Wound Infection Model Research Articles

Bactericidal effectiveness of high-intensity pulsed broadband irradiation in treating infected wounds

The study aimed to investigate the bactericidal eŠcacy of high-intensity pulsed broadband irradiation in the treatment of infected wounds. An experimental study was conducted on 90 mature male Wistar rats. An infected wound model was created by contaminating with Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumoniae, and Candida albicans. Animals in Group 1 received high-intensity pulsed broadband irradiation. Animals in Group 2 received traditional UV irradiation. Animals in Group 3 had their wounds cleaned with 0.1% chlorhexidine solution. By the 3rd day of treatment, animals that received pulsed high-intensity broadband irradiation showed a signifiant reduction in contamination by Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa compared to Group 3. By the 7th day of treatment, half or the majority of animals in Groups 1 and 2 showed complete decontamination of wounds concerning Staphylococcus aureus and Klebsiella pneumoniae. Most animals in Group 1 showed complete wound clearance of Pseudomonas aeruginosa. By the 10th day, nearly all animals in Group 1 demonstrated complete decontamination of wounds. Statistical analysis revealed a signifiant difference in the reduction of wound contamination with Staphylococcus aureus and Klebsiella pneumoniae by the 10th day in Groups 1 and 2 compared to Group 3. Thus, the use of high-intensity pulsed broadband irradiation of wounds reduces the degree of pathogenic microorganism contamination in a shorter time frame.

Amino Acid-Conjugated Polymer-Silver Bromide Nanocomposites for Eradicating Polymicrobial Biofilms and Treating Burn Wound Infections.

The rise in antimicrobial resistance, the increasing occurrence of bacterial, and fungal infections, and the challenges posed by polymicrobial biofilms necessitate the exploration of innovative therapeutic strategies. Silver-based antimicrobials have garnered attention for their broad-spectrum activity and multimodal mechanisms of action. However, their effectiveness against single-species or polymicrobial biofilms remains limited. In this study, we present the fabrication of polymer-silver bromide nanocomposites using amino acid conjugated polymers (ACPs) through a green and water-based in situ technique. The nanocomposite architecture facilitated prolonged and controlled release of the active components. Remarkably, the nanocomposites exhibited broad-spectrum activity against multidrug-resistant (MDR) human pathogenic bacteria (MIC = 2-16 μg/mL) and fungi (MIC = 1-8 μg/mL), while displaying no detectable toxicity to human erythrocytes (HC50 > 1024 μg/mL). In contrast to existing antimicrobials and silver-based therapies, the nanocomposite effectively eradicated bacterial, fungal, and polymicrobial biofilms, and prevented the development of microbial resistance due to their membrane-active properties. Furthermore, the lead polymer-silver bromide nanocomposite demonstrated a 99% reduction in the drug-resistant Pseudomonas aeruginosa burden in a murine model of burn wound infection, along with excellent in vivo biocompatibility.

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.

Advanced Fe-COF-based photothermal cascade nano-generator for sterilization and promoting wound healing

Pharmacological treatments of diabetic ulcers remain a huge challenge due to the impaired angiogenesis and uncontrolled bacterial infection. Here, iminopyrazine-based Fe-covalent organic frameworks (Fe-COF) were synthesized via a subcomponent assembly strategy, and functionalized through covalent modification of L-arginine and encapsulated with photosensitizer IR780 and hyaluronic acid for enhancing diabetic wound healing. The functionalized Fe-COF (Fe-COF NRs) showed peroxidase-like activity and near-infrared (NIR)-controlled NO generation property, which can be used for synergistic photothermal/photodynamic antibacterial therapy and NO-based gas therapy. Treatment with Fe-COF NRs + NIR caused pathogenic elimination and enhanced angiogenesis, subsequently leading to accelerated wound healing in a rat model of infected diabetic wound. Mechanistically, the results from RNA sequencing analysis indicated that Fe-COF NRs treatment significantly induced the expression of genes involved in angiogenesis, but obviously inhibited the expression of proinflammatory cytokines. Gene Ontology enrichment and Kyoto Encyclopedia of Genes and Genomes pathway analysis revealed that collagen-containing extracellular matrix, hair follicle development, PI3K-Akt signaling pathway, wound healing and skin development were significantly enriched after Fe-COF NRs treatment. Taken together, Fe-COF NRs provide a novel therapeutic strategy for the treatment of infected diabetic wound.

Exploring the wound healing activity of phytosomal gel of Annona squamosa and Cinnamomum tamala leaves ethanolic extracts with antioxidant and antimicrobial activities in S aureus infected excision wound model

Wound healing is a natural process but it is impaired in certain conditions like age, stress, health, immunity status and microbial infection. Particularly in cases of chronic wounds, infection is nearly often the main and unavoidable obstacle to wound healing. For this purpose, leaves of Annona squamosa and Cinnamomum tamala were selected based on their ethnopharmacological uses and reported pharmacological activities. The ethanolic extracts of both plant parts i.e. ethanolic extracts of Annona squamosa (ASEE) and Cinnamomum tamala (CTEE) were evaluated for their antioxidant and antimicrobial activities individually as well as in 1:1 combination as Polyherbal Ethanolic extract (PHEE). In our previous work both these ethanolic extracts were combined and phytosomes were prepared by thin layer hydration method and optimized for vesicle size and entrapment efficiency. The phytosomes were then incorporated into Carbopol gel matrix. In this present study the selected phytosomal gel was tested in two different concentrations (2% and 5%) for in vivo wound healing activity using S. aureus infected excision wound model. The various parameters examined were percentage wound contraction, epithelization period, bacteriological quantification, biochemical parameters like Superoxide dismutase (SOD), Catalase and hydroxyproline. The PHEE exhibited synergistic antioxidant activity. The PHEE also showed enhanced antimicrobial activity against bacteria namely gram-positive S. aureus, gram-negative E. Coli. The phytosomal gel showed increased wound contraction, reduced time of epithelization, increased hydroxyproline content, increased levels of SOD and Catalase enzymes and reduced bacterial load when compared with Povidone iodine ointment as standard in S. aureus infected excision wound model.

Stimuli-Responsive Release-Active Dressing: A Promising Solution for Eradicating Biofilm-Mediated Wound Infections.

Biofilm-mediated wound infections pose a significant challenge due to the limitations of conventional antibiotics, which often exhibit narrow-spectrum activity, fail to eliminate recurrent bacterial contamination, and are unable to penetrate the biofilm matrix. While the search for alternatives has explored the use of metal nanoparticles and synthetic biocides, these solutions often suffer from unintended toxicity to surrounding tissues and lack controlled administration and release. In this study, we engineered a pH-responsive release-active dressing film based on carboxymethyl cellulose, incorporating a synthetic antibacterial molecule (SAM-17). The dressing film exhibited optimal mechanical stability for easy application and demonstrated excellent fluid absorption properties, allowing for prolonged moisturization at the site of injury. The film exhibited pH-dependent release of cargo, with 78% release within 24 h at acidic pH, enabling targeted antibacterial drug delivery within the wound microenvironment. Furthermore, the release-active film effectively eliminated repeated challenges of bacterial contamination. Remarkably, the film demonstrated a minimal toxicity profile in both in vitro and in vivo models. The film eliminated preformed bacterial biofilms, achieving a reduction of 2.5 log against methicillin-resistant Staphylococcus aureus (MRSA) and 4.1 log against vancomycin-resistant S. aureus (VRSA). In a biofilm-mediated MRSA wound infection model, this release-active film eradicated the biofilm-embedded bacteria by over 99%, resulting in accelerated wound healing. These findings highlight the potential of this film as an effective candidate for tackling biofilm-associated wound infections.

Modulating the morphology and protonation degree of chitosan coatings for enabling controlled fabric functionalization

Chitosan (CS), a versatile biopolymer known for its diverse bioactivity, is commonly used as a coating or finishing agent to enhance fabric performance and broaden their applications. However, conventional methods for introducing CS coating layer on the fabrics often relies on using composition to control their functionality, limiting the ability to tailor properties for specific needs. In this study, we introduce an innovative coating platform utilizing drying, ionic gelation, or a combination of both to control the morphology and amino-protonation degree of CS. This approach allows the development of three distinct functional CS coatings from the same material composition. The method is effectively applied to cotton and polylactic acid (PLA)-based non-woven fabrics, preserving the permeability, breathability, and mechanical properties of the substrates. By varying processing conditions, it is found that CS coatings can impart distinct functions to the fabrics upon their morphology, such as attaining high degree of hydrophobicity (with a water contact angle reaching 129°), broad-spectrum antibacterial activity (>99.99 %) for the sample prepared by combined drying and ionic gelation methods. Additionally, our CS-coated fabrics can exhibit good biocompatibility, as demonstrated by cytocompatibility and histocompatibility evaluations, while excellent anti-adhesive properties and healing performance in infected wound models in rats can be obtained with the presence of CS microsphere. Our methods are straightforward and potentially scalable, enabling modular control over the functionality of CS-coated fabrics to meet diverse requirements. This work offers a promising strategy for modifying fabric properties with CS coatings, making it suitable for various applications such as facial masks, dressings, and antibacterial textiles.

Transformation of Natural Resin Resina Draconis to 3D Functionalized Fibrous Scaffolds for Efficient Chronic Wound Healing.

Chronic wound healing is a major challenge in clinical practice. Secondary dressing damage and antibiotic resistance are the main obstacles for traditional wound dressings. Resina draconis (RD), a natural resin traditionally used in powder form for wound care, is now considered unsuitable due to the lack of gas permeability and moist environment required for wound healing. Here, RD is incorporated in situ by constructing a 3D coiled fibrous scaffold with polycaprolactone/polyethylene oxide. Due to the high porosity of 3D scaffold, the RD-3D dressings have a favorable swelling capacity, providing permeability and moisture for wound repair. Meanwhile, the transformation of RD powder into 3D dressings fully demonstrates capabilities of RD in rapid hemostasis, bactericidal, and inflammation-regulating activities. In vivo evaluations using pressure ulcer and infected wound models confirm the high efficacy of RD-3D dressing in early wound healing, particularly beneficial in the infected wound model compared to recombinant bovine FGF-basic. Further biological analysis shows that resveratrol, loureirin A, and loureirin B, as potentially bioactive components of RD, individually contribute to different aspects of wound healing. Collectively, RD-3D integrated dressings represent a simple, cost-effective, and safe approach to wound healing, providing an alternative therapy for translating medical dressings from bench to bedside.

A novel multifunction of wearable ionic conductive hydrogel sensor for promoting infected wound healing

Conductive hydrogels have attracted widespread attention in applications of artificial biological tissues and ionic skin. Herein, a highly ionically conductive and biocompatibility hydrogels that integrate sensing, low swelling, and antimicrobial are prepared by the composition of chitosan (CS) chains, tannic acid (TA), polyacrylic acid (PAA), and metal cations. The hydrogels with high conductivity had tensile strain repeatable adhesion, wide strain detection, biocompatibility, and motion sensing capabilities. Particularly, in the aspect of hydrogel strain sensing based on ion conduction, it has high nonliearity (GF=2.05) with a large strain (20 %-1400 %), and excellent cycle stability. In addition, owing to the low-swelling effect and dipole-dipole interaction between the existence of free catechol groups of the zwitterionic group and TA in the zwitterionic sulfobetaine methacrylate (SBMA), the hydrogels display repeatable and controllable adhesiveness. Meanwhile, the covalent cross-linking between AA and SBMA synergistically enhances the mechanical properties of the hydrogels (169 kPa, 1474 %). Furthermore, as demonstrated in the L929 mouse wound infection model, the results indicated that the prepared hydrogel group had antimicrobial activity and reduced inflammation, thereby accelerating wound healing. The biocompatible and mutli-functional conductive hydrogels provide a new method for the design of novel type ionic skin device.

Discovery of Antimicrobial Lysins from the "Dark Matter" of Uncharacterized Phages Using Artificial Intelligence.

The rapid rise of antibiotic resistance and slow discovery of new antibiotics have threatened global health. While novel phage lysins have emerged as potential antibacterial agents, experimental screening methods for novel lysins pose significant challenges due to the enormous workload. Here, the first unified software package, namely DeepLysin, is developed to employ artificial intelligence for mining the vast genome reservoirs ("dark matter") for novel antibacterial phage lysins. Putative lysins are computationally screened from uncharacterized Staphylococcus aureus phages and 17 novel lysins are randomly selected for experimental validation. Seven candidates exhibit excellent in vitro antibacterial activity, with LLysSA9 exceeding that of the best-in-class alternative. The efficacy of LLysSA9 is further demonstrated in mouse bloodstream and wound infection models. Therefore, this study demonstrates the potential of integrating computational and experimental approaches to expedite the discovery of new antibacterial proteins for combating increasing antimicrobial resistance.

Biohybrid Nanorobots Carrying Glycoengineered Extracellular Vesicles Promote Diabetic Wound Repair through Dual-Enhanced Cell and Tissue Penetration.

Considerable progress has been made in the development of drug delivery systems for diabetic wounds. However, underlying drawbacks, such as low delivery efficiency and poor tissue permeability, have rarely been addressed. In this study, a multifunctional biohybrid nanorobot platform comprising an artificial unit and several biological components is constructed. The artificial unit is a magnetically driven nanorobot surface modified with antibacterial 2-hydroxypropyltrimethyl ammonium chloride chitosan, which enables the entire platform to move and has excellent tissue penetration capacity. The biological components are two-step engineered extracellular vesicles that are first loaded with mangiferin, a natural polyphenolic compound with antioxidant properties, and then glycoengineered on the surface to enhance cellular uptake efficiency. As expected, the platform is more easily absorbed by endothelial cells and fibroblasts and exhibits outstanding dermal penetration performance and antioxidant properties. Encouraging results are also observed in infected diabetic wound models, showing improved wound re-epithelialization, collagen deposition, angiogenesis, and accelerated wound healing. Collectively, a biohybrid nanorobot platform that possesses the functionalities of both artificial units and biological components serves as an efficient delivery system to promote diabetic wound repair through dual-enhanced cell and tissue penetration and multistep interventions.

Green synthesis-inspired antibacterial, antioxidant and adhesive hydrogels with ultra-fast gelation and hemostasis for promoting infected skin wound healing

Bacterial infections are a serious threat to wound healing and skin regeneration. In recent years, photothermal therapy (PTT) has become one of the most promising tools in the treatment of infectious diseases. However, wound dressings with photo-responsive properties are currently still limited by the difficulties of biosafety and thermal stability brought by the introduction of photosensitizers or photothermal agents. Therefore, how to improve the therapeutic efficiency and biosafety from material design is still a major challenge at present. In this study, the carboxymethyl chitosan (CMCS) and protocatechuic aldehyde (PA) hydrogels based on horseradish peroxidase (HRP) and hydrogen peroxide (H2O2) enzymatic catalysis was developed. Therein, HRP and H2O2 catalyzed cross-linking while polymerizing PA, which not only endowed the hydrogels with photothermal responsiveness but also with good biosafety through this enzyme-catalyzed green approach. Meanwhile, the hydrogels possessed highly efficient bacteriostatic ability with the assistance of near infrared (NIR). Moreover, the ultra-rapid gelation, strong tissue adhesion, high swelling ability, good antioxidant property and hemostatic property of the CMCS-PA hydrogels based on HRP/H2O2 enzymatic catalysis were suitable for the treatment of skin wounds. Meanwhile, NIR-assistant CMCS-PA hydrogels based on HRP/H2O2 enzymatic catalysis reduced inflammation, decreased bacterial infection, and promoted collagen deposition and angiogenesis, which showed remarkable therapeutic effects in a skin wound infection model. All results indicate that this green approach to introduce photothermal property by HRP-catalyzed PA polymerization endows the hydrogels with efficient photothermal conversion efficiency, suggesting that they are promising to provide new options for replacing photothermal agents and photosensitizers. Statement of significanceIn recent years, wound dressings with photo-responsive properties are currently still limited by the difficulties of biosafety and thermal stability brought by the introduction of agent photosensitizers or photothermal agents. In this study, the carboxymethyl chitosan and protocatechuic aldehyde hydrogels based on horseradish peroxidase and hydrogen peroxide enzymatic catalysis was developed. The photothermal properties of hydrogels were transformed from absent to present just by horseradish peroxidase-catalyzed protocatechuic aldehyde polymerization in a green approach. Meanwhile, the hydrogels possessed highly efficient bacteriostatic ability with the assistance of near infrared. The green approach of introducing photothermal properties from material design solves the biosafety challenge. Therefore, this study is expected to provide new options for alternative photothermal agents and photosensitizers.

Dual-Mechanism Peptide SR25 has Broad Antimicrobial Activity and Potential Application for Healing Bacteria-infected Diabetic Wounds.

The rise of antibiotic resistance poses a significant public health crisis, particularly due to limited antimicrobial options for the treatment of infections with Gram-negative pathogens. Here, an antimicrobial peptide (AMP) SR25 is characterized, which effectively kills both Gram-negative and Gram-positive bacteria through a unique dual-targeting mechanism without detectable resistance. Meanwhile, an SR25-functionalized hydrogel is developed for the efficient treatment of infected diabetic wounds. SR25 is obtained through genome mining from an uncultured bovine enteric actinomycete named Nonomuraea Jilinensis sp. nov. Investigations reveal that SR25 has two independent cellular targets, disrupting bacterial membrane integrity and restraining the activity of succinate:quinone oxidoreductase (SQR). In a diabetic mice wound infection model, the SR25-incorporated hydrogel exhibits high efficacy against mixed infections of Escherichia coli (E. coli) and methicillin-resistant Staphylococcus aureus (MRSA), accelerating wound healing. Overall, these findings demonstrate the therapeutic potential of SR25 and highlight the value of mining drugs with multiple mechanisms from uncultured animal commensals for combating challenging bacterial pathogens.

Bioactive Metal Ion-Coordinated Dynamic Hydrogel with Antibacterial, Immunomodulatory, and Angiogenic Activities for Infected Wound Repair.

The repair of infected wounds is a complex physiopathologic process. Current studies on infected wound treatment have predominantly focused on infection treatment, while the factors related to delayed healing caused by vascular damage and immune imbalance are commonly overlooked. In this study, an extracellular matrix (ECM)-like dynamic and multifunctional hyaluronic acid (HA) hydrogel with antimicrobial, immunomodulatory, and angiogenic capabilities was designed as wound dressing for the treatment of infected skin wounds. The dynamic network in the hydrogel dressing was based on reversible metal-ligand coordination formed between sulfhydryl groups and bioactive metal ions. In our design, antibacterial silver and immunomodulatory zinc ions were employed to coordinate with sulfhydrylated HA and a vasculogenic peptide. In addition to the desired bioactivities for infected wounds, the hydrogel could also exhibit self-healing and injectable abilities. Animal experiments with infected skin wound models indicated that the hydrogel dressings enabled minimally invasive injection and seamless skin wound covering and then facilitated wound healing by efficient bacterial killing, continuous inflammation inhibition, and improved blood vessel formation. In conclusion, the metal ion-coordinated hydrogels with wound-infection-desired bioactivities and ECM-like dynamic structures represent a class of tissue bionic wound dressings for the treatment of infected and chronic inflammation wounds.

Nisin-preconditioned mesenchymal stem cells combatting nosocomial Pseudomonas infections

BackgroundNosocomial infections caused by multidrug-resistant Pseudomonas aeruginosa are a considerable public health threat, requiring innovative therapeutic approaches. ObjectivesThis study explored preconditioning mesenchymal stem cells (MSCs) with the antimicrobial peptide Nisin to enhance their antibacterial properties while maintaining regenerative capacity. MethodsHuman MSCs were preconditioned with varying concentrations of Nisin (0.1–1000 IU/mL) to determine an optimal dose. MSCs preconditioned with Nisin were characterized using microscopy, flow cytometry, gene expression analysis, and functional assays. The effects of preconditioning on the viability, phenotype, differentiation capacity, antimicrobial peptide expression, and antibacterial activity of MSCs against Pseudomonas aeruginosa were tested in vitro. The therapeutic efficacy was evaluated by topically applying conditioned media from Nisin-preconditioned versus control MSCs to infected wounds in a rat model, assessing bacterial burden, healing, host response, and survival. ResultsAn optimal Nisin dose of 500 IU/mL was identified, which increased MSC antibacterial gene expression and secretome activity without compromising viability or stemness. Nisin-preconditioned MSCs showed upregulated expression of LL37 and hepcidin. Conditioned media from Nisin-preconditioned MSCs exhibited about 4-fold more inhibition of P. aeruginosa growth compared to non-preconditioned MSCs. In the wound infection model, the secretome of Nisin-preconditioned MSCs suppressed bacterial load, accelerated wound closure, modulated inflammation, and improved survival compared to standard MSC treatments. ConclusionThis study explores the effect of preconditioning MSCs with the antimicrobial peptide Nisin on enhancing their antibacterial properties while maintaining regenerative capacity. Secreted factors from Nisin-preconditioned MSCs have the potential to attenuate infections and promote healing in vivo. The approach holds translational promise for managing antibiotic-resistant infections and warrants further development. Preconditioned MSCs with Nisin may offer innovative, multifaceted therapies for combating nosocomial pathogens and promoting tissue regeneration.

A study of the effect of natural brown cotton gauze on the healing of infected wounds.

Medical dressings are designed to promote wound healing and reduce infection. The aim of project is to investigate the effect of natural brown colored cotton dressings on the healing of infected wounds in E.coli animals. In this study, degreased white cotton gauze was used as the control group, with degreased brown cotton gauze and degreased bleached brown cotton gauze as the experimental group 1 and experimental group 2, to investigate the effect on the repair of post-infectious wound damage in animals by establishing an infected wound model in rats with E.coli as the infecting organism. The ability to promote healing of infected wounds was investigated by analyzing the wound healing status, macroscopic wound healing rate, hematoxylin-eosin staining, Masson staining, secretion of inflammatory factors by Elisa assay. The result showed that at day 14 of wound healing, the macroscopic wound healing rate was greater than 98% for all three groups of dressings; the collagen content reached 49.85±5.84% in the experimental group 1 and 53.48±5.32% in the experimental group 2, which was higher than the control group; brown cotton gauze promotes skin wound healing by shortening the inflammatory period in both groups. The expression of three inflammatory factors THF-α, IL-2, and IL-8 and three cytokines MMP-3, MMP-8, and MMP-9 were lower than that of the control group. It was found that natural brown cotton gauze has better repairing and promoting healing effect on infected wounds. It opens up the application of natural brown cotton gauze in the treatment of infected wounds.

Staphylococcus pseudintermedius and Pseudomonas aeruginosa Lubbock Chronic Wound Biofilm (LCWB): a suitable dual-species model for in vitro studies

Antimicrobial treatment of methicillin-resistant Staphylococcus pseudintermedius associated with canine wounds represents an important challenge. The aim of this study was to create a canine wound infection model, Lubbock Chronic Wound Biofilm (LCWB), with a focus on S. pseudintermedius, drawing inspiration from the established human model involving Staphylococcus aureus. Methicillin-resistant S. pseudintermedius 115 (MRSP) and Pseudomonas aeruginosa 700 strains, isolated from dog wounds, were used to set up the LCWB at 24, 48 and 72 h. The LCWBs were evaluated in terms of volume, weight, and microbial CFU/mg. The microbial spatial distribution in the LCWBs was assessed by SEM and CLSM imaging. The best incubation time for the LCWB production in terms of volume (3.38 cm3 ± 0.13), weight (0.86 gr ± 0.02) and CFU/mg (up to 7.05 × 106 CFU/mg ± 2.89 × 105) was 48 h. The SEM and CLSM images showed a major viable microbial colonization at 48 h with non-mixed bacteria with a prevalence of MRSP on the surface and P. aeruginosa 700 in the depth of the wound. The obtained findings demonstrate the capability of S. pseudintermedius to grow together P. aeruginosa in the LCWB model, representing the suitable model to reproduce the animal chronic wound in vitro.

Sequential Regulation of Local Reactive Oxygen Species by Ir@Cu/Zn-MOF Nanoparticles for Promoting Infected Wound Healing.

Most antimicrobials treat wound infections by an oxidation effect, which is induced by the generation of reactive oxygen species (ROS). However, the potential harm of the prolonged high level of ROS should not be ignored. In this study, we presented a novel cascade-reaction nanoparticle, Ir@Cu/Zn-MOF, to effectively regulate the ROS level throughout the healing progress of the infected wound. The nanoparticles consisted of a copper/zinc-modified metal-organic framework (Cu/Zn-MOF) serving as the external structure and an inner core composed of Ir-PVP NPs, which were achieved through a process known as "bionic mineralization". The released Cu2+ and Zn2+ from the shell structure contributed to the production of ROS, which acted as antimicrobial agents during the initial stage. With the disintegration of the shell, the Ir-PVP NP core was gradually released, exhibiting the property of multiple antioxidant enzyme activities, thereby playing an important role in clearing excessive ROS and alleviating oxidative stress. In a full-layer infected rat wound model, Ir@Cu/Zn-MOF nanoparticles presented exciting performance in promoting wound healing by clearing the bacteria and accelerating neovascularization as well as collagen deposition. This study provided a promising alternative for the repair of infected wounds.

The interplay of Pseudomonas aeruginosa and Staphylococcus aureus in dual-species biofilms impacts development, antibiotic resistance and virulence of biofilms in in vitro wound infection models.

Due to high tolerance to antibiotics and pronounced virulence, bacterial biofilms are considered a key factor and major clinical challenge in persistent wound infections. They are typically composed of multiple species, whose interactions determine the biofilm's structural development, functional properties and thus the progression of wound infections. However, most attempts to study bacterial biofilms in vitro solely rely on mono-species populations, since cultivating multi-species biofilms, especially for prolonged periods of time, poses significant challenges. To address this, the present study examined the influence of bacterial composition on structural biofilm development, morphology and spatial organization, as well as antibiotic tolerance and virulence on human skin cells in the context of persistent wound infections. By creating a wound-mimetic microenvironment, the successful cultivation of dual-species biofilms of two of the most prevalent wound pathogens, Pseudomonas aeruginosa and Staphylococcus aureus, was realized over a period of 72 h. Combining quantitative analysis with electron microscopy and label-free imaging enabled a comprehensive evaluation of the dynamics of biofilm formation and matrix secretion, revealing a twofold increased maturation of dual-species biofilms. Antibiotic tolerance was comparable for both mono-species cultures, however, dual-species communities showed a 50% increase in tolerance, mediated by a significantly reduced penetration of the applied antibiotic into the biofilm matrix. Further synergistic effects were observed, where dual-species biofilms exacerbated wound healing beyond the effects observed from either Pseudomonas or Staphylococcus. Consequently, predicting biofilm development, antimicrobial tolerance and virulence for multi-species biofilms based solely on the results from mono-species biofilms is unreliable. This study underscores the substantial impact of a multi-species composition on biofilm functional properties and emphasizes the need to tailor future studies reflecting the bacterial composition of the respective in vivo situation, leading to a more comprehensive understanding of microbial communities in the context of basic microbiology and the development of effective treatments.

Berberine and chlorogenic acid-assembled nanoparticles for highly efficient inhibition of multidrug-resistant Staphylococcus aureus

Due to the bacteria resistant to various first-line antibiotics, it is urgent to develop efficient antibiotic alternatives and formulate multidimensional strategies. Herein, supramolecular Chinese medicine nanoparticles are synthesized by self-assembly of berberine (BBR) and chlorogenic acid (CGA), which exhibit higher inhibitory effect against Staphylococcus aureus and multidrug-resistant Staphylococcus aureus (MRSA) than ampicillin, oxacillin, BBR, CGA, as well as mixture of BBR and CGA (minimum inhibitory concentration, MIC = 1.5 µM). The inhibition by BBR/CGA nanoparticles (2.5 µM) reaches 99.06 % for MRSA, which is significantly higher than ampicillin (29.03 %). The nanoparticles with 1/2 MIC can also synergistically restore the antimicrobial activity of ampicillin against MRSA. Moreover, in vivo therapeutic outcome in the murine skin wound infection model suggests that the nanoparticles are able to promote wound healing. This study provides new insights in the application of Chinese medicines self-assembly for MRSA inhibition, as well as solutions for potential persistent clinical infections and drug deficiencies.