Polyphenol-driving assembly for constructing chitin-polyphenol-metal hydrogel as wound dressing

Photothermal switch by gallic acid-calcium grafts synthesized by coordination chemistry for sequential treatment of bone tumor and regeneration

The residual bone tumor and defects which is caused by surgical therapy of bone tumor is a major and important problem in clinicals. And the sequential treatment for irradiating residual tumor and repairing bone defects has wildly prospects. In this study, we developed a general modification strategy by gallic acid (GA)-assisted coordination chemistry to prepare black calcium-based materials, which combines the sequential photothermal therapy of bone tumor and bone defects. The GA modification endows the materials remarkable photothermal properties. Under the near-infrared (NIR) irradiation with different power densities, the black GA-modified bone matrix (GBM) did not merely display an excellent performance in eliminating bone tumor with high temperature, but showed a facile effect of the mild-heat stimulation to accelerate bone regeneration. GBM can efficiently regulate the microenvironments of bone regeneration in a spatial-temporal manner, including inflammation/immune response, vascularization and osteogenic differentiation. Meanwhile, the integrin/PI3K/Akt signaling pathway of bone marrow mesenchymal stem cells (BMSCs) was revealed to be involved in the effect of osteogenesis induced by the mild-heat stimulation. The outcome of this study not only provides a serial of new multifunctional biomaterials, but also demonstrates a general strategy for designing novel blacked calcium-based biomaterials with great potential for clinical use.

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.

A strong and tough supramolecular assembled β-cyclodextrin and chitin nanocrystals protein adhesive: Synthesis, characterization, bonding performance on three-layer plywood

The development of a biomass adhesive as a substitute for petroleum-derived adhesives has been considered a viable option. However, achieving both superior bonding strength and toughness in biomass adhesives remains a significant challenge. Inspired by the human skeletal muscles structure, this study reveals a promising supramolecular structure using tannin acid (TA) functionalized poly-β-cyclodextrin (PCD) (TA@PCD) as elastic tissues and chitin nanocrystals (ChNCs) as green reinforcements to strengthen the soybean meal (SM) adhesive crosslinking network. TA@PCD acts as a dynamic crosslinker that facilitates reversible host-guest interactions, hydrogen bonds, and electrostatic interactions between adjacent stiff ChNCs and SM matrix, resulting in satisfactory strength and toughness. The resulting SM/TA@PCD/ChNCs-2 adhesive has demonstrated satisfactory wet and dry shear strength (1.25 MPa and 2.57 MPa, respectively), toughness (0.69 J), and long-term solvents resistance (80 d). Furthermore, the adhesive can exhibit desirable antimildew characteristics owing to the phenol hydroxyl groups of TA and amino groups of ChNCs. This work showcases an effective supramolecular chemistry strategy for fabricating high-performance biomass adhesives with great potential for practical applications.

Biodegradable chitin nanofiber-alginate dialdehyde hydrogel: An injectable, self-healing scaffold for anti-tumor drug delivery

Injectable hydrogels fabricated from natural polymers have attracted increasing attentions for their potential in biomedical application owing to the biocompatibility and biodegradability. A new class of natural polymer based self-healing hydrogel is constructed through dynamic covalent bonds. The injectable self-healing hydrogels are fabricated by introducing alginate aldehyde to form Schiff base bonds with the chitin nanofibers. These hydrogels demonstrate excellent self-healing properties, injectability, and pH-responsive sol-gel transition behaviors. As a result, they can serve as carriers to allow an effective encapsulation of doxorubicin (DOX) for drug delivery. Furthermore, these hydrogels exhibit excellent biocompatibility and degradability in vitro and in vivo. The sustained release of DOX from the hydrogels effectively suppresses tumor growth in animal models without causing significant systemic toxicity, suggesting their potential application in anti-tumor therapies.

A hyaluronic acid hydrogel as a mild photothermal antibacterial, antioxidant, and nitric oxide release platform for diabetic wound healing

Hyaluronic acid (HA)-based biopolymer hydrogels are promising therapeutic dressings for various wounds but still underperform in treating diabetic wounds. These wounds are extremely difficult to heal and undergo a prolonged and severe inflammatory process due to bacterial infection, overexpression of reactive oxygen species (ROS), and insufficient synthesis of NO. In this study, a dynamic crosslinked hyaluronic acid (HA) hydrogel dressing (Gel-HAB) loaded with allomelanin (AMNP)-N, N'-dis-sec-butyl-N, N'-dinitroso-1, 4-phenylenediamine (BNN6) nanoparticles (AMNP-BNN6) was developed for healing diabetic wounds. The dynamic acylhydrazone bond formed between hydrazide-modified HA (HA-ADH) and oxidized HA (OHA) makes the hydrogel injectable, self-healing, and biocompatible. The hydrogel, loaded with AMNP-BNN6 nanoparticles, exhibits promising ROS scavenging ability and on-demand release of nitric oxide (NO) under near-infrared (NIR) laser irradiation to achieve mild photothermal antibacterial therapy (PTAT) (∼ 48 °C). Notably, the Gel-HAB hydrogel effectively reduced the oxidative stress level, controlled infections, accelerated vascular regeneration, and promoted angiogenesis, thereby achieving rapid healing of diabetic wounds. The injectable self-healing nanocomposite hydrogel could serve as a mild photothermal-enhanced antibacterial, antioxidant, and nitric oxide release platform for the treatment of diabetic wounds.

Polyhedral Oligomeric Sesquioxane Cross-Linked Chitosan-Based Multi-Effective Aerogel Preparation and Its Water-Driven Recovery Mechanism

The use of environmentally friendly and non-toxic biomass-based interfacial solar water evaporators has been widely reported as a method for water purification in recent years. However, the poor stability of the water transport layer made from biomass materials and its susceptibility to deformation when exposed to harsh environments limit its practical application. To address this issue, water-driven recovery aerogel (PCS) was prepared by cross-linking epoxy-based polyhedral oligomeric silsesquioxane (EP-POSS) epoxy groups with chitosan (CS) amino groups. The results demonstrate that PCS exhibits excellent water-driven recovery performance, regaining its original volume within a very short time (1.9 s) after strong compression (ε > 80%). Moreover, PCS has a water absorption rate of 2.67 mm s-1 and exhibits an excellent water absorption capacity of 22.09 g g-1 even after ten cycles of absorption-removal. Furthermore, a photothermal evaporator (PCH) was prepared by loading the top layer with hydrothermally reacted tannins (HAs) and Zn2+ complexes. The results indicate that PCH achieves an impressive evaporation rate of 1.89 kg m-2 h-1 under one sun illumination. Additionally, due to the antimicrobial properties of Zn2+, PCH shows inhibitory effects against Staphylococcus aureus and Escherichia coli, thereby extending the application of solar water evaporators to include antimicrobial purification in natural waters.

Efficient fabrication of anisotropic regenerated cellulose films from bamboo via a facile wet extrusion strategy

Bamboo, featuring fast growth rate and high cellulose content, is considered to be one of the most attractive feedstocks for degradable bio-materials as a substitute for plastics. However, those was limited to the fields of bamboo structural materials mainly by physical processes. Herein, we report a facile continuous wet extrusion strategy for scalable manufacturing of anisotropic regenerated cellulose films in alkali/urea aqueous solution for the first time. The bamboo cellulose solution was regenerated in H2SO4/Na2SO4/ZnSO4 aqueous solution to facilitate the construction of dense fibrils networks. Moreover, under the synergistic effect of shear orientations and stretching processes in wet extrusion molding, the cellulose networks promoted further orientated assembly into aligned fibrils. Therefore, these anisotropic cellulose hydrogels exhibited good mechanical properties, and the tensile strength was increased from 1.67 MPa of anisotropic cellulose hydrogel with 1.0 of stretching ration (ACH-1.0) to 2.13 MPa of ACH-1.4 with increasing stretching ratio from 1.0 to 1.4, which was about 1.34 times higher than that of the isotropic hydrogel fabricated by tape-casting. Moreover, ACH-1.4 exhibited commendable thermal stability and air barrier properties. This work demonstrated a simple and continuous bottom-up approach for fabrication of anisotropic bamboo-based cellulose hydrogels and films with excellent mechanical properties.

Gallic acid: design of a pyrogallol-containing hydrogel and its biomedical applications

Polyphenol hydrogels have garnered widespread attention due to their excellent adhesion, antioxidant, and antibacterial properties. Gallic acid (GA) is a typical derivative of pyrogallol that is used as a hydrogel crosslinker or bioactive additive and can be used to make multifunctional hydrogels with properties superior to those of widely studied catechol hydrogels. Furthermore, compared to polymeric tannic acid, gallic acid is more suitable for chemical modification, thus broadening its range of applications. This review focuses on multifunctional hydrogels containing GA, aiming to inspire researchers in future biomaterial design. We first revealed the interaction mechanisms between GA molecules and between GA and polymers, analyzed the characteristics GA imparts to hydrogels and compared GA hydrogels with hydrogels containing catechol. Subsequently, in this paper, various methods of integrating GA into hydrogels and the applications of GA in biomedicine are discussed, finally assessing the current limitations and future development potential of GA. In summary, GA, a natural small molecule polyphenol with excellent functionality and diverse interaction modes, has great potential in the field of biomedical hydrogels.

Facile General Injectable Gelatin/Metal/Tea Polyphenol Double Nanonetworks Remodel Wound Microenvironment and Accelerate Healing

Treating the most widespread complication of diabetes: diabetic wounds poses a significant clinical obstacle due to the intricate nature of wound healing in individuals with diabetes. Here a novel approach is proposed using easily applicable injectable gelatin/metal/tea polyphenol double nanonetworks, which effectively remodel the wound microenvironment and accelerates the healing process. The gelatin(Gel) crosslink with metal ions (Zr4+ ) through the amino acids, imparting advantageous mechanical properties like self-healing, injectability, and adhesion. The nanonetwork's biological functions are further enhanced by incorporating the tea polyphenol metal nanonetwork through in situ doping of the epigallocatechin gallate (EGCG) with great antibacterial, self-healing, antioxidant, and anticancer capabilities. The in vitro and in vivo tests show that this double nanonetworks hydrogel exhibits faster cell migration and favorable anti-inflammatory and antioxidant properties and can greatly reshape the microenvironment of diabetic wounds and accelerate the wound healing rate. In addition, this hydrogel is completely degraded after subcutaneous injection for 7 days, with nondetectable cytotoxicity in H&E staining of major mice organs and the serum level of liver function indicators. Considering the above-mentioned merits of this hydrogel, it is believed that the injectable gelatin/metal/tea polyphenol double nanonetworks have broad biomedical potential, especially in diabetic wound repair and tissue engineering.

Arginine-Nanoenzyme with Timely Angiogenesis for Promoting Diabetic Wound Healing

The successful treatment of diabetic wounds requires strategies that promote anti-inflammation, angiogenesis, and re-epithelialization of the wound. Excessive oxidative stress in diabetic ulcers (DUs) inhibits cell proliferation and hinders timely vascular formation and macrophage polarization from pro-inflammatory M1 to anti-inflammatory M2, resulting in a persistent inflammatory environment and a nonhealing wound. We designed arginine-nanoenzyme (FTA) with mimic-catalase and arginine-loading. 2,3,4-trihydroxy benzaldehyde and arginine (Arg) were connected by a Schiff base bond, and the nanoassembly of Arg to FTA was driven by the coordination force between a ferric ion and polyphenol and noncovalent bond force such as a hydrogen bond. FTA could remove excess reactive oxygen species at the wound site in situ and convert it to oxygen to improve hypoxia. Meanwhile, Arg was released and catalytically metabolized by NO synthase in M1 to promote vascular repair in the early phase. In the late phase, the metabolite of Arg catalyzed by arginase in M2 was mainly ornithine, which played a vital role in promoting tissue repair, which implemented angiogenesis timely and prevented hypertrophic scars. Mechanistically, FTA activated the cAMP signaling pathway combined with reducing inflammation and ameliorating angiogenesis, which resulted in excellent therapeutic effects on a DU mice model.

Natural polyphenols for drug delivery and tissue engineering construction: A review

Polyphenols, natural compounds rich in phenolic structures, are gaining prominence due to their antioxidant, anti-inflammatory, antibacterial, and anticancer properties, making them valuable in biomedical applications. Through covalent and noncovalent interactions, polyphenols can bind to biomaterials, enhancing their performance and compensating for their shortcomings. Such polyphenol-based biomaterials not only increase the efficacy of polyphenols but also improve drug stability, control release kinetics, and boost the therapeutic effects of drugs. They offer the potential for targeted drug delivery, reducing off-target impacts and enhancing therapeutic outcomes. In tissue engineering, polyphenols promote cell adhesion, proliferation, and differentiation, thus aiding in the formation of functional tissues. Additionally, they offer excellent biocompatibility and mechanical strength, essential in designing scaffolds. This review explores the significant roles of polyphenols in tissue engineering and drug delivery, emphasizing their potential in advancing biomedical research and healthcare.

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.

Designing Composite Stimuli-Responsive Hydrogels for Wound Healing Applications: The State-of-the-Art and Recent Discoveries

Effective wound treatment has become one of the most important challenges for healthcare as it continues to be one of the leading causes of death worldwide. Therefore, wound care technologies significantly evolved in order to provide a holistic approach based on various designs of functional wound dressings. Among them, hydrogels have been widely used for wound treatment due to their biocompatibility and similarity to the extracellular matrix. The hydrogel formula offers the control of an optimal wound moisture level due to its ability to absorb excess fluid from the wound or release moisture as needed. Additionally, hydrogels can be successfully integrated with a plethora of biologically active components (e.g., nanoparticles, pharmaceuticals, natural extracts, peptides), thus enhancing the performance of resulting composite hydrogels in wound healing applications. In this review, the-state-of-the-art discoveries related to stimuli-responsive hydrogel-based dressings have been summarized, taking into account their antimicrobial, anti-inflammatory, antioxidant, and hemostatic properties, as well as other effects (e.g., re-epithelialization, vascularization, and restoration of the tissue) resulting from their use.

Supramolecular chitin-based hydrogels with self-adapting and fast-degradation properties for enhancing wound healing

Due to the features of high porosity, high water content, and tunable viscoelasticity, hydrogels have attracted numerous attentions in the promotion of wound closure. However, the lack of abilities to adapt the wounds of complex shapes and prevent postoperative adhesion limits their therapeutic outcomes in wound healing. To address the above challenges, the supramolecular chitin-based (SMCT) hydrogels are created via the host-guest pre-assembly strategy of β-cyclodextrin (βCD) and adamantane (Ad). The reversible host-guest crosslinks endow the SMCT hydrogels with highly dynamic networks, which can better accommodate irregularly shaped wounds compared with the covalent chitin-based hydrogels with similar mechanical properties. In addition, the SMCT hydrogels show rapid in vivo degradability (degradation time ≈ 2 days) due to the enzyme-triggered degradability of chitin, which do not need to be removed from the wounds after service and thus avoid the secondary damage to skin during dressing change. Owing to the hydrophobic cavity of βCD, the SMCT hydrogels can facilitate the load and release of curcumin with anti-inflammatory, antibacterial, and antioxidative activities, thereby significantly improving the wound healing efficiency. This work provides valuable guidance to the design of self-adaptive and fast-degradable hydrogels that hold great potential for enhancing the wound healing in skin and other tissues.

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.

Glucose-primed PEEK orthopedic implants for antibacterial therapy and safeguarding diabetic osseointegration

Diabetic infectious microenvironment (DIME) frequently leads to a critical failure of osseointegration by virtue of its main peculiarities including typical hyperglycemia and pathogenic infection around implants. To address the plaguing issue, we devise a glucose-primed orthopedic implant composed of polyetheretherketone (PEEK), Cu-chelated metal-polyphenol network (hauberk coating) and glucose oxidase (GOx) for boosting diabetic osseointegration. Upon DIME, GOx on implants sostenuto consumes glucose to generate H2O2, and Cu liberated from hauberk coating catalyzes the H2O2 to highly germicidal •OH, which massacres pathogenic bacteria through photo-augmented chemodynamic therapy. Intriguingly, the catalytic efficiency of the coating gets greatly improved with the turnover number (TON) of 0.284 s-1. Moreover, the engineered implants exhibit satisfactory cytocompatibility and facilitate osteogenicity due to the presence of Cu and osteopromotive polydopamine coating. RNA-seq analysis reveals that the implants enable to combat infections and suppress pro-inflammatory phenotype (M1). Besides, in vivo evaluations utilizing infected diabetic rat bone defect models at week 4 and 8 authenticate that the engineered implants considerably elevate osseointegration through pathogen elimination, inflammation dampening and osteogenesis promotion. Altogether, our present study puts forward a conceptually new tactic that arms orthopedic implants with glucose-primed antibacterial and osteogenic capacities for intractable diabetic osseointegration.

Metal-Phenolic Networks for Chronic Wounds Therapy

Chronic wounds are recalcitrant complications of a variety of diseases, with pathologic features including bacterial infection, persistent inflammation, and proliferation of reactive oxygen species (ROS) levels in the wound microenvironment. Currently, the use of antimicrobial drugs, debridement, hyperbaric oxygen therapy, and other methods in clinical for chronic wound treatment is prone to problems such as bacterial resistance, wound expansion, and even exacerbation. In recent years, researchers have proposed many novel materials for the treatment of chronic wounds targeting the disease characteristics, among which metal-phenolic networks (MPNs) are supramolecular network structures that utilize multivalent metal ions and natural polyphenols complexed through ligand bonds. They have a flexible and versatile combination of structural forms and a variety of formations (nanoparticles, coatings, hydrogels, etc.) that can be constructed. Functionally, MPNs combine the chemocatalytic and bactericidal properties of metal ions as well as the anti-inflammatory and antioxidant properties of polyphenol compounds. Together with the excellent properties of rapid synthesis and negligible cytotoxicity, MPNs have attracted researchers' great attention in biomedical fields such as anti-tumor, anti-bacterial, and anti-inflammatory. This paper will focus on the composition of MPNs, the mechanisms of MPNs for the treatment of chronic wounds, and the application of MPNs in novel chronic wound therapies.

Metallic elements combine with herbal compounds upload in microneedles to promote wound healing: a review

Wound healing is a dynamic and complex restorative process, and traditional dressings reduce their therapeutic effectiveness due to the accumulation of drugs in the cuticle. As a novel drug delivery system, microneedles (MNs) can overcome the defect and deliver drugs to the deeper layers of the skin. As the core of the microneedle system, loaded drugs exert a significant influence on the therapeutic efficacy of MNs. Metallic elements and herbal compounds have been widely used in wound treatment for their ability to accelerate the healing process. Metallic elements primarily serve as antimicrobial agents and facilitate the enhancement of cell proliferation. Whereas various herbal compounds act on different targets in the inflammatory, proliferative, and remodeling phases of wound healing. The interaction between the two drugs forms nanoparticles (NPs) and metal-organic frameworks (MOFs), reducing the toxicity of the metallic elements and increasing the therapeutic effect. This article summarizes recent trends in the development of MNs made of metallic elements and herbal compounds for wound healing, describes their advantages in wound treatment, and provides a reference for the development of future MNs.

A hydrogel system for drug loading toward the synergistic application of reductive/heat-sensitive drugs

The preparation of hydrogels as drug carriers via radical-mediated polymerization has significant prospects, but the strong oxidizing ability of radicals and the high temperatures generated by the vigorous reactions limits the loading for reducing/heat-sensitive drugs. Herein, an applicable hydrogel synthesized by radical-mediated polymerization is reported for the loading and synergistic application of specific drugs. First, the desired sol is obtained by polymerizing functional monomers using a radical initiator, and then tannic-acid-assisted specific drug mediates sol-branched phenylboric acid group to form the required functional hydrogel (New-gel). Compared with the conventional single-step radical-mediated drug-loading hydrogel, the New-gel not only has better chemical/physical properties but also efficiently loads and releases drugs and maintains drug activity. Particularly, the New-gel has excellent loading capacity for oxygen, and exhibits significant practical therapeutic effects for diabetic wound repair. Furthermore, owing to its high light transmittance, the New-gel synergistically promotes the antibacterial effect of photosensitive drugs. This gelation strategy for loading drugs has further promising biomedical applications.

Molecularly engineered dual-network photothermal hydrogel delivery system with enhanced mechanical properties, antibacterial ability and angiogenic effect for accelerating wound healing

Bacterial infection caused by trauma and chronic wounds in the most mobile area remains a challenge in clinic. It is difficult to achieve the synergistic effects of antibacterial capacity and skin regeneration using conventional therapeutic methods. Developing a multi-functional hydrogel dressing that can cope with the complex wound environment will contribute to the healing and therapeutic effects. In this work, a novel Cur@PAM/TA-Cu photothermal hydrogel delivery system was prepared by engineering tannic acid (TA) into covalent cross-linked polyacrylamide (PAM) on which the chelating tannic acid-copper metal-polyphenolic network (TA-Cu MPN) was imposed to form dual-crosslinked networks, and the natural medicine curcumin was loaded eventually. The molecularly engineered dual-crosslinked networks resulted in enhanced mechanical properties including bio-adhesion, tensile strength and self-healing, which made the hydrogel suitable for dynamic wound and various application scenarios. In addition, the excellent photothermal capacity, antioxidant effect and biocompatibility of the hydrogel were demonstrated. Notably, this curcumin loaded photothermal hydrogel exhibited superior antibacterial capacity (almost 100% killing ratio to E. coli and S. aureus) under 808 nm laser irradiation. Meanwhile, the in vivo wound healing experiment results revealed that the anti-inflammation and proangiogenic effect of Cur@PAM/TA-Cu hydrogel successfully shortened the healing time of wound and the reconstruction of skin structure and function. Thus, this dual-crosslinked multi-functional hydrogel delivery system is a promising wound dressing for accelerating wound healing.

Recent Advances of Metal-Polyphenol Coordination Polymers for Biomedical Applications

Nanomedicine has provided cutting-edge technologies and innovative methods for modern biomedical research, offering unprecedented opportunities to tackle crucial biomedical issues. Nanomaterials with unique structures and properties can integrate multiple functions to achieve more precise diagnosis and treatment, making up for the shortcomings of traditional treatment methods. Among them, metal-polyphenol coordination polymers (MPCPs), composed of metal ions and phenolic ligands, are considered as ideal nanoplatforms for disease diagnosis and treatment. Recently, MPCPs have been extensively investigated in the field of biomedicine due to their facile synthesis, adjustable structures, and excellent biocompatibility, as well as pH-responsiveness. In this review, the classification of various MPCPs and their fabrication strategies are firstly summarized. Then, their significant achievements in the biomedical field such as biosensing, drug delivery, bioimaging, tumor therapy, and antibacterial applications are highlighted. Finally, the main limitations and outlooks regarding MPCPs are discussed.

Highly transparent, hydrophobic, and durable anisotropic cellulose films as electronic screen protectors

Cellulose films have attracted extensive interest in the field of burgeoning electronic devices. However, it remains a challenge to simultaneously address the difficulties including facile methodology, hydrophobicity, optical transparency, and mechanical robustness. Herein, we reported a coating-annealing approach to fabricate highly transparent, hydrophobic, and durable anisotropic cellulose films, where poly(methyl methacrylate)-b-poly(trifluoroethyl methacrylate) (PMMA-b-PTFEMA) as low surface energy chemicals was coated onto regenerated cellulose films via physical (hydrogen bonds) and chemical (transesterification) interactions. The resultant films with nano-protrusions and low surface roughness exhibited high optical transparency (92.3 %, 550 nm) and good hydrophobicity. Moreover, the tensile strength of the hydrophobic films was 198.7 MPa and 124 MPa in dry and wet states, respectively, which also showed excellent stability and durability under various conditions, such as hot water, chemicals, liquid foods, tape peeling, finger pressing, sandpaper abrasion, ultrasonic treatment, and water jet. This work provided a promising large-scale production strategy for the preparation of transparent and hydrophobic cellulose-based films for electronic device protection as well as other emerging flexible electronics.

Artificial ovaries constructed from biodegradable chitin-based hydrogels with the ability to restore ovarian endocrine function and alleviate osteoporosis in ovariectomized mice

BACKGROUND

Artificial ovary (AO) is an alternative approach to provide physiological hormone to post-menopausal women. The therapeutic effects of AO constructed using alginate (ALG) hydrogels are limited by their low angiogenic potential, rigidity, and non-degradability. To address these limitations, biodegradable chitin-based (CTP) hydrogels that promote cell proliferation and vascularization were synthesized, as supportive matrix.

METHODS

In vitro, follicles isolated from 10-12-days-old mice were cultured in 2D, ALG hydrogels, and CTP hydrogels. After 12 days of culture, follicle growth, steroid hormone levels, oocyte meiotic competence, and expression of folliculogenesis-related genes were monitored. Additionally, follicles isolated from 10-12-days-old mice were encapsulated in CTP and ALG hydrogels and transplanted into the peritoneal pockets of ovariectomised (OVX) mice. After transplantation, steroid hormone levels, body weight, rectal temperature, and visceral fat of the mice were monitored every two weeks. At 6 and 10 weeks after transplantation, the uterus, vagina, and femur were collected for histological examination.

RESULTS

The follicles developed normally in CTP hydrogels under in vitro culture conditions. Additionally, follicular diametre and survival rate, oestrogen production, and expression of folliculogenesis-related genes were significantly higher than those in ALG hydrogels. After one week of transplantation, the numbers of CD34-positive vessels and Ki-67-positive cells in CTP hydrogels were significantly higher than those in ALG hydrogels (P < 0.05), and the follicle recovery rate was significantly higher in CTP hydrogels (28%) than in ALG hydrogels (17.2%) (P < 0.05). After two weeks of transplantation, OVX mice implanted with CTP grafts exhibited normal steroid hormone levels, which were maintained until week eight. After 10 weeks of transplantation, CTP grafts effectively ameliorated bone loss and atrophy of the reproductive organs, as well as prevented the increase in body weight and rectal temperature in OVX mice, which were superior to those elicited by ALG grafts.

CONCLUSIONS

Our study is the first to demonstrate that CTP hydrogels support follicles longer than ALG hydrogels in vitro and in vivo. The results highlight the clinical potential of AO constructed using CTP hydrogels in the treatment of menopausal symptoms.

Alginate-modulated continuous assembly of iron/tannic acid composites as photothermally responsive wound dressings for hemostasis and drug resistant bacteria eradication

Multifunctional dressing materials are highly required to combat multidrug resistant bacteria in wound infections. Here an alginate-based aerogel dressing is reported that combines photothermal bactericidal activity, hemostatic property, and free radical scavenging for skin wound disinfection and accelerated wound healing. The aerogel dressing is facilely constructed by immersing a clean nail (Fe) in a mixed solution of sodium alginate (Alg) and tannic acid (TA), followed by freezing, solvent replacement, and air drying. The Alg matrix plays an essential role in modulating the continuous assembly process between TA and Fe to allow the homogenous distribution of TA-Fe metal-phenolic networks (MPN) in the resulting composite, without forming aggregates. The photothermally responsive Nail-TA/Alg aerogel dressing is successfully applied in a murine skin wound model infected with Methicillin-resistant Staphylococcus aureus (MRSA). This work provides a facile strategy to integrate MPN with the hydrogel/aerogel matrix through in situ chemistry, which is promising for developing multifunctional biomaterials and biomedicine.

Interfacial assembly of chitin/Mn3O4 composite hydrogels as photothermal antibacterial platform for infected wound healing

To combat bacteria and even biofilm infections, developing alternative antibacterial wound dressings independent of antibiotics is imperative. Herein, this study developed a series of bioactive chitin/Mn₃O₄ composite hydrogels under mild conditions for infected wound healing application. The in situ synthesized Mn₃O₄ NPs homogeneously distribute throughout chitin networks and strongly interact with chitin matrix, and as well as endow the chitin/Mn₃O₄ hydrogels with NIR-assisted outstanding photothermal antibacterial and antibiofilm activities. Meantime, the chitin/Mn₃O₄ hydrogels exhibit favorable biocompatibility and antioxidant property. Furthermore, the chitin/Mn₃O₄ hydrogels with the assist of NIR show an excellent skin wound healing performance in a mouse full-thickness S. aureus biofilms-infected wound model, by accelerating the phase transition from inflammation to remodeling. This study broadens the scope for the fabrication of chitin hydrogels with antibacterial property, and offers an excellent alternative for the bacterial-associated wound infection therapy.

Engineered Injectable Cell-Laden Chitin/Chitosan Hydrogel with Adhesion and Biodegradability for Calvarial Defect Regeneration

Trade-off of high-strength and dynamic crosslinking of hydrogels remains an enormous challenge. Motivated by the self-healing property of biological tissues, the strategy of combining multiple dynamic bond mechanisms and a polysaccharide network is proposed to fabricate biomimetic hydrogels with sufficient mechanical strength, injectability, biodegradability, and self-healing property for bone reconstruction engineering. Stable acylhydrazone bonds endowed hydrogels with robust mechanical strength (>10 kPa). The integration of dynamic imine bonds and acylhydrazone bonds optimized the reversible characteristic to protect the cell during the injection and mimicked ECM microenvironment for cell differentiation as well as rapid adapting bone defect area. Furthermore, due to the slow enzymatic hydrolysis kinetics of chitosan and the self-healing properties of resulting networks, hydrogels exhibited a satisfactory biodegradation period (>8 weeks) that highly matches with bone regeneration. Additionally, rBMSC-laden hydrogels exhibited splendid osteogenic induction and bone reconstruction without prefabrication scaffolds and incubation, demonstrating tremendous potential for clinical application. This work proposes an efficient strategy for the construction of a low-cost multifunctional hydrogel, making polysaccharide-based hydrogels as the optimal carrier for enabling cellular functions in bone repair.

Synthesis of biologically derived poly(pyrogallol) nanofibers for antibacterial applications

Herein, we present the facile synthesis of poly(pyrogallol) biopolymers and their application as antibacterial agents. Pyrogallol is a class of phenolic compounds that can be found in various plants. Polymerization was performed by the auto-oxidation of pyrogallol under a hydrated condition. The microscopic image of poly(pyrogallol) shows a highly homogenous nanofibrous structure with a diameter of 100.3 ± 16.3 nm. Spectroscopic analysis by FT-IR spectroscopy, Raman spectroscopy, and XPS corroborated the formation of ether (C-O-C) bonds between the hydroxyl group and adjacent carbons of pyrogallol during polymerization. The FT-IR and XPS spectra also revealed redox-active gallol functional groups on poly(pyrogallol) nanofibers, which can be used to release free electrons and protons during oxidation followed by the generation of reactive oxygen species (ROS). The generated ROS from poly(pyrogallol) was used to inhibit the growth of bacteria, Escherichia coli, at a inhibition rates of 56.3 ± 9.7% and 95.5 ± 2.0% within 0.5 and 2 h, respectively. This finding suggests that poly(pyrogallol) can be used as a naturally occurring antibacterial agent for various biomedical and environmental applications.

Mussel-Inspired Multifunctional Hydrogels with Adhesive, Self-Healing, Antioxidative, and Antibacterial Activity for Wound Healing

Antibacterial hydrogel wound dressings with adhesive and antioxidant activity are desirable for treating skin injuries in clinical care. Hereby, a series of multifunctional hydrogel wound dressings with high adhesive, self-healing, antioxidant, and antibacterial activity were designed and fabricated using dopamine (DA) and quercetin (QT). The multifunctional hydrogels were constructed by the interpenetrated quaternized chitosan chain segments and polyacrylamide network. The catechol groups on DA, QT, and the quaternary ammonium groups in the hydrogel system endow hydrogels with high strength, excellent adhesion, and self-healing ability. The results confirmed the admirable hemocompatibility and remarkable antibacterial activity of the multifunction hydrogels against Staphylococcus aureus and Escherichia coli. Consequently, multifunction hydrogels with satisfactory adhesive and antibacterial activity are appropriate alternative materials in the fields of tissue adhesive and wound dressing applications.

Ink Based on the Tunable Swollen Microsphere for a 3D Printing Hydrogel with Broad-Range Mechanical Properties

The development of the effective 3D printing strategy for diverse functional monomers is still challenging. Moreover, the conventional 3D printing hydrogels are usually soft and fragile due to the lack of an energy dissipation mechanism. Herein, a microsphere mediating ink preparation strategy is developed to provide tailored rheological behavior for various monomer direct ink writings. The chitosan microspheres are used as an exemplary material due to their tunable swelling ratio under the acid-drived electrostatic repulsion of the protonated amino groups. The rheological behaviors of the swollen chitosan microsphere (SCM) are independent on the monomer types, and various functional secondary polymers could be carried at a wide loading ratio by the acid driving. The SCM reinforces the hydrogel as the sacrificial bonds. With the adjustable composition, the 3D printing hydrogel mechanical properties are tunable in wide windows: strength (0.4-1.01 MPa), dissipated energy (0.11-3.25 MJ m^-3), and elongation at break (47-626%). With the excellent printing and mechanical properties, the SCM inks enable multi-functional integration for soft device production, such as 4D printing robots and wearable strain sensors. We anticipate that this microsphere mediating 3D printing strategy can inspire new possibilities for the design of the robust hydrogels with a broad range of functionalities and mechanical performances.

Facile preparation of polyphenol-crosslinked chitosan-based hydrogels for cutaneous wound repair

The design and facile preparation of the smart hydrogel wound dressings with inherent excellent antioxidant and antibacterial capacity to effectively promote wound healing processes is highly desirable in clinical applications. Herein, a series of multifunctional hydrogels were prepared by the dynamic Schiff base and boronate ester crosslinking among phenylboronic acid (PBA) grafted carboxymethyl chitosan (CMCS), polyphenols and Cu²⁺-crosslinked polyphenol nanoparticles (CuNPs). The dynamic crosslinking bonds endowed hydrogels with excellent self-healing and degradable properties. Three polyphenols including tannic acid (TA), oligomeric proanthocyanidins (OPC) and (-)-epigallocatechin-3-O-gallate (EGCG) contributed to the outstanding antibacterial and antioxidant abilities of these hydrogels. The tissue adhesive capacity of hydrogels gave them good hemostatic effect. Through a full-thickness skin defect model of mice, these biocompatible hydrogels could accelerate wound healing processes by promoting granulation tissue formation, collagen deposition, M2 macrophage polarization and cytokine secretion, demonstrating that these natural-derived hydrogels with inherent physiological properties and low-cost preparation approaches could be promising dressing materials.

Polysaccharide-Based Multifunctional Hydrogel Bio-Adhesives for Wound Healing: A Review

Wound healing is a long-term and complex biological process that involves multiple hemostasis, inflammation, proliferation, and remodeling stages. In order to realize comprehensive and systematic wound management, appropriate wound treatment bio-adhesives are urgently needed. Hydrogel bio-adhesives have excellent properties and show unique and remarkable advantages in the field of wound management. This review begins with a detailed description of the design criteria and functionalities of ideal hydrogel bio-adhesives for wound healing. Then, recent advances in polysaccharide-based multifunctional hydrogel bio-adhesives, which involve chitosan, hyaluronic acid, alginate, cellulose, dextran, konjac glucomannan, chondroitin sulfate, and other polysaccharides, are comprehensively discussed. Finally, the current challenges and future research directions of polysaccharide-based hydrogel bio-adhesives for wound healing are proposed to stimulate further exploration by researchers.

Construction of multifunctional hydrogel with metal-polyphenol capsules for infected full-thickness skin wound healing

Damaged skin cannot prevent harmful bacteria from invading tissues, causing infected wounds or even severe tissue damage. In this study, we developed a controlled-release antibacterial composite hydrogel system that can promote wound angiogenesis and inhibit inflammation by sustained releasing Cu-Epigallocatechin-3-gallate (Cu-EGCG) nano-capsules. The prepared SilMA/HAMA/Cu-EGCG hydrogel showed an obvious inhibitory effect on Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). It could also promote the proliferation and migration of L929 fibroblasts. In vivo full-thickness infected wound healing experiments confirmed the angiogenesis and inflammation regulating effect. Accelerate collagen deposition and wound healing speed were also observed in the SilMA/HAMA/Cu-EGCG hydrogel treated group. The findings of this study show the great potential of this controlled-release antibacterial composite hydrogel in the application of chronic wound healing.