Pd-Cu nanoalloy for dual stimuli-responsive chemo-photothermal therapy against pathogenic biofilm bacteria

Acidic biofilm microenvironment-responsive ROS generation via a protein nanoassembly with hypoxia-relieving and GSH-depleting capabilities for efficient elimination of biofilm bacteria

Reactive oxygen species (ROS) are widely considered to the effective therapeutics for fighting bacterial infections especially those associated with biofilm. However, biofilm microenvironments including hypoxia, limited H2O2, and high glutathione (GSH) level seriously limit the therapeutic efficacy of ROS-based strategies. Herein, we have developed an acidic biofilm microenvironment-responsive antibacterial nanoplatform consisting of copper-dopped bovine serum albumin (CBSA) loaded with copper peroxide (CuO2) synthesized in situ and indocyanine green (ICG). The three-in-one nanotherapeutics (CuO2/ICG@CBSA) are capable of releasing Cu2+ and H2O2 in a slightly acidic environment, where Cu2+ catalyzes the conversion of H2O2 into hydroxyl radical (•OH) and consumes the highly expressed GSH to disrupt the redox homeostasis. With the assistance of an 808 nm laser, the loaded ICG not only triggers the production of singlet oxygen (1O2) by a photodynamic process, but also provides photonic hyperpyrexia that further promotes the Fenton-like reaction for enhancing •OH production and induces thermal decomposition of CuO2 for the O2-self-supplying 1O2 generation. The CuO2/ICG@CBSA with laser irradiation demonstrates photothermal-augmented multi-mode synergistic bactericidal effect and is capable of inhibiting biofilm formation and eradicating the biofilm bacteria. Further in vivo experiments suggest that the CuO2/ICG@CBSA can effectively eliminate wound infections and accelerate wound healing. The proposed three-in-one nanotherapeutics with O2/H2O2-self-supplied ROS generating capability show great potential in treating biofilm-associated bacterial infections. STATEMENT OF SIGNIFICANCE: Here, we have developed an acidic biofilm microenvironment-responsive nanoplatform consisting of copper-dopped bovine serum albumin (CBSA) loaded with copper peroxide (CuO2) synthesized in situ and indocyanine green (ICG). The nanotherapeutics (CuO2/ICG@CBSA) are capable of releasing Cu2+ and H2O2 in an acidic environment, where Cu2+ catalyzes the conversion of H2O2 into •OH and consumes the overexpressed GSH to improve oxidative stress. With the aid of an 808 nm laser, ICG provides photonic hyperpyrexia for enhancing •OH production, and triggers O2-self-supplying 1O2 generation. CuO2/ICG@CBSA with laser irradiation displays photothermal-augmented multi-mode antibacterial and antibiofilm effect. Further in vivo experiments prove that CuO2/ICG@CBSA effectively eliminates wound infection and promotes wound healing. The proposed three-in-one nanotherapeutics show great potential in treating biofilm-associated bacterial infections.

Recent Progress in Multifunctional Stimuli-Responsive Combinational Drug Delivery Systems for the Treatment of Biofilm-Forming Bacterial Infections

Drug-resistant infectious diseases pose a substantial challenge and threat to medical regimens. While adaptive laboratory evolution provides foresight for encountering such situations, it has inherent limitations. Novel drug delivery systems (DDSs) have garnered attention for overcoming these hurdles. Multi-stimuli responsive DDSs are particularly effective due to their reduced background leakage and targeted drug delivery to specific host sites for pathogen elimination. Bacterial infections create an acidic state in the microenvironment (pH: 5.0-5.5), which differs from normal physiological conditions (pH: 7.4). Infected areas are characterized by the overexpression of hyaluronidase, gelatinase, phospholipase, and other virulence factors. Consequently, several effective stimuli-responsive DDSs have been developed to target bacterial pathogens. Additionally, biofilms, structured communities of bacteria encased in a self-produced polymeric matrix, pose a significant challenge by conferring resistance to conventional antimicrobial treatments. Recent advancements in nano-drug delivery systems (nDDSs) show promise in enhancing antimicrobial efficacy by improving drug absorption and targeting within the biofilm matrix. nDDSs can deliver antimicrobials directly to the biofilm, facilitating more effective eradication of these resilient bacterial communities. Herein, this review examines challenges in DDS development, focusing on enhancing antibacterial activity and eradicating biofilms without adverse effects. Furthermore, advances in immune system modulation and photothermal therapy are discussed as future directions for the treatment of bacterial diseases.

Phytic Acid-Promoted Deposition of Gold Nanoparticles with Grafted Cationic Polymer Brushes for the Construction of Synergistic Contact-Killing and Photothermal Bactericidal Coatings

Medical implants are constantly facing the risk of bacterial infections, especially infections caused by multidrug resistant bacteria. To mitigate this problem, gold nanoparticles with alkyl bromide moieties (Au NPs-Br) on the surfaces were prepared. Xenon light irradiation triggered the plasmon effect of Au NPs-Br to induce free radical graft polymerization of 2-(dimethylamino)ethyl methacrylate (DMAEMA), leading to the formation of poly(DMAEMA) brush-grafted Au NPs (Au NPs-g-PDM). The Au NPs-g-PDM nanocomposites were conjugated with phytic acid (PA) via electrostatic interaction and van der Waals interaction. The as-formed aggregates were deposited on the titanium (Ti) substrates to form the PA/Au NPs-g-PDM (PAP) hybrid coatings through surface adherence of PA and the gravitational effect. Synergistic bactericidal effects of contact-killing caused by the cationic PDM brushes, and local heating generated by the Au NPs under near-infrared irradiation, conferred strong antibacterial effects on the PAP-deposited Ti (Ti-PAP) substrates. The synergistic bactericidal effects reduced the threshold temperature required for the photothermal sterilization, which in turn minimized the secondary damage to the implant site. The Ti-PAP substrates exhibited 97.34% and 99.97% antibacterial and antiadhesive efficacy, respectively, against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), compared to the control under in vitro antimicrobial assays. Furthermore, the as-constructed Ti-PAP surface exhibited a 99.42% reduction in the inoculated S. aureus under in vivo assays. In addition, the PAP coatings exhibited good biocompatibility in the hemolysis and cytotoxicity assays as well as in the subcutaneous implantation of rats.

Tunable Zeolitic Imidazolate Framework-8 Nanoparticles for Biomedical Applications

Zeolite imidazole framework-8 (ZIF-8) is the most prestigious one among zeolitic imidazolate framework (ZIF) with tunable dimensions and unique morphological features. Utilizing its synthetic adjustability and structural regularity, ZIF-8 exhibits enhanced flexibility, allowing for a wide range of functionalities, such as loading of nanoparticle components while preserving biomolecules activity. Extensive efforts are made from investigating synthesis techniques to develop novel applications over decades. In this review, the development and recent progress of various synthesis approaches are briefly summarized. In addition, its interesting properties such as adjustable porosity, excellent thermal, and chemical stabilities are introduced. Further, five representative biomedical applications are highlighted based on above physicochemical properties. Finally, the remaining challenges and offered insights into the future outlook are also discussed. This review aims to understand the co-relationships between structures and biomedical functionalities, offering the opportunity to construct attractive materials with promising characteristics.

Strategies to Promote the Journey of Nanoparticles Against Biofilm-Associated Infections

Biofilm-associated infections are one of the most challenging healthcare threats for humans, accounting for 80% of bacterial infections, leading to persistent and chronic infections. The conventional antibiotics still face their dilemma of poor therapeutic effects due to the high tolerance and resistance led by bacterial biofilm barriers. Nanotechnology-based antimicrobials, nanoparticles (NPs), are paid attention extensively and considered as promising alternative. This review focuses on the whole journey of NPs against biofilm-associated infections, and to clarify it clearly, the journey is divided into four processes in sequence as 1) Targeting biofilms, 2) Penetrating biofilm barrier, 3) Attaching to bacterial cells, and 4) Translocating through bacterial cell envelope. Through outlining the compositions and properties of biofilms and bacteria cells, recent advances and present the strategies of each process are comprehensively discussed to combat biofilm-associated infections, as well as the combined strategies against these infections with drug resistance, aiming to guide the rational design and facilitate wide application of NPs in biofilm-associated infections.

One-Stop Integrated Nanoagent for Bacterial Biofilm Eradication and Wound Disinfection

To meet the requirements of biomedical applications in the antibacterial realm, it is of great importance to explore nano-antibiotics for wound disinfection that can prevent the development of drug resistance and possess outstanding biocompatibility. Therefore, we attempted to synthesize an atomically dispersed ion (Fe) on phenolic carbon quantum dots (CQDs) combined with an organic photothermal agent (PTA) (Fe@SAC CQDs/PTA) via a hydrothermal/ultrasound method. Fe@SAC CQDs adequately exerted peroxidase-like activity while the PTA presented excellent photothermal conversion capability, which provided enormous potential in antibacterial applications. Based on our work, Fe@SAC CQDs/PTA exhibited excellent eradication of Escherichia coli (>99% inactivation efficiency) and Staphylococcus aureus (>99% inactivation efficiency) based on synergistic chemodynamic therapy (CDT) and photothermal therapy (PTT). Moreover, in vitro experiments demonstrated that Fe@SAC CQDs/PTA could inhibit microbial growth and promote bacterial biofilm destruction. In vivo experiments suggested that Fe@SAC CQDs/PTA-mediated synergistic CDT and PTT exhibited great promotion to wound disinfection and recovery effects. This work indicated that Fe@SAC CQDs/PTA could serve as a broad-spectrum antimicrobial nano-antibiotic, which was simultaneously beneficial for bacterial biofilm eradication, wound disinfection, and wound healing.

A multifunctional hydrogel dressing with high tensile and adhesive strength for infected skin wound healing in joint regions

Most hydrogel dressings are designed for skin wounds in flat areas, and few are focused on the joint skin regions which undergo frequent movement. The mismatch of mechanical properties and poor fit between a hydrogel dressing and a wound in joint skin results in hydrogel shedding, bacterial infection and delayed healing. Therefore, it is of great significance to design and prepare a multifunctional hydrogel with high tensile and tissue-adhesive strength as well as other therapeutic effects for the treatment of joint skin wounds. In this work, a multifunctional hydrogel was reasonably prepared by simply mixing polyvinyl alcohol (PVA), borax, tannic acid (TA) and iron(III) chloride in certain proportions, which was further used to treat the skin wounds at the joint of the hind limb. Acting as the physical crosslinkers, borax and TA dynamically bond with PVA and provide the resulting hydrogel with strong tensile, fast shape-adaptive and self-healing properties. The photothermal bacteriostatic activity of the hydrogel is attributed to the formation of a metallic polyphenol network (MPN) between ferric ions and TA. In addition, the hydrogel exhibits high levels of adhesion, hemostatic performance, antioxidant abilities, and biocompatibility, and shows great potential to promote joint skin wound healing.

Hierarchically Released Liquid Metal Nanoparticles for Mild Photothermal Therapy/Chemotherapy of Breast Cancer Bone Metastases via Remodeling Tumor Stromal Microenvironment

Currently, the treatment strategy for bone metastasis is mainly to inhibit the growth of tumor cells and the activity of osteoclasts, while ignoring the influence of the tumor stromal microenvironment (TSM) on the progression of bone metastasis. Herein, a dual-target liquid metal (LM)-based drug delivery system (DDS) with favorable photothermal performance is designed to spatially program the delivery of multiple therapeutic agents to enhance the treatment of bone metastasis through TSM remodeling. Briefly, mesoporous silicon-coated LM is integrated into zeolitic imidazolate framework-8 (ZIF-8) with both bone-seeking and tumor-targeting capacities. Curcumin (Cur), a tumor microenvironment modulator, is encapsulated into ZIF-8, and doxorubicin (DOX) is enclosed inside mesoporous silicon. Specific accumulation of the LM-based DDS in bone metastases first relieves the tumor stroma by releasing Cur in response to the acidic tumor microenvironment and then releases DOX deep into the tumor under near-infrared light irradiation. The combined strategy of the LM-based DDS and mild photothermal therapy has been shown to effectively restrain cross-talk between osteoclasts and tumor cells by inhibiting the secretion of transforming growth factor-β, degrading extracellular matrix components, and increasing infiltration of CD4+ and CD8+ T cells, which provides a promising strategy for the treatment of bone metastases.

A CO-mediated photothermal therapy to kill drug-resistant bacteria and minimize thermal injury for infected diabetic wound healing

With an increasing proportion of drug-resistant bacteria, photothermal therapy (PTT) is a promising alternative to antibiotic treatment for infected diabetic skin ulcers. However, the inevitable thermal damage to the tissues restricts its clinical practice. Carbon monoxide (CO), as a bioactive gas molecule, can selectively inhibit bacterial growth and promote tissue regeneration, which may be coordinated with PTT for drug-resistant bacteria killing and tissue protection. Herein, a CO-mediated PTT agent (CO@mPDA) was engineered by loading manganese carbonyl groups into mesoporous polydopamine (mPDA) nanoparticles via coordination interactions between the metal center and a catechol group. Compared to the traditional PTT, the CO-mediated PTT increases the inhibition ratio of the drug-resistant bacteria both in vitro and in diabetic wound beds by selectively inhibiting the co-chaperone of the heat shock protein 90 kDa (Hsp90), and lowers the heat resistance of the bacteria rather than the mammalian tissues. Meanwhile, the tissue-protective proteins, such as Hsp90 and vimentin (Vim), are upregulated via the WNT and PI3K-Akt pathways to reduce thermal injury, especially with a laser with a high-power density. The CO-mediated PTT unified the bacterial killing with tissue protection, which offers a promising concept to improve PTT efficiency and minimize the side-effects of PTT when treating infected skin wounds.

Trends in Photothermal Nanostructures for Antimicrobial Applications

The rapid development of antimicrobial resistance due to broad antibiotic utilisation in the healthcare and food industries and the non-availability of novel antibiotics represents one of the most critical public health issues worldwide. Current advances in nanotechnology allow new materials to address drug-resistant bacterial infections in specific, focused, and biologically safe ways. The unique physicochemical properties, biocompatibility, and wide range of adaptability of nanomaterials that exhibit photothermal capability can be employed to develop the next generation of photothermally induced controllable hyperthermia as antibacterial nanoplatforms. Here, we review the current state of the art in different functional classes of photothermal antibacterial nanomaterials and strategies to optimise antimicrobial efficiency. The recent achievements and trends in developing photothermally active nanostructures, including plasmonic metals, semiconductors, and carbon-based and organic photothermal polymers, and antibacterial mechanisms of action, including anti-multidrug-resistant bacteria and biofilm removal, will be discussed. Insights into the mechanisms of the photothermal effect and various factors influencing photothermal antimicrobial performance, emphasising the structure-performance relationship, are discussed. We will examine the photothermal agents' functionalisation for specific bacteria, the effects of the near-infrared light irradiation spectrum, and active photothermal materials for multimodal synergistic-based therapies to minimise side effects and maintain low costs. The most relevant applications are presented, such as antibiofilm formation, biofilm penetration or ablation, and nanomaterial-based infected wound therapy. Practical antibacterial applications employing photothermal antimicrobial agents, alone or in synergistic combination with other nanomaterials, are considered. Existing challenges and limitations in photothermal antimicrobial therapy and future perspectives are presented from the structural, functional, safety, and clinical potential points of view.

Drug-Free Antimicrobial Nanomotor for Precise Treatment of Multidrug-Resistant Bacterial Infections

Manufacturing heteronanostructures with specific physicochemical characteristics and tightly controllable designs is very appealing. Herein, we reported NIR-II light-driven dual plasmonic (AuNR-SiO₂-Cu₇S₄) antimicrobial nanomotors with an intended Janus configuration through the overgrowth of copper-rich Cu₇S₄ nanocrystals at only one high-curvature site of Au nanorods (Au NRs). These nanomotors were applied for photoacoustic imaging (PAI)-guided synergistic photothermal and photocatalytic treatment of bacterial infections. Both the photothermal performance and photocatalytic activity of the nanomotors are dramatically improved owing to the strong plasmon coupling between Au NRs and the Cu₇S₄ component and enhanced energy transfer. The motion behavior of nanomotors promotes transdermal penetration and enhances the matter-bacteria interaction. More importantly, the directional navigation and synergistic antimicrobial activity of the nanomotors could be synchronously driven by NIR-II light. The marriage of active motion and enhanced antibacterial activity resulted in the expected good antibacterial effects in an abscess infection mouse model.

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.

Antibody conjugated Au/Ir@Cu/Zn-MOF probe for bacterial lateral flow immunoassay and precise synergistic antibacterial treatment

Staphylococcus aureus is one of the most prevalent threats to public health. Rapid detection with high sensitivity and targeted killing is crucial to curb its spread. Herein, a metal-bearing nanocomposite, consisting of a bimetallic nanoparticle and a metal-organic framework (Au/Ir@Cu/Zn-MOF) was constructed. Upon conjugation with anti-S. aureus antibody, this nanocomposite (Ab-Au/Ir@Cu/Zn-MOF) was exploited for its dual functions, i.e. as a reporting probe in a lateral flow immunoassay and a high efficiency antibacterial reagent. Benefiting from the enrichment of Au/Ir NPs by the Cu/Zn-MOF, the Au/Ir@Cu/Zn-MOF-based lateral flow immunoassay sensor exhibited a visual limit of detection of 10³ CFU/mL, which was100 times more sensitive than Au/Ir-based sensor. Moreover, the Ab-Au/Ir@Cu/Zn-MOF probe possessed synergistic photothermal-chemodynamic bactericidal effect that specifically targeted against S. aureus. Under a co-treatment by H₂O₂ (0.4 mM) and 808 nm near infrared irradiation (1 W/cm², 5 min), complete sterilization of 5 × 10⁵-10⁶ CFU/mL S. aureus was achieved at a nanocomposite concentration as low as 6.25 μg/mL. The superior antibacterial efficiency was attributable to the three-fold properties of the Ab-Au/Ir@Cu/Zn-MOF probe: (1) enhanced multi-enzyme mimicking activities that promote reactive oxygen species generation, (2) high photothermal activity (efficiency of 53.70%), and (3) bacteria targeting ability via the antibody coating. By changing the antibody, this nanocomposite can be tailored to target a wide range of bacteria species, for detection and for precise antibacterial treatment.

Modulating the local coordination environment of cobalt single-atomic nanozymes for enhanced catalytic therapy against bacteria

Single-atomic nanozymes (SANZs) characterized by atomically dispersed single metal atoms have recently contributed to breakthroughs in biomedicine due to their satisfactory catalytic activity and superior selectivity compared to their nanoscale counterparts. The catalytic performance of SANZs can be improved by modulating their coordination structure. Therefore, adjusting the coordination number of the metal atoms in the active center is a potential method for enhancing the catalytic therapy effect. In this study, we synthesized various atomically dispersed Co nanozymes with different nitrogen coordination numbers for peroxidase (POD)-mimicking single-atomic catalytic antibacterial therapy. Among the single-atomic Co nanozymes with nitrogen coordination numbers of 3 (SACNZs-N₃-C) and 4 (SACNZs-N₄-C), single-atomic Co nanozymes with a coordination number of 2 (SACNZs-N₂-C) had the highest POD-like catalytic activity. Kinetic assays and Density functional theory (DFT) calculations indicated that reducing the coordination number can lower the reaction energy barrier of single-atomic Co nanozymes (SACNZs-N_x-C), thereby increasing their catalytic performance. In vitro and in vivo antibacterial assays demonstrated that SACNZs-N₂-C had the best antibacterial effect. This study provides proof of concept for enhancing single-atomic catalytic therapy by regulating the coordination number for various biomedical applications, such as tumor therapy and wound disinfection. STATEMENT OF SIGNIFICANCE: The use of nanozymes that contain single-atomic catalytic sites has been shown to effectively promote the healing of bacteria-infected wounds by exhibiting peroxidase-like activity. The homogeneous coordination environment of the catalytic site has been associated with high antimicrobial activity, which provides insight into designing new active structures and understanding their mechanisms of action. In this study, we designed a series of cobalt single-atomic nanozymes (PSACNZs-N_x-C) with different coordination environments by shearing the Co-N bond and modifying polyvinylpyrrolidone (PVP). The synthesized PSACNZs-N_x-C demonstrated enhanced antibacterial activity against both Gram-positive and Gram-negative bacterial strains, and showed good biocompatibility in both in vivo and in vitro experiments.

Smart delivery systems for microbial biofilm therapy: Dissecting design, drug release and toxicological features

Bacterial biofilms are highly protected surface attached communities of bacteria that typically cause chronic infections. To address their recalcitrance to antibiotics and minimise side effects of current therapies, smart drug carriers are being explored as promising platforms for antimicrobials. Herein, we briefly summarize recent efforts and considerations that have been applied in the design of these smart carriers. We guide readers on a journey on how they can leverage the inherent biofilm microenvironment, external stimuli, or combine both types of stimuli in a predictable manner. The specific carrier features that are responsible for their 'on-demand' properties are detailed and their impact on antibiofilm property are further discussed. Moreover, an analysis on the impact of such features on drug release profiles is provided. Since nanotechnology represents a significant slice of the drug delivery pie, some insights on the potential toxicity are also depicted. We hope that this review inspires researchers to use their knowledge and creativity to design responsive systems that can eradicate biofilm infections.

Novel Microbial Palladium Nanoparticles with a High Photothermal Effect for Antibacterial Applications

Novel biocompatible palladium nanoparticles (Pd-NPs) have been prepared by microorganisms via Bacillus megaterium Y-4. It was demonstrated that ultrasonication treatment of biologically reduced Pd-NPs impart a much higher absorption in NIR regions and a better photothermal conversion efficiency to the material. The as-prepared material showed excellent biocompatibility and antibacterial activity under NIR irradiation. In less than 10 min, the disinfection efficiency for a low dosage of Pd-NPs (20 mg/L) was 99.99% toward both Staphylococcus aureus and Escherichia coli. The exclusive and even dispersed microbial Pd-NPs display a high efficiency of photothermal conversion under the irradiation of NIR, which endows them with excellent antibacterial activity in a low dosage.

Multifunctional hydrogel with reactive oxygen species scavenging and photothermal antibacterial activity accelerates infected diabetic wound healing

Management of diabetic wound has long been a clinical challenge due to pathological microenvironment of excessive inflammation, persistent hyperglycemia, and biofilm infection caused by overdue reactive oxygen species (ROS) production and defective blood vessels. Herein, a multifunctional hydrogel with ROS scavenging and photothermal antibacterial activity based on oxidized dextran (Odex), gallic acid-grafted gelatin (GAG) and Ferric ion, named OGF, was developed for treatment of infected wound in a diabetic mouse. This hydrogel was double-crosslinked by the dynamically Schiff-base bonds formed between aldehyde groups in Odex and amino groups in GAG and the metal coordination bonds formed between Ferric ion and polyphenol groups or carboxyl groups in GAG, which endowed the resulted OGF hydrogel with well injectable, self-healing and adhesive properties. Due to the high-efficiency photothermal effect of Ferric ion/polyphenol chelate, this hydrogel killed Staphylococcus aureus and Escherichia coli rapidly and completely within 3.5 min under near-infrared light radiation. Furthermore, this composed hydrogel presented good antioxidation, hemostasis and biocompatibility. It also remarkably accelerated the complete re‑epithelialization of Staphylococcus aureus‑infected wound in diabetic mice within 18 days by eliminating infection, mitigating oxidative stress and inflammation, and facilitating angiogenesis. Therefore, the proposed multifunctional hydrogel exerts a great potential for translation in the clinical management of diabetic wounds. STATEMENT OF SIGNIFICANCE: High reactive oxygen species (ROS) levels and vascular defects in diabetic wounds can lead to excessive inflammation, persistent hyperglycemia, biofilm infection and other pathological microenvironments, which can further develop to the chronic wounds. In this study, we designed a multifunctional hydrogel with ROS-scavenging ability and photothermal antibacterial activity for the treatment of infected diabetic wound. As expected, this multifunctional hydrogel dressing highly accelerated the complete re‑epithelialization of Staphylococcus aureus‑infected wound in diabetic mouse by eliminating infection, mitigating oxidative stress and inflammation, as well as facilitating angiogenesis. This work provides a promising therapeutic strategy for infected diabetic wound by inhibition of oxidative stress and biofilm infection.

Stimuli-Activable Metal-Bearing Nanomaterials and Precise On-Demand Antibacterial Strategies

Bacterial infections remain the leading cause of death worldwide today. The emergence of antibiotic resistance has urged the development of alternative antibacterial technologies to complement or replace traditional antibiotic treatments. In this regard, metal nanomaterials have attracted great attention for their controllable antibacterial functions that are less prone to resistance. This review discusses a particular family of stimuli-activable metal-bearing nanomaterials (denoted as SAMNs) and the associated on-demand antibacterial strategies. The various SAMN-enabled antibacterial strategies stem from basic light and magnet activation, with the addition of bacterial microenvironment responsiveness and/or bacteria-targeting selectivity and therefore offer higher spatiotemporal controllability. The discussion focuses on nanomaterial design principles, antibacterial mechanisms, and antibacterial performance, as well as emerging applications that desire on-demand and selective activation (i.e., medical antibacterial treatments, surface anti-biofilm, water disinfection, and wearable antibacterial materials). The review concludes with the authors' perspectives on the challenges and future directions for developing industrial translatable next-generation antibacterial strategies.

Photothermally responsive chitosan-coated iron oxide nanoparticles for enhanced eradication of bacterial biofilms

This work developed a pH/NIR responsive antibacterial agent (CS-FeNPs) composed of chitosan (CS) and Fe₃O₄ nanoparticles (FeNPs). CS triggers bacterial attraction through surface charge, while Fe acts as a photothermal agent (PTA). The CS-Fe NPs exhibited antibacterial and antibiofilm activity against both bacteria (G+/G-). However, higher activity was observed against bacteria (G-) due to electrostatic interactions. The CS-FeNPs bind with the bacterial membrane through electrostatic interactions and disturb bacterial cells. Later, in an acidic environment, CS-FeNPs bind with bacterial membrane, and NIR irradiation leads the antibacterial activity. CS-FeNPs exhibited a potential photothermal conversion efficiency (η) of 21.53 %. Thus, it converts NIR irradiation into heat to kill the bacterial pathogen. The CS-FeNPs were found to be less cytotoxic with great antibacterial efficiency on planktonic bacteria and their biofilm, which indicates that they deserve to develop potential and safe treatment strategies for the treatment of bacterial infections.

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

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

Synergistic chemo-/photothermal therapy based on supercritical technology-assisted chitosan-indocyanine green/luteolin nanocomposites for wound healing

Despite the success, it is highly challenging to battle against pathogenic biofilms-based chronic bacterial infections by conventional antibiotic therapy. Herein, we report a near-infrared (NIR)/acid-induced nanoplatform based on chitosan (CS)-coated indocyanine green (ICG, photosensitizer)/luteolin (LUT, a natural quorum sensing inhibitor) nanocomposites (ICG/LUT-CS) as antibacterial and antibiofilm agents for skin wound healing. Initially, the ICG/LUT nanoplatforms are prepared by the supercritical antisolvent technology and coated with the CS layer. The obtained ICG/LUT-CS with ultra-high encapsulation efficiency exhibited more favorable photothermal conversion effects and improved NIR laser/acid dual-induced drug release behavior than individual modalities, achieving exceptional bacteria-killing and biofilm elimination effects. Moreover, the ICG/LUT-CS realized the synergetic effects of chemotherapy and photothermal therapy outcomes for wound healing. Together, our findings provided an appealing strategy for the rapid preparation and future translational application of ICG/LUT-CS as an ideal agent for fighting against biofilm infections.

Progress and prospects of nanomaterials against resistant bacteria

Drug-resistant bacterial infections are increasingly heightening, which lead to more severe illness, higher cost of treatment and increased risk of death. Nanomaterials-based therapy, an "outrider", serving as a kind of innovative antimicrobial therapeutics, showing promise in replacing antimicrobial agents and enhancing the activity of antibiotics, generally bases on the various inorganic and/or organic materials. When the size of those materials is below to a certain nano-level and the content of nanomaterials is above a certain amount, they are lethal to the resistant bacteria, which bypass the traditional bacterial resistance mechanisms. This review highlights the effect of nanomaterials in combating extracellular/intracellular bacteria and eradicating biofilms. Based on the studies searched on the Web of Science through relevant keywords, this review article starts with analyzing the current situation, resistance mechanisms, and treatment difficulties of bacteria resistance. Then, the efficacy of nanomaterials against resistant bacteria and their mechanisms (e.g., physical impairment, biofilm lysis, regulating bacterial metabolism, protein and DNA replication as well as enhancing the antibiotics concentration in infected cells) are collected. Lastly, the factors affecting the antibacterial efficacy are argued from the side of nanomatrials and bacterium, which followed by the emerging challenges and recent perspectives of achieving higher targeting released nanomaterials as antibacterial therapeutics.

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.

Application of Metal–Organic Framework in Diagnosis and Treatment of Diabetes

Diabetes-related chronic wounds are often accompanied by a poor wound-healing environment such as high glucose, recurrent infections, and inflammation, and standard wound treatments are fairly limited in their ability to heal these wounds. Metal–organic frameworks (MOFs) have been developed to improve therapeutic outcomes due to their ease of engineering, surface functionalization, and therapeutic properties. In this review, we summarize the different synthesis methods of MOFs and conduct a comprehensive review of the latest research progress of MOFs in the treatment of diabetes and its wounds. State-of-the-art in vivo oral hypoglycemic strategies and the in vitro diagnosis of diabetes are enumerated and different antimicrobial strategies (including physical contact, oxidative stress, photothermal, and related ions or ligands) and provascular strategies for the treatment of diabetic wounds are compared. It focuses on the connections and differences between different applications of MOFs as well as possible directions for improvement. Finally, the potential toxicity of MOFs is also an issue that we cannot ignore.

Antibody-targeted and streptomycin-chitosan oligosaccharide-modified gold nanoshells for synergistic chemo-photothermal therapy of drug-resistant bacterial infection

Despite the many advanced strategies that are available, rapid gene mutation in multidrug-resistant bacterial infections remains a major challenge. Combining new therapeutic strategies such as chemo-photothermal therapy (PTT) with high antibacterial efficiency against drug-resistant Listeria monocytogenes (LM) is urgently needed. Here, we report synergistic chemo-PTT against drug-resistant LM based on antibody-targeted and streptomycin-chitosan oligosaccharide-modified gold nanoshells (anti-STR-CO-GNSs) as all-in-one nanotheranostic agents for the first time, which was used for accurate antibacterial applications. The anti-STR-CO-GNSs showed excellent photothermal conversion efficiency (31.97%) and were responsive to near-infrared (NIR) and pH dual stimuli-triggered antibiotic release, resulting in outstanding chemo-photothermal effects against LM. In vitro chemo-photothermal effect of anti-STR-CO-GNSs with laser irradiation caused a greater antibacterial effect (1.37%), resulting in more rapid killing of LM and prevention of LM regrowth. Most importantly, the mice receiving the anti-STR-CO-GNSs with laser irradiation specifically at the sites of LM infections healed almost completely, leaving only scars on the surface of the skin and resulting in superior inhibitory effects from combined chemo-PTT. Overall, our findings suggest that chemo-PTT using smart biocompatible anti-STR-CO-GNSs is a favorable potential alternative to combat the increasing threat of drug-resistant LM, which opens a new door for clinical anti-infection therapy in the future.

High-Efficiency Near-Infrared Light Responsive Antibacterial System for Synergistic Ablation of Bacteria and Biofilm

Bacterial infection is seriously threatening human health, and the design of high-efficiency and good biocompatibility antibacterial agents is an urgent problem to be solved. However, with the emergence of drug-resistant bacteria, the existing antibacterial agents have low killing efficiency, and the formation of biofilms has further weakened the therapeutic effect. Herein, we constructed an efficient antibacterial system mediated by near-infrared light for synergistic antibacterial and biofilm dissipation. Specifically, the ZnO/Ti₃C₂T_x with heterojunction was synthesized by hydrothermal growth of ZnO on the surface of lamellar Ti₃C₂T_x-MXene. The prepared ZnO/Ti₃C₂T_x had better photothermal ability than ZnO and Ti₃C₂T_x, respectively. The local thermal effect can not only destroy the integrity of the bacterial membrane but also promote the release of Zn²⁺ ions and further improve the antibacterial performance. ZnO/Ti₃C₂T_x achieved a 100% sterilization rate (better than either ZnO or Ti₃C₂T_x) at 150 μg mL^-1. The biofilm dissipation experiment further proved its excellent biofilm ablation effect. More importantly, the results of in vitro cell culture and animal experiments have demonstrated its good biological safety. In summary, this new type of nanomaterial shows strong local chemical photothermal sterilization ability and has great potential to replace traditional antibacterial agents.

Application of nanotechnology in the diagnosis and treatment of acute pancreatitis

Acute pancreatitis (AP) is a common digestive system disease. The severity of AP ranges from mild edema in the pancreas to severe systemic inflammatory responses leading to peripancreatic/pancreatic necrosis, multi-organ failure and death. Improving the sensitivity of AP diagnosis and developing alternatives to traditional methods to treat AP have gained the attention of researchers. With the continuous rise of nanotechnology, it is being widely used in daily life, biomedicine, chemical energy and many other fields. Studies have demonstrated the effectiveness of nanotechnology in the diagnosis and treatment of AP. Nanotechnology has the advantages of simplicity, rapidity and sensitivity in detecting biomarkers of AP, as well as enhancing imaging, which helps in the early diagnosis of AP. On the other hand, nanoparticles (NPs) have oxidative stress inhibiting and anti-inflammatory effects, and can also be loaded with drugs as well as being used in anti-infection therapy, providing a new approach for the treatment of AP. In this article, we elaborate and summarize on the potential of nanoparticles for diagnostic and therapeutic applications in AP from the current reported literature and experimental results to provide useful guidelines for further research on the application of nanotechnology.