Photothermal-enhanced antibacterial and antioxidant hydrogels dressings based on catechol-modified chitosan derived carbonized polymer dots for effective treatment of wound infection

Augmenting Neutrophil Extracellular Traps with Carbonized Polymer Dots: A Potential Treatment for Bacterial Sepsis

Sepsis is a life-threatening condition that can progress to septic shock as the body's extreme response to pathogenesis damages its own vital organs. Staphylococcus aureus (S. aureus) accounts for 50% of nosocomial infections, which are clinically treated with antibiotics. However, methicillin-resistant strains (MRSA) have emerged and can withstand harsh antibiotic treatment. To address this problem, curcumin (CCM) is employed to prepare carbonized polymer dots (CPDs) through mild pyrolysis. Contrary to curcumin, the as-formed CCM-CPDs are highly biocompatible and soluble in aqueous solution. Most importantly, the CCM-CPDs induce the release of neutrophil extracellular traps (NETs) from the neutrophils, which entrap and eliminate microbes. In an MRSA-induced septic mouse model, it is observed that CCM-CPDs efficiently suppress bacterial colonization. Moreover, the intrinsic antioxidative, anti-inflammatory, and anticoagulation activities resulting from the preserved functional groups of the precursor molecule on the CCM-CPDs prevent progression to severe sepsis. As a result, infected mice treated with CCM-CPDs show a significant decrease in mortality even through oral administration. Histological staining indicates negligible organ damage in the MRSA-infected mice treated with CCM-CPDs. It is believed that the in vivo studies presented herein demonstrate that multifunctional therapeutic CPDs hold great potential against life-threatening infectious diseases.

Gelatin/carboxymethyl chitosan/aloe juice hydrogels with skin-like endurance and quick recovery: Preparation, characterization, and properties

Gelatin-based hydrogels have gained considerable attention due to their resemblance to the extracellular matrix and hydrophilic three-dimensional network structure. Apart from providing an air-permeable and moist environment, these hydrogels optimize the inflammatory microenvironment of the wounds. These properties make gelatin-based hydrogels highly competitive in the field of wound dressings. In this study, a series of composite hydrogels were prepared using gelatin (Gel) and carboxymethyl chitosan (CMCh) as primary materials, glutaraldehyde as a crosslinker, and aloe vera juice as an anti-inflammatory component. The properties of the hydrogel, including its rheological properties, microscopic structures, mechanical properties, swelling ratios, thermal stability, antibacterial properties, and biocompatibility, were investigated. The results demonstrate that the gelatin-based hydrogels exhibit good elasticity and rapid self-healing ability. The hydrogels exhibited slight shear behavior, which is advantageous for skin care applications. Furthermore, the inclusion of aloe vera juice into the hydrogel resulted in a dense structure, improved mechanical properties and enhanced swelling ratio. The Gel/CMCh/Aloe hydrogels tolerate a compressive strength similar to that of human skin. Moreover, the hydrogels displayed excellent cytocompatibility with HFF-1 cells, and exhibited antibacterial activity against E. coli and S. aureus. Lomefloxacin was used as a model drug to study the releasing behavior of the Gel/CMCh/aloe hydrogels. The results showed that the drug was released rapidly at the initial stage, and could continue to be released for 12 h, the maximum releasing rate exceeded 20 %. These findings suggest that the gelatin-based hydrogels hold great promise as effective wound dressings.

Construction methods and biomedical applications of PVA-based hydrogels

Polyvinyl alcohol (PVA) hydrogel is favored by researchers due to its good biocompatibility, high mechanical strength, low friction coefficient, and suitable water content. The widely distributed hydroxyl side chains on the PVA molecule allow the hydrogels to be branched with various functional groups. By improving the synthesis method and changing the hydrogel structure, PVA-based hydrogels can obtain excellent cytocompatibility, flexibility, electrical conductivity, viscoelasticity, and antimicrobial properties, representing a good candidate for articular cartilage restoration, electronic skin, wound dressing, and other fields. This review introduces various preparation methods of PVA-based hydrogels and their wide applications in the biomedical field.

Facile Bond Exchanging Strategy for Engineering Wet Adhesion and Antioxidant/Antibacterial Thin Layer over a Dynamic Hydrogel via the Carbon Dots Derived from Tannic Acid/ε-Polylysine

Adhesive hydrogels, playing an essential role in stretchable electronics, soft robotics, tissue engineering, and so forth, upon functioning often need to adhere to various substrates in wet conditions and simultaneously exhibit antibacterial/antioxidant properties while possessing the intrinsic stretchability and elasticity of the hydrogel network intact. Therefore, simple approaches to conveniently access adhesive hydrogels with multifunctional surfaces are being pursued. Herein, a facile strategy has been proposed to construct multifunctional adhesive hydrogels via surface engineering of a multifunctional carbon dot (CD)-decorated polymeric thin layer by dynamic bond exchange. By this strategy, a double cross-linked network hydrogel of polyacrylamide (PAM) and oxidized dextran (ODA) was engineered with a unique dense layer over the Schiff base hydrogel matrix by aqueous solution immersion of PA-120, versatile CDs derived from tannic acid (TA) and ε-polylysine (PL). Without any additional agents, the PA-120 CDs with residual polyphenolic/catechol and amine moieties were incorporated into the surface structure of the hydrogel network by the combined action of the Schiff base and hydrogen bonds to form a dense surface layer that can exhibit high wet adhesive performance via the amine-polyphenol/catechol pair. The armor-like dense architecture also endowed hydrogels with considerably enhanced tensile/compression properties and excellent antioxidant/antibacterial abilities. Besides, the single-sided modified Janus hydrogel and completely surface-modified hydrogel can be flexibly developed through this approach. This strategy will provide new insights into the preparation and application of surface-modified hydrogels featuring multiple functions and tunable interfacial properties.

Bioadhesives with Antimicrobial Properties

Bioadhesives with antimicrobial properties enable easier and safer treatment of wounds as compared to the traditional methods such as suturing and stapling. Composed of natural or synthetic polymers, these bioadhesives seal wounds and facilitate healing while preventing infections through the activity of locally released antimicrobial drugs, nanocomponents, or inherently antimicrobial polers. Although many different materials and strategies are employed to develop antimicrobial bioadhesives, the design of these biomaterials necessitates a prudent approach as achieving all the required properties including optimal adhesive and cohesive properties, biocompatibility, and antimicrobial activity can be challenging. Designing antimicrobial bioadhesives with tunable physical, chemical, and biological properties will shed light on the path for future advancement of bioadhesives with antimicrobial properties. In this review, the requirements and commonly used strategies for developing bioadhesives with antimicrobial properties are discussed. In particular, different methods for their synthesis and their experimental and clinical applications on a variety of organs are reviewed. Advances in the design of bioadhesives with antimicrobial properties will pave the way for a better management of wounds to increase positive clinical outcomes.

Antibacterial functionalized carbon dots and their application in bacterial infections and inflammation

Bacterial infections and inflammation pose a severe threat to human health and the social economy. The existence of super-bacteria and the increasingly severe phenomenon of antibiotic resistance highlight the development of new antibacterial agents. Due to low cytotoxicity, high biocompatibility, and different antibacterial mechanisms from those for antibiotics, functionalized carbon dots (FCDs) promise a new platform for the treatment of bacterial infectious diseases. However, few articles have systematically sorted out the available antibacterial mechanisms for FCDs and their application in the treatment of bacterial inflammation. This review focuses on the available antibacterial mechanisms for FCDs, including covalent and non-covalent interactions, reactive oxygen species, photothermal therapy, and size effect. Meanwhile, the design of antibacterial FCDs is introduced, including surface modification, doping, and combination with other nanomaterials. Furthermore, this review specifically concentrates on the research advances of antibacterial FCDs in the treatment of bacterial inflammation. Finally, the advantages and challenges of applying FCDs in practical antimicrobial applications are discussed.

Antibacterial Carbon Dots: Mechanisms, Design, and Applications

The increase in antibiotic resistance promotes the situation of developing new antibiotics at the forefront, while the development of non-antibiotic pharmaceuticals is equally significant. In the post-antibiotic era, nanomaterials with high antibacterial efficiency and no drug resistance make them attractive candidates for antibacterial materials. Carbon dots (CDs), as a kind of carbon-based zero-dimensional nanomaterial, are attracting much attention for their multifunctional properties. The abundant surface states, tunable photoexcited states, and excellent photo-electron transfer properties make sterilization of CDs feasible and are gradually emerging in the antibacterial field. This review provides comprehensive insights into the recent development of CDs in the antibacterial field. The topics include mechanisms, design, and optimization processes, and their potential practical applications are also highlighted, such as treatment of bacterial infections, against bacterial biofilms, antibacterial surfaces, food preservation, and bacteria imaging and detection. Meanwhile, the challenges and outlook of CDs in the antibacterial field are discussed and proposed.

Photothermal Hydrogels for Promoting Infected Wound Healing

Photothermal therapies (PTT), with spatiotemporally controllable antibacterial capabilities without inducing resistance, have shown encouraging prospects in the field of infected wound treatments. As an important platform for PTT, photothermal hydrogels exhibit attractive advantages in the field of infected wound treatment due to their excellent biochemical properties and have been intensively explored in recent years. This review summarizes the progress of the photothermal hydrogels for promoting infected wound healing. Three major elements of photothermal hydrogels, i.e., photothermal materials, hydrogel matrix, and construction methods, are introduced. Furthermore, different strategies of photothermal hydrogels in the treatment of infected wounds are summarized. Finally, the challenges and prospects in the clinical treatment of photothermal hydrogels are discussed.

Antibacterial and antibiofilm mechanisms of carbon dots: a review

Due to the increasing bacterial resistance to conventional antibiotics, developing safe and effective approaches to combat infections caused by bacteria and biofilms has become an urgent clinical problem. Recently, carbon dots (CDs) have received great attention as a promising alternative to conventional antimicrobial agents due to their excellent antimicrobial efficacy and biocompatibility. Although CDs have been widely used in the field of antibacterial applications, their antibacterial and antibiofilm mechanisms have not been systematically discussed. This review provides a systematic overview on the complicated mechanisms of antibacterial and antibiofilm CDs based on recent development.

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.

A Self-Healing, Magnetic and Injectable Biopolymer Hydrogel Generated by Dual Cross-Linking for Drug Delivery and Bone Repair

Injectable hydrogels based on various functional biocompatible materials have made rapid progress in the field of bone repair. In this study, a self-healing and injectable polysaccharide-based hydrogel was prepared for bone tissue engineering. The hydrogel was made of carboxymethyl chitosan (CMCS) and calcium pre-cross-linked oxidized gellan gum (OGG) cross-linked by the Schiff-base reaction. Meanwhile, magnetic hydroxyapatite/gelatin microspheres (MHGMs) were prepared by the emulsion cross-linking method. The antibacterial drugs, tetracycline hydrochloride (TH) and silver sulfadiazine (AgSD), were embedded into the MHGMs. To improve the mechanical and biological properties of the hydrogels, composite hydrogels were prepared by compounding hydroxyapatite (HAp) and drug-embedded MHGMs. The physical, chemical, mechanical and rheological properties of the composite hydrogels were characterized, as well as in vitro antibacterial tests and biocompatibility assays, respectively. Our results showed that the composite hydrogel with 6% (w/v) HAp and 10 mg/mL MHGMs exhibited good magnetic responsiveness, self-healing and injectability. Compared with the pure hydrogel, the composite hydrogel showed a 38.8% reduction in gelation time (196 to 120 s), a 65.6% decrease in swelling rate (39.4 to 13.6), a 51.9% increase in mass residual after degradation (79.5 to 120.8%), and a 143.7% increase in maximum compressive stress (53.6 to 130.6 KPa). In addition, this composite hydrogel showed good drug retardation properties and antibacterial effects against both S. aureus and E. coli. CCK-8 assay showed that composite hydrogel maintained high cell viability (> 87%) and rapid cell proliferation after 3 days, indicating that this smart hydrogel is expected to be an alternative scaffold for drug delivery and bone regeneration. STATEMENT OF SIGNIFICANCE: Biopolymer hydrogels have been considered as the promising materials for the treatment of tissue engineering and drug delivery. Injectable hydrogels with and self-healing properties and responsiveness to external stimuli have been extensively investigated as cell scaffolds and bone defects, due to their diversity and prolonged lifetime. Magnetism has also been involved in biomedical applications and played significant roles in targeted drug delivery and anti-cancer therapy. We speculate that development of dual cross-linked hydrogels basing biopolymers with multi-functionalities, such as injectable, self-healing, magnetic and anti-bacterial properties, would greatly broaden the application for bone tissue regeneration and drug delivery.