Targeting and arginine-driven synergizing photodynamic therapy with nutritional immunotherapy nanosystems for combating MRSA biofilms

Pt-Induced Sublattice Distortion Facilitates Enzyme Cascade Reactions for Eradicating Intracellularly Methicillin-Resistant Staphylococcus aureus and Enhancing Diabetic Wound Healing

Metal oxide nanozymes hold significant potential in combating bacterial infections; however, their ordered crystal structures limit the enhancement of catalytic activity, posing challenges in addressing clinical needs for eliminating intracellularly colonized bacteria. Here, we report the development of an integrated diagnostic-therapeutic microneedle patch incorporates the Res@PtZ-Z nanozyme hybrid. Res@PtZ-Z consists of a ZIF shell loaded with the natural compound resveratrol (Res), encapsulating a Pt-doped zinc oxide (ZnO) nanozyme core (PtZ). The Res component modulates charge distribution on the ZIF shell and attenuates bacterial virulence, thereby promoting the uptake of Res@PtZ-Z by host cells. The PtZ core, doped with Pt4+ to induce sublattice distortion in ZnO, exhibits oxidase-like, peroxidase-like, and catalase-like activities. Under intracellular hypoxic conditions, the cascade of these enzyme-like activities ensures a sustained generation of reactive oxygen species (ROS), enabling robust antibacterial effects. Additionally, Res@PtZ-Z enables real-time infection monitoring by oxidizing the 3,3',5,5'-tetramethylbenzidine (TMB) substrate to produce a distinct colorimetric response. This approach addresses both methicillin-resistant Staphylococcus aureus (MRSA) invasion and intracellular persistence, contributing to improved infection management and promoting wound healing.

On-demand celastrol delivery by hyaluronic acid-porphyrinic metal-organic frameworks for synergistic sonodynamic/pharmacological antibacterial therapy

Methicillin-resistant Staphylococcus aureus (MRSA) is one of the most prevalent bacterial pathogens. The multi-drug resistance and strong biofilm-forming ability make the treatment of MRSA infections challenging. It is urgent to develop antibiotic-free, noninvasive and effective strategies against MRSA infections. Recently, celastrol (CLT), a natural phytochemical, showed potent antimicrobial activity against planktonic MRSA. However, its further development was hindered by low solubility, short plasma half-life, poor bioavailability and severe systemic toxicity. To address these issues, hyaluronic acid-porphyrinic metal-organic frameworks loaded with CLT (HA@PCN-CLT) were fabricated for combating MRSA biofilms. Once encountering the overexpressed HAases in biofilm, their surface charge reversed to positive to facilitate biofilm penetration under ultrasound irradiation, which was revealed by 3D fluorescence image. In vitro release profiles suggested that HA@PCNCLT exhibited ultrasound promoted pH/HAase-responsive release properties. Taking advantage of superior sonodynamic performance and on-demand CLT release, HA@PCN-CLT NPs effectively reduced biofilm biomass and killed planktonic and biofilm-embedded MRSA. Moreover, HA@PCN-CLT NPs completely eradicated the MRSA infection in mice under ultrasound irradiation and promoted abscess healing by stimulating angiogenesis and collagen deposition, accompanied by excellent biocompatibility and negligible toxicity in vivo. HA@PCN-CLT NPs provided a promising antibiotic-free strategy against MRSA biofilms through synergistic combination of sonodynamic therapy and phytochemicals.

An ATP-activated spatiotemporally controlled hydrogel prodrug system for treating multidrug-resistant bacteria-infected pressure ulcers

Adenosine triphosphate (ATP)-activated prodrug approaches demonstrate potential in antibacterial uses. However, their efficacy frequently faces obstacles due to uncontrolled premature activation and spatiotemporal distribution differences under physiological circumstances. Herein, we present an endogenous ATP-activated prodrug system (termed ISD3) consisting of nanoparticles (indole-3-acetic acid/zeolitic imidazolate framework-8@polydopamine@platinum, IZPP) embedded in a silk fibroin-based hydrogel, aimed at treating multidrug-resistant (MDR) bacteria-infected pressure ulcers. Initially, an ultraviolet-triggered adhesive ISD3 barrier is formed over the pressure ulcer wound by a simple local injection. Subsequently, the bacteria-secreted ATP prompts the degradation of IZPP, allowing the loaded IAA prodrug and nanozyme to encounter spatiotemporally on a single carrier, thereby efficiently generating reactive oxygen species (ROS). Exposure to 808 nm near-infrared light enhances the catalytic reaction speed, boosting ROS levels for stronger antibacterial action. Once optimal antibacterial action is reached, ISD3 switches to a dormant state, halting any further ROS production. Moreover, the bioactive components in ISD3 can exert anti-inflammatory functions, aiding in pressure ulcer recovery. Overall, our research introduces a hydrogel prodrug strategy activated by bacterial endogenous ATP, which precisely manages ROS generation and accelerates the recovery of MDR bacteria-infected pressure ulcers.

The Purification and Characterization of a Novel Neutral Protease from Volvariella volvacea Fruiting Bodies and the Enzymatic Digestion of Soybean Isolates

A novel protease was isolated from the fruiting bodies of the straw mushroom Volvariella volvacea. The protease was purified 13.48-fold using a series of techniques, including ammonium sulfate precipitation, ultrafiltration, diethylaminoethyl fast-flow (DEAE FF) ion-exchange chromatography, and Superdex 75 gel filtration chromatography, resulting in a specific enzyme activity of 286.82 U/mg toward casein as a substrate. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) analysis revealed that the purified protease had a molecular weight of 24 kDa. The enzyme exhibited optimal activity at pH 7 and 50 °C, showing sensitivity to alkaline conditions and instability at elevated temperatures. The presence of Ca2+ significantly enhanced enzyme activity, whereas Ni2+ and Cu2+ exerted strong inhibitory effects, with other metal ions showing weak inhibition. β-mercaptoethanol, Tween-80, and Triton X-100 had more pronounced inhibitory effects, whereas PMSF, EDTA, and CTAB had weaker inhibitory effects. The Michaelis constant (Km) and maximum velocity (Vm) of the protease were determined to be 1.34 g/L and 3.45 μg/(mL·min), respectively. The protease exhibited a greater degree of enzymatic degradation of soybean-isolate protein (7.58%) compared to trypsin (5.24%), with the enzyme product containing a high percentage of medicinal amino acids (73.54%), particularly phenylalanine (Phe) and arginine (Arg), suggesting their presence at the enzyme's active site. These findings suggest that the protease from V. volvacea holds promising potential for applications in the food industry, particularly in protein hydrolysate production and flavor enhancement.

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).

Oxygenous and biofilm-targeted nanosonosensitizer anchored with Pt nanozyme and antimicrobial peptide in the gelatin/sodium alginate hydrogel for infected diabetic wound healing

Sonodynamic therapy is an emerging therapeutic approach for combating bacterial infections. However, the characteristics of hypoxia, high H2O2 microenvironment, and the formation of persistent biofilms in diabetic wound sites limit its efficacy in this field. To address these issues, we developed a multifunctional antibacterial hydrogel dressing PPCN@Pt-AMPs/HGel with the cross-linked gelatin and sodium alginate as the matrix, where the nanosonosensitizer PCN-224 was decorated with the oxygen-generating Pt nanoenzyme and further coupled with a biofilm-targeting antimicrobial peptide via an interacting polydopamine layer. This nano-composite hydrogel displayed improved mechanical properties as well as good biocompatibility and biodegradability. The catalase-like activity of the nanoparticles facilitated the ultrasound-induced generation of the singlet oxygen due to the catalytic decomposition of the H2O2 into O2. In vitro results showed that the hydrogel dressing exhibited excellent antimicrobial ability under low-intensity ultrasound stimulation, which could effectively inhibit the newly formed biofilm and eliminate the full-grown biofilms. In the infected diabetic wound of rats, PPCN@Pt-AMPs/HGel significantly enhanced the wound healing rate under low-intensity ultrasound stimulation and improved the regeneration outcomes by promoting granulation tissue formation, angiogenesis, and type III collagen deposition. In conclusion, our study provides a novel and effective antibacterial hydrogel dressing for sonodynamic treatment of diabetic wounds.

Phenylboronic acid-modified carbon dot-proteinase K nanohybrids for enhanced photodynamic therapy against bacterial biofilm infections

Nanohybrids combining phenylboronic acid-modified carbon dots (PCDs) and proteinase K have been engineered for addressing the formidable challenges of antimicrobial photodynamic therapy (aPDT) against bacterial biofilm infections, overcoming biofilm barrier obstruction, the limited diffusion of reactive oxygen species (ROS), and the inadequate ROS generation of traditional photosensitizers. PCDs are formulated for superior water solubility and robust singlet oxygen (1O2) production, mitigating issues related to dispersion and aggregation-induced quenching typical of conventional photosensitizers. The conjugation of phenylboronic acid to CDs not only enhanced 1O2 generation through increased electron-hole separation but also imparted strong bacterial binding capabilities to the PCDs, enabling broad-spectrum sterilization by maximizing the ROS-mediated bacterial destruction. Proteinase K, serving as a structural "glue", actively breaks down biofilms and facilitates the deep penetration of functional PCDs, aiding effective treatment of biofilm infections. In vivo studies confirm that PCDs-proteinase K nanohybrids dramatically accelerate healing in biofilm-infected wounds by synergizing enhanced photosensitization, potent bacterial adherence, and efficient biofilm elimination and penetration. This approach highlights a straightforward strategy to significantly advance aPDT, promoting the clinical adoption of non-antibiotic methods for combating bacterial biofilm infections. STATEMENT OF SIGNIFICANCE: 1) Phenylboronic acid-modified carbon dots (PCDs) were designed for enhanced water solubility and efficient singlet oxygen generation through surface modulation, also suggesting that surface modification can improve the inherent photosensitizing activity of CDs by promoting electron-hole separation; 2) The conjugation of phenylboronic acid endowed PCDs with strong bacterial binding capabilities, enabling highly efficient and broad-spectrum sterilization by maximizing reactive oxygen species-mediated bacterial destruction; 3) Incorporation of proteinase K (PK) leveraged its specific extracellular polymeric substance degrading capability, along with the stimuli-responsive release of PCDs from the PCDs-PK nanohybrids, facilitating biofilm breakdown and enabling deeper penetration of PCDs, thereby improving the treatment of biofilm infections.

NIR light-driven nanomotor with cascade photodynamic therapy for MRSA biofilm eradication and diabetic wound healing

Background: Diabetic wounds infected with methicillin-resistant Staphylococcus aureus (MRSA) are challenging to heal due to biofilm formation, which impairs conventional antibiotics with limited penetration and severe side effects. Near-infrared (NIR)-driven nanomotors with autonomous motion and photothermal effects show promise for antibacterial therapy but often lack targeted specificity. Lysostaphin (Ly), an enzyme targeting bacterial cell walls, offers excellent potential against drug-resistant MRSA. Methods: A novel NIR-driven CSIL nanomotor has fabricated by co-loading indocyanine green (ICG) and lysostaphin onto spinous yolk-shell structured C/SiO2@C nanoparticles. The autonomous motion, biofilm penetration, and antibacterial efficacy of CSIL nanomotors are evaluated in vitro, while their biofilm eradication and wound healing performance are assessed in an MRSA-infected diabetic mouse model using a cascade photodynamic therapy (CPDT) strategy. Results: CSIL nanomotors exhibit photothermal and photodynamic properties with MRSA-targeting specificity. They can effectively eradicate MRSA biofilms both in vitro and in vivo, suppress virulence and biofilm-related genes, thus promoting diabetic wound healing by shaping a microenvironment dominated by M2 macrophages. The CPDT strategy is able to avoid excessive ROS production and thermal damage, enabling safe and effective therapy. Conclusion: CSIL nanomotors, with integrated photothermal, photodynamic, and MRSA-targeting properties, represent a novel, efficient and targeted approach to antibacterial therapy in diabetic wounds, offering significant advantages over conventional antibiotics.

Arginine and colorectal cancer: Exploring arginine-related therapeutic strategies and novel insights into cancer immunotherapies

Concerning the progression of societies and the evolution of lifestyle and dietary habits, the potential for the development of human malignancies, particularly colorectal cancer (CRC), has markedly escalated, positioning it as one of the most prevalent and lethal forms of cancer globally. Empirical evidence indicates that the metabolic processes of cancerous and healthy cells can significantly impact immune responses and the fate of tumors. Arginine, a multifaceted amino acid, assumes a crucial and paradoxical role in various metabolic pathways, as certain tumors exhibit arginine auxotrophy while others do not. Notably, CRC is classified as arginine non-auxotrophic, possessing the ability to synthesize arginine from citrulline. Systemic arginine deprivation and the inhibition of arginine uptake represent two prevalent therapeutic strategies in oncological treatment. However, given the divergent behaviors of tumors concerning the metabolism and synthesis of arginine, one of these therapeutic approaches-namely systemic arginine deprivation-does not apply to CRC. This review elucidates the characteristics of arginine uptake inhibition and systemic arginine deprivation alongside their respective benefits and limitations in CRC. Furthermore, the involvement of arginine in immunotherapeutic strategies is examined in light of the most recent discoveries on various human malignancies.

Deep Red-Light-Mediated Nitric Oxide and Photodynamic Synergistic Antibacterial Therapy for the Treatment of Drug-Resistant Bacterial Infections

Infections caused by persistent, drug-resistant bacteria pose significant challenges in inflammation treatment, often leading to severe morbidity and mortality. Herein, the photosensitizer rhodamine derivatives are selected as the light-trapping dye and the electron-rich substituent N-nitrosoaminophen as the nitric oxide (NO)-releasing component to develop a multifunctional (deep) red-light activatable NO photocage/photodynamic prodrug for efficient treatment of wounds and diabetic foot infections. The prodrug, RhB-NO-2 integrates antimicrobial photodynamic therapy (aPDT), NO sterilization, and NO-mediated anti-inflammatory properties within a small organic molecule and is capable of releasing NO and generating Reactive oxygen species (ROS) when exposed to (deep) red laser (660 nm). This strategy overcomes the limitation of using a single photosensitizer, which is often inadequate for eliminating drug-resistant bacteria. Additionally, it demonstrates that NO released from the prodrug can interact with superoxide anions (O2 •-) generated by PDT to form a more reactive and oxidative agent, peroxynitrite (ONOO-). These three components act synergistically to enhance the antimicrobial effects. Furthermore, the released NO can inhibit the NF-κB pathway by regulating the expression of toll-like receptor 2 (TRL2) and tumor necrosis factor-α (TNF-α), thereby alleviating tissue inflammation. The developed prodrug ， RhB-NO-2 has the potential to expedite the healing of superficial infected wounds and offer a promising approach for treating diabetic foot ulcers (DFUs).

Photothermal Nano-Immunotherapy Against Methicillin-Resistant Staphylococcus aureus (MRSA) Biofilm Infections

Methicillin-resistant Staphylococcus aureus (MRSA) biofilm infections are a prevalent type of biofilm-associated infection with a poor prognosis and antibiotic resistance. The senescence of immune cells in the immune microenvironment contributes to biofilm formation. In this study, Ti₃C₂ MXene-PVA nanosheets loaded with metformin (Met@TiC) are developed for the treatment of MRSA biofilm infections. Nanosheets utilize near-infrared light to induce photothermal effects and provide direct bactericidal activity against biofilm structures. Met, which is known for its anti-inflammatory and anti-senescence properties, modulates immune responses by revitalizing the function of senescent macrophages within the biofilm microenvironment, thereby enhancing their phagocytic and biofilm-eradicating capabilities. The efficacy of this nanoplatform both in vitro and in an MRSA biofilm infection mouse model, demonstrating its potential as a photothermal nanoimmunotherapy for combating MRSA biofilm infections is validated. In summary, the Met@TiC nanoplatform offers a significant alternative to clinical solutions for MRSA biofilm infections.

Exploring the antibiofilm potential of chitosan nanoparticles by functional modification with chloroquine and deoxyribonuclease

Planktonic bacteria tend to form sessile community architectures to shield resident bacteria from various environmental stresses. The formed biofilm leads to the failure of conventional antimicrobial therapy. Extracellular macromolecules, including extracellular DNA (eDNA), proteins, lipids, and polysaccharides, crosslink into gel-like structures through electrostatic forces in the mature biofilm matrix. The stereo-structural integrity and chemical inertia of the extracellular polymeric matrix result in comprehensive antimicrobial resistance to antibacterial polysaccharides. Herein, an ionic gelation method was employed to functionalize cationic chitosan nanoparticles (CSNPs) with chloroquine and deoxyribonuclease. The modification involved shifting eDNA chirality through a DNA-intercalating agent, chloroquine, and hydrolyzing an eDNA scaffold with deoxyribonuclease. The antibiofilm activity was assessed against a standard Staphylococcus aureus strain and clinical subtype isolates. Functional modifications targeting eDNA improved the chitosan anti-biofilm efficiency (residual biomass decreased from 74.2 to 90.3 % to 16.7-24.6 %) by disrupting the biofilm matrix. The functional CSNPs worked as a sensitizer prodrug, contributing to a bactericidal process of chitosan itself (cell wall damage increased from 11.38-18.16 % to 55.2-61.4 %) by dispersing the biofilm-enclosed bacteria. In vivo, the bacterial burden of infected mouse joints was reduced by 4.1 lg CFU/mL. Our results indicate the potential of this chitosan-based anti-infection strategy in biofilm-related infections.

Blue light-activated 5,10,15,20-tetrakis(4-bromophenyl)porphyrin for photodynamic eradication of drug-resistant Staphylococcus aureus

Photodynamic therapy (PDT) has emerged as an effective way to deal with drug-resistant bacterial infections. Especially, blue light (BL) mediated PDT (BL-PDT) presents unique advantages in the treatments of skin infection due to the strong light absorption of superficial skin, weak penetration of BL and little damage to deep tissues. However, the photosensitizers used for BL-PDT are very limited, and the ongoing development of novel BL photosensitizers is indispensable. Porphyrins are good sources for developing efficient photosensitizers. Herein, for developing more effective BL photosensitizers, five porphyrin derivatives that can be excited by BL [5,10,15,20-tetraphenylporphyrin (TPP), 5,10,15,20-tetrakis(4-bromophenyl)porphyrin (TBPP), 5,10,15,20-tetrakis(4-chlorophenyl)porphyrin (TCPP), 5,10,15,20-tetrakis(4-fluorophenyl)porphyrin (TFPP), 5,10,15,20-tetrakis(4-iodophenyl)porphyrin (TIPP)] are subjected to the investigation of PDT against MRSA (methicillin resistant Staphylococcus aureus). The results reveal that TBPP-mediated BL-PDT shows outstanding bactericidal effects. Mechanism studies show that TBPP + BL can induce reactive oxygen species (ROS) up-regulated in MRSA, rupture cell membrane, inhibit ATP (adenosine triphosphate) production and virulence factor expression. Furthermore, TBPP + BL effectively eliminates MRSA form biofilms, inhibits biofilm formation and disintegrates mature biofilms. More importantly, TBPP-PDT significantly accelerate mouse skin wound healing in a biofilm infection model. Our work offers new insights into the development of novel BL photosensitizers.

Nanocatalytic medicine enabled next-generation therapeutics for bacterial infections

The rapid rise of antibiotic-resistant strains and the persistence of biofilm-associated infections have significantly challenged global public health. Unfortunately, current clinical high-dose antibiotic regimens and combination therapies often fail to completely eradicate these infections, which can lead to adverse side effects and further drug resistance. Amidst this challenge, however, the burgeoning development in nanotechnology and nanomaterials brings hopes. This review provides a comprehensive summary of recent advancements in nanomaterials for treating bacterial infections. Firstly, the research progress of catalytic therapies in the field of antimicrobials is comprehensively discussed. Thereafter, we systematically discuss the strategies of nanomaterials for anti-bacterial infection therapies, including endogenous response catalytic therapy, exogenous stimulation catalytic therapy, and catalytic immunotherapy, in order to elucidate the mechanism of nanocatalytic anti-infections. Based on the current state of the art, we conclude with insights on the remaining challenges and future prospects in this rapidly emerging field.

Anti-inflammatory effects of 1,7-dihydroxy-3,4-dimethoxyxanthone through inhibition of M1-phenotype macrophages via arginine/mitochondrial axis

It is known that 1,7-dihydroxy-3,4-dimethoxyxanthone (XAN), derived from Securidaca inappendiculata Hassk., exhibits anti-inflammatory and analgesic activities and inhibits M1 polarization of macrophages. However, its ability to alleviate inflammation induced by pro-inflammatory cytokines in THP-1 cells and its anti-inflammatory mechanisms remain unclear. THP-1 cells were treated with phorbol 12-myristate-13-acetate to differentiate and divided into three groups. They were stimulated with lipopolysaccharide (LPS) and interferon-γ (IFN-γ). The toxicity of XAN was assessed using Cell Counting Kit-8, and the expression of various genes and proteins was analyzed using real-time quantitative polymerase chain reaction, flow cytometry, and western blotting. Transmission electron microscopy was used to observe changes in mitochondrial structure. XAN at concentrations ≤ 10 µg/mL did not affect THP-1 cell viability and reduced the mRNA expression of pro-inflammatory factors, including interleukin (IL)-1β, inducible nitric oxide synthase (iNOS), NOD-like receptor thermal protein domain protein 3 (NLRP3), and tumor necrosis factor-α (TNF-α). XAN also increased the levels of anti-inflammatory factors, including chemokine ligand 22, mannose receptor (CD206), IL-10, peroxisome proliferator-activated receptor-γ, and transglutaminase 2. Additionally, XAN downregulated the expression of inflammation-related proteins iNOS, NLRP3, and IL-1β; significantly increased the expression of arginase 1, ornithine decarboxylase, and arginine metabolism-related proteins and genes; inhibited mitochondrial damage; and reduced reactive oxygen species (ROS) generation. XAN enhanced the arginine metabolism pathway, prevented mitochondrial damage, reduced ROS levels, and provided an effective defensive response against LPS/IFN-γ-induced inflammation.

mRNA-based platform for preventing and treating Staphylococcus aureus by targeted staphylococcal enterotoxin B

Staphylococcus aureus (S. aureus) possesses numerous virulence factors, with the increasing prevalence of drug-resistant strains heightening the threat posed by this pathogen. Staphylococcal enterotoxin B (SEB), a highly conserved toxin secreted by S. aureus, is also recognized as a potential bioweapon with super-antigenic activity. SEB represents a promising target in efforts to combat infections caused by S. aureus. We developed mRNA-based vaccine and antibody targeting SEB for both prophylactic and therapeutic purposes in varying S. aureus infection conditions. The mSEB mRNA vaccine (10 μg per mouse) induces more robust and persistent immune responses, including higher antibody titers and specific cellular immune responses, compared to immunization with 30 μg of mSEB protein adjuvanted with aluminum phosphate. Additionally, the anti-SEB mRNA antibody maintains secretion of anti-SEB monoclonal antibody (mAb) with a dosage that is 10 times lower than purified protein administration. The mRNA-based antibody exhibits superior pharmacokinetic profiles compared to its protein counterparts, efficiently neutralizing SEB and clearing S. aureus from circulation. Both the mRNA vaccine and mRNA antibody demonstrate preventive and therapeutic effects by eliciting specific immune responses and generating high-affinity antibodies in mice. We have laid the groundwork for the development and evaluation of mRNA-based vaccines and antibodies targeting SEB produced by S. aureus. Our studies demonstrate that these approaches are more effective than traditional protein-based vaccines and antibodies in terms of inducing immune responses, pharmacokinetics, and their prophylactic or therapeutic efficacy against S. aureus infections.

Dual osmotic controlled release platform for antibiotics to overcome antimicrobial-resistant infections and promote wound healing

Methicillin-Resistant Staphylococcus aureus forming into biofilms can trigger chronic inflammation and disrupt skin wound healing processes. Prolonged and excessive use of antibiotics can expedite the development of resistance, primarily because of their limited ability to penetrate microbial membranes and biofilms, especially antibiotics with intracellular drug targets. Herein, we devise a strategy in which virus-inspired nanoparticles control the release of antibiotics through rapid penetration into both bacterial cells and biofilms, thereby combating antimicrobial-resistant infections and promoting skin wound healing. Lipid-based nanoparticles based on stearamine and cholesterol were designed to mimic viral highly ordered nanostructures. To mimic the arginine-rich fragments in viral protein transduction domains, the primary amines on the surface of the lipid-based nanoparticles were exchanged by guanidine segments. Levofloxacin, an antibiotic that inhibits DNA replication, was chosen as the model drug to be incorporated into nanoparticles. Hyaluronic acid was coated on the surface of nanoparticles acting as a capping agent to achieve bacterial-specific degradation and guanidine explosion in the bacterial microenvironment. Our virus-inspired nanoparticles displayed long-acting antibacterial effects and powerful biofilm elimination to overcome antimicrobial-resistant infections and promote skin wound healing. This work demonstrates the ability of virus-inspired nanoparticles to achieve a dual penetration of microbial cell membranes and biofilm structures to address antimicrobial-resistant infections and trigger skin wound healing.

Light-activated nanoclusters with tunable ROS for wound infection treatment

Infected wounds pose a significant clinical challenge due to bacterial resistance, recurrent infections, and impaired healing. Reactive oxygen species (ROS)-based strategies have shown promise in eradicating bacterial infections. However, the excess ROS in the infection site after treatments may cause irreversible damage to healthy tissues. To address this issue, we developed bovine serum albumin-iridium oxide nanoclusters (BSA-IrOx NCs) which enable photo-regulated ROS generation and scavenging using near infrared (NIR) laser. Upon NIR laser irradiation, BSA-IrOx NCs exhibit enhanced photodynamic therapy, destroying biofilms and killing bacteria. When the NIR laser is off, the nanoclusters' antioxidant enzyme-like activities prevent inflammation and repair damaged tissue through ROS clearance. Transcriptomic and metabolomic analyses revealed that BSA-IrOx NCs inhibit bacterial nitric oxide synthase, blocking bacterial growth and biofilm formation. Furthermore, the nanoclusters repair impaired skin by strengthening cell junctions and reducing mitochondrial damage in a fibroblast model. In vivo studies using rat infected wound models confirmed the efficacy of BSA-IrOx NCs. This study presents a promising strategy for treating biofilm-induced infected wounds by regulating the ROS microenvironment, addressing the challenges associated with current ROS-based antibacterial approaches.

Precise Clearance of Intracellular MRSA via Internally and Externally Mediated Bioorthogonal Activation of Micro/Nano Hydrogel Microspheres

Traditional high-dose antibiotic treatments of intracellular methicillin-resistant staphylococcus aureus (MRSA) are highly inefficient and associated with a high rate of infection relapse. As an effective antibacterial technology, sonodynamic therapy (SDT) may be able to break the dilemma. However, indiscriminate reactive oxygen species (ROS) release leads to potential side effects. This study incorporates Staphylococcal Protein A antibody-modified Cu2+/tetracarboxyphenylporphyrin nanoparticles (Cu(II)NS-SPA) into hydrogel microspheres (HAMA@Cu(II)NS-SPA) to achieve precise eradication of intracellular bacteria. This eradication is under bioorthogonal activation mediated by bacillithiol (BSH) (internally) and ultrasound (US) (externally). To specify, the US responsiveness of Cu(II)NS-SPA is restored when it is reduced to Cu(I)NS-SPA by the BSH secreted characteristically by intracellular MRSA, thus forming a bioorthogonal activation with the external US, which confines ROS production within the infected MΦ. Under external US activation at 2 W cm-2, over 95% of intracellular MRSA can be cleared. In vivo, a single injection of HAMA@Cu(II)NS-SPA achieves up to two weeks of antibacterial sonodynamic therapy, reducing pro-inflammatory factor expression by 90%, and peri-implant bone trabeculae numbers exceed the control group by five times. In summary, these micro/nano hydrogel microspheres mediated by internal and external bioorthogonal activation can precisely eliminate intracellular MRSA, effectively treating multi-drug resistant intracellular bacterial infections.

Metal-Organic Frameworks for Sustainable Crop Disease Management: Current Applications, Mechanistic Insights, and Future Challenges

Efficient management of crop diseases and yield enhancement are essential for addressing the increasing food demands due to global population growth. Metal-organic frameworks (MOFs), which have rapidly evolved throughout the 21st century, are notable for their vast surface area, porosity, and adaptability, establishing them as highly effective vehicles for controlled drug delivery. This review methodically categorizes common MOFs employed in crop disease management and details their effectiveness against various pathogens. Additionally, by critically evaluating existing research, it outlines strategic approaches for the design of drug-delivery MOFs and explains the mechanisms through which MOFs enhance disease resistance. Finally, this paper identifies the current challenges in MOF research for crop disease management and suggests directions for future research. Through this in-depth review, the paper seeks to enrich the understanding of MOFs applications in crop disease management and offers valuable insights for researchers and practitioners.

Magnetic silk fibroin nanospheres loaded with amphiphilic polypeptides and antibiotics for biofilm eradication

The eradication of established biofilms is a highly challenging task, due to the protective barrier effect of extracellular polymeric substances (EPS) and the presence of persister cells. Both increased drug permeability and elimination of persister cells are essential for the eradication of biofilms. Here, magnetic silk fibroin nanospheres loaded with antibiotics and host defense peptide (HDP) mimics (MPSN/S@P) were developed to demonstrate a new strategy for biofilm eradication. As an HDP mimic, an amphiphilic polypeptide containing 90% L-lysine and 10% L-valine (Lys90Val10) was selected for loading onto magnetic silk fibroin nanospheres via electrostatic interactions. Lys90Val10 exhibited excellent antibacterial activities against both planktonic and persister cells of Staphylococcus aureus (S. aureus). As a representative of the hydrophobic drug, spiramycin (SPM) was conveniently embedded into the β-sheet domain during the self-assembly process of silk fibroin. The sustained release of SPM during biofilm eradication enhanced the antibacterial efficacy of MPSN/S@P. The antibacterial test demonstrated that the extract from the MPSN/S@P suspension can kill both planktonic and persister cells of S. aureus, as well as inhibiting biofilm formation. Importantly, with the assistance of magnetic guidance and photothermal effects derived from Fe3O4 nanoparticles (Fe3O4 NPs), over 92% of bacteria in the biofilm were killed by MPSN/S@P, indicating the successful eradication of mature biofilms. The simple preparation method, integration of photothermal and magnetic responsiveness, and persister cell killing functions of MPSN/S@P provide an accessible strategy and illustrative paradigm for efficient biofilm eradication.

Fast fabrication of "all-in-one" injectable hydrogels as antibiotic alternatives for enhanced bacterial inhibition and accelerating wound healing

Skin wound infection has become a notable medical threat. Herein, the polysaccharide-based injectable hydrogels with multifunctionality were developed by a simple and fast gelation process not only to inactivate bacteria but also to accelerate bacteria-infected wound healing. Sodium nitroprusside (SNP) loaded PCN-224 nanoparticles were introduced into the polymer matrix formed by the dynamic and reversible coordinate bonds between Ag+ with carboxyl and amino or hydroxyl groups on carboxymethyl chitosan (CMCS), hydrogen bonds and electrostatic interactions in the polymer to fabricate SNP@PCN@Gel hydrogels. SNP@PCN@Gel displayed interconnected porous structure, excellent self-healing capacity, low cytotoxicity, good blood compatibility, and robust antibacterial activity. SNP@PCN@Gel could produce reactive oxygen species (ROS) and NO along with Fe2+, and showed long-term sustained release of Ag+, thereby effectively killing bacteria by synergistic photothermal (hyperthermia), photodynamic (ROS), chemodynamic (Fenton reaction), gas (NO) and ion (Ag+ and -NH3+ in CMCS) therapy. Remarkably, the hydrogels significantly promoted granulation tissue formation, reepithelization, collagen deposition and angiogenesis as well as wound contraction in bacteria-infected wound healing. Taken together, the strategy represented a general method to engineer the unprecedented photoactivatable "all-in-one" hydrogels with enhanced antibacterial activity and paved a new way for development of antibiotic alternatives and wound dressing.

Polydopamine Nanocarriers with Cascade-Activated Nitric Oxide Release Combined Photothermal Activity for the Therapy of Drug-Resistant Bacterial Infections

Antibiotic abuse leads to increased bacterial resistance, and the surviving planktonic bacteria aggregate and secrete extracellular polymers to form biofilms. Conventional antibacterial agents find it difficult to penetrate the biofilm, remove the bacteria wrapped in it, and produce an excellent therapeutic effect. In this study, a dual pH- and NIR-responsive nanocomposite (A-Ca@PDA) was developed to remove drug-resistant bacteria through a cascade of catalytic nitric oxide (NO) release and photothermal clearance. NO can melt in the outer package of the biofilm, facilitating the nanocomposites to have better permeability. Thermal therapy further inhibits the growth of planktonic bacteria. The locally generated high temperature and the burst release of NO together aggravate the biofilm collapse and bacterial death after NIR irradiation. The nanocomposites achieved a remarkable photothermal conversion efficiency of 47.5%, thereby exhibiting significant advancements in energy conversion. The nanocomposites exhibited remarkable efficacy in inhibiting multidrug-resistant (MDR) Escherichia coli and MDR Staphylococcus aureus, thus achieving an inhibition rate of >90%. Moreover, these nanocomposites significantly improved the wound-healing process in the MDR S. aureus-infected mice. Thus, this novel nanocomposite offers a novel strategy to combat drug-resistant bacterial infections.

Advances in the targeted theragnostics of osteomyelitis caused by Staphylococcus aureus

Bone infections caused by Staphylococcus aureus may lead to an inflammatory condition called osteomyelitis, which results in progressive bone loss. Biofilm formation, intracellular survival, and the ability of S. aureus to evade the immune response result in recurrent and persistent infections that present significant challenges in treating osteomyelitis. Moreover, people with diabetes are prone to osteomyelitis due to their compromised immune system, and in life-threatening cases, this may lead to amputation of the affected limbs. In most cases, bone infections are localized; thus, early detection and targeted therapy may prove fruitful in treating S. aureus-related bone infections and preventing the spread of the infection. Specific S. aureus components or overexpressed tissue biomarkers in bone infections could be targeted to deliver active therapeutics, thereby reducing drug dosage and systemic toxicity. Compounds like peptides and antibodies can specifically bind to S. aureus or overexpressed disease markers and combining these with therapeutics or imaging agents can facilitate targeted delivery to the site of infection. The effectiveness of photodynamic therapy and hyperthermia therapy can be increased by the addition of targeting molecules to these therapies enabling site-specific therapy delivery. Strategies like host-directed therapy focus on modulating the host immune mechanisms or signaling pathways utilized by S. aureus for therapeutic efficacy. Targeted therapeutic strategies in conjunction with standard surgical care could be potential treatment strategies for S. aureus-associated osteomyelitis to overcome antibiotic resistance and disease recurrence. This review paper presents information about the targeting strategies and agents for the therapy and diagnostic imaging of S. aureus bone infections.

Bactericidal and biofilm eradication efficacy of a fluorinated benzimidazole derivative, TFBZ, against methicillin-resistant Staphylococcus aureus

Methicillin-resistant Staphylococcus aureus (MRSA) is a major inducement of nosocomial infections and its biofilm formation render the high tolerance to conventional antibiotics, which highlights the requirement to develop new antimicrobial agents urgently. In this study, we identified a fluorinated benzimidazole derivative, TFBZ, with potent antibacterial efficacy toward planktonic MRSA (MIC = 4 μg/mL, MBC = 8 μg/mL) and its persistent biofilms (≥99%, MBEC = 8 μg/mL). TFBZ manifested significant irreversible time-dependent killing against MRSA as characterized by diminished cell viability, bacterial morphological change and protein leakage. Furthermore, the results from CBD devices, crystal violet assay in conjunction with live/dead staining and scanning electron microscopy confirmed that TFBZ was capable of eradicating preformed MRSA biofilms with high efficiency. Simultaneously, TFBZ reduced the bacterial invasiveness and exerted negligible hemolysis and cytotoxicity toward mammalian cells, which ensuring the robust therapeutic effect on mouse skin abscess model. The transcriptome profiling and quantitative RT-PCR revealed that a set of encoding genes associated with cell adhesion, biofilm formation, translation process, cell wall biosynthesis was consistently downregulated in MRSA biofilms upon exposure to TFBZ. In conclusion, TFBZ holds promise as a valuable candidate for therapeutic applications against MRSA chronic infections.

Targeted Light-Induced Immunomodulatory Strategy for Implant-Associated Infections via Reversing Biofilm-Mediated Immunosuppression

The clinical treatment efficacy for implant-associated infections (IAIs), particularly those caused by Methicillin-resistant Staphylococcus aureus (MRSA), remains unsatisfactory, primarily due to the formation of biofilm barriers and the resulting immunosuppressive microenvironment, leading to the chronicity and recurrence of IAIs. To address this challenge, we propose a light-induced immune enhancement strategy, synthesizing BSA@MnO2@Ce6@Van (BMCV). The BMCV exhibits precise targeting and adhesion to the S. aureus biofilm-infected region, coupled with its capacity to catalyze oxygen generation from H2O2 in the hypoxic and acidic biofilm microenvironment (BME), promoting oxygen-dependent photodynamic therapy efficacy while ensuring continuous release of manganese ions. Notably, targeted BMCV can penetrate biofilms, producing ROS that degrade extracellular DNA, disrupting the biofilm structure and impairing its barrier function, making it vulnerable to infiltration and elimination by the immune system. Furthermore, light-induced reactive oxygen species (ROS) around the biofilm can lyse S. aureus, triggering bacterium-like immunogenic cell death (ICD), releasing abundant immune costimulatory factors, facilitating the recognition and maturation of antigen-presenting cells (APCs), and activating adaptive immunity. Additionally, manganese ions in the BME act as immunoadjuvants, further amplifying macrophage-mediated innate and adaptive immune responses and reversing the immunologically cold BME to an immunologically hot BME. We prove that our synthesized BMCV elicits a robust adaptive immune response in vivo, effectively clearing primary IAIs and inducing long-term immune memory to prevent recurrence. Our study introduces a potent light-induced immunomodulatory nanoplatform capable of reversing the biofilm-induced immunosuppressive microenvironment and disrupting biofilm-mediated protective barriers, offering a promising immunotherapeutic strategy for addressing challenging S. aureus IAIs.

Antibiofilm activity of polyethylene glycol-quercetin nanoparticles-loaded gelatin-N,O-carboxymethyl chitosan composite nanogels against Staphylococcus epidermidis

BACKGROUND

Biofilms, such as those from Staphylococcus epidermidis, are generally insensitive to traditional antimicrobial agents, making it difficult to inhibit their formation. Although quercetin has excellent antibiofilm effects, its clinical applications are limited by the lack of sustained and targeted release at the site of S. epidermidis infection.

OBJECTIVES

Polyethylene glycol-quercetin nanoparticles (PQ-NPs)-loaded gelatin-N,O-carboxymethyl chitosan (N,O-CMCS) composite nanogels were prepared and assessed for the on-demand release potential for reducing S. epidermidis biofilm formation.

METHODS

The formation mechanism, physicochemical characterization, and antibiofilm activity of PQ-nanogels against S. epidermidis were studied.

RESULTS

Physicochemical characterization confirmed that PQ-nanogels had been prepared by the electrostatic interactions between gelatin and N,O-CMCS with sodium tripolyphosphate. The PQ-nanogels exhibited obvious pH and gelatinase-responsive to achieve on-demand release in the micro-environment (pH 5.5 and gelatinase) of S. epidermidis. In addition, PQ-nanogels had excellent antibiofilm activity, and the potential antibiofilm mechanism may enhance its antibiofilm activity by reducing its relative biofilm formation, surface hydrophobicity, exopolysaccharides production, and eDNA production.

CONCLUSIONS

This study will guide the development of the dual responsiveness (pH and gelatinase) of nanogels to achieve on-demand release for reducing S. epidermidis biofilm formation.

On-demand release of enrofloxacin-loaded chitosan oligosaccharide-oxidized hyaluronic acid composite nanogels for infected wound healing

In this study, enrofloxacin (ENR) was encapsulated by oxidized hyaluronic acid (OHA) containing aldehyde groups and chitosan oligosaccharide (COS) containing amino groups through Schiff's base reaction to achieve on-demand release in the micro-environment (pH 5.5 and HAase) of bacterial-infected wounds (Escherichia coli and Staphylococcus aureus). The formation mechanism, physicochemical characterization, responsive release performance, in vitro and in vivo antimicrobial activities, and in vivo regeneration in full-thickness wounds in a bacterial-infected mouse model of the ENR nanogels were systematically studied. According to the single-factor experiment and Design-Expert software, the optimized formula was 3.8 mg/ml COS, 0.5 mg/ml OHA, and 0.3 mg/ml ENR, respectively. The mean particle diameter, polydispersity index, zeta potential, loading capacity, and encapsulation efficiency were 35.6 ± 1.7 nm, -6.7 ± 0.5 mV, 0.25 ± 0.02, 30.4 % ± 1.3 %, and 76.3 % ± 2.6 %, respectively. The appearance, optical microscopy images, SEM, TEM, PXRD, and FTIR showed that the ENR nanogels were successfully prepared. The ENR nanogels exhibited obvious pH and HAase-responsiveness by swelling ratios and in vitro release and had stronger antibacterial activity with time-dependent and concentration-dependent effects, as well as accelerating infected wound healing. In vitro and in vivo biosafety studies suggested the great promise of ENR nanogels as biocompatible wound dressings for infected wounds.