Design of Near-Infrared-Triggered Cellulose Nanocrystal-Based In Situ Intelligent Wound Dressings for Drug-Resistant Bacteria-Infected Wound Healing

Iron Nano Biocomposite-Infused Biopolymeric Films: A Multifunctional Approach for Robust Skin Repair

Sodium alginate (SA) biopolymeric films have various limitations such as poor mechanical properties, high vapor permeability, lack of antibacterial activity, excessive burst release, and weak cell adhesion. To overcome these limitations, a strategy involving the integration of nanofillers into an SA film matrix is explored. In this context, a cost-effective iron-containing carbon nano biocomposite (FeCNB) nanofiller is developed using a solvent-free technique. This nanocomposite is successfully incorporated into the alginate film matrix at varying concentrations (0.05, 0.1, and 0.15%) aimed at enhancing its physicochemical and biological properties for biomedical applications. Characterization through FESEM and BET analyses confirms the porous nature of the FeCNB. EDX shows the FeCNB's uniform distribution upon its integration into the film matrix, albeit without strong chemical interaction with SA. Instead, hydrogen bonding interactions become apparent in the FTIR spectra. By incorporating the FeCNB, the mechanical attributes of the films are improved and the water vapor permeability approaches the desired range (2000-2500 g/m2day). The film's swelling ratio reduction contributes to a decrease in water permeability. The antibacterial activity and sustained release property of the FeCNB-incorporated film are established using tetracycline hydrochloride (TCl), a model drug. The drug release profile resembled Korsmeyer-Peppas's release pattern. In vitro assessments via the MTT assay and scratch assay on NIH-3T3 cells reveal that FeCNB has no adverse effects on the biocompatibility of alginate films. The cell proliferation and adhesion to the SA film are significantly enhanced after infusion of the FeCNB. The in vivo study performed on the rat model demonstrates improved wound healing by FeCNB-impregnated films. Based on the comprehensive findings, the proposed FeCNB-incorporated alginate films prove to be a promising candidate for robust skin repair.

In situ light-activated materials for skin wound healing and repair: A narrative review

Dermal wounds are a major global health burden made worse by common comorbidities such as diabetes and infection. Appropriate wound closure relies on a highly coordinated series of cellular events, ultimately bridging tissue gaps and regenerating normal physiological structures. Wound dressings are an important component of wound care management, providing a barrier against external insults while preserving the active reparative processes underway within the wound bed. The development of wound dressings with biomaterial constituents has become an attractive design strategy due to the varied functions intrinsic in biological polymers, such as cell instructiveness, growth factor binding, antimicrobial properties, and tissue integration. Using photosensitive agents to generate crosslinked or photopolymerized dressings in situ provides an opportunity to develop dressings rapidly within the wound bed, facilitating robust adhesion to the wound bed for greater barrier protection and adaptation to irregular wound shapes. Despite the popularity of this fabrication approach, relatively few experimental wound dressings have undergone preclinical translation into animal models, limiting the overall integrity of assessing their potential as effective wound dressings. Here, we provide an up-to-date narrative review of reported photoinitiator- and wavelength-guided design strategies for in situ light activation of biomaterial dressings that have been evaluated in preclinical wound healing models.

Accelerated Wound Healing by Electrospun Multifunctional Fibers with Self-Powered Performance

Wound healing has been a persistent clinical challenge for a long time. Electrical stimulation is an effective therapy with the potential to accelerate wound healing. In this work, the self-powered electrospun nanofiber membranes (triples) were constructed as multifunctional wound dressings with electrical stimulation and biochemical capabilities. Triple was composed of a hydrolyzable inner layer with antiseptic and hemostatic chitosan, a hydrophilic core layer loaded with conductive AgNWs, and a hydrophobic outer layer fabricated by self-powered PVDF. Triple exhibited presentable wettability and acceptable moisture permeability. Electrical performance tests indicated that triple can transmit electrical signals formed by the piezoelectric effect to the wound. High antibacterial activities were observed for triple against Staphylococcus aureus, Escherichia coli, and Pseudomonas aeruginosa, with inhibition rates of 96.52, 98.63, and 97.26%, respectively. In vitro cell assays demonstrated that triple cells showed satisfactory proliferation and mobility. A whole blood clotting test showed that triple can enhance hemostasis. The innovative self-powered multifunctional fibers presented in this work offer a promising approach to addressing complications and expediting the promotion of chronic wound healing.

Exudate-Induced Gelatinizable Nanofiber Membrane with High Exudate Absorption and Super Bactericidal Capacity for Bacteria-Infected Wound Management

Invasion of bacteria and continuous oozing of exudate are significant causes of interference with the healing of infected wounds. Therefore, an exudate-induced gelatinizable and near-infrared (NIR)-responsive nanofiber membrane composed of polyvinyl alcohol (PVA), carboxymethyl chitosan (CMC), and Fe-doped phosphomolybdic acid (Fe-PMA) with exceptional exudate absorption capacity and potent bactericidal efficacy is developed and denoted as the PVA-FP-CMC membrane. After absorbing exudate, the fiber membrane can transform into a hydrogel membrane, forming coordination bonds between the Fe-PMA and CMC. The unique exudate-induced gelation process imparts the membrane with high exudate absorption and retention capability, and the formed hydrogel also traps the bacteria that thrive in the exudate. Moreover, it is discovered for the first time that the Fe-PMA exhibits an enhanced photothermal conversion capability and photocatalytic activity compared to the PMA. Therefore, the presence of Fe-PMA provides the membrane with a photothermal and photodynamic therapeutic effect for killing bacteria. The PVA-FP-CMC membrane is proven with a liquid absorption ratio of 520.7%, a light-heat conversion efficiency of 41.9%, high-level generation of hydroxyl radical (•OH) and singlet oxygen (1O2), and a bacterial killing ratio of 100% for S. aureus and 99.6% for E. coli. The treatment of infected wounds on the backs of rats further confirms the promotion of wound healing by the PVA-FP-CMC membrane with NIR irradiation. Overall, this novel functional dressing for the synergistic management of bacteria-infected wounds presents a promising therapeutic strategy for tissue repair and regeneration.

Cationized orthogonal triad as a photosensitizer with enhanced synergistic antimicrobial activity

Single-molecule-based synergistic phototherapy holds great potential for antimicrobial treatment. Herein, we report an orthogonal molecular cationization strategy to improve the reactive oxygen species (ROS) and hyperthermia generation of heptamethine cyanine (Cy7) for photodynamic and photothermal treatments of bacterial infections. Cationic pyridine (Py) is introduced at the meso‑position of the asymmetric Cy7 with intramolecular charge transfer (ICT) to construct an atypical electron-transfer triad, which reduces ΔES1-S0, circumvents rapid charge recombination, and simultaneously enhances intersystem crossing (ISC) based on spin-orbit charge-transfer ISC (SOCT-ISC) mechanism. This unique molecular construction produces anti-Stokes luminescence (ASL) because the rotatable CN bond enriched in high vibrational-rotational energy levels improves hot-band absorption (HBA) efficiency. The obtained triad exhibits higher singlet oxygen quantum yield and photothermal conversion efficiency compared to indocyanine green (ICG) under irradiation above 800 nm. Cationization with Py enables the triad to target bacteria via intense electrostatic attractions, as well as biocidal property against a broad spectrum of bacteria in the dark. Moreover, the triad under irradiation can enhance biofilm eradication performance in vitro and statistically improve healing efficacy of MRSA-infected wound in mice. Thus, this work provides a simple but effective strategy to design small-molecule photosensitizers for synergistic phototherapy of bacterial infections. STATEMENT OF SIGNIFICANCE: We developed an orthogonal molecular cationization strategy to enhance the reactive oxygen species and thermal effects of heptamethine cyanine (Cy7) for photodynamic and photothermal treatments of bacterial infections. Specifically, cationic pyridine (Py) was introduced at the meso‑position of the asymmetric Cy7 to construct an atypical electron-transfer triad, which reduced ΔES1-S0, circumvented rapid charge recombination, and simultaneously enhanced intersystem crossing (ISC). This triad, with a rotatable CN bond, produced anti-Stokes luminescence due to hot-band absorption. The triad enhanced antimicrobial performance and statistically improved the healing efficacy of MRSA-infected wounds in mice. This site-specific cationization strategy may provide insights into the design of small molecule-based photosensitizers for synergistic phototherapy of bacterial infections.

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.

Green, pH-Sensitive, Highly Stretchable, and Hydrogen Bond-Dominated Ionogel for Wound Healing Activity

Traditional hydrogel dressings generally have poor mechanical properties and stability when subjected to external stress due to the undesirable chain entanglement structure of their single valence bond compositions. Therefore, it is particularly important to develop a type of gel dressing with good mechanical strength, stability, and environment-friendly monitoring. In this work, a transparent, pH-sensitive, highly stretchable, and biocompatible anthocyanidin ionogel dressing was prepared, realizing green and accurate detection. Attributed to the antibacterial activity of the ionic liquid, the biocompatibility of the pectin, and the ability to scavenge free radicals of the anthocyanidin, the ionogel dressing exhibited excellent re-epithelialization in the 14 day wound healing process. Besides, changes in pH values monitoring of the ionogel over 3 days coincided with normal wound exudate. The obtained ionogel also showed good water retention, swelling properties, mechanical stretchability, and 5 week stability, illustrating great potential in wound dressings.

PMN-incorporated multifunctional chitosan hydrogel for postoperative synergistic photothermal melanoma therapy and skin regeneration

Melanoma excision surgery is usually accompanied by neoplasm residual, tissue defect, and bacterial infection, resulting in high tumor recurrence and chronic wound. Nanocomposite hydrogels can satisfy the twin requirements of avoiding tumor recurrence and skin wound healing following skin melanoma surgery due to their photothermal anti-tumor and anti-bacterial activities. In this study, carboxymethyl chitosan, oxidized fucoidan and polyphenol-metal nanoparticle (PMN) of tannic acid capped gold nanoparticles were used to fabricate multifunctional nanocomposite hydrogels through Schiff base reaction. The prepared hydrogel demonstrated outstanding photothermal effect, and the controlled high temperature will rapidly kill melanoma cells as well as bacteria within 10 min. Good injectability, self-healing and adhesion combined with high reactive oxygen species (ROS) scavenging capacity, hemostasis and biocompatibility made this hydrogel platform perfect for the postoperative treatment of melanoma and promoting wound healing. With the assistance of NIR irradiance, hydrogel can inhibit tumor tissue proliferation and promote tumor cell apoptosis, thereby helping to prevent melanoma recurrence after surgical removal of tumors. Simultaneously, the irradiance heat and polyphenol component kill bacteria on the wound surface, eliminate ROS, inhibit inflammatory responses, and promote angiogenesis, collagen deposition, and skin regeneration, all of which help to speed up wound healing.

A Temperature and pH Dual-Sensitive Multifunctional Polyurethane with Bacteria-Triggered Antibacterial Activity

An effective and practical antibacterial strategy is to design multifunctional and stimuli-responsive materials that exhibit antibacterial activity in response to bacterial triggers. In this study, because the metabolism of Staphylococcus aureus (S. aureus) can acidify the surrounding environment and pH level can affect the lower critical solution temperature of temperature/pH dual-sensitive polymers, a monomer containing a temperature-sensitive N-isopropyl amide derivative and pH-sensitive tertiary amine groups is first synthesized. Then, the monomer is copolymerized with a polyurethane chain, and partial tertiary amine groups are quaternized to obtain bactericidal activity. The modified polyurethane exhibits temperature/pH sensitivity, antibacterial adhesion activity, bactericidal activity, and good cytocompatibility. An in situ investigation of bacterial behavior and pH changes in the bacterial suspension during the process confirms that the temperature/pH dual-sensitive polyurethane successfully achieves antibacterial activity though the metabolic activity of S. aureus without external intervention. This design concept provides a new perspective for antibacterial material design.

Dialdehyde carbohydrates - Advanced functional materials for biomedical applications

Dialdehyde carbohydrates (DCs) have found applications in a wide range of biomedical field due to their great versatility, biocompatibility/biodegradability, biological properties, and controllable chemical/physical characteristics. The presence of dialdehyde groups in carbohydrate structure allows cross-linking of DCs to form versatile architectures serving as interesting matrices for biomedical applications (e.g., drug delivery, tissue engineering, and regenerative medicine). Recently, DCs have noticeably contributed to the development of diverse physical forms of advanced functional biomaterials i.e., bulk architectures (hydrogels, films/coatings, or scaffolds) and nano/-micro formulations. We underline here the current scientific knowledge on DCs, and demonstrate their potential and newly developed biomedical applications. Specifically, an update on the synthesis approach and functional/bioactive attributes is provided, and the selected in vitro/in vivo studies are reviewed comprehensively as examples of the latest progress in the field. Moreover, safety concerns, challenges, and perspectives towards the application of DCs are deliberated.

Nanoarchitectonics of cellulose nanocrystal conjugated with a tetrasaccharide-glycoprobe for targeting oligodendrocyte precursor cells

Demyelination is a serious complication of neurological disorders, which can be reversed by oligodendrocyte precursor cell (OPC) as the available source of myelination. Chondroitin sulfate (CS) plays key roles in neurological disorders, which still attracted less attention on how CS modulates the fate of OPCs. Nanoparticle coupled with glycoprobe is a potential strategy for investigating the carbohydrate-protein interaction. However, there is lack of CS-based glycoprobe with enough chain length that interact with protein effectively. Herein, we designed a responsive delivery system, in which CS was the target molecule, and cellulose nanocrystal (CNC) was the penetrative nanocarrier. A coumarin derivative (B) was conjugated at the reducing end of an unanimal-sourced chondroitin tetrasaccharide (4mer). This glycoprobe (4B) was grafted to the surface of a rod-like nanocarrier, which had a crystalline core and a poly(ethylene glycol) shell. This glycosylated nanoparticle (N4B-P) displayed a uniform size, improved water-solubility, and responsive release of glycoprobe. N4B-P displayed strong green fluorescence and good cell-compatibility, which imaged well the neural cells including astrocytes and OPCs. Interestingly, both of glycoprobe and N4B-P were internalized selectively by OPCs when they were incubated in astrocytes/OPCs mixtures. This rod-like nanoparticle would be a potential probe for studying carbohydrate-protein interaction in OPCs.

New antibacterial hydrogels based on sodium alginate

Nowadays, the combined knowledge and experience in biomedical research and material sciences results in the innovation of smart materials that could efficiently overcome the problems of microbial contaminations. Herein, a new drug delivery platform prepared by grafting sodium alginate with β-carboxyethyl acrylate and acrylamide was described and characterized. 9-Aminoacridine (9-AA), and kanamycin sulfate (KS) were separately loaded into the hydrogel in situ during graft polymerization. The grafting efficiency for the resulting hydrogels was 70.01-78.08 %. The chemical structure of the hydrogels, thermogravimetric analysis, and morphological features were investigated. The swelling study revealed that the hydrogel without drugs achieved a superior swelling rate compared to drug-loaded hydrogels. The hydrogel tuned the drug-release rate in a pH-dependent manner. Furthermore, the antibacterial study suggested that the hydrogels encapsulating 9-AA (88.6 %) or KS (89.3 %) exhibited comparable antibacterial activity against Gram-positive and Gram-negative bacterial strains. Finally, the cytocompatibility study conducted on normal lung cell line (Vero cells) demonstrated neglectable to tolerable toxicity for the drug-loaded hydrogel. More interestingly, the cell viability for the blank hydrogel was 92.5 %, implying its suitability for biomedical applications.

Living Chinese Herbal Scaffolds from Microfluidic Bioprinting for Wound Healing

Biological scaffolds have been widely employed in wound healing applications, while their practical efficiency is compromised by insufficient oxygen delivery to the 3-dimensional constructs and inadequate nutrient supply for the long-term healing process. Here, we present an innovative living Chinese herbal scaffold to provide a sustainable oxygen and nutrient supply for promoting wound healing. Through a facile microfluidic bioprinting strategy, a traditional Chinese herbal medicine (Panax notoginseng saponins [PNS]) and a living autotrophic microorganism (microalgae Chlorella pyrenoidosa [MA]) were successfully encapsulated into the scaffolds. The encapsulated PNS could be gradually released from the scaffolds, which promoted cell adhesion, proliferation, migration, and tube formation in vitro. In addition, benefiting from the photosynthetic oxygenation of the alive MA, the obtained scaffolds would produce sustainable oxygen under light illumination, exerting a protective effect against hypoxia-induced cell death. Based on these features, we have demonstrated through in vivo experiments that these living Chinese herbal scaffolds could efficiently alleviate local hypoxia, enhance angiogenesis, and thereby accelerate wound closure in diabetic mice, indicating their great potential in wound healing and other tissue repair applications.

pH-Responsive wound dressings: advances and prospects

Wound healing is a complex and dynamic process, in which the pH value plays an important role in reflecting the wound status. Wound dressings are materials that are able to accelerate the healing process. Among the multifunctional advanced wound dressings developed in recent years, pH-responsive wound dressings, especially hydrogels, show great potential owing to their unique properties of adjusting their functions according to the wound conditions, thereby allowing the wound to heal in a regulated manner. However, a comprehensive review of pH-responsive wound dressings is lacking. This review summarizes the design strategies and advanced functions of pH-responsive hydrogel wound dressings, including their excellent antibacterial properties and significant pro-healing abilities. Other advanced pH-responsive materials, such as nanofibers, composite films, nanoparticle clusters, and microneedles, are also classified and discussed. Next, the pH-monitoring functions of pH-responsive wound dressings and the related pH indicators are summarized in detail. Finally, the achievements, challenges, and future development trends of pH-responsive wound dressings are discussed.