Thermoresponsive Hydrogel-Enabled Thermostatic Photothermal Therapy for Enhanced Healing of Bacteria-Infected Wounds

Aggregation-induced emission-based phototheranostics to combat bacterial infection at wound sites: A review

The healing of chronic wounds infected by bacteria has attracted increasing global concerns. In the past decades, antibiotics have certainly brought hope to cure bacteria-infected chronic wounds. However, the misuse of antibiotics leads to the emergence of numerous multidrug-resistant bacteria, which aggravate the health threat to clinical patients. To address these increasing challenges, scientists are committed to creating novel non-antibiotic strategies to kill bacteria and promote bacteria-infected chronic wound healing. Fortunately, with the quick development of nanotechnology, the representatives of phototherapy, such as photothermal therapy (PTT) and photodynamic therapy (PDT), exhibit promising possibilities in promoting bacteria-infected wound healing. Well-known, photothermal agents and photosensitizers largely determine the effects of PTT and PDT. A common problem for these molecules is the aggregation-induced quenching effect, which highly limits their further applicability in biomedical and clinical fields. Fortunately, the occurrence of aggregation-induced emission luminogens (AIEgens) efficiently overcomes the photobleaching and exhibit advantages, such as strongly aggregated emission, superior photostability, aggregation-enhanced reactive oxygen species (ROS), and heat generation, which makes great sense to the development of PTT and PDT. This article reviews various studies conducted on novel AIEgen-based materials that can mediate potent PDT, PTT, and a combination of PDT and PTT to promote bacteria-infected chronic wound healing.

Synergistic NIR and ultrasound-responsive tellurium nanorods for enhanced antibacterial and osteogenic activity

Bacterial infections and deficient osteogenic activity are the primary factors contributing to the failure of orthopedic implants. In recent years, light- and sound-based external stimulus-responsive therapies have emerged as highly effective in killing drug-resistant bacteria. In this study, we successfully synthesized tellurium nanorods coated with bovine serum albumin (Te@BSA). This novel nanomaterial exhibits excellent biocompatibility and possesses near-infrared light (NIR) and ultrasound (US) synergistic response properties. At a concentration of 100 μg/mL, Te@BSA nanorods, under combined NIR and US treatment, achieved 94 % bacterial eradication against drug-resistant strains, while maintaining cell viability above 90 % in osteoblast cultures. This dual-modality approach minimizes the risk of local thermal damage associated with conventional photothermal therapy, enhancing osteogenic activity by up to 150 % upon NIR exposure. By combining photothermal therapy and sonodynamic therapy, we achieved a remarkable antibacterial effect and enhanced osteogenic capacities in a mild and controlled manner. This study successfully balances antibacterial and osteogenic capabilities. These light- and sound-based external stimulus-responsive strategies aslo offer new perspectives and valuable insights for the surface modification of orthopedic implants.

Chitosan-based hydrogel incorporated with polydopamine and protoporphyrin for photothermal-oxidation sterilization of bacteria-infected wound therapy

Phototherapy has emerged as a potential treatment strategy for bacteria-infected wounds, but the inadequate bacteria-capturing ability and excessive damage to normal tissues from single phototherapy are huge limitations. To solve the issues, herein we report the design of chitosan-based hydrogel with bacteria capturing and combined photothermal/photodynamic sterilization functions. Such hydrogel is prepared by mixing chitosan (CS) as matrix, protoporphyrin (PpIX) as photosensitizer and polydopamine (PDA) as photothermal agent and then chemically cross-linking CS with glutaraldehyde. The resulting CS-PpIX-PDA hydrogel possesses a porous architecture (average pore porosity = 60.9 %), excellent swelling capabilities (swelling ratio = 1855 %) and rheological property (G' > G″). The hydrogel can effectively produce reactive oxygen species (ROS) under 660 nm light irradiation due to the photodynamic effect of PpIX. Owing to the presence of PDA, the hydrogel displays a photoabsorption range between 600 and 1500 nm and can generate maximal temperature of 60 °C within 10 min under 808 nm laser illumination (0.6 W/cm2) through photothermal effect. Besides, under synergetic illumination of 808/660 nm laser, CS-PpIX-PDA hydrogel can induce the death of 99.9999 % of E. coli and 99.99999 % of S. aureus. Importantly, when coated on the wound site, the hydrogel exhibits a remarkable bacteria-trapping ability due to its porous structure and the presence of amino groups on chitosan. Under the excitation of 660/808 nm, the combined photothermal and photodynamic effects can effectively eradicate bacteria. Simultaneously, the hydrogel also demonstrates anti-inflammatory properties and upregulates Heat Shock Protein 90 (HSP90) expression, thereby promoting collagen deposition and facilitating wound healing. Therefore, the study may provide some new insights into the development of multifunctional hydrogel for photothermal-oxidation sterilization of bacteria-infected wound therapy.

Bioinspired Adhesive Hydrogel Platform with Photothermal Antimicrobial, Antioxidant, and Angiogenic Properties for Whole-Process Management of Diabetic Wounds

Diabetic wound healing remains a major challenge in modern medicine. The persistent inflammation and immune dysfunction hinder angiogenesis by producing excessive ROS and increasing the susceptibility to bacterial infection. In this study, we developed an integrated strategy for whole-process management of diabetic wounds based on a bioinspired adhesive hydrogel platform with hemostasis, photothermal antimicrobial, antioxidant, anti-inflammatory, and angiogenic properties. A composite hydrogel (termed AQTGF) using poly(acrylic acid) (PAA) and quaternized chitosan (QCS) as the backbone materials and loaded with a TA-Gd/Fe-bimetallic-phenolic coordination polymer was prepared. The AQTGF hydrogel displayed favorable mechanical properties, self-healing capabilities, adhesion characteristics, and photothermal response performance. In vitro experiments demonstrated that the AQTGF hydrogel exhibits excellent photothermal antimicrobial capacity and antioxidant, angiogenic, and M2 macrophage phenotype polarizing properties. In addition, the rat tail amputation and liver hemostasis experiments demonstrated that the AQTGF hydrogel had excellent hemostasis performance. Moreover, in vivo studies have indicated that AQTGF hydrogel can facilitate diabetic wound healing by accelerating epidermal growth, promoting collagen deposition, modulating macrophage M2 polarization, inhibiting inflammation, and promoting angiogenesis. In conclusion, this study provides an adaptable hydrogel that holds promise for the treatment of chronic diabetic wounds.

Multifunctional hydrogels for the healing of oral ulcers

Oral ulcers are one of the most common oral diseases in clinical practice. Its etiology is complex and varied. Due to the dynamic nature of the oral environment, the wound surface is painful due to contact and wear, which seriously affects the quality of life of patients. Oral ulcers are often treated with topical drug therapy. Studies have shown that functional hydrogels play a positive role in promoting wound healing, showing unique advantages in wound dressings. In this paper, the causes and healing characteristics of oral ulcers are discussed in depth, and then the common treatment methods for oral ulcers are summarized and compared. Finally, the potential of functional hydrogels in the treatment of oral ulcers is discussed and projected through a review of the literature in recent years.

A thermosensitive chitin hydrogel with mild photothermal-chemotherapy for facilitating multidrug-resistant bacteria infected wound healing

Bacterial infection of skin wounds leads to serious health problems, including skin defects, inflammatory pain, and even death. To meet the requirements for successful treatment of complicated wounds, a multifunctional dressing is thus highly desirable. In this work, a thermosensitive hydrogel dressing (HBCA) exhibiting injectability, adaptiveness and mild photothermal antibacterial activity was developed for effective infected wound treatment. The HBCA hydrogel was constructed by integrating Ag NPs-incorporated quaternized chitin (DQCA) into the matrix of hydroxybutyl chitin. Laser irradiation could activate the photothermal DQCA to generate heat and rapidly induce the destruction of the bacterial integrity. Meanwhile, the release of DQCA can be accelerated by laser-mediated heating in a controllable manner, quickly reaching the effective concentration and leading to bacterial inactivation in a combined way. The HBCA hydrogel possessed broad-spectrum antibacterial and antibiofilm effect under mild temperature (~48 °C), through combining photothermal therapy (PTT) with chemotherapeutic DQCA. Furthermore, the mouse full-thickness MRSA-infected wound healing test demonstrated that the HBCA hydrogel could accelerate wound regeneration by reducing the inflammatory response, promoting re-epithelialization as well as collagen maturation. This work presents an efficacious and straightforward antibacterial hydrogel dressing that incorporates mild-temperature PTT, particularly in the realm of multidrug-resistant bacterial infection therapies.

Supramolecular Switching-Enabled Quorum Sensing Trap for Pathogen-Specific Recognition and Eradication to Treat Enteritis

Intestinal bacterial infections have become a significant threat to human health. However, the current typical antibiotic-based therapies not only contribute to drug resistance but also disrupt gut microbiota balance, resulting in additional adverse effects on life activities. There is an urgent need to develop new antibacterial materials that selectively eliminate pathogenic bacteria without disrupting beneficial bacterial communities or promoting drug resistance. Herein, we utilize bacterial quorum sensing (QS), a universal mechanism for regulating community behavior, to develop a supramolecular QS trap by encapsulating cucurbit[7]uril (CB[7]) on 1-vinyl-3-pentylimidazolium bromide ([VPIM]Br) to form a supramolecular switch ([VPIM]Br⊂CB[7]) through host-guest interactions followed by grafting it onto bacterial cell surfaces using atom transfer radical polymerization. Subsequently, the matched pathogens are recognized and aggregated through interbacterial QS signals. Furthermore, the addition of amantadine (AD) facilitates the release of [VPIM]Br by competitive binding of CB[7] on [VPIM]Br⊂CB[7] for sterilization. This QS trap specifically triggers the self-aggregation and efficient elimination of matched bacteria. The [VPIM]Br⊂CB[7]-based trap can increase the diversity and abundance of intestinal microorganisms in mice, effectively treating Escherichia coli K88-induced intestinal damage without perturbing gut microbiota balance. This supramolecular-switched QS trap opens up a promising avenue to specifically recognize and eradicate pathogens for the antibiotic-free treatment of intestinal bacterial infections and other inflammatory diseases.

External Stimuli-Responsive Strategies for Surface Modification of Orthopedic Implants: Killing Bacteria and Enhancing Osteogenesis

Bacterial infection and insufficient osteogenic activity are the main causes of orthopedic implant failure. Conventional surface modification methods are difficult to meet the requirements for long-term implant placement. In order to better regulate the function of implant surfaces, especially to improve both the antibacterial and osteogenic activity, external stimuli-responsive (ESR) strategies have been employed for the surface modification of orthopedic implants. External stimuli act as "smart switches" to regulate the surface interactions with bacteria and cells. The balance between antibacterial and osteogenic capabilities of implant surfaces can be achieved through these specific ESR manifestations, including temperature changes, reactive oxygen species production, controlled release of bioactive molecules, controlled release of functional ions, etc. This Review summarizes the recent progress on different ESR strategies (based on light, ultrasound, electric, and magnetic fields) that can effectively balance antibacterial performance and osteogenic capability of orthopedic implants. Furthermore, the current limitations and challenges of ESR strategies for surface modification of orthopedic implants as well as future development direction are also discussed.

Adhesive, Stretchable, and Photothermal Antibacterial Hydrogel Dressings for Wound Healing of Infected Skin Burn at Joints

Dressings for infectious skin burn wounds at joints should have therapeutic functions as well as high tissue-adhesion, stretching, and self-healing properties. This makes it difficult for most hydrogel dressings to simultaneously meet the above-mentioned requirements. In this study, poly(vinyl alcohol), anhydrous sodium borax, epigallocatechin gallate, and copper chloride were used to prepare a hydrogel dressing (PBEC) for the infected burn wound healing at joints. The PBEC hydrogel can adhere to a variety of substrates, has a stretching capacity, and quickly self-healing after being damaged. Additionally, the PBEC hydrogel has the properties of reactive oxygen species scavenging, photothermal sterilization, hemostatic ability, and biocompatibility. Finally, the hydrogel could accelerate the process of wound healing in vivo, especially with the assistance of near-infrared radiation. Therefore, the hydrogel dressing shows great potential for clinical application in the healing of infected burn wounds at joints.

Charge Engineering of Star-Shaped Organic Photosensitizers Enables Efficient Type-I Radicals for Photodynamic Therapy of Multidrug-Resistant Bacterial Infection

Infection induced by multidrug-resistant bacteria is now the second most common cause of accidental death worldwide. However, identifying a high-performance strategy with good efficiency and low toxicity is still urgently needed. Antibacterial photodynamic therapy (PDT) is considered a non-invasive and efficient approach with minimal drug resistance. Whereas, the precise molecular design for highly efficient oxygen-independent type-I photosensitizers is still undefined. In this work, the regulation of the positive charge of star-shaped NIR-emissive organic photosensitizers can boost radical generation for the efficient treatment of wounds infected with multidrug-resistant bacteria. With positive charge engineering, TPAT-DNN, which has six positive charges, mainly produces hydroxyl radicals via the type-I pathway, while TPAT-DN, which has three positive charges, tends to generate singlet oxygen and superoxide radicals. For multidrug-resistant bacteria, TPAT-DNN exhibited specific killing effects on multidrug-resistant gram-positive bacteria at low concentrations, while TPAT-DN is similar antibacterial effects on both multidrug-resistant gram-negative and gram-positive bacteria. Furthermore, the efficiency and safety of TPAT-DNN for eradicating multidrug-resistant bacteria methicillin-resistant S. aureus (MRSA) infection and accelerating wound healing in an MRSA-infected mouse model are demonstrated. This work offers a new approach toward manipulating efficient type-I photosensitizers for MRSA treatment.

Self-healing hydrogel from poly(aspartic acid) and dextran with antibacterial property for burn wound healing

Designing hydrogel dressing with intrinsic antibacterial property to promote skin injury recovery remains a significant challenge. In this research, poly(aspartic hydrazide) with grafted betaine (PAHB) was designed and reacted with oxidized dextran (OD) to fabricate biodegradable PAHB/OD hydrogel and its application as wound dressing was systematically investigated. The PAHB/OD hydrogels exhibited fast gelation, strong tissue adhesion, preferable mechanical properties and biocompatibility. The grafted betaine endowed the hydrogel with antibacterial property and antibacterial rate enhanced through photothermal performance of composited CuS nanoparticles under near infrared (NIR) radiation. The CuS composited PAHB/OD hydrogel (CuS/hydrogel) with microporous morphology was used as burn wound dressing with loaded anti-inflammatory drug diclofenac sodium (DS) in mouse model. The results showed the DS loaded CuS/hydrogel (CuS@DS/hydrogel) promoted the tissue regeneration and suppressed the inflammatory response. The histological analysis and immunohistochemical expression confirmed the CuS@DS/hydrogel promote angiogenesis of the burn wound by regulating the expression of inflammatory cytokines (IL-6 and CD68) and vascular endothelial growth factor (VEGF). Overall, the CuS@DS/hydrogel hydrogel is a promising candidate as wound dressing due to its tissue adhesive, antioxidant, antibacterial and anti-inflammatory activities.

Nanofibrous membrane/thermoresponsive hydrogel composites with temperature-controlled capability for enhancing infected wounds healing

As a novel treatment, photothermal therapy (PTT) has been widely employed to deal with bacterial infection. Nevertheless, the high temperature in conventional PTT unavoidably results in damages to normal tissues. Herein, a nanofibrous membrane/thermoresponsive hydrogel composites (PB NCs@PLA/P(NIPAM-AM) hydrogels) with the ability to regulate heat generation are developed for the treatment of infected wound. Under NIR light laser irradiation, a large amount of heat generated by PB NCs@PLA nanofibrous membrane can be transferred to thermoresponsive P(NIPAM-AM) hydrogel. After reaching a lower critical solution temperature, P(NIPAM-AM) hydrogel rapidly undergoes phase transformation and generate considerable light-scattering centers to prevent NIR penetration. Through this dynamic and reversible process, temperature of PB NCs@PLA/P(NIPAM-AM) hydrogels can maintain at the predefined level to avoid overheating at the wound site. The PB NCs@PLA/P(NIPAM-AM) hydrogels not only exhibit excellent antibacterial effect, but also effectively protect normal tissues from damage, which improve the rate of wound closure. Therefore, the PB NCs@PLA/P(NIPAM-AM) hydrogels provide a promising alternative for infected wound healing.

Glucose and pH dual-responsive hydrogels with antibacterial, reactive oxygen species scavenging, and angiogenesis properties for promoting the healing of infected diabetic foot ulcers

The healing process of diabetic foot ulcers is challenging due to the presence of a complex and severe inflammatory microenvironment, characterized by hyperglycemia, low pH, susceptibility to infection, vascular dysfunction, and over-expression of reactive oxygen species (ROS), which can potentially lead to amputation or even mortality. Herein, a glucose and pH dual-responsive hydrogel was designed and prepared by crosslinking phenylboronic acid-grafted quaternary chitosan (QF, 4 wt%) with dopamine-grafted oxidized hyaluronic acid (OD, 5 wt%) through phenylboronation, schiff-base reaction, and other techniques. The multifunctional QO/@PV@AB7 hydrogel was prepared by incorporating pravastatin-loaded chitosan nanoparticles (CSNPs@PV, 2 mg/mL) and antimicrobial peptide AMP-AB7 loaded silica nanoparticles (SiO2NPs@AB7, 0.5 mg/mL). The results demonstrate that the QO/@PV@AB7 hydrogel exhibits good responsiveness to acidic conditions and high glucose levels, while effectively scavenging various types of ROS. Moreover, it exerted protective effects against oxidative stress on cells, enhanced HUVECs viability, and promoted angiogenesis. Notably, the QO/@PV@AB7 hydrogel displayed potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and Escherichia coli. Additionally, in an MRSA-infected rat model of diabetic foot wounds, administration of the QO/@PV@AB7 hydrogel led to increased secretion of pro-angiogenic factors such as vascular endothelial nitric oxide synthase (eNOS), vascular endothelial-generating factor (VEGF), and endothelial cell adhesion molecule (CD31). Furthermore, the hydrogel significantly reduced the levels of inflammatory factors such as interleukin-6 (IL-6) and tumor necrosis factor-α (TNF-α), while simultaneously increasing the levels of anti-inflammatory cytokines such as interleukin-10 (IL-10). The findings suggest that multifunctional hydrogels incorporating PV@CSNPs and SiO2NPs@AB7 demonstrate promising potential as a therapeutic approach for the treatment of diabetic foot. STATEMENT OF SIGNIFICANCE: Here, a glucose and pH dual-responsive QO/@PV@AB7 hydrogel with antimicrobial and angiogenesis-promoting properties was developed for the treatment of infected wounds in diabetic feet. Our findings demonstrate that the proposed hydrogel exhibits good responsiveness, effectively scavenges various types of reactive oxygen species (DPPH, O2-, -OH, and ABTS+), provides protection against oxidative stress, enhances HUVECs cell viability, and promotes angiogenesis. Notably, it also demonstrates potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) and E. coli. Additionally, in vivo experiments demonstrated that the hydrogel exhibited accelerated wound healing in MRSA-infected diabetic foot ulcers, with a reduction of four days compared to the control group.

A gold nanoparticle-based photothermal hydrogel assisted by an N-halamine polymer for bacteria-infected skin wound healing

Bacteria-infected wounds and antibiotic misuse have become a challenge in the treatment of clinical infections. Therefore, there is an urgent need to design non-antibiotic-dependent multifunctional wound dressings for the treatment of bacterially infected wounds. In this study, an injectable antibacterial hydrogel (pAMPS-Cl/AuNR@HA-DA) based on gold nanorods (AuNR) and N-halamine (pAMPS-Cl) with significant photothermal antibacterial properties was developed. The obtained pAMPS-Cl/AuNR@HA-DA hydrogel showed a sponge-like structure with excellent injectability, self-healing, tissue adhesion, and good hemocompatibility. In addition, the hydrogel exhibited excellent in vitro antibacterial capacity under near-infrared (NIR) laser irradiation through the synergistic action of photothermal therapy (PTT) and chemical release therapy. It also showed an excellent ability to eliminate bacterial infection and promote wound healing, indicating that the pAMPS-Cl/AuNR@HA-DA composite hydrogel could be a promising dressing for the treatment of skin wounds.

Engineering Coatings Inspired by Cell Membrane Thermal Dynamics to Enhance Photothermal Therapy and Osteogenesis for Implant Infections

Photothermal therapy (PTT) encounters challenges of rapid thermal loss and potential tissue damage. In response, we propose a Heat-Boost and Lock implant coating strategy inspired by the thermal adaptation of biological membranes, enabling precise local photothermal utilization. This coating incorporates a poly(tannic acid) (pTA) bridging layer on implants, facilitating stable layer-by-layer integration of a black phosphorus (BP) photothermal layer and a top cell membrane Heat-Boost and Lock layer. The cell membrane layer significantly curtails photothermal loss (extending the heat retention by 17.62%) and stores energy within its phospholipid bilayer, boosting photothermal effects near implants (achieving a temperature increasement of 275%). Theoretical analysis indicates that these local heat preservation properties of the cell membrane arise from its low thermal conductivity and phase-change properties. In a Staphylococcus aureus-infected bone implant model, our coating demonstrates precise antibacterial action around implants (reach an antibacterial ratio of 99.52%). The synergetic locking function of cell membrane and pTA delays BP biodegradation, ensuring favorable photothermal stability and long-term osteo-inductive performance (increasing the bone volume fraction by 53.45%). Beyond providing an endogenic biointerface, this strategy extends the application of cell membrane in local thermal management, offering possibilities for effective and safe PTT modalities.

A Comprehensive Review of Stimuli-Responsive Smart Polymer Materials-Recent Advances and Future Perspectives

Today, smart materials are commonly used in various fields of science and technology, such as medicine, electronics, soft robotics, the chemical industry, the automotive field, and many others. Smart polymeric materials hold good promise for the future due to their endless possibilities. This group of advanced materials can be sensitive to changes or the presence of various chemical, physical, and biological stimuli, e.g., light, temperature, pH, magnetic/electric field, pressure, microorganisms, bacteria, viruses, toxic substances, and many others. This review concerns the newest achievements in the area of smart polymeric materials. The recent advances in the designing of stimuli-responsive polymers are described in this paper.

D-Peptide cell culture scaffolds with enhanced antibacterial and controllable release properties

The development of peptide-based hydrogels characterized by both high biostability and potent antimicrobial activity, aimed at combating multidrug-resistant bacterial infections and providing scaffolds for cell cultures, continues to pose a significant challenge. The susceptibility of antimicrobial peptides (AMPs) to degradation by cations, serum, and proteases restricted their applications in clinical environments. In this study, we designed a peptide sequence (termed D-IK1) entirely consisting of D-amino acids, an enantiomer of a previously reported AMP IK1. Our results demonstrated remarkably improved antibacterial and anticancer activities of D-IK1 as compared to IK1. D-IK1 self-assembled into hydrogels that effectively inhibited bacterial and cancer cell growth by the controlled and sustained release of D-IK1. Importantly, D-IK1 was extremely stable in salt solutions and resisted serum and protease degradation. In addition, the D-IK1 hydrogel fostered cell adhesion and proliferation, proving its viability as a 3D scaffold for cell culture applications. Our research presents a versatile, highly stable antibacterial hydrogel scaffold with potential widespread applications in cell culture, wound healing, and the eradication of multidrug-resistant bacterial infections.

Photo-triggered AuAg@g-C3N4 composite nanoplatform for multimodal broad-spectrum antibacterial therapy

Strategies based on nanomaterials for sterilization address the problem of antibiotic resistance faced by conventional antimicrobials, with the contribution of photocatalytic compounds being particularly prominent. Herein, to integrate multiple bactericidal techniques into a system for generating synergistic antibacterial effects, a novel photo-triggered AuAg@g-C3N4 composite nanoplatform was constructed by anchoring AuAg on the surface of a g-C3N4 layer. As the composite nanoplatform had a lower bandgap and superior visible light utilization efficiency, it could facilitate free electron transfer better and exhibit superior photocatalytic activity under light conditions. Moreover, the AuAg@g-C3N4 composite nanoplatform integrated the bactericidal modes of silver ion toxicity, physical disruption of bacterial cell membranes by the multilayer structure, and excellent photocatalytic activity, exhibiting extremely superior bactericidal effects against Escherichia coli, Staphylococcus aureus, Pseudomonas aeruginosa and Bacillus subtilis, with a bactericidal efficiency of up to 100%.

Multifunctional Microneedle Patch Based on Metal-Phenolic Network with Photothermal Antimicrobial, ROS Scavenging, Immunomodulatory, and Angiogenesis for Programmed Treatment of Diabetic Wound Healing

In diabetic patients with skin injuries, bacterial proliferation, accumulation of reactive oxygen species (ROS) in the tissues, and impaired angiogenesis make wound healing difficult. Therefore, eliminating bacteria, removing ROS, and promoting angiogenesis are necessary for treating acute diabetic wounds. In this study, benefiting from the ability of polyphenols to form a metal-phenolic network (MPN) with metal ions, TA-Eu MPN nanoparticles (TM NPs) were synthesized. The prepared photothermal agent CuS NPs and TM NPs were then loaded onto the supporting base and needle tips of PVA/HA (PH) microneedles, respectively, to obtain PH/CuS/TM microneedles. Antibacterial experiments showed that microneedles loaded with CuS NPs could remove bacteria by the photothermal effect. In vitro experiments showed that the microneedles could effectively scavenge ROS, inhibit macrophage polarization to the M1 type, and induce polarization to the M2 type as well as have the ability to promote vascular endothelial cell migration and angiogenesis. Furthermore, in vivo experiments showed that PH/CuS/TM microneedles accelerated wound healing by inhibiting pro-inflammatory cytokines and promoting angiogenesis in a diabetic rat wound model. Therefore, PH/CuS/TM microneedles have efficient antibacterial, ROS scavenging, anti-inflammatory, immunomodulatory, and angiogenic abilities and hold promise as wound dressings for treating acute diabetic wounds.

Harnessing the potential of hydrogels for advanced therapeutic applications: current achievements and future directions

The applications of hydrogels have expanded significantly due to their versatile, highly tunable properties and breakthroughs in biomaterial technologies. In this review, we cover the major achievements and the potential of hydrogels in therapeutic applications, focusing primarily on two areas: emerging cell-based therapies and promising non-cell therapeutic modalities. Within the context of cell therapy, we discuss the capacity of hydrogels to overcome the existing translational challenges faced by mainstream cell therapy paradigms, provide a detailed discussion on the advantages and principal design considerations of hydrogels for boosting the efficacy of cell therapy, as well as list specific examples of their applications in different disease scenarios. We then explore the potential of hydrogels in drug delivery, physical intervention therapies, and other non-cell therapeutic areas (e.g., bioadhesives, artificial tissues, and biosensors), emphasizing their utility beyond mere delivery vehicles. Additionally, we complement our discussion on the latest progress and challenges in the clinical application of hydrogels and outline future research directions, particularly in terms of integration with advanced biomanufacturing technologies. This review aims to present a comprehensive view and critical insights into the design and selection of hydrogels for both cell therapy and non-cell therapies, tailored to meet the therapeutic requirements of diverse diseases and situations.

Degradable Microneedle Patch with Photothermal-Promoted Bacteria-Infected Wound Healing and Microenvironment Remodeling

Bacteria-infected wound healing is one of the most challenging issues in health management that is attracting worldwide concerns. Despite great achievements with antibiotics, emergence of antibiotic-resistance retarded the wound healing process and also led to severe outcomes. Exploration of novel antibiotics together with amelioration of wound healing efficacy is desirable. Herein, a degradable microneedle patch (AAZH@MNs) was fabricated through incorporating near-infrared light responsive photothermal agents for sustained bacteria killing and prevention of biofilm formation. In addition, the antibacterial microneedle patch could even remold the microenvironment of bacteria-infected wounds through an antibacterial effect, significantly facilitating the wound healing process.

Mussel-inspired tissue adhesive composite hydrogel with photothermal and antioxidant properties prepared from pectin for burn wound healing

Biodegradable self-healing hydrogels with antibacterial property attracted growing attentions in biomedication as wound dressings since they can prevent bacterial infection and promote wound healing process. In this research, a biodegradable self-healing hydrogel with ROS scavenging performance and enhanced tissue adhesion was fabricated from dopamine grafted oxidized pectin (OPD) and naphthoate hydrazide terminated PEO (PEO NH). At the same time, Fe3+ ions were incorporated to endow the hydrogel with near-infrared (NIR) triggered photothermal property to obtain antibacterial activity. The composite hydrogel showed good hemostasis performance based on mussel inspired tissue adhesion with biocompatibility well preserved. As expected, the composition of FeCl3 improved conductivity and endowed photothermal property to the hydrogel. The in vivo wound repairing experiment revealed the 808 nm NIR light triggered photothermal behavior of the hydrogel reduced the inflammation response and promoted wound repairing rate. As a result, this composite FeCl3/hydrogel shows great potential to be an excellent wound dressing for the treatment of infection prong wounds with NIR triggers.

Recent advances on thermosensitive hydrogels-mediated precision therapy

Precision therapy has become the preferred choice attributed to the optimal drug concentration in target sites, increased therapeutic efficacy, and reduced adverse effects. Over the past few years, sprayable or injectable thermosensitive hydrogels have exhibited high therapeutic potential. These can be applied as cell-growing scaffolds or drug-releasing reservoirs by simply mixing in a free-flowing sol phase at room temperature. Inspired by their unique properties, thermosensitive hydrogels have been widely applied as drug delivery and treatment platforms for precision medicine. In this review, the state-of-the-art developments in thermosensitive hydrogels for precision therapy are investigated, which covers from the thermo-gelling mechanisms and main components to biomedical applications, including wound healing, anti-tumor activity, osteogenesis, and periodontal, sinonasal and ophthalmic diseases. The most promising applications and trends of thermosensitive hydrogels for precision therapy are also discussed in light of their unique features.

A universal strategy to enhance photothermal conversion efficiency by regulating the molecular aggregation states for safe photothermal therapy of bacterial infections

Photothermal therapy (PTT) has emerged as a promising approach for treating bacterial infections. However, achieving a high photothermal conversion efficiency (PCE) of photothermal agents (PTAs) remains a challenge. Such a problem is usually compensated by the use of a high-intensity laser, which inevitably causes tissue damage. Here, we present a universal strategy to enhance PCE by regulating the molecular aggregation states of PTAs within thermoresponsive nanogels. We demonstrate the effectiveness of this approach using aggregation-induced emission (AIE) and aggregation-caused quenching (ACQ) PTAs, showing significant enhancements in PCE without the need for intricate molecular modifications. Notably, the highest PCEs reach up to 80.9% and 64.4% for AIE-NG and ACQ-NG, respectively, which are nearly 2-fold of their self-aggregate counterparts. Moreover, we elucidate the mechanism underlying PCE enhancement, highlighting the role of strong intermolecular π-π interactions facilitated by nanogel-induced volume contraction. Furthermore, we validate the safety and efficacy of this strategy in in vitro and in vivo models of bacterial infections at safe laser power densities, demonstrating its potential for clinical translation. Our findings offer a straightforward, universal, and versatile method to improve PTT outcomes while minimizing cytotoxicity, paving the way for enhanced treatment of bacterial infections with safe PTT protocols.

A comprehensive review on the inherent and enhanced antifouling mechanisms of hydrogels and their applications

Biofouling remains a persistent challenge within the domains of biomedicine, tissue engineering, marine industry, and membrane separation processes. Multifunctional hydrogels have garnered substantial attention due to their complex three-dimensional architecture, hydrophilicity, biocompatibility, and flexibility. These hydrogels have shown notable advances across various engineering disciplines. The antifouling efficacy of hydrogels typically covers a range of strategies to mitigate or inhibit the adhesion of particulate matter, biological entities, or extraneous pollutants onto their external or internal surfaces. This review provides a comprehensive review of the antifouling properties and applications of hydrogels. We first focus on elucidating the fundamental principles for the inherent resistance of hydrogels to fouling. This is followed by a comprehensive investigation of the methods employed to enhance the antifouling properties enabled by the hydrogels' composition, network structure, conductivity, photothermal properties, release of reactive oxygen species (ROS), and incorporation of silicon and fluorine compounds. Additionally, we explore the emerging prospects of antifouling hydrogels to alleviate the severe challenges posed by surface contamination, membrane separation and wound dressings. The inclusion of detailed mechanistic insights and the judicious selection of antifouling hydrogels are geared toward identifying extant gaps that must be bridged to meet practical requisites while concurrently addressing long-term antifouling applications.

Cellulose nanofibers embedded chitosan/tannin hydrogel with high antibacterial activity and hemostatic ability for drug-resistant bacterial infected wound healing

Millions of patients annually suffer life-threatening illnesses caused by bacterial infections of skin wounds. However, the treatment of wounds infected with bacteria is a thorny issue in clinical medicine, especially with drug-resistant bacteria infections. Therefore, there is an increasing interest in developing wound dressings that can efficiently fight against drug-resistant bacterial infections and promote wound healing. In this work, an anti-drug-resistant bacterial chitosan/cellulose nanofiber/tannic acid (CS/CNF/TA) hydrogel with excellent wound management ability was developed by electrospinning and fiber breakage-recombination. The hydrogel exhibited an outstanding antibacterial property exceeding 99.9 %, even for drug-resistant bacteria. This hydrogel could adhere to the tissue surface due to its abundant catechol groups, which avoided the shedding of hydrogel during the movement. Besides, it exhibited extraordinary hemostatic ability during the bleeding phase of the wound and then regulated the wound microenvironment by absorbing water and moisturizing. Moreover, the CS/CNF/TA also promoted the regrowth of vessels and follicles, accelerating the healing of infected wound tissue, with a healing rate exceeding 95 % within a 14-day timeframe. Therefore, the CS/CNF/TA hydrogel opens a new approach for the healing of drug-resistant bacterial infected wounds.

Photothermal hydrogels for infection control and tissue regeneration

In this review, we report investigating photothermal hydrogels, innovative biomedical materials designed for infection control and tissue regeneration. These hydrogels exhibit responsiveness to near-infrared (NIR) stimulation, altering their structure and properties, which is pivotal for medical applications. Photothermal hydrogels have emerged as a significant advancement in medical materials, harnessing photothermal agents (PTAs) to respond to NIR light. This responsiveness is crucial for controlling infections and promoting tissue healing. We discuss three construction methods for preparing photothermal hydrogels, emphasizing their design and synthesis, which incorporate PTAs to achieve the desired photothermal effects. The application of these hydrogels demonstrates enhanced infection control and tissue regeneration, supported by their unique photothermal properties. Although research progress in photothermal hydrogels is promising, challenges remain. We address these issues and explore future directions to enhance their therapeutic potential.

Mussel-inspired "all-in-one" sodium alginate/carboxymethyl chitosan hydrogel patch promotes healing of infected wound

Hydrogels have been widely used as wound dressings to accelerate wound healing. However, due to the impaired skin barrier at the wound site, external bacteria can easily invade the wound and cause infection. In this study, we designed a dopamine-modified sodium alginate/carboxymethyl chitosan/polyvinylpyrrolidone (CPD) hydrogel, which was able to promote wound healing while preventing wound infection. Due to the high content of catechol groups, the CPD hydrogel exhibited good tissue adhesion ability and a significant scavenging ability for DPPH• and PTIO• radicals. Under near-infrared laser irradiation, the temperature of CPD hydrogel increased significantly, which significantly killed the Staphylococcus aureus and Escherichia coli. The cell migration test confirmed that CPD hydrogel could promote the cell migration ratio. In the in vivo wound healing test for infected full-thickness skin defect, CPD hydrogel significantly inhibited bacterial proliferation and enhanced wound healing rate. Therefore, the multifunctional hydrogel is expected to be applied to wound healing.

Injectable hydrogels doped with PDA nanoparticles for photothermal bacterial inhibition and rapid wound healing in vitro

The difficulty of wound healing due to skin defects has been a great challenge due to the complex inflammatory microenvironment. Delayed wound healing severely affects the quality of life of patients and represents a significant economic burden for public health systems worldwide. Therefore, there is an urgent need for the development of novel wound dressings that can efficiently resist drug-resistant bacteria and have superior wound repair capabilities in clinical applications. In this study, we designed an adhesive antimicrobial hydrogel dressing (GMH) based on methacrylic-anhydride-modified gelatin and oxidized hyaluronic acid formed by Schiff base and UV-induced double cross-linking for infected wound repair. By inserting PDA nanoparticles into the hydrogel (GMH/PDA), the hydrogel has the capability of photothermal conversion and exhibits good photothermal antimicrobial properties under near-infrared (NIR) light irradiation, which helps to reduce the inflammatory response and avoid bacterial infections during the wound healing process. In addition, GMH/PDA hydrogel exhibits excellent injectability, allowing the hydrogel dressings to be adapted to complex wound surfaces, making them promising candidates for wound therapy. In conclusion, the multifunctional injectable GMH/PDA hydrogel possesses high antimicrobial efficiency, antioxidant properties and good biocompatibility, making them promising candidates for the treatment of infected skin wounds.

A nanocomposite hydrogel for co-delivery of multiple anti-biofilm therapeutics to enhance the treatment of bacterial biofilm-related infections

The characteristics of biofilms have exacerbated the issue of clinical antibiotic resistance, rendering it a pressing challenge in need of resolution. The combination of biofilm-dispersing agents and antibiotics can eliminate biofilms and promote healing synergistically in infected wounds. In this study, we developed a novel nanocomposite hydrogel (NC gel) comprised of the poly(lactic acid)-hyperbranched polyglycerol (PLA-HPG) based bioadhesive nanoparticles (BNPs) and a hydrophilic carboxymethyl chitosan (CS) network. The NC gel was designed to co-deliver two biofilm-dispersing agents (an NO-donor SNO, and an α-amylase Am) and an antibiotic, cefepime (Cef), utilizing a synergistic anti-biofilm mechanism in which Am loosens the matrix structure and NO promotes the release of biofilm bacteria via quorum sensing, and Cef kills bacteria. The drug-loaded NC gel (SNO/BNP/CS@Am-Cef) demonstrated sustained drug release, minimal cytotoxicity, and increased drug-bacterial interactions at the site of infection. When applied to mice infected with methicillin-resistant Staphylococcus aureus (MRSA) biofilms in vivo, SNO/BNP/CS@Am-Cef enhanced biofilm elimination and promoted wound healing compared to traditional antibiotic treatments. Our work demonstrates the feasibility of the co-delivery of biofilm-dispersing agents and antibiotics using the NC gel and presents a promising approach for the polytherapy of bacterial biofilm-related infections.

Smart Responsive and Controlled-Release Hydrogels for Chronic Wound Treatment

Chronic wounds are a major health challenge that require new treatment strategies. Hydrogels are promising drug delivery systems for chronic wound healing because of their biocompatibility, hydration, and flexibility. However, conventional hydrogels cannot adapt to the dynamic and complex wound environment, which involves low pH, high levels of reactive oxygen species, and specific enzyme expression. Therefore, smart responsive hydrogels that can sense and respond to these stimuli are needed. Crucially, smart responsive hydrogels can modulate drug release and eliminate pathological factors by changing their properties or structures in response to internal or external stimuli, such as pH, enzymes, light, and electricity. These stimuli can also be used to trigger antibacterial responses, angiogenesis, and cell proliferation to enhance wound healing. In this review, we introduce the synthesis and principles of smart responsive hydrogels, describe their design and applications for chronic wound healing, and discuss their future development directions. We hope that this review will inspire the development of smart responsive hydrogels for chronic wound healing.

Reconstituting Low-Density Lipoprotein with NIR-Absorbing Organic Photothermal Agents for Targeted Killing of Cancer Cells

Photothermal therapy (PTT) systems typically do not possess intrinsic tumor-targeting capability, resulting in indiscriminate thermal damage to both cancer and normal cells. Herein, a low-density lipoprotein (LDL)-based nanosystem (denoted as MTTQ@LDL) is reported for targeted photothermal killing of cancer cells. Such a nanosystem is fabricated by reconstituting the lipophilic core of LDL with an organic photothermal agent MTTQ. The reconstitution process improves the supramolecular photothermal effects of MTTQ assemblies, which contributes to the significantly enhanced photothermal conversion efficiency (41.3% vs. 16.2%). MTTQ@LDL can actively target LDL receptor-overexpressed cancer cells via receptor-mediated endocytosis, enabling the selective killing of cancer cells over normal cells (98% vs. 7%) post-NIR irradiation. Reconstituted LDL can serve as a promising platform for targeted delivery of functional materials, holding great promise in tumor eradication in vivo.

Development of an Antiswelling Hydrogel System Incorporating M2-Exosomes and Photothermal Effect for Diabetic Wound Healing

Diabetic wounds represent a persistent global health challenge with a substantial impact on patients' health and overall well-being. Herein, a hydrogel system that integrates functionalized gold nanorods (AuNRs) and M2 macrophage-derived exosomes (M2-Exos) was developed to achieve an efficient and synergistic therapy for diabetic wounds. We introduced an ion-cross-linked dissipative network into a prefabricated covalent cross-linked network (long-chain polymer network), which was prepared using AuNRs as a specific cross-linker. The ion network was then cross-linked with the long-chain polymer in situ to form a specific network structure, imparting antiswelling and photothermal effects to the hydrogel. This integrated hydrogel system effectively scavenged reactive oxygen species levels, inhibited inflammation, promoted angiogenesis, and stimulated photothermal antibacterial activity through near-infrared (NIR) irradiation. To demonstrate the potential of the hydrogel, we established experimental animal models of oral mucosa ulceration and full-thickness skin defects. In vivo results confirmed that M2-Exos released from the hydrogels played a crucial role in wound closure. Furthermore, the synergistic effect of AuNRs and NIR photothermal effects eradicated bacterial infections in the wound area. Overall, our integrated hydrogel system is a promising tool for accelerating chronic diabetic wound healing and tissue regeneration. This study highlights the potential benefits of combining bioactive M2-Exos and the photothermal effect of AuNRs into an antiswelling hydrogel platform to achieve satisfactory wound healing in patients with diabetes.

Recent Advances of Composite Nanomaterials for Antibiofilm Application

A biofilm is a microbial community formed by bacteria that adsorb on the surface of tissues or materials and is wrapped in extracellular polymeric substances (EPS) such as polysaccharides, proteins and nucleic acids. As a protective barrier, the EPS can not only prevent the penetration of antibiotics and other antibacterial agents into the biofilm, but also protect the bacteria in the biofilm from the attacks of the human immune system, making it difficult to eradicate biofilm-related infections and posing a serious threat to public health. Therefore, there is an urgent need to develop new and efficient antibiofilm drugs. Although natural enzymes (lysozyme, peroxidase, etc.) and antimicrobial peptides have excellent bactericidal activity, their low stability in the physiological environment and poor permeability in biofilms limit their application in antibiofilms. With the development of materials science, more and more nanomaterials are being designed to be utilized for antimicrobial and antibiofilm applications. Nanomaterials have great application prospects in antibiofilm because of their good biocompati-bility, unique physical and chemical properties, adjustable nanostructure, high permeability and non-proneness to induce bacterial resistance. In this review, with the application of composite nanomaterials in antibiofilms as the theme, we summarize the research progress of three types of composite nanomaterials, including organic composite materials, inorganic materials and organic-inorganic hybrid materials, used as antibiofilms with non-phototherapy and phototherapy modes of action. At the same time, the challenges and development directions of these composite nanomaterials in antibiofilm therapy are also discussed. It is expected we will provide new ideas for the design of safe and efficient antibiofilm materials.

Recent Advances of Natural-Polymer-Based Hydrogels for Wound Antibacterial Therapeutics

Hydrogels have a three-dimensional network structure and high-water content, are similar in structure to the extracellular matrix, and are often used as wound dressings. Natural polymers have excellent biocompatibility and biodegradability and are commonly utilized to prepare hydrogels. Natural-polymer-based hydrogels can have excellent antibacterial and bioactive properties by loading antibacterial agents or being combined with therapeutics such as phototherapy, which has great advantages in the field of treatment of microbial infections. In the published reviews of hydrogels used in the treatment of infectious wounds, the common classification criteria of hydrogels include function, source of antibacterial properties, type of antibacterial agent, etc. However, there are few reviews on the classification of hydrogels based on raw materials, and the description of natural-polymer-based hydrogels is not comprehensive and detailed. In this paper, based on the principle of material classification, the characteristics of seven types of natural polymers that can be used to prepare hydrogels are discussed, respectively, and the application of natural-polymer-based hydrogels in the treatment of infectious wounds is described in detail. Finally, the research status, limitations, and prospects of natural-polymer-based hydrogels are briefly discussed.