Bifunctional Smart Hydrogel Dressing with Strain Sensitivity and NIR-Responsive Performance

MXenes in the application of diabetic foot: mechanisms, therapeutic implications and future perspectives

Diabetic foot represents a significant healthcare challenge, accounting for a substantial portion of diabetes-related hospitalizations and amputations globally. The complexity of diabetic foot management stems from the interplay of poor glycemic control, neuropathy, and peripheral vascular disease, which hinder wound healing processes. The high incidence, recurrence, and amputation rates associated with diabetic foot underscore the urgency for innovative treatment strategies. Recent advancements in nanotechnology, particularly the emergence of MXenes (two-dimensional transition metal carbides and/or nitrides), have shown promising potential in addressing these challenges by offering unique physicochemical and biological properties suitable for various biomedical applications. It is a novel potential strategy for diabetic foot wound healing in the future. This review comprehensively summarizes current knowledge, unique characteristics, and underlying mechanisms of MXenes in the context of diabetic foot management. Additionally, we propose the potential application of MXenes-based therapeutic strategies in diabetes foot. Furthermore, we also provide an overview of their current challenges and the future perspectives in related fields of diabetic wound healing.

A flexible multifunctional sensor with a conductive network based on silk nanofibers and MXene for monitoring physiological activity, capacitive pens, photothermal conversion and antibacterial

Flexible electronic sensors that can capture subtle physical, chemical and biological signals and generate real-time stimulus responses are of great importance in the fields of human-computer interaction, biomedicine, etc. Herein, a multifunctional sensing hydrogel was developed by tightly adhering two-dimensional rigid conductive MXene nanosheets to the surface of vimineous silk nanofibers (SNFs) and assembling them into an SNF@MXene network structure. Polyvinyl alcohol (PVA) was then in situ polymerized in SNF@MXene as a filling matrix. MXene nanosheets were attached to the SNF network skeleton, avoiding the settlement and aggregation of MXene and forming a PSM composite hydrogel with a uniform and dense conductive network. The designed PSM hydrogel-based sensor showed excellent mechanical properties (tensile strength = 5.07 MPa), wide operating range (700.6 %), high sensitivity (gauge factor = 8.2), high electrical conductivity (1.64 S m-1), and adhesion. The sensor could detect various physiological activities of the human body. In addition, it also showed the application potential in speech recognition, capacitive pen, etc. PSM exhibited excellent photothermal conversion efficiency. It could be rapidly heated to 82.8 °C under NIR irradiation and used for photothermal therapy. This study provides a simple conductive network design strategy for the fabrication of flexible electronic devices with multiple functions.

An adhesive, antibacterial hydrogel wound dressing fabricated by dopamine-grafted oxidized sodium alginate and methacrylated carboxymethyl chitosan incorporated with Cu(II) complex

Effective wound dressings play an important role in preventing infections and promoting wound healing. Most polysaccharide-based hydrogel dressings have the drawbacks of weak tissue adhesion and poor antibacterial properties. Herein, a multifunctional dopamine-grafted oxidized sodium alginate-methacrylated carboxymethyl chitosan/gallic acid‑copper(II) complex (OD-CM/GA-CuIIUV) hydrogel was fabricated through Schiff base bonds and photo-crosslinked polymerization between dopamine-grafted oxidized sodium alginate (OSA-DA) and methacrylated carboxymethyl chitosan (CMC-MA), with the integration of gallic acid‑copper(II) complexes (GA-CuII). The double cross-linked network and mussel-inspired adhesion mechanism endowed the hydrogel with attractive physicochemical properties, including excellent self-healing properties, pH-responsive biodegradability, robust toughness, and a maximum adhesion strength of 15.06 kPa. Moreover, the composite hydrogel exhibited an antibacterial ratio of > 99 % against Escherichia coli and Staphylococcus aureus, as well as good antioxidant activity. The MTT assay showed that the cell viability of the composite hydrogel reached > 85 %. The in vivo full-thickness skin defect healing assays in rats demonstrated that the composite hydrogel remarkably accelerated wound repair by attenuating the inflammatory response and promoting epithelial tissue remodeling. Therefore, this novel multifunctional hydrogel has potential applications in biomedical wound dressing.

Engineered MXene Biomaterials for Regenerative Medicine

MXene-based materials have attracted significant interest due to their distinct physical and chemical properties, which are relevant to fields such as energy storage, environmental science, and biomedicine. MXene has shown potential in the area of tissue regenerative medicine. However, research on its applications in tissue regeneration is still in its early stages, with a notable absence of comprehensive reviews. This review begins with a detailed description of the intrinsic properties of MXene, followed by a discussion of the various nanostructures that MXene can form, spanning from 0 to 3 dimensions. The focus then shifts to the applications of MXene-based biomaterials in tissue engineering, particularly in immunomodulation, wound healing, bone regeneration, and nerve regeneration. MXene's physicochemical properties, including conductivity, photothermal characteristics, and antibacterial properties, facilitate interactions with different cell types, influencing biological processes. These interactions highlight its potential in modulating cellular functions essential for tissue regeneration. Although the research on MXene in tissue regeneration is still developing, its versatile structural and physicochemical attributes suggest its potential role in advancing regenerative medicine.

Thermoresponsive and Strain-Sensitive Hydrogels with Inscribable Transparency-Based Dynamic Memory Behaviors

Personal health management drives the development of intelligent hydrogel dressings, which pursue optical transparency, stretchability, and conductivity and are required to perceive specific environmental stimuli by dynamic structure, shape, or color memory. However, the incorporation of weak perceptive elements or black conductive polymers limits the fabrication of these hydrogels. Herein, we propose smart hydrogels with inscribable dynamic memorizing-forgetting transparency behavior by in situ degrading and immobilizing conductive polydopamine-doped polypyrrole (PDA-PPy) nanodots into an interpenetrating poly(NIPAm-co-acrylic acid) copolymer/polyacrylamide (PNAc/PAM) network. These hydrogels are not only optically transparent (∼64.99%), stretchable (∼1052%), self-adhesive (21-105 kPa), and highly conductive (∼0.8 S/m), but also can perceive temperature changes via structure shifts, which enables temperature-induced reversible transparency control. Especially, the temperature-dependent transparent-opaque transition kinetics of the hydrogels are tuned by the protonation of -COOH groups at pH < pKa, utilizing which the hydrogels achieve inscribed programmed dynamic memory for information memorizing-forgetting-recalling based on a pH-engraved dynamic transparency evolution of the hydrogel in response to temperature changes. These intelligent hydrogels can not only be used as efficient near-infrared (NIR) light-controlled drug release carriers to realize on-demand drug release, but also serve as a soft sensor to recognize different body postures and movement behaviors with high strain sensitivity (gauge factor, GF = 5.98), broad working strain (5-500%), rapid response (139 ms), and excellent sensing reliability (≈1000 cycles at 50% strain).

Crafting nature's wonders: nanoarchitectonics developments in bioinspired nanocellulose-based stimuli-responsive supramolecular matrices

Stimuli-responsive supramolecular assemblies have recently gained extensive attention in the biomedical field. Research focusing mainly on bioinspired functional supramolecular materials has shown great promise for potential drug delivery applications. Such materials can be engineered into 'smart' materials by utilizing various external stimuli such as pH, heat, light, and magnetic fields. Combining stimuli-responsive properties with bioinspired and biodegradable nanocellulose as a supramolecular matrix can offer a synergistic strategy for targeted and on-demand delivery of therapeutic drugs. The limitations of traditional drug delivery techniques may be greatly mitigated using this combination. In this review, we aim to provide a comprehensive overview of the recent advances in the development of stimuli-responsive nanocellulose-based drug delivery systems. Finally, we have highlighted the current challenges and future perspectives in the field, emphasizing the need for further research to overcome existing barriers and fully realize the potential of stimuli-responsive nanocellulose in drug-releasing applications. Reviewing the state-of-the-art developments and identifying critical areas for future exploration will provide valuable insights for researchers and practitioners working in nanomedicine and drug delivery, fostering the advancement of innovative and effective drug-releasing technologies.

Preparation of Gradient HEA-DAC/HPA Hydrogels by Limited Domain Swelling Method

Hydrogels are widely used in biological dressing, tissue scaffolding, drug delivery, sensors, and other promising applications owing to their water-rich soft structures, biocompatibility, and adjustable mechanical properties. However, most of the conventional hydrogels are isotropic. The anisotropic structures existed widely in the organizational structure of plants and animals, which played a crucial role in biological systems. In this work, a method of limited domain swelling to prepare anisotropic hydrogels is proposed. Through spatially controlled swelling, the extension direction of hydrogels can be limited by a tailored mold, further achieving anisotropic hydrogels with concentration gradients. The external solution serves as a swelling solution to promote swelling and extension of the hydrogel matrix in a mold which can control the extension direction. Due to the diversity of external solutions, the method can be applied to prepare a variety of stimulus-responsive polymers. The limited domain swelling method is promising for the construction of anisotropic hydrogels with different structures and properties.

Thermo-Responsive and Electroconductive Nano Au-PNiPAAm Hydrogel Nanocomposites: Influence of Synthesis Method and Nanoparticle Shape on Physicochemical Properties

Hydrogel nanocomposites that respond to external stimuli and possess switchable electrical properties are considered as emerging materials with potential uses in electrical, electrochemical, and biological devices. This work reports the synthesis and characterization of thermo-responsive and electroconductive hydrogel nanocomposites based on poly(N-isopropylacrylamide) (PNiPAAm) and gold nanoparticles (nanospheres-AuNPs and nanorods-AuNRs) using two different synthetic techniques. Method I involved γ-irradiation-induced crosslinking of a polymer matrix (hydrogel), followed by radiolytic in situ formation of gold nanoparticles, while Method II included the chemical synthesis of nanoparticles, followed by radiolytic formation of a polymer matrix around the gold nanoparticles. UV-Vis spectral studies revealed the presence of local surface plasmon resonance (LSPR) bands characteristic of nanoparticles of different shapes, confirming their formation and stability inside the polymer matrix. Morphological, structural, and physicochemical analyses indicated the existence of a stable porous polymer matrix, the formation of nanoparticles with a face-centered cubic structure, increased swelling capacity, and a slightly higher volume phase transition temperature (VPTT) for the hydrogel nanocomposites. Comparative electrochemical impedance spectroscopy (EIS) showed an increase in conductivity for the nano Au-PNiPAAm hydrogel nanocomposites compared to the PNiPAAm hydrogel, with a considerable rise detected above the VPTT. By reverting to room temperature, the conductivity decreased, indicating that the investigated hydrogel nanocomposites exhibited a remarkable reversible "on-off" thermo-switchable mechanism. The highest conductivity was observed for the sample with rod-shaped gold nanoparticles. The research findings, which include optical, structural, morphological, and physicochemical characterization, evaluation of the efficiency of the chosen synthesis methods, and conductivity testing, provide a starting point for future research on the given nanocomposite materials with integrated multifunctionality.

Intelligent bacteria-targeting ZIF-8 composite for fluorescence imaging-guided photodynamic therapy of drug-resistant superbug infections and burn wound healing

Infected burn wounds are characterized by persistent drug-resistant bacterial infection coupled with an inflammatory response, impeding the wound-healing process. In this study, an intelligent nanoparticle system (CCM+TTD@ZIF-8 NPs) was prepared using curcumin (CCM), an aggregation-induced emission luminogens (TTD), and ZIF-8 for infection-induced wound healing. The CCM+TTD@ZIF-8 NPs showed multiple functions, including bacteria targeting, fluorescence imaging and pH response-guided photodynamic therapy (PDT), and anti-inflammatory. The positive charges of ZIF-8 NPs allowed the targeting of drug-resistant bacteria in infected wounds, thereby realizing fluorescence imaging of bacteria by emitting red fluorescence at the infected site upon blue light irradiation. The pH-responsive characteristics of the CCM+TTD@ZIF-8 NPs also enabled controllable CCM release onto the infected wound site, thereby promoting the specific accumulation of ROS at the infected site, with outstanding bactericidal efficacy against drug-resistant Staphylococcus aureus (S. aureus) and Pseudomonas aeruginosa (P. aeruginosa) strains in vitro/in vivo. Additionally, due to the excellent bactericidal effect and anti-inflammatory properties of CCM+TTD@ZIF-8 NPs combined with blue light irradiation, the regeneration of epidermal tissue, angiogenesis, and collagen deposition was achieved, accelerating the healing process of infected burn wounds. Therefore, this CCM+TTD@ZIF-8 NPs with multifunctional properties provides great potential for infected burn wound healing.

Thermal and light-driven soft actuators based on a conductive polypyrrole nanofibers integrated poly(N-isopropylacrylamide) hydrogel with intelligent response

The development of soft hydrogel actuators with outstanding mechanical properties, fast actuation speed, and available quantification of self-sensing actuation remains a challenging endeavor. In this work, dopamine-decorated polypyrrole nanofibers (DAPPy) were introduced into the polyethylene glycol diacrylate (PEGDA)-crosslinked poly(N-isopropyl acrylamide) network to generate a stretchable, NIR-responsive, and strain sensitive DAPPy/PNIPAM hydrogel layer. Besides, this active layer was combined with the passive ligninsulfonate sodium/polyacrylamide (LS/PAAM) to give DAPPy/PNIPAM//LS/PAAM bilayer hydrogel actuator, which exhibits ultrafast thermo-responsive actuation (19°/s) and underwater grasping and lifting performance. Moreover, the DAPPy/PNIPAM layer has excellent electrical conductivity (0.29 S/m) and thermal conversion ability (10.8 °C/min), which enable such a conductive hydrogel to act as a highly sensitive strain and temperature sensor with real-time resistance change in response to tensile strain (gauge factor up to 3.4), applied pressure, temperature, and remote NIR light irradiation. More importantly, the bilayer hydrogel actuator can integrate both actuation and self-sensing functions through the bending angle-surface temperature-relative resistance change relationship of the photothermal process. With excellent mechanical actuation and self-sensing ability, the resulting bilayer hydrogel showed a promising application potential as soft biomimetic actuating materials and soft intelligent actuators.

Dynamic hydrazone crosslinked salecan/chondroitin sulfate hydrogel platform as a promising wound healing Strategy: A comparative study on antibiotic and probiotic delivery

Natural polysaccharide-based active-ingredient carriers have been a source of great concern for a long time. In order to explore potential antibiotics and probiotics carriers, a novel injectable chondroitin sulfate/salecan (CS) hydrogel was constructed by forming dynamic hydrazone bonds. Scanning electron microscope (SEM), proton nuclear magnetic resonance (1H NMR), Fourier transform infrared spectroscopy (FTIR), bacteriostatic test, and rheological experiments were used to investigate the chemical structure, inherent morphology, and enzymatic corruption of the hydrogel in vitro. The resulting hydrogels exhibited ideal probiotics loading capacity, drug release behavior, excellent antimicrobial activity and variable properties. Crucially, owing to its exceptional biocompatibility and reversible crosslinking network, this hydrogel can function as a three-dimensional extracellular matrix for cells, enabling cells to maintain high vitality and proliferation, and promote wound healing. The aforementioned findings indicated that this novel hydrogel can be a promising candidate as an active-ingredient carrier and scaffold material for tissue engineering.

Biopolymer hydrogels and synergistic blends for tailored wound healing

Biopolymers have a transformative role in wound repair due to their biocompatibility, ability to stimulate collagen production, and controlled drug and growth factor delivery. This article delves into the biological parameters critical to wound healing emphasizing how combinations of hydrogels with reparative properties can be strategically designed to create matrices that stimulate targeted cellular responses at the wound site to facilitate tissue repair and recovery. Beyond a detailed examination of various biopolymer types and their functionalities in wound dressings acknowledging that the optimal choice depends on the specific wound type and application, this evaluation provides concepts for developing synergistic biopolymer blends to create next-generation dressings with enhanced efficiencies. Furthermore, the incorporation of therapeutic agents such as medications and wound healing accelerators into dressings to enhance their efficacy is examined. These agents often possess desirable properties such as antibacterial activity, antioxidant effects, and the ability to promote collagen synthesis and tissue regeneration. Finally, recent advancements in conductive hydrogels are explored, highlighting their capabilities in treatment and real-time wound monitoring. This comprehensive resource emphasizes the importance of optimizing ingredient efficiency besides assisting researchers in selecting suitable materials for personalized wound dressings, ultimately leading to more sophisticated and effective wound management strategies.

Advanced approaches in skin wound healing - a review on the multifunctional properties of MXenes in therapy and sensing

In recent years, the use of MXenes, a class of two-dimensional materials composed of transition metal carbides, nitrides, or carbonitrides, has shown significant promise in the field of skin wound healing. This review explores the multifunctional properties of MXenes, focusing on their electrical conductivity, photothermal effects, and biocompatibility in this field. MXenes have been utilized to develop advanced wound healing devices such as hydrogels, patches, and smart bandages for healing examination. These devices offer enhanced antibacterial activity, promote tissue regeneration, and provide real-time monitoring of parameters. The review highlights the synthesis methods, chemical features, and biological effects of MXenes, emphasizing their role in innovative skin repair strategies. Additionally, it discusses the potential of MXene-based sensors for humidity, pH, and temperature monitoring, which are crucial for preventing infections and complications in wound healing. The integration of MXenes into wearable devices represents a significant advancement in wound management, promising improved clinical outcomes and enhanced quality of life for patients.

Advances in Smart-Response Hydrogels for Skin Wound Repair

Hydrogels have emerged as promising candidates for biomedical applications, especially in the treatment of skin wounds, as a result of their unique structural properties, highly tunable physicochemical properties, and excellent biocompatibility. The integration of smart-response features into hydrogels allows for dynamic responses to different external or internal stimuli. Therefore, this paper reviews the design of different smart-responsive hydrogels for different microenvironments in the field of skin wound therapy. First, the unique microenvironments of three typical chronic difficult-to-heal wounds and the key mechanisms affecting wound healing therapeutic measures are outlined. Strategies for the construction of internal stimulus-responsive hydrogels (e.g., pH, ROS, enzymes, and glucose) and external stimulus-responsive hydrogels (e.g., temperature, light, electricity, and magnetic fields) are highlighted from the perspective of the wound microenvironment and the in vitro environment, and the constitutive relationships between material design, intelligent response, and wound healing are revealed. Finally, this paper discusses the severe challenges faced by smart-responsive hydrogels during skin wound repair and provides an outlook on the combination of smart-responsive hydrogels and artificial intelligence to give scientific direction for creating and using hydrogel dressings that respond to stimuli in the clinic.

Nanoengineered Injectable Hydrogel: An Advanced Radioprotective Barrier with Magnetic Hyperthermia Synergy

Despite its effectiveness in eradicating cancer cells, current tumor radiotherapy often causes irreversible damage to the surrounding healthy tissues. To address this issue and enhance therapeutic outcomes, we developed a multifunctional injectable hydrogel that integrates electromagnetic shielding and magnetothermal effects. This innovation aims to improve the efficacy of brachytherapy while protecting adjacent normal tissues. Recognizing the limitations of existing hydrogel materials in terms of stretchability, durability, and single functionality, we engineered a composite hydrogel by self-assembling nickel nanoparticles on the surface of liquid metal particles and embedding them into an injectable hydrogel matrix. The resulting composite material demonstrates superior electromagnetic interference shielding performance (74.89 dB) and a rapid magnetothermal heating rate (10.9 °C/min), significantly enhancing its in vivo applicability. The experimental results confirm that this innovative nanocomposite hydrogel effectively attenuates electromagnetic waves during brachytherapy, thereby protecting normal tissues surrounding the tumor and enhancing radiotherapy efficacy through magnetothermal therapy. This study advances the safety and effectiveness of cancer treatments and provides new insights into the development of multifunctional biomedical materials, promoting the innovative application of nanotechnology in the medical field.

Dually-crosslinked ionic conductive hydrogels reinforced through biopolymer gellan gum for flexible sensors to monitor human activities

Human-machine interactions, monitoring of health equipment, and gentle robots all depend considerably on flexible strain sensors. However, making strain sensors have better mechanical behavior and an extensive sensing range remains an urgent difficulty. In this study, poly acrylamide-co-butyl acrylate with gellan gum (poly(AAm-co-BA)@GG) hydrophobic association networks and intermolecular hydrogen bonding interactions are used to fabricate dual cross-linked hydrogels for wearable resistive-type strain sensors. This could be an acceptable way to minimize the limitations in hydrogels previously identified. The robust fracture strength (870 kPa) and exceptional stretchability (1297 %) of the hydrogel arise from the collaborative action of intermolecular hydrogen bonding and hydrophobic associations. It also demonstrates exceptional resilience to repeated cycles of uninterrupted stretching and relaxation, retaining its structural integrity. The response and restoration times are 110 and 120 ms respectively. Furthermore, a wide sensing range (0-900 %), notable sensitivity across various strain levels, and an impressive gauge factor (GF) of 31.51 with high durability were observed by the dual cross-linked (DC) hydrogel-based strain sensors. The measured conductivity of the hydrogel was 0.32 S/m which is due to the incorporation of NaCl. Therefore, the hydrogels can be tailored to function as wearable strain sensors that can detect subtle human gestures like speech patterns, distinguish between distinct words, and recognize vibrations of the larynx during drinking, as well as large joint motions like wrist, finger, and elbow. Furthermore, these hydrogels are capable of reliably distinguishing and reproducing various printed text. These findings imply that any electronic device that demands strain-sensing functionality might make use of these developed materials.

Smart Dressings and Their Applications in Chronic Wound Management

During chronic wound healing, the inflammatory phase can endure for extended periods, heavily impeding or halting the process. Regular inspections and dressing changes are crucial. Modern dressings like hydrogels, hydrocolloids, and foam provide protection and an optimal healing environment. However, they have limitations in offering real-time wound bed status and healing rate. Evaluation relies heavily on direct observation, and passive dressings fail to identify subtle healing differences, preventing adaptive adjustments in biological factors and drug concentrations. In recent years, the clinical field recognizes the value of integrating intelligent diagnostic tools into wound dressings. By monitoring biomarkers linked to chronic wounds' inflammatory state, real-time data can be captured, reducing medical interventions and enabling more effective treatment plans. This fosters innovation in chronic wound care. Researchers have developed smart dressings with sensing, active drug delivery, and self-adjustment capabilities. These dressings detect inflammatory markers like temperature, pH, and oxygen content, enhancing drug bioavailability on the wound surface. As wound healing technology evolves, these smart dressings hold immense potential in chronic wound care and treatment. This comprehensive review updates our understanding on the role and mechanism of action of the smart dressings in chronic refractory wounds by summarizing and discussing the latest research progresses, including the intelligent monitoring of wound oxygen content, temperature, humidity, pH, infection, and enzyme kinetics; intelligent drug delivery triggered by temperature, pH, near-infrared, and electricity; as well as the intelligent self-adjustment of pressure and shape. The review also delves into the constraints and future perspectives of smart dressings in clinical settings, thereby advancing the development of smart wound dressings for chronic wound healing and their practical application in clinical practice.

MXene-based composites in smart wound healing and dressings

MXenes, a class of two-dimensional materials, exhibit considerable potential in wound healing and dressing applications due to their distinctive attributes, including biocompatibility, expansive specific surface area, hydrophilicity, excellent electrical conductivity, unique mechanical properties, facile surface functionalization, and tunable band gaps. These materials serve as a foundation for the development of advanced wound healing materials, offering multifunctional nanoplatforms with theranostic capabilities. Key advantages of MXene-based materials in wound healing and dressings encompass potent antibacterial properties, hemostatic potential, pro-proliferative attributes, photothermal effects, and facilitation of cell growth. So far, different types of MXene-based materials have been introduced with improved features for wound healing and dressing applications. This review covers the recent advancements in MXene-based wound healing and dressings, with a focus on their contributions to tissue regeneration, infection control, anti-inflammation, photothermal effects, and targeted therapeutic delivery. We also discussed the constraints and prospects for the future application of these nanocomposites in the context of wound healing/dressings.

Multicomponent Synergistic Antibacterial Hydrogel Based on Gelatin-Oxidized Carboxymethyl Cellulose for Wound Healing of Drug-Resistant Chronic Infection

Bacterial invasion hinders the healing process of wound, leading to the formation of chronic infected wound; meanwhile, the misuse of antibiotics has resulted in the emergence of numerous drug-resistant bacteria. The application of conventional antimicrobial methods and wound treatment techniques is not appropriate for wound dressings. In this paper, quaternized poly(vinyl alcohol) (QPVA) and pomegranate-like copper uniformly doped polydopamine nanoparticles (PDA@Cu) were introduced into a gelatin-oxidized carboxymethyl cellulose system to form a multicomponent synergistic antibacterial hydrogel (GOQ3P3). Polydopamine improves the biocompatibility and prevents the detachment of Cu nanoparticles. It can achieve synergistic antibacterial effects through quaternary ammonium salt-inorganic nanoparticle photothermal treatment under 808 nm near-infrared (NIR) irradiation. It exhibits highly efficient and rapid bactericidal properties against Escherichia coli, Staphylococcus aureus, and MRSA (methicillin-resistant Staphylococcus aureus) with an antibacterial rate close to 100%. The gel scaffold composed of macromolecules gives the hydrogel excellent mechanical properties, adhesive capabilities, self-healing characteristics, biocompatibility, and pH degradation and promotes cell adhesion and migration. In a full-thickness wound healing model infected with MRSA, GOQ3P3 controls inflammatory responses, accelerates collagen deposition, promotes angiogenesis, and enhances wound closure in the wound healing cascade reaction. This study provides a feasible strategy for constructing dressings targeting chronic infection wounds caused by drug-resistant bacteria.

A novel ZIF-8@IL-MXene/poly (N-isopropylacrylamide) nanocomposite hydrogel toward multifunctional adsorption

Phenols, dyes, and metal ions present in industrial wastewater can adversely affect the environment and leach biological carcinogens. Given that the current research focuses only on the removal of one or two of those categories. Herein, this work reports a novel ZIF-8@IL-MXene/Poly(N-isopropylacrylamide) (NIPAM) nanocomposite hydrogel that can efficiently and conveniently absorb and separate multiple pollutants from industrial wastewater. Ionic liquid (IL) was grafted onto MXene surfaces using a one-step method, and then incorporated into NIPAM monomer solutions to obtain the IL-MXene/PNIPAM composite hydrogel via in-situ polymerization. ZIF-8@IL-MXene/PNIPAM nanocomposite hydrogels were obtained by in-situ growth of ZIF-8 on the pore walls of composite hydrogels. As-prepared nanocomposite hydrogel showed excellent mechanical properties and can withstand ten repeated compressions without any damage, the specific surface area increased by 100 times, and the maximum adsorption capacities for p-nitrophenol (4-NP), crystal violet (CV), and copper ion (Cu2+) were 198.40, 325.03, and 285.65 mg g-1, respectively, at room temperature. The VPTTs of all hydrogels ranged from 33 to 35 °C, so the desorption process can be achieved in deionized water at 35-40 °C, and its adsorption capacities after five adsorption-desorption cycles decreased to 79%, 91%, and 29% for 4-NP, CV, and Cu2+, respectively. The adsorption data fitting results follow pseudo-second-order kinetics and Freundlich models, which is based on multiple interactions between the functional groups contained in hydrogels and adsorbent molecules. The hydrogel is the first to realize the high-efficiency adsorption of phenols, dyes and metal ions in industrial wastewater simultaneously, and the preparation process of hydrogels is environmentally friendly. Also, giving hydrogel multifunctional adsorption is beneficial to promote the development of multifunctional adsorption materials.

Bioactive materials for in vivo sweat gland regeneration

Loss of sweat glands (SwGs) commonly associated with extensive skin defects is a leading cause of hyperthermia and heat stroke. In vivo tissue engineering possesses the potential to take use of the body natural ability to regenerate SwGs, making it more conducive to clinical translation. Despite recent advances in regenerative medicine, reconstructing SwG tissue with the same structure and function as native tissue remains challenging. Elucidating the SwG generation mechanism and developing biomaterials for in vivo tissue engineering is essential for understanding and developing in vivo SwG regenerative strategies. Here, we outline the cell biology associated with functional wound healing and the characteristics of bioactive materials. We critically summarize the recent progress in bioactive material-based cell modulation approaches for in vivo SwG regeneration, including the recruitment of endogenous cells to the skin lesion for SwG regeneration and in vivo cellular reprogramming for SwG regeneration. We discussed the re-establishment of microenvironment via bioactive material-mediated regulators. Besides, we offer promising perspectives for directing in situ SwG regeneration via bioactive material-based cell-free strategy, which is a simple and effective approach to regenerate SwG tissue with both fidelity of structure and function. Finally, we discuss the opportunities and challenges of in vivo SwG regeneration in detail. The molecular mechanisms and cell fate modulation of in vivo SwG regeneration will provide further insights into the regeneration of patient-specific SwGs and the development of potential intervention strategies for gland-derived diseases.

Optimization of rapid self-healing and self-adhesive gluten/guar gum crosslinked gel for strain sensors and electronic devices

In this study, a smart strain sensor based on gluten/guar gum (GG) copolymer containing a combination of additives was developed. The mix proportions of strain sensors were designed using Taguchi method coupled with Grey relational analysis. L16 orthogonal array with three factors, viz. tannic acid (TA), glycerol and sodium chloride (NaCl) at four-levels each was optimized. The addition of TA substantially enhanced tensile strength, self-adhesion ability and conductivity. The self-adhesion ability could also be improved by adding NaCl in range of 0-5 wt%. The presence of glycerol in strain sensors could reduce the self-healing time which was found in the range of 28.75-150 s. In addition, the incorporation of glycerol into gel also improved stretchability of strain sensors. The best mix proportion of strain sensor was found to be 3.75 wt% TA, 30 vol% glycerol and 5 wt% NaCl. The best mixture of stain sensor showed the highest gauge factor (GF) of 0.61 % at a stretchability of 665 % and rapid self-healing at 70 s. This strain sensor could be applied to monitor human limb movements in a wide temperature range from -20 °C to 50 °C. Furthermore, the obtained gel was successfully used as electronic devices and self-powered sensors.

Cryptotanshinone-Doped Photothermal Synergistic MXene@PDA Nanosheets with Antibacterial and Anti-Inflammatory Properties for Wound Healing

Humans are threatened by bacteria and other microorganisms, resulting in countless pathogen-related infections and illnesses. Accumulation of reactive oxygen species (ROS) in infected wounds activates strong inflammatory responses. The overuse of antibiotics has led to increasing bacterial resistance. Therefore, effective ROS scavenging and bactericidal capacity are essential and the advanced development of collaborative therapeutic techniques to combat bacterial infections is needed. Here, this work developes an MXene@polydopamine-cryptotanshinone (MXene@PDA-CPT) antibacterial nanosystem with excellent reactive oxygen and nitrogen species scavenging ability, which effectively inactivates drug-resistant bacteria and biofilms, thereby promoting wound healing. In this system, the adhesion of polydopamine nanoparticles to MXene produced a photothermal synergistic effect and free radical scavenging activity, presenting a promising antibacterial and anti-inflammatory strategy. This nanosystem causes fatal damage to bacterial membranes. The loading of cryptotanshinone further expanded the advantages of the system, causing a stronger bacterial killing effect and inflammation mitigatory effect with desired biosafety and biocompatibility. In addition, combining nanomaterials and active ingredients of traditional Chinese medicine, this work provides a new rationale for the future development of wound dressings, which contributes to eliminating bacterial resistance, delaying disease deterioration, and alleviating the pain of patients.

Tailored biomedical materials for wound healing

Wound healing is a long-term, multi-stage biological process that mainly includes haemostatic, inflammatory, proliferative and tissue remodelling phases. Controlling infection and inflammation and promoting tissue regeneration can contribute well to wound healing. Smart biomaterials offer significant advantages in wound healing because of their ability to control wound healing in time and space. Understanding how biomaterials are designed for different stages of wound healing will facilitate future personalized material tailoring for different wounds, making them beneficial for wound therapy. This review summarizes the design approaches of biomaterials in the field of anti-inflammatory, antimicrobial and tissue regeneration, highlights the advanced precise control achieved by biomaterials in different stages of wound healing and outlines the clinical and practical applications of biomaterials in wound healing.

Polydopamine-Modified MXene-Integrated Poly(N-isopropylacrylamide) to Construct Ultrafast Photoresponsive Bilayer Hydrogel Actuators with Smart Adhesion

In nature, living organisms, such as octopuses, cabrito, and frogs, have already evolved admirable adhesive abilities for better movement and predation in response to the surroundings. Inspired by biological structures, researchers have made enormous efforts in developing actuators that can respond to external stimuli, while such adhesive property is very desired, yet there is still limited research in responsive hydrogel actuators. Here, a bilayer actuator with high stretchability and robust interface bonding is presented, which has a smart adhesion and thermoreception function. The system consists of an adhesive passive layer copolymerized of amphoteric ([2-(methacryloyloxy) ethyl] dimethyl-(3-sulfopropyl), SBMA) and acrylic acid (AA), and an active layer hydrogel composed of poly(N-isopropylacrylamide) (PNIPAm) containing polydopamine-modified MXene (P-MXene) and calcium chloride (CaCl2). The coordination of carboxylate and Ca2+ at the interface of the two layers enhances the interfacial bonding from 14 to 30 N m-1, which facilitates withstanding large strain and preventing stratification. The resulting hydrogel actuator can bend approximately 360° in a mere 10 s, exhibiting excellent photothermal effect, a large angle bending deformation, and ultrafast photoresponsive ability. As a proof of concept, the photothermal actuators are programmed to present various shapes and grab objects. Importantly, the hydrogel actuator exhibits remarkable adhesion capabilities toward diverse substrates, with a maximum peel force of up to 280 N m-1. Relying on their own adhesion and the photoresponse properties, these flexible adhesion actuators show outstanding gripping capability, enabling them to grip and release objects of different shapes and weights. More interestingly, the hydrogel exhibits a smart adjustable adhesion capability at different temperatures, which enables it as a gripper to recognize temperature signals through real-time different feedback actions based on its own adhesion. This study presents innovative insights into biomimetic hydrogel actuators, providing new opportunities for developing intelligent soft robots with multiple functions.

Injectable hydrogel nanoarchitectonics with near-infrared controlled drug delivery for in situ photothermal/endocrine synergistic endometriosis therapy

BACKGROUND

Endometriosis is a common gynecological disease in women of childbearing age. Commonly used treatment methods, such as endocrine and surgical therapies, display poor therapeutic effects with a high relapse probability. Thus, novel treatments for endometriosis are required.

METHODS

In our study, polydopamine (PDA), letrozole (LTZ), and agarose (AG) hydrogels were combined to construct an injectable hydrogel with near-infrared controlled drug delivery named LTZ-PDA@AG hydrogel for endometriosis treatment. The release of letrozole can be accurately controlled by the near-infrared light intensity, exposure duration, polydopamine concentration, and hydrogel composition. Meanwhile, we isolated endometrial stromal cells from endometrium in patients with endometriosis, and constructed the rats' model of endometriosis to verify the biological effects of LTZ-PDA@AG hydrogel.

RESULTS

Owing to the sufficiently deep penetration of near-infrared light, the LTZ-PDA@AG hydrogel displayed a high temperature increase for efficient photothermal therapy. In addition, high local temperatures can further enhance the diffusion and penetration of letrozole, thereby achieving excellent therapeutic effect in vivo. Importantly, the in vivo and vitro test demonstrated the capacity of the nanocomposite hydrogel for endocrine-photothermal synergistic therapy and the biocompatibility.

CONCLUSION

Our work proposes a novel concept for precision endometriosis therapy by photothermal-enhanced endocrine therapy for endometriosis, which is proposed for the first time for the treatment of endometriosis and demonstrates excellent potential for further clinical translation.

TRIAL REGISTRATION

Not applicable. LTZ-PDA@AG hydrogels were synthesized and displayed a high temperature increase for efficient photothermal therapy under NIR. The present study shows the capacity of the nanocomposite hydrogel for endocrine-photothermal synergistic therapy and the biocompatibility.

Antifouling Electrochemiluminescence Biosensor Based on Bovine Serum Albumin Hydrogel for the Accurate Detection of p53 Gene in Human Serum

To detect biomarkers in complex samples, it is fundamental to avoid the nonspecific adsorption of impurities to improve the selectivity of biosensors. In this study, a sensitive antifouling electrochemiluminescence biosensor was proposed based on bovine serum albumin (BSA)- and exonuclease III (Exo III)-mediated nucleic acid cycle signal amplification strategy. Ti3C2Tx-NH4, which has a large surface area and high metal conductivity, was crosslinked with BSA to improve the conductivity of the sensing interface, which shows antifouling performance excellently due to the electrical neutrality and good hydrophilicity of BSA hydrogel. The cyclic amplification strategy based on Exo III and DNA hybridization chain reaction significantly amplified the electrochemiluminescence signal and improved the sensitivity of p53 gene detection. The linear range of the biosensor is 1 fM-1 nM with a detection limit of 0.26 fM. More importantly, the sensor showed excellent selectivity when it was used to detect the p53 gene in real samples, such as serum. Thus, this unique antifouling sensing interface is expected to construct various electrochemical biosensors in clinical diagnosis and biopathological analysis.

Three-Dimensional Printing Multi-Drug Delivery Core/Shell Fiber Systems with Designed Release Capability

A hydrogel system with the ability to control the delivery of multiple drugs has gained increasing interest for localized disease treatment and tissue engineering applications. In this study, a triple-drug-loaded model based on a core/shell fiber system (CFS) was fabricated through the co-axial 3D printing of hydrogel inks. A CFS with drug 1 loaded in the core, drug 2 in the shell part, and drug 3 in the hollow channel of the CFS was printed on a rotating collector using a co-axial nozzle. Doxorubicin (DOX), as the model drug, was selected to load in the core, with the shell and channel part of the CFS represented as drugs 1, 2, and 3, respectively. Drug 2 achieved the fastest release, while drug 3 showed the slowest release, which indicated that the three types of drugs printed on the CFS spatially can achieve sequential triple-drug release. Moreover, the release rate and sustained duration of each drug could be controlled by the unique core/shell helical structure, the concentration of alginate gels, the cross-linking density, the size and number of the open orifices in the fibers, and the CFS. Additionally, a near-infrared (NIR) laser or pH-responsive drug release could also be realized by introducing photo-thermal materials or a pH-sensitive polymer into this system. Finally, the drug-loaded system showed effective localized cancer therapy in vitro and in vivo. Therefore, this prepared CFS showed the potential application for disease treatment and tissue engineering by sequential- or stimulus-responsively releasing multi-drugs.

Advances in the application of Mxene nanoparticles in wound healing

Skin is the largest organ of the human body. It plays a vital role as the body's first barrier: stopping chemical, radiological damage and microbial invasion. The importance of skin to the human body can never be overstated. Delayed wound healing after a skin injury has become a huge challenge in healthcare. In some situations, this can have very serious and even life-threatening effects on people's health. Various wound dressings have been developed to promote quicker wound healing, including hydrogels, gelatin sponges, films, and bandages, all work to prevent the invasion of microbial pathogens. Some of them are also packed with bioactive agents, such as antibiotics, nanoparticles, and growth factors, that help to improve the performance of the dressing it is added to. Recently, bioactive nanoparticles as the bioactive agent have become widely used in wound dressings. Among these, functional inorganic nanoparticles are favored due to their ability to effectively improve the tissue-repairing properties of biomaterials. MXene nanoparticles have attracted the interest of scholars due to their unique properties of electrical conductivity, hydrophilicity, antibacterial properties, and biocompatibility. The potential for its application is very promising as an effective functional component of wound dressings. In this paper, we will review MXene nanoparticles in skin injury repair, particularly its synthesis method, functional properties, biocompatibility, and application.

Functional hydrogels for the repair and regeneration of tissue defects

Tissue defects can be accompanied by functional impairments that affect the health and quality of life of patients. Hydrogels are three-dimensional (3D) hydrophilic polymer networks that can be used as bionic functional tissues to fill or repair damaged tissue as a promising therapeutic strategy in the field of tissue engineering and regenerative medicine. This paper summarises and discusses four outstanding advantages of hydrogels and their applications and advances in the repair and regeneration of tissue defects. First, hydrogels have physicochemical properties similar to the extracellular matrix of natural tissues, providing a good microenvironment for cell proliferation, migration and differentiation. Second, hydrogels have excellent shape adaptation and tissue adhesion properties, allowing them to be applied to a wide range of irregularly shaped tissue defects and to adhere well to the defect for sustained and efficient repair function. Third, the hydrogel is an intelligent delivery system capable of releasing therapeutic agents on demand. Hydrogels are capable of delivering therapeutic reagents and releasing therapeutic substances with temporal and spatial precision depending on the site and state of the defect. Fourth, hydrogels are self-healing and can maintain their integrity when damaged. We then describe the application and research progress of functional hydrogels in the repair and regeneration of defects in bone, cartilage, skin, muscle and nerve tissues. Finally, we discuss the challenges faced by hydrogels in the field of tissue regeneration and provide an outlook on their future trends.

Preparation, thermal response mechanisms and biomedical applications of thermosensitive hydrogels for drug delivery

INTRODUCTION

Drug treatment is one of the main ways of coping with disease today. For the disadvantages of drug management, thermosensitive hydrogel is used as a countermeasure, which can realize the simple sustained release of drugs and the controlled release of drugs in complex physiological environments.

AREAS COVERED

This paper talks about thermosensitive hydrogels that can be used as drug carriers. The common preparation materials, material forms, thermal response mechanisms, characteristics of thermosensitive hydrogels for drug release and main disease treatment applications are reviewed.

EXPERT OPINION

When thermosensitive hydrogels are used as drug loading and delivery platforms, desired drug release patterns and release profiles can be tailored by selecting raw materials, thermal response mechanisms, and material forms. The properties of hydrogels prepared from synthetic polymers will be more stable than natural polymers. Integrating multiple thermosensitive mechanisms or different kinds of thermosensitive mechanisms on the same hydrogel is expected to realize the spatiotemporal differential delivery of multiple drugs under temperature stimulation. The industrial transformation of thermosensitive hydrogels as drug delivery platforms needs to meet some important conditions.

Injectable In Situ Photocrosslinked Hydrogel Dressing for Infected Wound Healing

A traditional injectable photocrosslinked hydrogel had disadvantages of the residual photoinitiator and toxic crosslinker, slow in situ curing, and a complex preparation process. At the same time, hydrogels cannot act as artificial skin to restore skin sensory function during the wound healing cycle. In this work, an injectable photocrosslinked hydrogel was prepared which can be quickly in situ cured without photoinitiator. Oxidized sodium alginate was used as a natural macromolecular crosslinking agent to form an injectable hydrogel framework with the photosensitive polymer polyvinyl alcohol bearing styrylpyridinium group (PVA-SBQ). In addition, the hydrogel was endowed with photothermal therapy property after the introduction of biomass-like polydopamine particles. When used as a wound dressing, the hydrogel exhibited an excellent antibacterial property, with an antibacterial rate of 99.56% Escherichia coli and 97.96% Staphylococcus aureus. As a result, the hydrogel could significantly accelerate the repair of infected wounds, with a wound healing rate of 96.45% after 14 days. Moreover, the hydrogel exhibited a sensitive and stable sensing property, making it promising to reconstitute the sensory function of damaged skin during treatment. This work provides an idea for the development of injectable photocrosslinked hydrogel dressing.

A review on accelerated development of skin-like MXene electrodes: from experimental to machine learning

Foreshadowing future needs has catapulted the progress of skin-like electronic devices for human-machine interactions. These devices possess human skin-like properties such as stretchability, self-healability, transparency, biocompatibility, and wearability. This review highlights the recent progress in a promising material, MXenes, to realize soft, deformable, skin-like electrodes. Various structural designs, fabrication strategies, and rational guidelines adopted to realize MXene-based skin-like electrodes are outlined. We explicitly discussed machine learning-based material informatics to understand and predict the properties of MXenes. Finally, an outlook on the existing challenges and the future roadmap to realize soft skin-like MXene electrodes to facilitate technological advances in the next-generation human-machine interactions has been described.

Tailoring and application of a multi-responsive cellulose nanofibre-based 3D nanonetwork wound dressing

The rapid loss of drugs and the weak curative effects due to cyclical urination are the main reasons why wound heal with difficulty after bladder tumour resection. Here, a bioinspired cellulose nanofibre (CNF)-based magnetic 3D nanonetwork wound dressing with excellent tissue adhesion and biocompatibility is designed by the assembly of pH- and near infrared-responsive CNF nanoskeletons, magnetic switching Fe₃O₄ nanoparticles, and temperature switching Pluronic®F-127. The dressing with high loading capacity for mitomycin and indocyanine green can form a sticky 3D nanonetwork at the wound site and remain for a long time to release drugs through an external magnetic field. Interestingly, the dressing possessed excellent antibacterial activity, bacterial biofilm elimination, T24 tumour cell killing, and wound healing promotion through photothermal, photodynamic, and chemotherapy. Therefore, it has promising application for bladder postoperative infected wound healing to avoid rapid loss of drugs due to cyclical urination.

Intestine-inspired wrinkled MXene microneedle dressings for smart wound management

Composite MXene-based materials are prone to crack propagation, thus limiting their tensile properties. Numerous efforts have been devoted to removing material constraints and fabricating unitary MXene elastic films. Here, for the first time, inspired by the intestinal wrinkles and villi structure, we presented a ductile, biologically friendly, and highly conductive MXene-based microneedle (MMN) dressing composed of stacked MXene film and superfine microneedle arrays through a simple stretching and laser engraving strategy for wound healing. By utilizing photothermal responsive MXene, periodic porous structures, and a temperature-responsive polymer to construct the MMN dressing, the system can act as an effective route for facilitating controllable drug delivery controlled by near-infrared (NIR) irradiation. In addition, superior conductivity imparts them with the capacity to realize continuous and steady monitoring of motion sensing. The practical performance further demonstrated that the versatile MMN dressing showed obvious therapeutic efficacy in vivo animal wound models. Thus, it is believed that MMN dressings with biomimetic structures, controllable drug release, and conductive pathways will open a new chapter for wound management and widen other practical applications in biomedical fields, such as artificial tendons and soft robotics. STATEMENT OF SIGNIFICANCE: MXene-based materials have been demonstrated as critical tools in advancing our understanding of wound healing. However, the rapid crack propagation is a constraint on their tensile properties. Here, inspired by the intestinal wrinkles and villi structure, a single-step method has also been discussed to present a MXene-based microneedle dressing composed of unitary MXene elastic film and superfine microneedle arrays. At the same time, the dressing with biomimetic structures, controllable drug release, and conductive pathways has prospects in intelligent wound management and varieties of related biomedical fields.

Fabrication and desired properties of conductive hydrogel dressings for wound healing

Conductive hydrogels are platforms recognized as constituting promising materials for tissue engineering applications. This is because such conductive hydrogels are characterized by the inherent conductivity properties while retaining favorable biocompatibility and mechanical properties. These conductive hydrogels can be particularly useful in enhancing wound healing since their favorable conductivity can promote the transport of essential ions for wound healing via the imposition of a so-called transepithelial potential. Other valuable properties of these conductive hydrogels, such as wound monitoring, stimuli-response etc., are also discussed in this study. Crucially, the properties of conductive hydrogels, such as 3D printability and monitoring properties, suggest the possibility of its use as an alternative wound dressing to traditional dressings such as bandages. This review, therefore, seeks to comprehensively explore the functionality of conductive hydrogels in wound healing, types of conductive hydrogels and their preparation strategies and crucial properties of hydrogels. This review will also assess the limitations of conductive hydrogels and future perspectives, with an emphasis on the development trend for conductive hydrogel uses in wound dressing fabrication for subsequent clinical applications.

Room-Temperature Self-Healing Conductive Elastomers for Modular Assembly as a Microfluidic Electrochemical Biosensing Platform for the Detection of Colorectal Cancer Exosomes

Modular components for rapid assembly of microfluidics must put extra effort into solving leakage and alignment problems between individual modules. Here, we demonstrate a conductive elastomer with self-healing properties and propose a modular microfluidic component configuration system that utilizes self-healing without needing external interfaces as an alternative to the traditional chip form. Specifically, dual dynamic covalent bond crosslinks (imine and borate ester bonds) established between Polyurethane (PU) and 2-Formylbenzeneboronic acid (2-FPBA) are the key to a hard room-temperature self-healing elastomeric substrate PP (PU/2-FPBA). An MG (MXene/GO) conductive network with stable layer spacing (Al-O bonds) obtained from MXene and graphene oxide (GO) by in situ reduction of metals confers photothermal conductivity to PP. One-step liquid molding obtained a standardized modular component library of puzzle shapes from PP and MGPP (MG/PP). The exosomes were used to validate the performance of the constructed microfluidic electrochemical biosensing platform. The device has a wide detection range (50-10⁵ particles/μL) and a low limit of detection (LOD) (42 particles/μL) (S/N = 3), providing a disposable, reusable, cost-effective, and rapid analysis platform for quantitative detection of colorectal cancer exosomes. In addition, to our knowledge, this is the first exploration of self-healing conductive elastomers for a modular microfluidic electrochemical biosensing platform.

Stretchable, conductive, breathable and moisture-sensitive e-skin based on CNTs/graphene/GelMA mat for wound monitoring

Deep skin wound needs a long wound healing process, in which external force on skin around wound can result in a sharp pain, wound re-damage and interstitial fluid flowing out, increasing the risk of deterioration and even amputation. While the conventional wound dressings cannot provide timely feedback of abnormal wound status and lose best time for wound treatment, real-time monitoring wound status is thus urgently needed for wound management. In this work, a breathable and stretchable electronic skin (i.e., e-skin) named CNTs/graphene/GelMA mat has been developed through electrospinning, ice-templating and in-situ loading method for evaluating wound status. The obtained porosity, swelling ratio and vapor transmission rate of the CNTs/graphene/GelMA mat are 55 %, 180 % and 3378.2 h^-1 day^-1, respectively. And owing to the good porous, nanofibrous architecture and excellent breathability of the mat, L929 cells grow and well spread on the CNTs/graphene/GelMA mat. In addition, the gauge factors of the prepared conductive CNTs/graphene/GelMA mat as a strain sensor are 15.4 and 72.9 in the strain ranges of 0-70 % and 70-85 %, respectively, matching the mechanical performance of human skin. The sensitivity coefficient of the mat for moisture sensing is 12.05, indicating its high efficiency for monitoring and warning interstitial fluid outflow from wound. Furthermore, the integration of CNTs/graphene/GelMA mat with a portable device is feasible to monitor strain and moisture on a rat model with abdominal wound. The healing process of the wounds treated with CNTs/graphene/GelMA mat is similar to that of GelMA mat, indicating that the dosage of CNTs and graphene in the CNTs/graphene/GelMA mat has negligible effect on the mat histocompatibility. The CNTs/graphene/GelMA mat demonstrates the application potential in wound management, home medical diagnosis and human-machine interactions.

Supramolecular Hydrogel Dressing: Effect of Lignin on the Self-Healing, Antibacterial, Antioxidant, and Biological Activity Improvement

The functionalization and performance improvement of supramolecular hydrogels are very important for their application in the wound dressing field. Inspired by the role of lignin in plant cell walls, sulfonated lignin is introduced into the supramolecular hydrogel to improve functionality, mechanical strength, and biological activity. According to the chemical structure characteristics of the sulfonated lignin and the requirements for wound dressing, a novel polymer system is designed and successfully synthesized to cooperate with the sulfonated lignin to form the supramolecular hydrogel dressings. The introduction of the sulfonated lignin can effectively improve the mechanical strength, self-healing property, antioxidant activity, and biological activity of the obtained supramolecular hydrogel dressings. In the rat wound healing model experiment, the supramolecular hydrogel dressings can maintain the moist environment on the wound surface, clean up the excretion of wound tissue, promote wound healing, and reduce the occurrence of inflammation. This supramolecular hydrogel dressing shows obvious potential for wound management and treatment by a facile and effective approach and has great promise for long-term application of wound dressings. This strategy for designing polymers according to the chemical structure characteristics of the sulfonated lignin and the application requirements has reference value for further development of biomass-based compound materials.

Ultrastretchable, Self-Healable, and Tissue-Adhesive Hydrogel Dressings Involving Nanoscale Tannic Acid/Ferric Ion Complexes for Combating Bacterial Infection and Promoting Wound Healing

Preventing bacterial infections and accelerating wound closure are essential in the process of wound healing. Current wound dressings lack enough mechanical properties, self-healing ability, and tissue adhesiveness, and the bacterial killing also relies on the use of antibiotic drugs. Herein, a well-designed hybrid hydrogel dressing is constructed by simple copolymerization of acrylamide (AM), 3-acrylamido phenylboronic acid (AAPBA), chitosan (CS), and the nanoscale tannic acid (TA)/ferric ion (Fe³⁺) complex (TFe). The resulting hydrogel possesses lots of free catechol, phenylboronic acid, amine, and hydroxyl groups and contains many reversible and dynamic bonds such as multiple hydrogen bonds and boronate ester bonds, thereby showing satisfactory mechanical properties, fast self-healing ability, and desirable tissue-adhesive performance. Benefiting from the high photothermal conversion efficiency of the TFe, the hydrogel exhibits satisfactory antibacterial activity against both Gram-positive and Gram-negative bacteria. Moreover, the embedded TFe also endows the hydrogel with good antioxidant activity, anti-inflammatory property, and cell proliferation to promote tissue regeneration. Remarkably, in vivo animal assays reveal that the hybrid hydrogel effectively eliminates biofilm bacteria in the wound sites and accelerates the healing process of infected wounds. Taken together, the developed versatile hydrogels overcome the shortcomings of traditional wound dressings and are expected to become potential antibacterial dressings for future biomedical applications.

Pressure-sensitive antibacterial hydrogel dressing for wound monitoring in bed ridden patients

Pressure ulcer is a common chronic injury in the bedridden population. The wound is easily subjected to secondary pressure injury due to the inconvenient mobility of patients, which greatly prolongs the hospital stay of patients and is highly prone to wound infection or other complications. It is urgent to develop a multifunctional wound dressing with pressure sensing, real-time monitoring, and wound therapy to overcome the secondary pressure injury during treatment. Here, a polyvinyl alcohol/acrylamide-ionic liquid hydrogel dressing is designed based on the antibacterial property and electrical conductivity of imidazolidine ionic liquids. Compared with existing pressure-sensing hydrogels, the hydrogel exhibits extremely high pressure sensitivity (9.19 kPa^-1). Meanwhile, the good real-time responsiveness, stable signal output as well as excellent mechanical properties enable the hydrogel to monitor human movement on a large scale, and transmit the pressure status of patient wounds to nursing staff in a timely manner to avoid secondary pressure injuries. In addition, this hydrogel dressing exhibits a wide range of antibacterial activities against Gram-negative and Gram-positive bacteria as well as fungi, and has a significant therapeutic effect on full-thickness skin wounds by inhibiting wound infection, rapidly eradicating inflammation, promoting proliferation and tissue remodeling. This multifunctional hydrogel dressing opens a therapeutic and regulatory two-pronged strategy avenue through chronic wound management and pressure sensing monitoring.

Smart Polycationic Hydrogel Dressing for Dynamic Wound Healing

It is challenging for traditional wound dressings to adapt to the complex and changeable environment, due to the lack of stable, efficient, and continuous bactericidal activity. They also cannot be satisfied in a multifunctional sensing platform to reconstruct skin sensory functions for human health monitoring. A multifunctional hydrogel dressing is developed here for the treatment of infected wounds and human health monitoring, which is based on alginate and polycation. The in situ polymerization and solvent displacement method are used to functionalize the hydrogel for the improvement of antifreezing, water retention, and environmental adaptability, as well as the adhesion and photothermal property. As a wound dressing, the as-prepared hydrogel exhibits an excellent antibacterial property against both Escherichia coli and Staphylococcus aureus. In a rat model of full-thickness wound infection, it significantly accelerates the healing of infected wounds with a high healing rate of 96.49%. In the further multifunctional sensory tests, the hydrogel shows multiple response modes of strain, pressure and temperature, and sensing stability. An idea is provided here to develop a smart hydrogel dressing that can accelerate wound healing and achieve human health monitoring.

Poly(N-isopropylacrylamide) Based Electrically Conductive Hydrogels and Their Applications

Poly(N-isopropylacrylamide) (PNIPAM) based electrically conductive hydrogels (PNIPAM-ECHs) have been extensively studied in recent decades due to their thermal-responsive (leading to the volume change of hydrogels) and electrically conductive performance. The incorporation of conductive components into the PNIPAM hydrogel network makes it become conductive hydrogel, and as a result, the PNIPAM hydrogel could become sensitive to an electrical signal, greatly expanding its application. In addition, conductive components usually bring new stimuli-responsive properties of PNIPAM-based hydrogels, such as near-infrared light and stress/strain responsive properties. PNIPAM-ECHs display a wide range of applications in human motion detection, actuators, controlled drug release, wound dressings, etc. To summarize recent research advances and achievements related to PNIPAM-ECHs, this manuscript first reviews the design and structure of representative PNIPAM-ECHs according to their conductive components. Then, the applications of PNIPAM-ECHs have been classified and discussed. Finally, the remaining problems related to PNIPAM-ECHs have been summarized and a future research direction is proposed which is to fabricate PNIPAM-ECHs with integrated multifunctionality.

Silicene/poly(N-isopropylacrylamide) smart hydrogels as remote light-controlled switches

Smart hydrogels with good flexibility and biocompatibility have been widely used. The common near-infrared (NIR) photothermal agents are facing a trade-off between good photothermal-conversion efficiency and high biocompatibility. Therefore, developing new metal-free photothermal agents with low cost, high biocompatibility and excellent phase stability is still in urgent need. In this study, we successfully combined poly(N-isopropylacrylamide) (PNIPAM) with the two-dimensional (2D) silicene nanosheets via the in situ polymerization method. Attributed to the thermal-responsive nature of PNIPAM and the excellent photothermal properties of 2D silicene, the obtained silicene/PNIPAM composite hydrogels exhibited dual thermal and NIR responsive properties. This smart hydrogel showed rapid, reversible and repeatable NIR light-responsive behaviors. The volume of this smart hydrogels can shrink significantly under NIR irradiation and recover to its original size without the NIR irradiation. Remote near-infrared light-controlled microfluidic pipelines and electronic switches based on obtained silicene/PNIPAM composite hydrogels were also demonstrated. This work significantly broadens the application prospects of silicene-based hydrogels in remote light-controlled devices.