Engineered Sandwich-Structured Composite Wound Dressings with Unidirectional Drainage and Anti-Adhesion Supporting Accelerated Wound Healing

Exudate Management, Facile Detachment, and Immunometabolism Regulation for Wound Healing Using Breathable Dressings

Developing breathable dressings with multifunctional properties (such as exudate management, easy removal, and immunometabolism regulation) presents significant challenges in wound healing. This study employs the Hofmeister effect to prepare a sodium citrate-cross-linked cryogel (CA-CS) with versatile functions, including porous and loose structures, rapid shape recovery ability, superior fatigue resistance behavior, and outstanding biocompatibility capabilities. The CA-CS cryogels demonstrated strong anti-inflammatory properties by reversing the lipopolysaccharides-induced M1 macrophages and increasing M2 macrophage percentages in vitro. Additionally, these breathable CA-CS cryogels exhibited superior hemostatic activity in vivo. The easily detachable CA-CS cryogels enhanced nutrient exchange, promoted exudate absorption, regulated immune response, and induced metabolic reprogramming, thereby supporting skin regeneration and hair follicle formation in a full-thickness skin defect mouse model. We expect that these CA-CS cryogels will drive the development of next-generation dressings for effective wound regeneration in clinical practice.

Recent Advances in Asymmetric Wettability Dressings for Wound Exudate Management

The management of wound exudate is of vital importance for wound healing. Exudate accumulation around wound prolongs inflammation and hinders healing. Although traditional dressings can absorb wound exudate, they are unable to drain exudate in time, often resulting in a poor feature with wound healing. In recent years, the appearance of asymmetric wettability dressings has shown great potential in exudate management. Here, we summarize the latest progress of 3 kinds of asymmetric wettability wound dressings in exudate management, including Janus structure, sandwich structure, and gradient structure. The most common Janus structural dressing among asymmetric wettability dressings is highlighted from 2 aspects: single-layer modified Janus structure and double-layer Janus structure. The challenges faced by asymmetric wettability wound dressings are discussed, and the developing trends of smart wound dressings in this field are prospected.

Construction and Performance Study of a Dual-Network Hydrogel Dressing Mimicking Skin Pore Drainage for Photothermal Exudate Removal and On-Demand Dissolution

In recent years, negative pressure wound dressings have garnered widespread attentions. However, it is challenging to drain the accumulated fluid under negative pressures for hydrogel dressings. To address this issue, this study prepared a chemical/physical duel-network PEG-CMCS/AG/MXene hydrogel composed by chemical disulfide crosslinked network of four-arm polyethylene glycol/carboxymethyl chitosan (4-Arm-PEG-SH/CMCS), and the physical network of hydrogen bond of agar (AG). Under near-infrared light (NIR) irradiation, the PEG-CMCS/AG/MXene hydrogel undergoes photothermal heating due to integrate of MXene, which destructs the hydrogen bond network and allows the removal of exudate through a mechanism mimicking the sweat gland-like effect of skin pores. The photothermal heating effect also enables the antimicrobial activity to prevent wound infections. The excellent electrical conductivity of PEG-CMCS/AG/MXene can promote cell proliferation under the external electrical stimulation (ES) in vitro. The animal experiments of full-thickness skin defect model further demonstrate its ability to accelerate wound healing. The conversion between thioester and thiol achieved with L-cysteine methyl ester hydrochloride (L-CME) can provides the on-demand dissolution of the dressing in situ. This study holds promises to provide a novel solution to the issue of fluid accumulations under hydrogel dressings and offers new approaches to alleviating or avoiding the significant secondary injuries caused by frequent dressing changes.

Dextran-Based Antibacterial Hydrogel Dressings for Accelerating Infected Wound Healing by Reducing Inflammation Levels

Infected wounds pose challenges such as exudate management, bacterial infections, and persistent inflammation, making them a significant challenge for modern dressings. To address these issues in infected wounds more effectively, aerogel-hydrogel biphase gels based on dextran are developed. The gel introduced in this study exhibits antibacterial and anti-inflammatory properties in the process of wound therapy, contributing to accelerated wound healing. The aerogel phase exhibits exceptional water-absorption capabilities, rapidly soaking up exudate from infected wound, thereby fostering a clean and hygienic wound healing microenvironment. Concurrently, the aerogel phase is enriched with hydrogen sulfide donors. Following water absorption and the formation of the hydrogel phase, it enables the sustained release of hydrogen sulfide around the wound sites. The experiments confirm that hydrogen sulfide, by promoting M2 macrophage differentiation and reducing the levels of inflammatory factors, effectively diminishes local inflammation levels at the wound site. Furthermore, the sodium copper chlorophyllin component within the hydrogel phase demonstrates effective antibacterial properties through photodynamic antimicrobial therapy, providing a viable solution to wound infection challenges.

Robust Gradient Hydrogel-Loaded Nanofiber Fleshy Artificial Skin Via A Coupled Microfluidic Electrospinning-Reactive Coating Strategy

Skin regeneration attracts tremendous interest due to the important role of skin for human protection and beauty. Thus, methods allowing artificial skin to be carried out in a controllable fashion are potentially important for wound healing, which involves an intersection of materials, medicine, biology, and other disciplines. Herein, aiming at a new general methodology for fleshy materials, a new hydrogel-loaded hydrophobic-hydrophilic nanofiber fleshy artificial skin is designed and fabricated. The gradient hydrogel-loaded nanofiber artificial skin integrates both advantages of nanofiber and hydrogel, exhibiting fleshy feature (comparability to real skin in terms of appearance, texture, and function), excellent air permeability, compatibility, and good mechanical and antibacterial property. Interestingly, the efficient transport channels are formed throughout the hydrogel-loaded nanofiber structure, which is beneficial for water absorption and transfer. These advantages enable the establishment of a moist and favorable microenvironment; thus, greatly accelerating wound healing process. This work couples microfluidic electrospinning with reactive coating technique, which is in favor of material design and fabrication with controllable and uniform structures. The hydrogel-loaded nanofiber fleshy artificial skin shows comparability to real skin in terms of beauty, texture, and function, which would definitely provide new opportunities for the further optimization and upgrading of artificial skin.

Design, Modeling, and Experimental Validation of an Active Microcatheter Driven by Shape Memory Effects

Microcatheters capable of active guidance have been proven to be effective and efficient solutions to interventional surgeries for cardiovascular and cerebrovascular diseases. Herein, a novel microcatheter made of two biocompatible materials, shape memory alloy (SMA) and polyethylene (PE), is proposed. It consists of a reconfigurable distal actuator and a separate polyethylene catheter. The distal actuator is created via embedding U-shape SMA wires into the PE base, and its reconfigurability is mainly dominated by the shape memory effect (SME) of SMA wires, as well as the effect of thermal mismatch between the SMA and PE base. A mathematical model was established to predict the distal actuator's deformation, and the analytical solutions show great agreement with the finite element results. Structural optimization of such microcatheters was carried out using the verified analytical model, followed by fabrication of some typical prototypes. Experimental testing of their mechanical behaviors demonstrates the feasibility of the structural designs, and the reliability and accuracy of the mathematical model. The active microcatheter, together with the prediction model, will lay a solid foundation for rapid development and optimization of active navigation strategies for vascular interventions.

Multifunctional Hydrogel Enhances Inflammatory Control, Antimicrobial Activity, and Oxygenation to Promote Healing in Infectious Wounds

Chronic infected wounds often fail to heal through normal repair mechanisms, and the persistent response of reactive oxygen species (ROS) and inflammation is a major contributing factor to the difficulty in their healing. In this context, we developed an ROS-responsive injectable hydrogel. This hydrogel is composed of ε-polylysine grafted (EPL) with caffeic acid (CA) and hyaluronic acid (HA) grafted with phenylboronic acid (PBA). Before the gelation process, a mixture CaO2@Cur-PDA (CCP) consisting of calcium peroxide (CaO2) coated with polydopamine (PDA) and curcumin (Cur) is embedded into the hydrogel. Under the conditions of chronic refractory wound environments, the hydrogel gradually dissociates. HA mimics the function of the extracellular matrix, while the released caffeic acid-grafted ε-polylysine (CE) effectively eliminates bacteria in the wound vicinity. Additionally, released CA also clears ROS and influences macrophage polarization. Subsequently, CCP further decomposes, releasing Cur, which promotes angiogenesis. This multifunctional hydrogel accelerates the repair of diabetic skin wounds infected with Staphylococcus aureus in vivo and holds promise as a candidate dressing for the healing of chronic refractory wounds.

Nano-enabled antimicrobial thin films: design and mechanism of action

Antimicrobial thin films are types of protective coatings that are applied to surfaces such as medical devices, food packaging materials, water-resistant coatings, and other systems. These films prevent and reduce the spread of microbial organisms, including bacteria, fungi, and viruses. Antimicrobial thin films can be prepared from a variety of nanostructured materials including metal nanoparticles, metal oxides, plant materials, enzymes, bacteriocins and polymers. Their antimicrobial mechanism varies mostly based on the types of active agents from which the film is made of. Antimicrobial thin films are becoming increasingly popular microbial treatment methods due to their advantages such as enhanced stability, reduced toxicity levels, extended effectiveness over time and broad spectrum antimicrobial action without side effects on human health or the environment. This popularity and enhanced performance is mainly due to the extended possibility of film designs. Thin films offer convenient formulation methods which makes them suitable for commercial practices aiming at high turnover rates along with residential applications requiring frequent application cycles. This review focuses on recent developments in the possible processing methods and design approaches for assembling the various types of antimicrobial materials into nanostructured thin film-based delivery systems, along with mechanisms of action against microbes.

Cotton fiber-based dressings with wireless electrical stimulation and antibacterial activity for wound repair

Although cotton dressing is one of the most commonly used wound management materials, it lacks antimicrobial and healing-promoting activity. This work developed a multilayer electroactive composite cotton dressing (Ag/Zn@Cotton/Paraffin) with exudate-activated electrical stimulation and antibacterial activity by the green and sustainable magnetron-sputtering and spraying methods. The inner hydrophilic layer of the cotton dressing was magnetron sputtered with silver/zinc galvanic couple arrays (Ag/Zn), which can be activated by wound exudate, generating an electrical stimulation (ES) into the wound. The Ag/Zn@Cotton showed efficient antibacterial activities against S. aureus and E. coli. Meanwhile, the paraffin-sprayed outer surface showed excellent antibacterial adhesion rates for S. aureus (99.82 %) and E. coli (97.92 %). The in vitro cell experiments showed that the ES generated by Ag/Zn@Cotton/Paraffin increased the migration of fibroblasts, and the in vivo mouse model indicated that the Ag/Zn@Cotton/Paraffin could enhance wound healing via re-epithelialization, inflammatory inhibition, collagen deposition, and angiogenesis. MTT method and live/dead staining showed that Ag/Zn@Cotton/Paraffin had no significant cytotoxic effects. This work may shed some light on designing and fabricating multi-functional electroactive composited dressings based on traditional biomedical textiles.