Synergistical Starvation and Chemo-Dynamic Therapy for Combating Multidrug-Resistant Bacteria and Accelerating Diabetic Wound Healing

Nanofibrous membrane/self-healing hydrogel double-layer nanocomposite dressings based on oxidized dextran and carboxymethyl chitosan loading ZIF-nanozyme for enhanced bacterial-infected diabetic wound healing

Treatment of diabetic wounds at different stages remains a pressing challenge. By simulating the complex structure of natural skin, a multifunctional nanofibrous membrane/self-healing hydrogel double-layer nanocomposite dressing loading nanozyme was prepared to accelerate diabetic wound healing. The upper layer was prepared from a modified self-synthesized polyurethane (APU) nanofibrous membrane, and the bottom layer was made of an injectable self-healing hydrogel loaded with nanozyme based on oxidized dextran (ODex) and carboxymethyl chitosan (CMC). The APU nanofibrous membrane on the top can maintain a breathable and sterile environment, support the dressing, and promote cell proliferation and migration. Glucose oxidase (GOx) and l -arginine (L-Arg) at the bottom were co-doped with zinc-ZIF nanoparticles (GLZ) and acted as nanozymes for enzyme catalysis. Under the catalytic action of GOx, the high blood sugar in the wound was consumed, the pH of the microenvironment was reduced, and Zn2+ was released, achieving an effective antibacterial effect. L-Arg was catalyzed by H2O2 to generate NO in a lower pH environment, accelerating angiogenesis. Overall, the double-layer composite dressings loaded with ZIF-nanozyme exhibited comprehensive blood sugar regulation capabilities and antibacterial activity, which could promote angiogenesis and cell proliferation, and effectively treat chronic diabetic wounds.

Borax - and tannic acid-based post-3D-printing treatment to tune the mechanical properties of scaffolds

Digital light processing (DLP) methods are constrained by the narrow range of cell-compatible resins, limiting their use in biomedical applications that require varied mechanical and biofunctional properties. Current bioresins based on natural polymers such as methacrylated gelatine or alginate usually lack sufficient stretchability and toughness. In this study, we propose a post-processing strategy to tune the mechanical and functional properties of a DLP printable polyethylene glycol diacrylate (PEGDA)/polyvinyl alcohol (PVA) resin via simple treatment with 5% (w/v) tannic acid (TA) or borax (B). The TA treatment reduced the resin's toughness by ∼17% and compressive modulus by ∼16%, while B treatment increased the toughness by ∼53% and the compressive modulus by ∼44% compared with non-treated hydrogels. TA-treated hydrogels continuously released over 59% of the loaded TA, demonstrating antibacterial and radical scavenging activities. Moreover, TA-treated hydrogels, DLP-printed in a tubular shape, demonstrated the highest durability, remaining intact for ∼32 cycles before failure, which was ∼17 cycles more than that for the non-treated hydrogels. Our in vivo larval model further confirmed the hydrogels' biocompatibility. This study offers a practical approach for post-fabrication tuning of the mechanical and bioactive properties of DLP-printed PEGDA-PVA hydrogels, expanding the utility of existing resins for potential biomedical applications, such as soft tissue engineering.

Baicalein based nano-delivery system restores mitochondrial homeostasis through PPAR signaling pathway to promote wound healing in diabetes

Wound healing in diabetes is a substantial clinical challenge due to the hyperglycemic microenvironment, high pH, bacterial infection, persistent inflammation, and impaired cellular functions, attributed to mitochondrial dysfunction. Here, we have developed an injectable photo-crosslinking nanocomposite hydrogel (BA/GOx@ZIF-8@GelMA, BGZ@GelMA) with baicalein (BA) and glucose oxidase (GOx) loaded Zinc metal-organic framework (ZIF-8) based on methacrylated gelatin (GelMA) to accelerate diabetic infected wound healing by regulating subcellular and cellular functions. The combination of ZIF-8 and BA gives the hydrogel excellent antibacterial properties. A high blood sugar environment triggers the release of GOx in BGZ@GelMA, reducing local glucose and pH, producing hydrogen peroxide (H2O2), and releasing BA and Zinc ions (Zn2+). This process provides a suitable microenvironment for wound healing. Zn2+ can significantly inhibit the proliferation of Staphylococcus aureus (S.aureus) and Escherichia coli (E.coli). The released BA can clear ROS in cells and mitochondria, restore mitochondrial function and stability, and make the hydrogel fundamentally improve the cell function damage induced by hyperglycemia, and ultimately promote cell proliferation, migration and angiogenesis. In general, our multifunctional nanocomposite hydrogel provides a new strategy for diabetes wound healing at the subcellular and cellular functional levels.

Magnetothermal and ultrasound-activated nanoplatform for the inhalable therapy of bacterial lung infections

Antibiotic resistance in Klebsiella pneumoniae infections presents significant challenges in treating lung inflammation. To overcome tissue penetration barriers and modulate inflammatory responses, innovative therapeutic approaches are essential. This study introduces an inhalable nanoplatform, FexSy:Gd@PVP (FGP), based on polyvinylpyrrolidone-modified gadolinium-doped nonstoichiometric iron sulfide nanostructures. The platform integrates synergistic magnetic-ultrasound activation with magnetothermal therapy (mMHT), sonodynamic therapy (SDT), and gas therapy (GT) for targeted bacterial lung infection treatment. Gadolinium incorporation enhances the magnetothermal activation, improving magnetothermal conversion efficiency and sonodynamic performance by increasing magnetic anisotropy, narrowing the semiconductor bandgap, and enriching sulfur vacancies. Delivered via nebulized inhalation, FGP reaches infected lung tissues noninvasively. Exposure to alternating magnetic fields (AMF) and ultrasound (US) generates localized heat and reactive oxygen species (ROS), effectively eliminating bacteria. Simultaneously, AMF and US trigger hydrogen sulfide (H2S) release in the acidic microenvironment, reducing inflammation by inhibiting inflammatory factors such as TNF-α and IL-1β through suppression of STAT3 and ERK phosphorylation. This magnetic-ultrasound co-activated inhalable nanoplatform offers a powerful multimodal therapeutic strategy for overcoming clinical challenges associated with bacterial lung infections. STATEMENT OF SIGNIFICANCE: This study introduces an inhalable nanoplatform that effectively treats multidrug-resistant Klebsiella pneumoniae lung infections. By integrating magnetothermal, sonodynamic, and gas therapies, this system eradicates bacteria and reduces inflammation. It uses gadolinium-doped iron sulfide nanostructures to enhance heat, reactive oxygen species, and hydrogen sulfide production, targeting deep lung infections precisely. Unlike traditional antibiotics, this noninvasive approach has minimal side effects and addresses both bacterial clearance and inflammation. This innovative strategy offers a promising solution for antibiotic-resistant infections and could revolutionize respiratory disease management.

Microneedle technology for enhanced topical treatment of skin infections

Skin infections caused by microbes such as bacteria, fungi, and viruses often lead to aberrant skin functions and appearance, eventually evolving into a significant risk to human health. Among different drug administration paradigms for skin infections, microneedles (MNs) have demonstrated superiority mainly because of their merits in enhancing drug delivery efficiency and reducing microbial resistance. Also, integrating biosensing functionality to MNs offers point-of-care wearable medical devices for analyzing specific pathogens, disease status, and drug pharmacokinetics, thus providing personalized therapy for skin infections. Herein, we do a timely update on the development of MN technology in skin infection management, with a special focus on how to devise MNs for personalized antimicrobial therapy. Notably, the advantages of state-of-the-art MNs for treating skin infections are pointed out, which include hijacking sequential drug transport barriers to enhance drug delivery efficiency and delivering various therapeutics (e.g., antibiotics, antimicrobial peptides, photosensitizers, metals, sonosensitizers, nanoenzyme, living bacteria, poly ionic liquid, and nanomoter). In addition, the nanoenzyme-based multimodal antimicrobial therapy is highlighted in addressing intractable infectious wounds. Furthermore, the MN-based biosensors used to identify pathogen types, track disease status, and quantify antibiotic concentrations are summarized. The limitations of antimicrobial MNs toward clinical translation are offered regarding large-scale production, quality control, and policy guidance. Finally, the future development of biosensing MNs with easy-to-use and intelligent properties and MN-based wearable drug delivery for home-based therapy are prospected. We hope this review will provide valuable guidance for future development in MN-mediated topical treatment of skin infections.

Heterostructure Nanozyme with Hyperthermia-Amplified Enzyme-Like Activity and Controlled Silver Release for Synergistic Antibacterial Therapy

Heterostructure nanozymes as antibiotic-free antimicrobial agents exhibit great potential for multidrug-resistant (MDR) bacterial strains elimination. However, realization of heterostructure antimicrobials with enhanced interfacial interaction for synergistically amplified antibacterial therapy is still a great challenge. Herein, oxygen-vacancy-enriched glucose modified MoOx (G-MoOx) is exploited as a reducing agent to spontaneously reduce Ag (I) into Ag (0) that in situ grows onto the surface of G-MoOx. The resultant Ag doped G-MoOx (Ag/G-MoOx) heterostructure displays augmenting photothermal effect and NIR-enhanced oxidase-like activity after introducing Ag nanoparticles. What's more, NIR hyperthermia accelerate Ag+ ions release from Ag nanoparticles. Introduction of Ag greatly enhances antimicrobial activities of Ag/G-MoOx against MDR bacteria, especially the hybrid loading with 1 wt% Ag NPs exhibiting antibacterial efficacy up to 99.99% against Methicillin-resistant Staphylococcus aureus (MRSA, 1×106 CFU mL-1).

Glucose oxidase: An emerging multidimensional treatment option for diabetic wound healing

The healing of diabetic skin wounds is a complex process significantly affected by the hyperglycemic environment. In this context, glucose oxidase (GOx), by catalyzing glucose to produce gluconic acid and hydrogen peroxide, not only modulates the hyperglycemic microenvironment but also possesses antibacterial and oxygen-supplying functions, thereby demonstrating immense potential in the treatment of diabetic wounds. Despite the growing interest in GOx-based therapeutic strategies in recent years, a systematic summary and review of these efforts have been lacking. To address this gap, this review article outlines the advancements in the application of GOx and GOx-like nanozymes in the treatment of diabetic wounds, including reaction mechanisms, the selection of carrier materials, and synergistic therapeutic strategies such as multi-enzyme combinations, microneedle structures, and gas therapy. Finally, the article looks forward to the application prospects of GOx in aiding the healing of diabetic wounds and the challenges faced in translating these innovations to clinical practice. We sincerely hope that this review can provide readers with a comprehensive understanding of GOx-based diabetic treatment strategies, facilitate the rigorous construction of more robust multifunctional therapeutic systems, and ultimately benefit patients with diabetic wounds.

Glucose-fueled cationic nanomotors for promoting the healing of infected diabetic wounds

Hyperglycemia-promoted bacterial infection will seriously exacerbate diabetic wounds, and its current clinical treatments are suffering from the adverse effects associated with off-target, bacterial resistance, and glycemic fluctuation. Herein, we present a kind of glucose-fueled cationic nanomotors capable of remarkably enhancing antibacterial efficacy, and thus expediting diabetic wound healing. The nanomotors have positively charged surfaces, and consist of mesoporous bowl-shaped polydopamine nanoparticles grafted with quaternized polymer brushes and coupled with glucose oxidase (GOx) and catalase (CAT). Stemming from the GOx-CAT cascade reaction in diabetic wound microenvironment, they can perform robust chemotactic motion towards both high glucose regions, where bacteria proliferation predominantly occurs, and elevated H2O2 levels, which bacterial metabolism produced. This enables the nanomotors to facilitate targeted migration towards bacteria-rich regions and simultaneous downregulation of glycemic levels, as well as to significantly enhance the electrostatic interaction between antibacterial components and bacteria. Consequently, the nanomotors exhibit amplified contact-killing effects of their attached cationic molecules, leading to an almost 10-fold enhancement in antibacterial efficacy compared to previous counterparts. The in vivo experiments approved that the nanomotors demonstrated the accelerated healing of infected diabetic wounds by S. aureus and biosafety. The results herein provide an insight into the clinical treatment of infected diabetic wounds.

Surface charge switchable fluorinated small molecular micelles for enhanced photodynamic therapy for bacterial infections

Photodynamic therapy (PDT) employs reactive oxygen species (ROS) from a photosensitizer (PS) under light, inhibiting multi-drug resistance in bacteria. However, hypoxic conditions in infection sites and biofilms challenge PDT efficiency. We developed fluorinated small molecular micelles (PF-CBMs) as PS carriers to address this, relieving hypoxia and enhancing PS penetration into biofilms. Perfluorocarbons in PF-CBMs transport more oxygen due to their excellent oxygen-dissolving capability. Fluorination enhances loading capacity and serum stability, reduces premature release, and improves cellular uptake, to improve PDT efficacy. PF-CBMs, with acid-induced surface charge transformation, exhibit superior biofilm penetration, resulting in increased antibiofilm activity of PDT. Compared to fluorine-free micelles (PC-CBMs), PF-CBMs demonstrate better serum stability, higher drug loading, and reduced premature release, leading to significantly improved antibacterial efficacy in vitro and in vivo. In conclusion, fluorinated micelles with surface charge reversal enhance PDT for antibacterial and antibiofilm applications.

Application of Drug Delivery System Based on Nanozyme Cascade Technology in Chronic Wound

Chronic wounds are characterized by long-term inflammation, including diabetic ulcers, traumatic ulcers, etc., which provide an optimal environment for bacterial proliferation. At present, antibiotics are the main clinical treatment method for chronic wound infections. However, the overuse of antibiotics may accelerate the emergence of drug-resistant bacteria, which poses a significant threat to human health. Therefore, there is an urgent need to develop new therapeutic strategies for bacterial infections. Nanozyme-based antimicrobial therapy (NABT) is an emerging antimicrobial strategy with broad-spectrum activity and low drug resistance compared to traditional antibiotics. NABT has shown great potential as an emerging antimicrobial strategy by catalyzing the generation of reactive oxygen species (ROS) with its enzyme-like catalytic properties, producing a powerful bactericidal effect without developing drug resistance. Nanozyme-based cascade antimicrobial technology offers a new approach to infection control, effectively improving antimicrobial efficacy by activating cascades against bacterial cell membranes and intracellular DNA while minimizing potential side effects. However, it is worth noting that this technology is still in the early stages of research. This article comprehensively reviews wound classification, current methods for the treatment of wound infection, different types of nanozymes, the application of nanozyme cascade reaction technology in antimicrobial therapy, and future challenges and prospects.

Hypoxia-Activated Biodegradable Porphyrin-Based Covalent Organic Frameworks for Photodynamic and Photothermal Therapy of Wound Infection

Wound infections have gradually become a major threat to human health. Recently, covalent organic frameworks (COFs) have shown great potential in antibacterial and wound healing; however, difficult biodegradability and long-time in vivo retention limit their further application. Herein, biodegradable COFs containing porphyrin backbones and hypoxia-sensitive azobenzene group, namely, HRCOFs, are fabricated for photodynamic therapy (PDT) and photothermal therapy (PTT) of wound infection. Due to the introduction of a porphyrin molecule, HRCOFs can produce singlet oxygen (1O2) under 660 nm laser irradiation. The prepared HRCOFs can also generate thermal energy under 808 nm NIR laser irradiation. HRCOFs show excellent synergetic antibacterial ability against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) in vitro. The in vivo experiments also demonstrate synergistic PDT and PTT effects of HRCOFs against wound infection. Importantly, HRCOFs are response to wound microenvironment, can be degraded for clearance, and avoid some adverse effects caused by long-time retention in vivo, exhibiting good biocompatibility. In general, the obtained biodegradable HRCOFs with both photodynamic and photothermal effects can be used for antibacterial infections and provide great value for promoting wound healing.

Endogenous/exogenous stimuli‐responsive smart hydrogels for diabetic wound healing

Diabetes significantly impairs the body's wound‐healing capabilities, leading to chronic, infection‐prone wounds. These wounds are characterized by hyperglycemia, inflammation, hypoxia, variable pH levels, increased matrix metalloproteinase activity, oxidative stress, and bacterial colonization. These complex conditions complicate effective wound management, prompting the development of advanced diabetic wound care strategies that exploit specific wound characteristics such as acidic pH, high glucose levels, and oxidative stress to trigger controlled drug release, thereby enhancing the therapeutic effects of the dressings. Among the solutions, hydrogels emerge as promising due to their stimuli‐responsive nature, making them highly effective for managing these wounds. The latest advancements in mono/multi‐stimuli‐responsive smart hydrogels showcase their superiority and potential as healthcare materials, as highlighted by relevant case studies. However, traditional wound dressings fall short of meeting the nuanced needs of these wounds, such as adjustable adhesion, easy removal, real‐time wound status monitoring, and dynamic drug release adjustment according to the wound's specific conditions. Responsive hydrogels represent a significant leap forward as advanced dressings proficient in sensing and responding to the wound environment, offering a more targeted approach to diabetic wound treatment. This review highlights recent advancements in smart hydrogels for wound dressing, monitoring, and drug delivery, emphasizing their role in improving diabetic wound healing. It addresses ongoing challenges and future directions, aiming to guide their clinical adoption.

Doughnut-shaped bimetallic Cu-Zn-MOF with peroxidase-like activity for colorimetric detection of glucose and antibacterial applications

Metal-organic frameworks (MOFs), especially bimetallic MOFs, have attracted widespread attention for simulating the structure and function of natural enzymes. In this study, different morphologies of bimetallic Cu-Zn-MOF with different peroxidase (POD)-like activities were prepared by simply controlling the molar ratio of Cu2+ and Zn2+. Among them, the doughnut-shaped Cu9-Zn1-MOF exhibited the largest POD-like activity. Cu9-Zn1-MOF was combined with glucose oxidase to construct a sensitive and selective glucose colorimetric biosensor with a linear detection range of 10-300 μM and a detection limit of 7.1 μm. Furthermore, Cu9-Zn1-MOF can efficiently convert hydrogen peroxide (H2O2) into hydroxyl radicals that effectively kill both gram-negative and gram-positive bacteria at low H2O2 level. The results of this study may promote the synthesis of bimetallic MOFs and broaden their applications in the biomedical field.

MOF-encapsulated copper-doped carbon dots nanozymes with excellent biological activity promote diabetes wound healing

Poor wound healing in diabetics is primarily caused by persistently high levels of inflammation and recurrent bacterial infections. The catalytic therapy technique based on nanozyme medicine has emerged as a beacon of hope for patients with diabetic wounds. However, the use of a single-atom nanozyme may still have limitations, including nanozyme burst release, immunological clearance and insufficient antibacterial activity. To address the aforementioned problems, we provide a new nano-catalytic therapeutic agent for diabetic skin ulcers that incorporates a single-atom nanozyme with high antioxidant activity into a metal-organic framework (ZIF-Cu/C-dots). First, a Cu single-atom nanozyme supported by ultra-small carbon dots (Cu/C-dots) with high antioxidant activity was created. A nanozyme-integrated metal-organic framework was then created, utilizing Cu/C-dots as ligands and Zn2+ as the core metal. Cu/C-dots have good oxidase-like activity, shielding the biological system from ROS damage and reducing the expression of TNF-α and IL-1β. Zn2+ also has good antibacterial activity (the antibacterial rate was more than 90%). This integrated technique prevents nanozyme aggregation, improves nanozyme biocompatibility, slows down the breakdown of ZIF and allows for the regulated release of Cu/C-dots and Zn2+ as needed. Finally, in vivo studies have shown that ZIF-Cu/C-dots can effectively alleviate inflammation at the site of diabetic wounds, accelerate vascular regeneration, promote collagen deposition and enhance tissue remodeling, serving as a novel nano-catalytic platform for the treatment of wounds that are difficult to heal.

Carbon dots-supported Zn single atom nanozymes for the catalytic therapy of diabetic wounds

Diabetic wound treatment continues to be a significant clinical issue due to higher levels of oxidative stress, susceptibility to bacterial infections, and chronic inflammatory responses during healing. We rationally developed and synthesized an ultra-small carbon dots (C-dots) loaded with zinc single-atom nanozyme (Zn/C-dots) with the aim of promoting wounds healing by nanocatalytic treatment, especially targeting its complex pathological microenvironment. Zinc single atoms and C-dots form a dual catalytic system with higher enzymatic activity. Furthermore, the Zn/C-dots nanozyme effectively enters cells, accumulates at mitochondria, and removes excess ROS, protecting cells from oxidative stress damage and limiting the release of pro-inflammatory cytokines, hence reducing inflammation. Zinc can synergistically increase the antibacterial action of C-dots (the effective antibacterial rate of 100 µg/mL Zn/C-dots was above 90 %). Unlike traditional C-dots, Zn/C-dots can cause endothelial cell migration and the formation of new blood vessels. In vitro cytotoxicity, blood compatibility, and in vivo toxicity studies of Zn/C-dots show that they are biocompatible. We subsequently utilized the Zn/C-dots nanozymes to treat diabetic rats' chronic wounds for external use, combining them with ROS-responsive hydrogels to create an antioxidative system (H-Zn/C-dots). The hydrogels anchored the Zn/C-dots nanozymes to the wound, allowing for long-term treatment. The results revealed that H-Zn/C-dots can considerably reduce inflammation, accelerate angiogenesis, collagen deposition, and promote tissue remodeling at the diabetic wound site. After 14 days, the wound area had decreased to approximately 9.19 %, making it a potential treatment. STATEMENT OF SIGNIFICANCE: An ultra-small carbon dot with a zinc single-atom nanozyme was designed and manufactured. Zn/C-dots possess antibacterial, ROS-scavenging, and angiogenesis activities. In vivo, the multifunctional ROS-responsive hydrogel incorporating Zn/C-dots could speed up diabetic wound healing.

Nanozymes for the Therapeutic Treatment of Diabetic Foot Ulcers

Diabetic foot ulcers (DFU) are chronic, refractory wounds caused by diabetic neuropathy, vascular disease, and bacterial infection, and have become one of the most serious and persistent complications of diabetes mellitus because of their high incidence and difficulty in healing. Its malignancy results from a complex microenvironment that includes a series of unfriendly physiological states secondary to hyperglycemia, such as recurrent infections, excessive oxidative stress, persistent inflammation, and ischemia and hypoxia. However, current common clinical treatments, such as antibiotic therapy, insulin therapy, surgical debridement, and conventional wound dressings all have drawbacks, and suboptimal outcomes exacerbate the financial and physical burdens of diabetic patients. Therefore, development of new, effective and affordable treatments for DFU represents a top priority to improve the quality of life of diabetic patients. In recent years, nanozymes-based diabetic wound therapy systems have been attracting extensive interest by integrating the unique advantages of nanomaterials and natural enzymes. Compared with natural enzymes, nanozymes possess more stable catalytic activity, lower production cost and greater maneuverability. Remarkably, many nanozymes possess multienzyme activities that can cascade multiple enzyme-catalyzed reactions simultaneously throughout the recovery process of DFU. Additionally, their favorable photothermal-acoustic properties can be exploited for further enhancement of the therapeutic effects. In this review we first describe the characteristic pathological microenvironment of DFU, then discuss the therapeutic mechanisms and applications of nanozymes in DFU healing, and finally, highlight the challenges and perspectives of nanozyme development for DFU treatment.

From hemostasis to proliferation: Accelerating the infected wound healing through a comprehensive repair strategy based on GA/OKGM hydrogel loaded with MXene@TiO2 nanosheets

The treatment of infected wounds poses a formidable challenge in clinical practice due to the detrimental effects of uncontrolled bacterial infection and excessive oxidative stress, resulting in prolonged inflammation and impaired wound healing. In this study, we presented a MXene@TiO2 (MT) nanosheets loaded composite hydrogel named as GA/OKGM/MT hydrogel, which was formed based on the Schiff base reaction between adipic dihydrazide modified gelatin (GA)and Oxidized Konjac Glucomannan (OKGM), as the wound dressing. During the hemostasis phase, the GA/OKGM/MT hydrogel demonstrated effective adherence to the skin, facilitating rapid hemostasis. In the subsequent inflammation phase, the GA/OKGM/MT hydrogel effectively eradicated bacteria through MXene@TiO2-induced photothermal therapy (PTT) and eliminated excessive reactive oxygen species (ROS), thereby facilitating the transition from the inflammation phase to the proliferation phase. During the proliferation phase, the combined application of GA/OKGM/MT hydrogel with electrical stimulation (ES) promoted fibroblast proliferation and migration, leading to accelerated collagen deposition and angiogenesis at the wound site. Overall, the comprehensive repair strategy based on the GA/OKGM/MT hydrogel demonstrated both safety and reliability. It expedited the progression through the hemostasis, inflammation, and proliferation phases of wound healing, showcasing significant potential for the treatment of infected wounds.

Manipulation of protein corona for nanomedicines

Nanomedicines have significantly advanced the development of diagnostic and therapeutic strategies for various diseases, while they still encounter numerous challenges. Upon entry into the human body, nanomedicines interact with biomolecules to form a layer of proteins, which is defined as the protein corona that influences the biological properties of nanomedicines. Traditional approaches have primarily focused on designing stealthy nanomedicines to evade biomolecule adsorption; however, due to the intricacies of the biological environment within body, this method cannot completely prevent biomolecule adsorption. As research on the protein corona progresses, manipulating the protein corona to modulate the in vivo behaviors of nanomedicines has become a research focus. In this review, modern strategies focused on influencing the biological efficacy of nanomedicines in vivo by manipulating protein corona, along with their wide-ranging applications across diverse diseases are critically summarized, highlighted and discussed. Finally, future directions for this important yet challenging research area are also briefly discussed. This article is categorized under: Nanotechnology Approaches to Biology > Nanoscale Systems in Biology Therapeutic Approaches and Drug Discovery > Emerging Technologies Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Deferoxamine-Loaded Injectable Chitosan-Grafted Chlorogenic Acid/Oxidized Hyaluronic Acid Hybrid Hydrogel with Antibacterial, Anti-inflammatory, and Angiogenesis-Promoting Properties for Diabetic Wound Repair

Diabetic chronic wounds are notoriously difficult to heal as a result of their susceptibility to infection. To address this issue, we constructed an innovated and adaptable solution in the form of injectable chitosan (CS) hydrogel, denoted as CCOD, with enhanced antibacterial and anti-inflammatory properties. This hydrogel is created through a Schiff base reaction that combines chitosan-grafted chlorogenic acid (CS-CGA) and oxidized hyaluronic acid (OHA) with deferoxamine (DFO) as a model drug. The combination of CS and CGA has demonstrated excellent antibacterial and anti-inflammatory properties, while grafting played a pivotal role in making these positive effects stable. These unique features make it possible to customize injectable hydrogel and fit any wound shape, allowing for more effective and personalized treatment of complex bacterial infections. Furthermore, the hydrogel system is not only effective against inflammation and bacterial infections but also possesses antioxidant and angiogenic abilities, making it an ideal solution for the repair of chronic wounds that have been previously thought of as unmanageable.

Chitosan-based GOx@Co-MOF composite hydrogel: A promising strategy for enhanced antibacterial and wound healing effects

A novel composite hydrogel was synthesized via Schiff base reaction between chitosan and di-functional poly(ethylene glycol) (DF-PEG), incorporating glucose oxidase (GOx) and cobalt metal-organic frameworks (Co-MOF). The resulting CS/PEG/GOx@Co-MOF composite hydrogel was characterized using Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), thermogravimetric analysis (TGA), and energy-dispersive X-ray spectroscopy (EDS). The results confirmed successful integration and uniform distribution of Co-MOF within the hydrogel matrix. Functionally, the hydrogel exploits the catalytic decomposition of glucose by GOx to generate gluconic acid and hydrogen peroxide (H2O2), while Co-MOF gradually releases metal ions and protects GOx. This synergy enhanced the antibacterial activity of the composite hydrogel against both Gram-positive (S. aureus) and Gram-negative bacteria (E. coli), outperforming conventional chitosan-based hydrogels. The potential of the composite hydrogel in treating wound infections was evaluated through antibacterial and wound healing experiments. Overall, CS/PEG/GOx@Co-MOF hydrogel holds great promise for the treatment of wound infections, paving the way for further research and potential clinical applications.

Topical delivery of insulin using novel organogel formulations: An approach for the management of diabetic wounds

Diabetes mellitus is a growing chronic form of diabetes, with lengthy health implications. It is predicted as poor diabetic wound recovery affects roughly 25% of all diabetes mellitus patients, frequently resulting in lower traumatic injury and severe external factors and emotional expenses. The insulin-resistant condition increases biofilm development, making diabetic wounds harder to treat. Nowadays, medical treatment and management of diabetic wounds, which have a significant amputation rate, a high-frequency rate, and a high death rate, have become a global concern. Topical formulations have played a significant part in diabetic wound management and have been developed to achieve a number of features. Because of its significant biocompatibility, moisture retention, and therapeutic qualities, topical insulin has emerged as an appealing and feasible wound healing process effector. With a greater comprehension of the etiology of diabetic wounds, numerous functionalized topical insulins have been described and shown good outcomes in recent years, which has improved some diabetic injuries. The healing of wounds is a physiological phenomenon that restores skin integrity and heals damaged tissues. Insulin, a powerful wound-healing factor, is also used in several experimental and clinical studies accelerate healing of diverse injuries.

Recent design strategies for boosting chemodynamic therapy of bacterial infections

The emergence of drug-resistant bacteria poses a significant threat to people's lives and health as bacterial infections continue to persist. Currently, antibiotic therapy remains the primary approach for tackling bacterial infections. However, the escalating rates of drug resistance coupled with the lag in the development of novel drugs have led to diminishing effectiveness of conventional treatments. Therefore, the development of nonantibiotic-dependent therapeutic strategies has become imperative to impede the rise of bacterial resistance. The emergence of chemodynamic therapy (CDT) has opened up a new possibility due to the CDT can convert H2O2 into •OH via Fenton/Fenton-like reaction for drug-resistant bacterial treatment. However, the efficacy of CDT is limited by a variety of practical factors. To overcome this limitation, the sterilization efficiency of CDT can be enhanced by introducing the therapeutics with inherent antimicrobial capability. In addition, researchers have explored CDT-based combined therapies to augment its antimicrobial effects and mitigate its potential toxic side effects toward normal tissues. This review examines the research progress of CDT in the antimicrobial field, explores various strategies to enhance CDT efficacy and presents the synergistic effects of CDT in combination with other modalities. And last, the current challenges faced by CDT and the future research directions are discussed.

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.

Research progress of metal-organic framework nanozymes in bacterial sensing, detection, and treatment

The high efficiency and specificity of enzymes make them play an important role in life activities, but the high cost, low stability and high sensitivity of natural enzymes severely restrict their application. In recent years, nanozymes have become convincing alternatives to natural enzymes, finding utility across diverse domains, including biosensing, antibacterial interventions, cancer treatment, and environmental preservation. Nanozymes are characterized by their remarkable attributes, encompassing high stability, cost-effectiveness and robust catalytic activity. Within the contemporary scientific landscape, metal-organic frameworks (MOFs) have garnered considerable attention, primarily due to their versatile applications, spanning catalysis. Notably, MOFs serve as scaffolds for the development of nanozymes, particularly in the context of bacterial detection and treatment. This paper presents a comprehensive review of recent literature pertaining to MOFs and their pivotal role in bacterial detection and treatment. We explored the limitations and prospects for the development of MOF-based nanozymes as a platform for bacterial detection and therapy, and anticipate their great potential and broader clinical applications in addressing medical challenges.

A multimodal therapy for infected diabetic wounds based on glucose-responsive nanocomposite-integrated microneedles

Diabetic wounds in a state of high glucose are refractory to treatment and healing, especially if they are infected with bacteria. Herein, a novel nanocomposite (CIP/GOx@ZIF-8) was synthesized by loading ciprofloxacin hydrochloride (CIP) and glucose oxidase (GOx) into zeolitic imidazole framework-8 (ZIF-8) that exhibited good glucose sensitivity and catalytic activity. The high glucose in diabetic wounds could be decomposed into hydrogen peroxide (H2O2) and gluconic acid via the catalysis of GOx, which further destroyed CIP/GOx@ZIF-8 to release Zn2+ and cargos. The combination of glucose starvation, Zn2+, H2O2 and CIP could elevate the antibacterial effect and reduce bacterial resistance. Subsequently, the nanocomposite was fabricated into dissolving microneedles (CIP/GOx@ZIF-8 MNs) using polyvinylpyrrolidone (PVP). The microneedles exhibited good mechanical strength, puncture performance, dissolving performance, glucose responsiveness, antibacterial performance and biocompatibility. For in vivo wound healing, CIP/GOx@ZIF-8 MNs with good biosafety facilitated neovascularization and collagen deposition as well as reduced inflammation, and the wounds were almost healed after treatment. This multimodal therapeutic strategy is created to provide a unique treatment for infected diabetic wounds.

Metal-Organic Frameworks and Their Composites for Chronic Wound Healing: From Bench to Bedside

Chronic wounds are characterized by delayed and dysregulated healing processes. As such, they have emerged as an increasingly significant threat. The associated morbidity and socioeconomic toll are clinically and financially challenging, necessitating novel approaches in the management of chronic wounds. Metal-organic frameworks (MOFs) are an innovative type of porous coordination polymers, with low toxicity and high eco-friendliness. Documented anti-bacterial effects and pro-angiogenic activity predestine these nanomaterials as promising systems for the treatment of chronic wounds. In this context, the therapeutic applicability and efficacy of MOFs remain to be elucidated. It is, therefore, reviewed the structural-functional properties of MOFs and their composite materials and discusses how their multifunctionality and customizability can be leveraged as a clinical therapy for chronic wounds.

Hydrogen sulfide releasing poly(γ-glutamic acid) biocomposite hydrogel with monitoring, antioxidant, and antibacterial properties for diabetic wound healing

Adverse factors such as high levels of glucose, oxidative stress, inflammation, and bacterial infection impede diabetic wound healing and even worsen wounds. Owing to its outstanding anti-inflammatory and antioxidant properties as well as the potential to promote cell migration and proliferation, hydrogen sulfide(H2S) gas therapy is promising for chronic diabetic wound recovery. In this work, a multifunctional poly(γ-glutamic acid)(PGA) hydrogel encapsulated with keratin-based H2S donor(KTC), ciprofloxacin(Cip), and anthocyanins(Ant) was developed. The resultant hydrogel was capable of releasing H2S, thereby promoting cell proliferation and enhancing anti-inflammation and antioxidant activity. The release of antibiotic Cip was accelerated under a diabetic wound microenvironment, thereby enhancing the antibacterial activity of the hydrogel. The encapsulated Ant could serve as a pH monitor, sensitively indicating wound pH conditions in situ and indirectly reflecting wound infection. In vivo results in diabetic wound healing suggested that PGA/Ant/KTC/Cip hydrogel reduced inflammation and promoted angiogenesis and collagen deposition, thereby accelerating wound healing.

An erythrocyte membrane-camouflaged fluorescent covalent organic framework for starving/nitric oxide/immunotherapy of triple-negative breast cancer

It is a great challenge to effectively treat triple-negative breast cancer (TNBC) due to lack of therapeutic targets and drug resistance of systemic chemotherapy. Rational design of nanomedicine with good hemocompatibility is urgently desirable for combination therapy of TNBC. Herein, an erythrocyte membrane-camouflaged fluorescent covalent organic framework (COF) loaded with an NO donor (hydroxyurea, Hu), glucose oxidase (GOx) and cytosine-phosphate-guanine oligonucleotides (CPG) (COF@HGC) was developed for imaging-guided starving/nitric oxide (NO)/immunization synergistic treatment of TNBC. The substances of HGC are easily co-loaded onto the COF due to the ordered pore structure and large surface area. And a folic acid-modified erythrocyte membrane (FEM) is coated on the surface of COF@HGC to improve targeted therapy and haemocompatibility. When COF@HGC@FEM is internalized into tumor cells, hemoglobin (Hb) on FEM and GOx loaded on the COF can trigger cascade reactions to kill tumor cells due to the simultaneous production of NO and exhaustion of glucose. Meanwhile, the COF with excellent fluorescence properties can be used as a self-reporter for bioimaging. Furthermore, the CPG can reprogram tumor-associated macrophages from tumor-supportive phenotype to anti-tumor phenotype and enhance immunotherapy. Through the "three-in-one" strategy, the biomimetic nanoplatform can effectively inhibit tumor growth and reprogram the tumor immunosuppression microenvironment in the TNBC mouse model.

Biomimetic dual-nanozymes with catalytic cascade reactions against diabetic wound infection

Diabetes-related chronic wounds characterized by hyperglycemia and weak alkaline milieu provide numerous advantages for bacteria growth and biofilm formation, setting a myriad of stumbling blocks for wound healing. Therefore, reshaping the spatially and temporally pathological wound microenvironment against bacterial infection is critical to rescue stalled healing progress in diabetes-related chronic wounds. Herein, we demonstrate on the room-temperature construction of a glucose oxidase (GOx)-mimicking and peroxidase (POD)-mimicking dual-nanozymes catalytic cascade system upon the partial reduction of Fe3+ to Fe2+ and the deposition of Au nanoparticles, simultaneously. The as-prepared dual-nanozymes catalytic cascade system possesses the capabilities of reshaping the pathological microenvironments of diabetic wound via glucose consumption and acidification, leading to amplified catalytic cascade activities for sterilization. On the one hand, the GOx-mimicking enzymatic activity of the catalytic cascade system can not only deplete glucose and acidize wound milieu to inhibit bacteria growth, but also utilize the weak alkaline milieu of diabetic wound to provide sufficient H2O2 and a favorable pH for subsequent OH generation. On the other hand, the POD-mimicking enzymatic activity of the catalytic cascade system can continuously produce OH for sterilization under the weak acidic milieu in the presence of abundant H2O2. Benefiting from the simply and mild preparation process and the excellent dual-nanozymes catalytic cascade activities under the deliberate evolved milieus of diabetes-related chronic wounds, our catalytic cascade system exhibits the promising healing effect and clinical translation potential against diabetic wound infection.

Double-Layer Hydrogel with Glucose-Activated Two-Stage ROS Regulating Properties for Programmed Diabetic Wound Healing

Slow healing of wounds induces great pain in diabetic patients. However, developing new approaches to promote diabetic wound healing is still one of the toughest challenges in the medical field. Here, we constructed a new double-layer hydrogel to effectively regulate reactive oxygen species (ROS) on the wound and promote diabetic wound healing. The inner layer contains glucose oxidase (Gox), ferrocene-modified quaternary ammonium chitosan (Fc-QCs), and poly(β-cyclodextrin) (Pβ-CD), which is used to generate hydroxyl radicals (•OH) for antibacterial in the early stage of wound healing and collapses gradually. The outer layer is composed of gelatin and dopamine. In the later stage of wound healing, the outer layer contacts the skin, which is beneficial for ROS clearance on the wound. Antibacterial, ROS scavenging, and wound healing experiments have shown that the double-layer hydrogel possesses two-stage ROS regulating properties for programmed diabetic wound healing. In conclusion, it will be one of the most potential dressings for treating diabetic wounds in the future.

Oxygen releasing patches based on carbohydrate polymer and protein hydrogels for diabetic wound healing: A review

Diabetic wounds are among the major healthcare challenges, consuming billions of dollars of resources and resulting in high numbers of morbidity and mortality every year. Lack of sufficient oxygen supply is one of the most dominant causes of impaired healing in diabetic wounds. Numerous clinical and experimental studies have demonstrated positive outcomes as a result of delivering oxygen at the diabetic wound site, including enhanced angiogenesis, antibacterial and cell proliferation activities. However, prolonged and sustained delivery of oxygen to improve the wound healing process has remained a major challenge due to rapid release of oxygen from oxygen sources and limited penetration of oxygen into deep skin tissues. Hydrogels made from sugar-based polymers such as chitosan and hyaluronic acid, and proteins such as gelatin, collagen and hemoglobin have been widely used to deliver oxygen in a sustained delivery mode. This review presents an overview of the recent advances in oxygen releasing hydrogel based patches as a therapeutic modality to enhance diabetic wound healing. Various types of oxygen releasing wound healing patch have been discussed along with their fabrication method, release profile, cytocompatibility and in vivo results. We also briefly discuss the challenges and prospects related to the application of oxygen releasing biomaterials as wound healing therapeutics.

Research advances in smart responsive-hydrogel dressings with potential clinical diabetic wound healing properties

The treatment of chronic and non-healing wounds in diabetic patients remains a major medical problem. Recent reports have shown that hydrogel wound dressings might be an effective strategy for treating diabetic wounds due to their excellent hydrophilicity, good drug-loading ability and sustained drug release properties. As a typical example, hyaluronic acid dressing (Healoderm) has been demonstrated in clinical trials to improve wound-healing efficiency and healing rates for diabetic foot ulcers. However, the drug release and degradation behavior of clinically-used hydrogel wound dressings cannot be adjusted according to the wound microenvironment. Due to the intricacy of diabetic wounds, antibiotics and other medications are frequently combined with hydrogel dressings in clinical practice, although these medications are easily hindered by the hostile environment. In this case, scientists have created responsive-hydrogel dressings based on the microenvironment features of diabetic wounds (such as high glucose and low pH) or combined with external stimuli (such as light or magnetic field) to achieve controllable drug release, gel degradation, and microenvironment improvements in order to overcome these clinical issues. These responsive-hydrogel dressings are anticipated to play a significant role in diabetic therapeutic wound dressings. Here, we review recent advances on responsive-hydrogel dressings towards diabetic wound healing, with focus on hydrogel structure design, the principle of responsiveness, and the behavior of degradation. Last but not least, the advantages and limitations of these responsive-hydrogels in clinical applications will also be discussed. We hope that this review will contribute to furthering progress on hydrogels as an improved dressing for diabetic wound healing and practical clinical application.

Recent progress in nanozymes for the treatment of diabetic wounds

The slow healing of diabetic wounds has seriously affected human health. Meanwhile, the open wounds are susceptible to bacterial infection. Clinical therapeutic methods such as antibiotic therapy, insulin treatment, and surgical debridement have made great achievements in the treatment of diabetic wounds. However, drug-resistant bacteria will develop after long-term use of antibiotics, resulting in decreased efficacy. To improve the therapeutic effect, increasing drug concentration is a common strategy in clinical practice, but it also brings serious side effects. In addition, hyperglycemia control or surgical debridement can easily bring negative effects to patients, such as hypoglycemia or damage of normal tissue. Therefore, it is essential to develop novel therapeutic strategies to effectively promote diabetic wound healing. In recent years, nanozyme-based diabetic wound therapeutic systems have received extensive attention because they possess the advantages of nanomaterials and natural enzymes. For example, nanozymes have the advantages of a small size and a high surface area to volume ratio, which can enhance the tissue penetration of nanozymes and increase the reactive active sites. Moreover, compared with natural enzymes, nanozymes have more stable catalytic activity, lower production cost, and stronger operability. In this review, we first reviewed the basic characteristics of diabetic wounds and then elaborated on the catalytic mechanism and action principle of different types of nanozymes in diabetic wounds from three aspects: controlling bacterial infection, controlling hyperglycemia, and relieving inflammation. Finally, the challenges, prospects and future implementation of nanozymes for diabetic wound healing are outlined.

Antibacterial Chemodynamic Therapy: Materials and Strategies

The wide and frequent use of antibiotics in the treatment of bacterial infection can cause the occurrence of multidrug-resistant bacteria, which becomes a serious health threat. Therefore, it is necessary to develop antibiotic-independent treatment modalities. Chemodynamic therapy (CDT) is defined as the approach employing Fenton and/or Fenton-like reactions for generating hydroxyl radical (•OH) that can kill target cells. Recently, CDT has been successfully employed for antibacterial applications. Apart from the common Fe-mediated CDT strategy, antibacterial CDT strategies mediated by other metal elements such as copper, manganese, cobalt, molybdenum, platinum, tungsten, nickel, silver, ruthenium, and zinc have also been proposed. Furthermore, different types of materials like nanomaterials and hydrogels can be adopted for constructing CDT-involved antibacterial platforms. Besides, CDT can introduce some toxic metal elements and then achieve synergistic antibacterial effects together with reactive oxygen species. Finally, CDT can be combined with other therapies such as starvation therapy, phototherapy, and sonodynamic therapy for achieving improved antibacterial performance. This review first summarizes the advancements in antibacterial CDT and then discusses the present limitations and future research directions in this field, hoping to promote the development of more effective materials and strategies for achieving potentiated CDT.

Photothermal Controlled-Release Immunomodulatory Nanoplatform for Restoring Nerve Structure and Mechanical Nociception in Infectious Diabetic Ulcers

Infectious diabetic ulcers (IDU) require anti-infection, angiogenesis, and nerve regeneration therapy; however, the latter has received comparatively less research attention than the former two. In particular, there have been few reports on the recovery of mechanical nociception. In this study, a photothermal controlled-release immunomodulatory hydrogel nanoplatform is tailored for the treatment of IDU. Due to a thermal-sensitive interaction between polydopamine-reduced graphene oxide (pGO) and the antibiotic mupirocin, excellent antibacterial efficacy is achieved through customized release kinetics. In addition, Trem2+ macrophages recruited by pGO regulate collagen remodeling and restore skin adnexal structures to alter the fate of scar formation, promote angiogenesis, accompanied by the regeneration of neural networks, which ensures the recovery of mechanical nociception and may prevent the recurrence of IDU at the source. In all, a full-stage strategy from antibacterial, immune regulation, angiogenesis, and neurogenesis to the recovery of mechanical nociception, an indispensable neural function of skin, is introduced to IDU treatment, which opens up an effective and comprehensive therapy for refractory IDU.

Biomimetic Enzyme Cascade Structural Color Hydrogel Microparticles for Diabetic Wound Healing Management

Hard-healing diabetic wound brings burgeoning physical and mental burdens to patients. Current treatment strategies tend to achieve multistage promotion and real-time reporting to facilitate wound management. Herein, a biomimetic enzyme cascade inverse opal microparticles system for wound healing, which is intergated with glucose oxidase (GOD) and copper peroxide (CP). Such microparticles are composed of biofriendly hyaluronic acid methacryloyl (HAMA) and pH-responsive acrylic acid (AA), which provided abundant binding sites and spaces for chemical immobilizing and physical doping of enzymes and metal bioinorganics. When the cascade catalytic system is applied on wound sites, hyperglycemia environment would serve as a hydrogen peroxide (H₂ O₂ ) generator through GOD catalysis, while acidic environment triggers the decomposition of CP, further catalyzing H₂ O₂ to generate reactive oxygen species (ROS). Additionally, the distinctive structural color of the microparticles can visually reflect the wound pH and intelligently estimate the healing state. It is demonstrated that such microparticle systems exhibit excellent broad-spectrum antibacterial and angiogenesis-promoting properties, as well as significant real-time reporting ability for wound healing. These features indicate that enzyme cascade structural color microparticles possess valuable potential in wound healing and related field.

Nanomaterials as multimodal photothermal agents (PTAs) against 'Superbugs'

Superbugs, also known as multidrug-resistant bacteria, have become a lethal and persistent threat due to their unresponsiveness toward conventional antibiotics. The main reason for this is that superbugs can rapidly mutate and restrict any foreign drug/molecule in their vicinity. Herein, nanomaterial-mediated therapies have set their path and shown burgeoning efficiency toward the ablation of superbugs. Notably, treatment modalities like photothermal therapy (PTT) have shown prominence in killing multidrug-resistant bacteria with their ability to generate local heat shock-mediated hyperthermia in such species. However, photothermal treatment has some serious limitations, such as high cost, complexity, and even toxicity to some extent. Hence, it is important to resolve such shortcomings of PTTs as they provide substantial tissue penetration. This is why multimodal PTTs have emerged and taken over this domain of research for the past few years. In this work, we have summarized and critically reviewed such exceptional works of recent times and provided a perspective to enhance their efficiencies. Profoundly, we discuss the design rationales of some novel photothermal agents (PTAs) and shed light on their mechanisms. Finally, challenges for PTT-derived multimodal therapy are presented, and capable synergistic bactericidal prospects are anticipated.

Microenvironment-Based Diabetic Foot Ulcer Nanomedicine

Diabetic foot ulcers (DFU), one of the most serious complications of diabetes, are essentially chronic, nonhealing wounds caused by diabetic neuropathy, vascular disease, and bacterial infection. Given its pathogenesis, the DFU microenvironment is rather complicated and characterized by hyperglycemia, ischemia, hypoxia, hyperinflammation, and persistent infection. However, the current clinical therapies for DFU are dissatisfactory, which drives researchers to turn attention to advanced nanotechnology to address DFU therapeutic bottlenecks. In the last decade, a large number of multifunctional nanosystems based on the microenvironment of DFU have been developed with positive effects in DFU therapy, forming a novel concept of "DFU nanomedicine". However, a systematic overview of DFU nanomedicine is still unavailable in the literature. This review summarizes the microenvironmental characteristics of DFU, presents the main progress of wound healing, and summaries the state-of-the-art therapeutic strategies for DFU. Furthermore, the main challenges and future perspectives in this field are discussed and prospected, aiming to fuel and foster the development of DFU nanomedicines successfully.

Mechanobactericidal, Gold Nanostar Hydrogel-Based Bandage for Bacteria-Infected Skin Wound Healing

The emergence of multidrug resistant (MDR) microorganisms has led to the development of alternative approaches for providing relief from microbial attacks. The mechano-bactericidal action as a substitute for antimicrobials has become the focus of intensive research. In this work, nanostructure-conjugated hydrogel are explored as a flexible dressing against Staphylococcus aureus (S. aureus)-infected skin wounds. Herein gold nanostars (AuNst) with spike lengths reaching 120 nm are probed for antibacterial action. The bacterial killing of >95% is observed for Pseudomonas aeruginosa (P. aeruginosa) and Escherichia coli (E. coli), while up to 60% for Gram-positive S. aureus. AuNst conjugated hydrogel (AuNst₁₂₀@H) reduced >80% colonies of P. aeruginosa and E. coli. In comparison, around 35.4% reduction of colonies are obtained for S. aureus. The viability assay confirmed the presence of about 85% of living NIH-3T3 cells when grown with hydrogels. An animal wound model is also developed to assess the efficiency of AuNst₁₂₀@H. A significant reduction in wound size is observed on the 10th day in AuNst₁₂₀@H treated animals with fully formed epidermal layers, hair follicles, new blood vessels, and arrector muscles. These findings suggest that novel dressing materials can be developed with antimicrobial nanotextured surfaces.

Preparation of biodegradable carboxymethyl cellulose/dopamine/Ag NPs cryogel for rapid hemostasis and bacteria-infected wound repair

Massive hemorrhage caused by accident or surgery is a major factor in accidental death. In addition, bacterial infection is also an important threat after bleeding. Cryogels with interpenetrating macroporous structures pose great application prospects in rapid hemostasis and infected wound repair. In this study, cryogels with different pore size are prepared by carboxymethyl cellulose (CMC) and dopamine (DA). The CMC grafted with different DA amounts is crosslinked by free DA through oxidative polymerization at low temperatures to form cryogels with different pore sizes. And the CMC/DA-3 cryogel is chosen as the optimal group for its high porosity, suitable mechanical, and good hemostatic ability. CMC/DA-3 cryogel is loaded with silver nanoparticles (Ag NPs) to prepare hemostatic cryogel with antibacterial properties. Antibacterial tests and animal hemostasis experiments confirm that the CMC/DA-3/Ag cryogel has good antibacterial properties and can finish rapid hemostasis. In the S. aureus infection skin defect model, the wound healing is significantly improved compared with commercial gelatin sponge. In summary, the novel cryogel has great potential in rapid hemostasis and infected wound healing.

α-Fe2O3 based nanotherapeutics for near-infrared/dihydroartemisinin dual-augmented chemodynamic antibacterial therapy

Due to the negligible bacterial resistance, chemodynamic therapy (CDT) is a promising treatment for bacterial infection. However, it is severely impeded by the constant body temperature, shortage of Fe(Ⅱ) ions and insufficient H₂O₂ level in infected tissue. To enhance the therapeutic efficiency of CDT, improved strategies are urgently needed to tackle these problems. Herein, we exploited an infection microenvironment-responsive nanotherapeutics for near-infrared (NIR)/dihydroartemisinin (DHA) dual-augmented antibacterial CDT. The convenient encapsulation of DHA-loaded α-Fe₂O₃ nanorods with metal-polyphenol networks (MPN) led to the generation of an antibacterial nanoagent Fe₂O₃@DHA@MPN (FDM). Afterwards, its photothermal and peroxidase-like activities were intensively studied. Furthermore, the bactericidal efficacy of FDM was evaluated through both in vitro and in vivo antibacterial assays. Firstly, FDM showed both satisfactory photothermal and NIR/DHA dual-augmented peroxidase-like activities. Besides, it exhibited a pH-responsive release behavior of both Fe(Ⅱ) ions and DHA. Moreover, it presented tannic acid-mediated bacterial adhesion effect. In vitro experiments demonstrated that FDM could achieve a satisfactory efficiency against both planktonic bacteria and biofilms. In vivo assays illustrated both the extraordinary synergistic antibacterial effect and efficient anti-inflammatory ability of FDM. The outcomes indicated that the exploited antibacterial agent could offer new insight on developing intelligent nanotherapeutics for clinical use in the future. STATEMENT OF SIGNIFICANCE: The antibacterial efficiency of chemodynamic therapy (CDT) is seriously limited by the constant body temperature, shortage of Fe(Ⅱ) ions and insufficient H₂O₂ level at the mildly acidic inflammatory microenvironment. To address these issues, we have developed a pH-responsive nanoagent (Fe₂O₃@DHA@MPN) for near-infrared (NIR)/dihydroartemisinin (DHA) dual-augmented CDT. Through the NIR-induced photothermal effect of exterior Fe(Ⅲ)/tannic acid complex, the increased local temperature led to a photothermal enhanced CDT. Besides, a continuous supply of Fe(Ⅱ) ions could be achieved by tannic acid-mediated Fe(Ⅲ) reduction. Moreover, DHA was adopted as a substitute for H₂O₂ to initiate DHA-mediated CDT. Both in vitro and in vivo assays demonstrated its outstanding bactericidal efficiency. Therefore, the developed nanotherapeutics could be a promising candidate for clinical trials.

Diabetes immunity-modulated multifunctional hydrogel with cascade enzyme catalytic activity for bacterial wound treatment

Diabetes immunity-modulated wound treatment in response to the varied microenvironments at different stages remains an urgent challenge. Herein, glucose oxidase (GOx) and quasi-amorphous Fe₂O₃ are co-incorporated into Zn-MOF nanoparticle (F-GZ) for cascade enzyme catalytic activities, where not only the high blood glucose in the wound is consumed via the GOx catalysis, but also the effective anti-bacteria is achieved via the degradedly released Zn²⁺ synergistically with the catalytically produced ·OH during the bacterial infection period with the low pH microenvironment. Simultaneously, the reactive oxygen species scavenging and hypoxia relief is realized via catalyzing H₂O₂ to produce O₂ at the relatively elevated pH environment during the wound recovery period. Subsequently, a multifunctional hydrogel with injectable, self-healing and hemostasis abilities, as well as uniformed F-GZ loading is prepared via the copolymerization reaction. This hydrogel behaves as F-GZ but reduces the toxic effects, which thus accelerates the diabetic wound healing. More importantly, this hydrogel is found to modulate the diabetes immunity possibly mediated via the released Zn²⁺, which thus contributes to the recovered pancreatic islet functions with improved glucose tolerance and increased insulin secretion for enhanced diabetic wound treatments. This work initiates a new strategy for simultaneous diabetic wound management and also suggests a potential way for diabetic immunity modulation.

Emerging nanozyme-based multimodal synergistic therapies in combating bacterial infections

Pathogenic infections have emerged as major threats to global public health. Multidrug resistance induced by the abuse of antibiotics makes the anti-infection therapies to be a global challenge. Thus, it is urgent to develop novel, efficient and biosafe antibiotic alternatives for future antibacterial therapy. Recently, nanozymes have emerged as promising antibiotic alternatives for combating bacterial infections. More significantly, the multimodal synergistic nanozyme-based antibacterial systems open novel disinfection pathways. In this review, we are mainly focusing on the recent research progress of nanozyme-based multimodal synergistic therapies to eliminate bacterial infections. Their antibacterial mechanism, the synergistic antibacterial systems are systematically summarized and discussed according to the combination of mechanisms and the purpose to improve their antibacterial efficiency, biosafety and specificity. Finanly, the current challenges and prospects of the multimodal synergistic antibacterial systems are proposed.

Confining enzymes in porous organic frameworks: from synthetic strategy and characterization to healthcare applications

Enzymes are a class of natural catalysts with high efficiency, specificity, and selectivity unmatched by their synthetic counterparts and dictate a myriad of reactions that constitute various cascades in living cells. The development of suitable supports is significant for the immobilization of structurally flexible enzymes, enabling biomimetic transformation in the extracellular environment. Accordingly, porous organic frameworks, including metal organic frameworks (MOFs), covalent organic frameworks (COFs) and hydrogen-bonded organic frameworks (HOFs), have emerged as ideal supports for the immobilization of enzymes because of their structural features including ultrahigh surface area, tailorable porosity, and versatile framework compositions. Specially, organic framework-encased enzymes have shown significant enhancement in stability and reusability, and their tailorable pore opening provides a gatekeeper-like effect for guest sieving, which is beneficial for mimicking intracellular biocatalysis processes. This immobilization technique brings new insight into the development of next-generation enzyme materials and shows huge potential in healthcare applications, such as biomarker diagnosis, biostorage, and cancer and antibacterial therapies. In this review, we describe the state-of-the-art strategies for the structural immobilization of enzymes using the well-explored MOFs and burgeoning COFs and HOFs as scaffolds, with special emphasis on how these porous framework-confined technologies can provide a favorable microenvironment for mimicking natural biocatalysis. Subsequently, advanced characterization techniques for enzyme conformation, the effect of the confined microenvironment on the activity of enzymes, and the emerging healthcare applications will be surveyed.

Photosensitizer-Polypeptide Conjugate for Effective Elimination of Candida albicans Biofilm

Persistent fungal infections caused by biofilms seriously endanger human health. In this study, a photosensitizer-polypeptide conjugate (PPa-cP) comprising a photosensitizer, pyropheophorbide a (PPa), and a cationic polypeptide (cP) is readily synthesized for effective antifungal and antibiofilm treatment. Compared with free PPa, the cationic PPa-cP shows enhanced binding ability to the negatively charged surface of Candida albicans (C. albicans) through electrostatic interactions. As a result, PPa-cP exhibits effective antifungal efficiency against both C. albicans and fluconazole-resistant C. albicans in vitro under light irradiation. The minimum inhibitory concentration (MIC) of PPa-cP for both C. albicans and fluconazole-resistant C. albicans is 1 µm. In addition, PPa-cP also shows improved penetration in a C. albicans biofilm, thus effectively eliminating the C. albicans biofilm by photodynamic effects. More importantly, PPa-cP demonstrats significantly enhanced therapeutic effects in a fluconazole-resistant C. albicans-infected rat model with minimal side effects. In conclusion, the current work presents an effective strategy to combat biofilm infections associated with biomedical equipment.

Cyanobacteria-based self-oxygenated photodynamic therapy for anaerobic infection treatment and tissue repair

Photodynamic therapy (PDT) is an important technique to deal with drug-resistant bacterial infections in the post-antibiotic era. However, the hypoxic environment in intractable infections such as refractory keratitis and periodontitis, makes PDT more difficult. In this work, spontaneous oxygen-producing cyanobacteria were used as the carrier of photosensitizer (Ce6), and ultrasmall Cu5.4O nanoparticles (Cu5.4O USNPs) with catalase activity for infection and inflammation elimination and rapid tissue repair (CeCycn-Cu5.4O). The loading of Ce6 and Cu5.4O USNPs onto cyanobacteria surface were confirmed by transmission electron microscopy, nano particle size analyzer, scanning electron microscopy. In vitro sterilization and biofilm removal experiments demonstrated that the restriction of hypoxic environment to PDT was significantly alleviated due to the oxygen production of cyanobacteria. Under laser irradiation, the close transfer of energy photons to oxygen produced by cyanobacteria reduced more than 90% of Ce6 dosages (660 nm, 200 mW/cm2, 2 min). It is worth mentioning that both rapid sterilization through PDT and long-term oxidized free radicals elimination were achieved by adjusting the ratio of Ce6 and Cu5.4O USNPs. Both periodontitis and refractory keratitis animal models proved the excellent self-oxygenation enhanced antibacterial property and promotion of tissue repair.