.2 %) and Staphyloccocus aureus (S. aureus) (99.9 ± 0.1 %), eliminated 75.9 ± 2.0 % of S. aureus biofilm under near-infrared (NIR) irradiation (808 nm, 1.5 W/cm²). In vivo experiments using a S. aureus-infected rat model showed HNTs@CuS@PDA-Lys could rapidly kill bacteria and accelerate wound healing process. Overall, this multifunctional nanoplatform combines the advantages of PTT and Lys, providing a cost-efficient, environmental friendly strategy for bacterial and biofilm eradication, demonstrating the potential applications in the field of biomedicine.

Synthesis and evaluation of water-soluble imidazolium salt chitin with broad-spectrum antimicrobial activity and excellent biocompatibility for infected wound healing

Infections caused by bacteria have long constituted a major threat to human health and the economy. Therefore, there is an urgent need to design broad-spectrum antibacterial materials possessing good biocompatibility to treat such infections. Herein, inspired by the good biocompatibility of chitin and antibacterial properties of imidazolium salts, a polysaccharide-based material, imidazolium salt chitin (IMSC), was homogeneously prepared using a facile method with epichlorohydrin as a chemical crosslinker to combine chitin with imidazole to enhance Staphylococcus aureus (S. aureus)-infected wound healing. The characteristics, antimicrobial properties, and biosafety of IMSC were evaluated. The results demonstrated successful grafting of imidazole onto chitin. Furthermore, IMSC exhibited good water solubility, broad-spectrum antimicrobial activity, hemocompatibility, and biocompatibility. Moreover, IMSC enabled complete healing of S. aureus-infected wound in Sprague-Dawley rats within 15 days of application, thus demonstrating that IMSC could reduce wound inflammation and remarkably accelerate wound healing owing to its efficient antibacterial activity and ability to promote collagen deposition in and around the wound area. Therefore, this study provides a promising and potential therapeutic strategy for infected wound healing by synthesizing a water-soluble and broad-spectrum antimicrobial material exhibiting good biocompatibility.

Nanoclays for wound management applications

Nanotechnology has been comprehensively applied as a new approach to managing wound healing. Particularly, nanoclays are being used to improve traditional wound healing approaches or new therapies. Nanoclays are nanoscale aluminosilicates with remarkable intrinsic properties, including the capacity to promote hemostatic response, anti-inflammatory effects, angiogenesis, and re-epithelization. The main purpose of the present review is focusing on skin lesions, post-surgical wounds, burn wounds, and chronic ulcer skin wounds that can be treated using nanoclays, not only as vehicles for therapeutic molecules' efficacy improvement but also alone due to their native beneficial features. A systematic search of the PubMed, ScienceDirect, Scopus, Web of Science, and Google Scholar databases revealed several studies satisfying the purpose of our study. In addition, the selected keywords were used to refine the information. Non-planar hydrous phyllosilicates have been compared with other nanoclays considering their acute specific surface area and loading capacity are strongly influenced by their structure. Nanocomposites in the powder form may be directly incorporated in polymers to form gels, biofilms, and scaffolds that may be adjustable to wound sites. Also, nanoclays can be directly incorporated into polymer mats. Regarding hydrogels/films and mats, nanoclays can improve their mechanical strength, thermal stability, viscosity, and cohesive strength. Additionally, nanoclays are able to control drug release, as well as their skin bioavailability, and seem to be promising candidates to overcome cytotoxicity problems; further in vivo toxicity studies are required.

Preparation of gum tragacanth/poly (vinyl alcohol)/halloysite hydrogel using electron beam irradiation with potential for bone tissue engineering

Nanocomposite hydrogels based on tyramine conjugated gum tragacanth, poly (vinyl alcohol) (PVA), and halloysite nanotubes (HNTs) were prepared by electron beam irradiation and characterized. The FTIR, ¹H NMR, and TGA results confirmed the chemical incorporation of HNTs into gum tragacanth. Gel content and swelling of hydrogels decreased with HNTs loading up to 20 % wt. The mechanical strength of hydrogels increased by increasing HNTs content up to 10 % with 371 kPa fracture stress at 0.95 fracture strain, compared to 312 kPa stress at 0.79 strain for gum tragacanth/PVA hydrogel. Hydrogel's biocompatibility and osteogenic activity were tested by seeding rabbit bone marrow mesenchymal stem cells. The cell viability was >85 % after 7 days of culture. In vitro secretion of ALP and calcium deposition on hydrogels in alizarin red assay after 21 days of culture indicated hydrogel potential for bone tissue engineering.

Fabrication and Properties of the Multifunctional Rapid Wound Healing Panax notoginseng@Ag Electrospun Fiber Membrane

The Panax notoginseng@Ag core/shell electrospun fiber membrane was prepared by coaxial electrospinning combined with the UV reduction method (254 nm). The prepared Panax notoginseng@Ag core/shell nanofiber membrane has a three-dimensional structure, and its swelling ratio could reach as high as 199.87%. Traditional Chinese medicine Panax notoginseng can reduce inflammation, and the silver nanoparticles have antibacterial effects, which synergistically promote rapid wound healing. The developed Panax notoginseng@Ag core/shell nanofiber membrane can effectively inhibit the growth of the Gram-negative bacteria Escherichia coli and the Gram-positive bacteria Staphylococcus aureus. The wound healing experiments in Sprague Dawley mice showed that the wound residual area rate of the Panax notoginseng@Ag core/shell electrospun nanofiber membrane group was only 1.52% on day 9, and the wound of this group basically healed on day 12, while the wound residual area rate of the gauze treatment group (control group) was 16.3% and 10.80% on day 9 and day 12, respectively. The wound of the Panax notoginseng@Ag core/shell electrospun nanofiber membrane group healed faster, which contributed to the application of the nanofiber as Chinese medicine rapid wound healing dressings.

Engineering design of asymmetric halloysite/chitosan/collagen sponge with hydrophobic coating for high-performance hemostasis dressing

Uncontrolled massive hemorrhage is a crucial cause of death, and developing efficient hemostatic materials are of great medical importance. Herein, we prepared a halloysite-chitosan-collagen composite sponge by directional freeze-drying method and coating the sponge by hydrophobic polydimethylsiloxane coating for rapid and effective hemostasis. The aligned channel structure of the sponge with a pore size of ~30 μm was beneficial for the transport of blood. Morphology and spectrum results suggested that chitosan and collagen are capable of adsorbing on the outer surface of HNTs due to the hydrogen bonding and electrostatic attractions. The directional freeze-dried sponge absorbed the majority of the blood within 10 s, and that process essentially completed in 30 s, which are faster than its non-directional counterpart. The composite sponges exhibited high antibacterial properties towards E. coli and S. aureus, and they are non-cytotoxic towards mouse fibroblasts and have high hemocompatibility. The hemostatic dressing avoided unnecessary blood loss because of excessive blood absorption. In vivo experiments of rats also confirmed the ability of the asymmetric sponges to rapidly clot and reduce reducing blood loss. This work developed a high-performance and hemostatic dressing by material design and processing technique, which shows a promising application in wound healing.

Sustainable sepiolite-based composites for fast clotting and wound healing

Uncontrolled bleeding and bacterial coinfection are the major causes of death after an injury. Fast hemostatic capacity, good biocompatibility, and bacterial coinfection inhibition pose great challenges to hemostatic agent development. A prospective sepiolite/Ag nanoparticles (sepiolite@AgNPs) composite has been prepared by using natural clay sepiolite as template. A tail vein hemorrhage mouse model and a rabbit hemorrhage model were used to evaluate the hemostatic properties of the composite. The sepiolite@AgNPs composite can quickly absorb fluid to subsequently stop bleeding due to the natural fibrous crystal structure of sepiolite, and inhibit bacterial growth with the antibacterial ability of AgNPs. Compared with commercially-available zeolite material, the as-prepared composite exhibits competitive hemostatic properties without exothermic reaction in the rabbit model of femoral and carotid artery injury. The rapid hemostatic effect was due to the efficient absorption of erythrocyte and activation of the coagulation cascade factors and platelets. Besides, after heat-treatment, the composites can be recycled without significant reduction of hemostatic performance. Our results also prove that sepiolite@AgNPs nanocomposites can stimulate wound healing. The sustainability, lower-cost, higher bioavailability, and stronger hemostatic efficacy of sepiolite@AgNPs composite render these nanocomposites as more favorable hemostatic agents for hemostasis and wound healing.

Assembly of Clay Nanotubes on Cotton Fibers Mediated by Biopolymer for Robust and High-Performance Hemostatic Dressing

Uncontrollable bleeding from military conflicts, accidents, and surgical procedures is a major life-threatening factor. Rapid, safe, and convenient hemostasis is critical to the survival of bleeding patients in prehospital care. However, the peel-off of hemostats such as kaolinite sheets from the cotton fibers often poses a risk of distal thrombosis. Here, an efficient clay hemostat of halloysite nanotubes is tightly bound onto commercial cotton fibers, which is capillary mediated by biopolymer alginate with Ca²⁺ crosslinking. The robust clay nanotube dressing materials maintain high procoagulant activity after harsh water treatment, and only a few residuals of halloysite exist in the wound area. Compared with commercial hemostat QuikClot Combat gauze, halloysite-alginate-cotton composite dressing exhibits hemostatic properties both in vivo and in vitro with high safety. The hemostatic mechanism of the dressing is attributed to activating platelets, locally concentrating clotting components in the nanoclay, halloysite coagulation factors, and alginate cross-linked with Ca²⁺ . This work inspires robust self-assembly of clay nanotubes on textile fibers and offers a hemostatic material with balanced high hemostatic activity, minimal ingredient loss, and biocompatibility. The robust dressing based on halloysite tightly bounded cotton shows great potential for military, medical, and civil bleeding control with low health risks.

Nanomaterials-Functionalized Hydrogels for the Treatment of Cutaneous Wounds

Hydrogels have been utilized extensively in the field of cutaneous wound treatment. The introduction of nanomaterials (NMs), which are a big category of materials with diverse functionalities, can endow the hydrogels with additional and multiple functions to meet the demand for a comprehensive performance in wound dressings. Therefore, NMs-functionalized hydrogels (NMFHs) as wound dressings have drawn intensive attention recently. Herein, an overview of reports about NMFHs for the treatment of cutaneous wounds in the past five years is provided. Firstly, fabrication strategies, which are mainly divided into physical embedding and chemical synthesis of the NMFHs, are summarized and illustrated. Then, functions of the NMFHs brought by the NMs are reviewed, including hemostasis, antimicrobial activity, conductivity, regulation of reactive oxygen species (ROS) level, and stimulus responsiveness (pH responsiveness, photo-responsiveness, and magnetic responsiveness). Finally, current challenges and future perspectives in this field are discussed with the hope of inspiring additional ideas.

Applications and prospects of different functional hydrogels in meniscus repair

The meniscus is a kind of fibrous cartilage structure that serves as a cushion in the knee joint to alleviate the mechanical load. It is commonly injured, but it cannot heal spontaneously. Traditional meniscectomy is not currently recommended as this treatment tends to cause osteoarthritis. Due to their good biocompatibility and versatile regulation, hydrogels are emerging biomaterials in tissue engineering. Hydrogels are excellent candidates in meniscus rehabilitation and regeneration because they are fine-tunable, easily modified, and capable of delivering exogenous drugs, cells, proteins, and cytokines. Various hydrogels have been reported to work well in meniscus-damaged animals, but few hydrogels are effective in the clinic, indicating that hydrogels possess many overlooked problems. In this review, we summarize the applications and problems of hydrogels in extrinsic substance delivery, meniscus rehabilitation, and meniscus regeneration. This study will provide theoretical guidance for new therapeutic strategies for meniscus repair.

Exploring maleimide-anchored halloysites as nanophotoinitiators for surface-initiated photografting strategies

Maleimide-functionalized HNTs (HNTs-I) were prepared and explored as a nanophotoinitiator. Vinyl monomers can be grafted onto the nanotubes following a spatially controllable, metal-free and non-contact photoinitiated approach. The obtained HNTs-I were further used in a 3D printing system to fabricate hydrogels with designed configurations.

Antimicrobial Nanomaterials Based on Halloysite Clay Mineral: Research Advances and Outlook

Bacterial infections represent one of the major causes of mortality worldwide. Therefore, over the years, several nanomaterials with antibacterial properties have been developed. In this context, clay minerals, because of their intrinsic properties, have been efficiently used as antimicrobial agents since ancient times. Halloysite nanotubes are one of the emerging nanomaterials that have found application as antimicrobial agents in several fields. In this review, we summarize some examples of the use of pristine and modified halloysite nanotubes as antimicrobial agents, scaffolds for wound healing and orthopedic implants, fillers for active food packaging, and carriers for pesticides in food pest control.

Inorganic nanomaterials for intelligent photothermal antibacterial applications

Antibiotics are currently the main therapeutic agent for bacterial infections, but they have led to bacterial resistance, which has become a worldwide problem that needs to be addressed. The emergence of inorganic nanomaterials provides a new opportunity for the prevention and treatment of bacterial infection. With the continuous development of nanoscience, more and more inorganic nanomaterials have been used to treat bacterial infections. However, single inorganic nanoparticles (NPs) are often faced with problems such as large dosage, strong toxic and side effects, poor therapeutic effect and so on, so the combination of inorganic nano-materials and photothermal therapy (PTT) has become a promising treatment. PTT effectively avoids the problem of bacterial drug resistance, and can also reduce the dosage of inorganic nanomaterials to a certain extent, greatly improving the antibacterial effect. In this paper, we summarize several common synthesis methods of inorganic nanomaterials, and discuss the advantages and disadvantages of several typical inorganic nanomaterials which can be used in photothermal treatment of bacterial infection, such as precious metal-based nanomaterials, metal-based nanomaterials and carbon-based nanomaterials. In addition, we also analyze the future development trend of the remaining problems. We hope that these discussions will be helpful to the future research of near-infrared (NIR) photothermal conversion inorganic nanomaterials.

Gold Nanorod-Incorporated Halloysite Nanotubes Functionalized with Antibody for Superior Antibacterial Photothermal Treatment

The global spread of antibiotic-resistant strains, and the need to protect the microflora from non-specific antibiotics require more effective and selective alternatives. In this work, we demonstrate for the first time a superior antibacterial photothermal effect of plasmonic gold nanorods (AuNRs) via their incorporation onto natural clay halloysite nanotubes (HNTs), which were functionalized with anti-E. coli antibodies (Ab-HNTs). AuNRs were incorporated onto the Ab-HNTs through a facile freeze-thaw cycle, and antibody integrity following the incorporation was confirmed via infrared spectroscopy and fluorescence immunolabeling. The incorporation efficiency was studied using UV-Vis absorption and transmission electron microscopy (TEM). Mixtures of E. coli and AuNR-Ab-HNTs hybrids or free AuNRs were irradiated with an 808 nm laser at 3-4 W cm^-2, and the resulting photothermal antibacterial activity was measured via plate count. The irradiated AuNR-Ab-HNTs hybrids exerted an 8-fold higher antibacterial effect compared to free AuNR under 3.5 W cm^-2; whereas the latter induced a 6 °C-higher temperature elevation. No significant antibacterial activity was observed for the AuNR-Ab-HNTs hybrid against non-target bacteria species (Serratia marcescens and Staphylococcus epidermidis). These findings are ascribed to the localization of the photothermal ablation due to the binding of the antibody-functionalized clay to its target bacteria, as supported through TEM imaging. In the future, the HNTs-based selective carriers presented herein could be tailored with other antibacterial nanoparticles or against another microorganism via the facile adjustment of the immobilized antibody.