Antibacterial Function Research Articles

Dual-functional acridine-based coatings with anti-bacterial adhesion and durable photocatalytic antibacterial

Bacterial infections are a major public health challenge around the world. The development of novel surface coatings that effectively inhibit bacterial adhesion, proliferation and growth is a critical step in addressing this global challenge. Photocatalytic antibacterial therapy has proven to be an effective approach and has received increasing attention. However, it is still a challenge to obtain coatings with both antibacterial adhesion and durable photocatalytic antibacterial functions. Herein, an acridine-based coating with antibacterial adhesion and photocatalytic antibacterial properties was prepared by simple methods (i.e., spin-coating, spray-coating, and drop-coating) and can be applied to various substrates. The bacterial anti-adhesion test results showed that the coating could effectively prevents the adhesion of Escherichia coli (E. coli), Staphylococcus aureus (S. aureus), and Pseudomonas aeruginosa (P. aeruginosa), indicating the strong anti-fouling capability. The acridine-based coating demonstrated durable photocatalytic antimicrobial activity, remaining 99.3 % antibacterial effective against all three bacterial strains even after 30 days exposed to visible light. The coating can significantly reduce or eliminate the risk of contamination and cross-contamination, making it ideal for use in public healthcare environments.

Enhancing the Biological Performance of Titanium Alloy through In Situ Modulation of the Surface Nanostructure: Near-Infrared-Responsive Antibacterial Function and Osteoinductivity.

The poor clinical performance of titanium and its alloy implants is mainly attributed to their lack of antibacterial ability and poor osseointegration. The key and challenge lie in how to enhance their osteoinductivity while imparting antibacterial capability. In this study, a titanium oxide metasurface with light-responsive behavior was constructed on the surface of titanium alloy using an alkaline-acid bidirectional hydrothermal method. The effects of the acid type, acid concentration, hydrothermal time, hydrothermal temperature, and subsequent heat treatments on the optical behavior of the metasurface were systematically investigated with a focus on exploring the influence of the metasurface and photodynamic reaction on the osteogenic activity of osteoblasts. Results show that the type of acid and heat treatment significantly affect the light absorption of the titanium alloy surface, with HCl and post-heat-treatment favoring redshift in the light absorption. Under 808 nm near-infrared (NIR) irradiation for 10 min, in vitro antibacterial experiments demonstrate that the antibacterial rate of the metasurface titanium alloy against Staphylococcus aureus and Escherichia coli were 96.87% and 99.27%, respectively. In vitro cell experiments demonstrate that the nanostructure facilitates cell adhesion, proliferation, differentiation, and expression of osteogenic-related genes. Surprisingly, the nanostructure promoted the expression of relevant osteogenic genes of MC3T3-E1 under 808 nm NIR irradiation. This study provides a method for the surface modification of titanium alloy implants.

Skin-like breathable wound dressings with antimicrobial and hemostatic properties

Wound healing requires a contamination-free, sterile, and breathable environment. However, to develop an ideal wound dressing with all these functionalities simultaneously poses significant challenges. In this study, we designed a wound dressing that mimics the structure of skin with good breathability and protective functions. The wound dressing consists of a hydrophilic Poly(3-hydroxybutyrate-co-4-hydroxybutyrate) (P34HB) membrane coated with zinc oxide nanoparticles and a hydrophobic polyvinylidene fluoride (PVDF) membrane. Meanwhile, plasma treatment was also utilized to bond the two layers, resulting in an enhancement of 60 % in mechanical properties. The crosslinked fibrous membranes exhibited uniform stress distribution when stretching. Due to the unique structures of the wound dressing, it demonstrates wound exudate management, antibacterial functions, and hemostatic properties. The hydrophobic layer guided wound exudate towards the hydrophilic layer and the zinc oxide nanoparticles acted as a barrier against external bacteria and released zinc ions to inhibit bacterial growth in the exudate. Moreover, the water vapor transmission rate (WVTR) was measured to be over 86.55 kg/m2/day, the hemolysis rate was 2.38 %, and an impressive 81.98 % healing rate was recorded during in vitro wound healing. This skin-mimicking wound dressing shows great potential as a promising solution for the therapy of chronic wounds and infections.

Design and Application of an In Situ Traceable Nitric OxideDonor for Promoting the Healing of Wound Infections.

Therapies for wound infections require medications with antibacterial and wound-healing functions. However, it remains a challenge to produce a single drug that can perform dual functions. Nitric oxide (NO), with its antibacterial and wound-healing activities, is an ideal solution to address this challenge. However, many controlled-release strategies for NO rely on external probes for tracing the release in situ, making it difficult to precisely assess the location and magnitude. To address this issue, this study describes a novel NO donor, DHU-NO1, capable of efficiently releasing NO under mild conditions (450nm illumination). Simultaneously, DHU-NO1 generates the fluorophore Azure B (AZB), which enables direct, non-consumptive tracing of the NO release by monitoring the fluorescence and absorption changes in AZB. Given that NO can be conveniently traced, the amount of released NO can be controlled during biological applications, thereby allowing both functions of NO to be performed. When applied to the affected area, DHU-NO1, illuminated by both a simple light-emitting diode (LED) light source and natural light, achieves significant antibacterial effects against wound infections and promotes wound healing in mice. This study offers a novel and effective approach for treating wound infections.

Sponge-like porous polyvinyl alcohol/chitosan-based hydrogel with integrated cushioning, pH-indicating and antibacterial functions

Developing a packaging material with integrated cushioning, intelligent and active functions is highly desired but remains challenging in the food industry. Here we show that a sponge-like porous hydrogel with pH-indicating and antibacterial additives can meet this requirement. We use polyvinyl alcohol and chitosan as the primary polymers to construct a hydrogel with hierarchical structures through a freeze-casting method in combination with salting-out treatment. The synergy of aggregated polymer chains and the sponge-like porous structure makes the hydrogel resilient and efficient in energy absorption. It also enables rapid movement of molecules/particles and fast reaction due to the large specific surface area of the pore structures and the large amount of free water in it, leading to a sensitive pH-indicating function. The hydrogel shows an obvious color variation within a wide pH range in 3 min. The silver nanoparticles are fixed in the dense polymer networks, enabling a lasting release of silver ions. The porous structure makes the silver ion reach the protected item in a short time, achieving an antibacterial effect against S. aureus and E. coli with little cytotoxicity. This work paves the way for fabricating multifunctional hydrogels for diverse advanced packaging systems.

Rational design of Bacteria-Targeted and Photo-Responsive MOF gel with antibacterial and anti-inflammatory function for infected wound healing

Damaged skin is prone to recurrent bacterial infections, which hinder proper wound healing and exacerbate inflammation. Urgent attention is required to devise versatile dressings possessing antibacterial and anti-inflammatory attributes to facilitate wound recovery. In this study, we engineered a photo-responsive metal–organic frameworks (MOFs) gel, targeting bacteria, and endowed it with antibacterial and anti-inflammatory effects to address infected wound healing. On the one hand, the anionic MOF was choose to support cationic natural drug Berberine (BBR) to achieve slow release of anti-inflammatory drugs. On the other hand, the incorporation of Ag nanoparticles onto MOFs not only facilitates the generation of reactive oxygen species (ROS) via photocatalysis under visible light but also furnishes sites for boric acid group attachment to target bacteria and expedites ROS transfer. The resultant MOFs@Ag-B@BBR exhibited potent photodynamic antibacterial activity against Staphylococcus aureus and MRSA at a low concentration of 37.5 µg mL−1, surpassing the efficacy of most reported MOFs-based nano-antimicrobials. Upon application of the MOFs@Ag-B@BBR composite hydrogel to infected wounds, the released BBR, in conjunction with photodynamic antibacterial action, significantly mitigated inflammatory responses and fostered wound healing. This study provides a widely applicable approach for rational design of MOFs materials with enhance antibacterial and anti-inflammatory functions.

Intestinal lysozyme engagement of Salmonella Typhimurium stimulates the release of barrier-impairing InvE and Lpp1

Lysozyme is a β-1,4-glycosidase that hydrolyzes the polysaccharide backbone of bacterial cell walls. With an additional bactericidal function mediated by a separate protein domain, lysozyme is considered a uniquely important antimicrobial molecule contributing to the host's innate immune response to infection. Elevated lysozyme production is found in various inflammatory conditions while patients with genetic risks for inflammatory bowel diseases demonstrate abnormal lysozyme expression, granule packaging, and secretion in Paneth cells. However, it remains unclear how a gain- or loss-of-function in host lysozyme may impact the host inflammatory responses to pathogenic infection. We challenged Lyz1-/- and ectopic Lyz1-expressing (Villin-Lyz1TG) mice with S. Typhimurium and then comprehensively assessed the inflammatory disease progression. We conducted proteomics analysis to identify molecules derived from human lysozyme-mediated processing of live Salmonella. We examined the barrier-impairing effects of these identified molecules in human intestinal epithelial cell monolayer and enteroids. Lyz1-/- mice are protected from infection in terms of morbidity, mortality, and barrier integrity, whereas Villin-Lyz1TG mice demonstrate exacerbated infection and inflammation. The growth and invasion of Salmonella invitro are not affected by human or chicken lysozyme, whereas lysozyme encountering of live Salmonella stimulates the release of barrier-disrupting factors, InvE-sipC and Lpp1, which directly or indirectly impair the tight junctions. The direct engagement of host intestinal lysozyme with an enteric pathogen such as Salmonella promotes the release of virulence factors that are barrier-impairing and pro-inflammatory. Controlling lysozyme function may help alleviate the inflammatory progression.

Dynamic hydrogel–metal–organic framework system promotes bone regeneration in periodontitis through controlled drug delivery

Periodontitis is a prevalent chronic inflammatory disease, which leads to gradual degradation of alveolar bone. The challenges persist in achieving effective alveolar bone repair due to the unique bacterial microenvironment’s impact on immune responses. This study explores a novel approach utilizing Metal–Organic Frameworks (MOFs) (comprising magnesium and gallic acid) for promoting bone regeneration in periodontitis, which focuses on the physiological roles of magnesium ions in bone repair and gallic acid's antioxidant and immunomodulatory properties. However, the dynamic oral environment and irregular periodontal pockets pose challenges for sustained drug delivery. A smart responsive hydrogel system, integrating Carboxymethyl Chitosan (CMCS), Dextran (DEX) and 4-formylphenylboronic acid (4-FPBA) was designed to address this problem. The injectable self-healing hydrogel forms a dual-crosslinked network, incorporating the MOF and rendering its on-demand release sensitive to reactive oxygen species (ROS) levels and pH levels of periodontitis. We seek to analyze the hydrogel’s synergistic effects with MOFs in antibacterial functions, immunomodulation and promotion of bone regeneration in periodontitis. In vivo and in vitro experiment validated the system's efficacy in inhibiting inflammation-related genes and proteins expression to foster periodontal bone regeneration. This dynamic hydrogel system with MOFs, shows promise as a potential therapeutic avenue for addressing the challenges in bone regeneration in periodontitis.Graphical

Light‐Assisted 3D‐Printed Hydrogels for Antibacterial Applications

Light‐assisted 3D printing technology, which uses a light source to solidify a photopolymerizable prepolymer solution, has shown great potential in the development of antibacterial hydrogels with high‐resolution, specific features and functionalities. 3D‐printed hydrogels with customized structures and antibacterial functions are widely used in tissue engineering, regenerative medicine, wound healing, and implants to advance the modeling and treatment of diseases. In the current review, an overview of light‐assisted 3D printing technologies is first provided for the development of antibacterial hydrogels. Novel strategies involving the integration of inorganic nanomaterials, antibiotics, and functional polymers into 3D‐printed hydrogels for the enhancement of antibacterial effects are then discussed. Finally, the perspective of advanced design using artificial intelligence and machine learning is proposed, providing a comprehensive yet succinct examination of 3D‐printed hydrogels for antibacterial purposes.

Green modifications for rendering cotton fabric with antibacterial, anti-mite, and mosquito-repellent functions using single natural eugenol

Cotton fabrics are widely used in everyday life; however, increasing their versatility through green modifications remains a challenge. The current mainstream approach merely physically attaches the additives onto the fibers, resulting in low binding affinity. In this study, novel cotton fabrics (Cotton-Si-EU) with long-lasting antibacterial, anti-mite, and mosquito-repellent properties were facilely fabricated in a green procedure. In contrast to conventional coating and physical addition methods, the eugenol graft modification ensured the safety, environmental friendliness and long-lasting functionality of the Cotton-Si-EU. In addition, Cotton-Si-EU fabrics retained the softness, comfort, breathability, and moisture absorption originating from the cotton fabric. Cotton-Si-EU also showed over 99.99% antibacterial, 73% anti-mite, and 75% mosquito repellent rates, simultaneously destroying microorganisms and insects through oxidative stress, inhibiting enzyme activity, affecting cell structure, and other mechanisms. More importantly, after 50 washing cycles, the fabrics still exhibited durable antibacterial properties higher than the AAA requirements, indicating high functional longevity. In addition, good cytocompatibility, hemocompatibility, and negligible skin irritation demonstrated excellent biological safety. Therefore, this study is of great significance in providing a reference for modifying cotton fabrics using an infinite number of natural products after screening, which will broaden the application scope and improve the safety level of functional cotton fabrics.

Janus liposozyme for the modulation of redox and immune homeostasis in infected diabetic wounds.

Diabetic foot ulcers often become infected, leading to treatment complications and increased risk of loss of limb. Therapeutics to manage infection and simultaneously promote healing are needed. Here we report on the development of a Janus liposozyme that treats infections and promotes wound closure and re-epithelialization. The Janus liposozyme consists of liposome-like selenoenzymes for reactive oxygen species (ROS) scavenging to restore tissue redox and immune homeostasis. The liposozymes are used to encapsulate photosensitizers for photodynamic therapy of infections. We demonstrate application in methicillin-resistant Staphylococcus aureus-infected diabetic wounds showing high ROS levels for antibacterial function from the photosensitizer and nanozyme ROS scavenging from the liposozyme to restore redox and immune homeostasis. We demonstrate that the liposozyme can directly regulate macrophage polarization and induce a pro-regenerative response. By employing single-cell RNA sequencing, T cell-deficient Rag1-/- mice and skin-infiltrated immune cell analysis, we further reveal that IL-17-producing γδ T cells are critical for mediating M1/M2 macrophage transition. Manipulating the local immune homeostasis using the liposozyme is shown to be effective for skin wound repair and tissue regeneration in mice and mini pigs.

Neutrophils Expressing Programmed Death-Ligand 1 Play an Indispensable Role in Effective Bacterial Elimination and Resolving Inflammation in Methicillin-Resistant Staphylococcus aureus Infection.

Programmed death ligand 1 (PD-L1) is a co-inhibitory molecule expressed on the surface of various cell types and known for its suppressive effect on T cells through its interaction with PD-1. Neutrophils also express PD-L1, and its expression is elevated in specific situations; however, the immunobiological role of PD-L1+ neutrophils has not been fully characterized. Here, we report that PD-L1-expressing neutrophils increased in methicillin-resistant Staphylococcus aureus (MRSA) infection are highly functional in bacterial elimination and supporting inflammatory resolution. The frequency of PD-L1+ neutrophils was dramatically increased in MRSA-infected mice, and this population exhibited enhanced activity in bacterial elimination compared to PD-L1- neutrophils. The administration of PD-L1 monoclonal antibody did not impair PD-L1+ neutrophil function, suggesting that PD-L1 expression itself does not influence neutrophil activity. However, PD-1/PD-L1 blockade significantly delayed liver inflammation resolution in MRSA-infected mice, as indicated by their increased plasma alanine transaminase (ALT) levels and frequencies of inflammatory leukocytes in the liver, implying that neutrophil PD-L1 suppresses the inflammatory response of these cells during the acute phase of MRSA infection. Our results reveal that elevated PD-L1 expression can be a marker for the enhanced anti-bacterial function of neutrophils. Moreover, PD-L1+ neutrophils are an indispensable population attenuating inflammatory leukocyte activities, assisting in a smooth transition into the resolution phase in MRSA infection.

Shear Flow-Assembled Janus Membrane with Bifunctional Osteogenic and Antibacterial Effects for Guided Bone Regeneration.

Guided bone regeneration (GBR) membranes that reside at the interface between the bone and soft tissues for bone repair attract increasing attention, but currently developed GBR membranes suffer from relatively poor osteogenic and antibacterial effects as well as limited mechanical property and biodegradability. We present here the design and fabrication of a bifunctional Janus GBR membrane based on a shear flow-driven layer by a layer self-assembly approach. The Janus GBR membrane comprises a calcium phosphate-collagen/polyethylene glycol (CaP@COL/PEG) layer and a chitosan/poly(acrylic acid) (CHI/PAA) layer on different sides of a collagen membrane to form a sandwich structure. The membrane exhibits good mechanical stability and tailored biodegradability. It is found that the CaP@COL/PEG layer and CHI/PAA layer contribute to the osteogenic differentiation and antibacterial function, respectively. In comparison with the control group, the Janus GBR membrane displays a 2.52-time and 1.84-time enhancement in respective volume and density of newly generated bone. The greatly improved bone repair ability of the Janus GBR membrane is further confirmed through histological analysis, and it has great potential for practical applications in bone tissue engineering.

Copper-phenolic coating constructed on silicone urinary catheters to prevent catheter-associated infections

Catheter-associated infections (CAIs) are serious issues in clinics, significantly affecting patient morbidity, mortality, and incurring substantial treatment costs. Hence, the development of a novel strategy to endow surfaces with antibacterial function is particularly important for catheter materials. In this work, Tannic acid (TA) and various concentrations of copper (Cu) were used to construct metal-phenolic network (MPN) coatings to impart silicone catheters antibacterial surfaces (TA/Cu5, TA/Cu5 and TA/Cu25). The prepared copper-phenolic coatings exhibited desirable biocompatibility towards mammalian cells and remarkable antibacterial properties against Staphylococcus aureus (S. aureus), Escherichia coli (E. coli) and even “superbug” such as methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococcus (VRE). The antibacterial properties of the MPN coatings were attributed to the combined effects of Cu and TA. Among all MPN coated silicone catheters, TA/Cu25 (10 mM TA and 250 mM CuCl2·2 H2O) exhibited the highest antibacterial activity with killing ratios of 99.84%, 98.67%, 99.85%, and 99.90% against S. aureus, E. Coli, MRSA and VRE, respectively. Thus, the MPN has significant potential for developing antibacterial surface coatings for silicone catheters, which can effectively mitigate CAIs.

Making the leap from technique to treatment - genetic engineering is paving the way for more efficient phage therapy.

Bacteriophages (phages) are viruses specific to bacteria that target them with great efficiency and specificity. Phages were first studied for their antibacterial potential in the early twentieth century; however, their use was largely eclipsed by the popularity of antibiotics. Given the surge of antimicrobial-resistant strains worldwide, there has been a renaissance in harnessing phages as therapeutics once more. One of the key advantages of phages is their amenability to modification, allowing the generation of numerous derivatives optimised for specific functions depending on the modification. These enhanced derivatives could display higher infectivity, expanded host range or greater affinity to human tissues, where some bacterial species exert their pathogenesis. Despite this, there has been a noticeable discrepancy between the generation of derivatives in vitro and their clinical application in vivo. In most instances, phage therapy is only used on a compassionate-use basis, where all other treatment options have been exhausted. A lack of clinical trials and numerous regulatory hurdles hamper the progress of phage therapy and in turn, the engineered variants, in becoming widely used in the clinic. In this review, we outline the various types of modifications enacted upon phages and how these modifications contribute to their enhanced bactericidal function compared with wild-type phages. We also discuss the nascent progress of genetically modified phages in clinical trials along with the current issues these are confronted with, to validate it as a therapy in the clinic.

Surface Topography Steer Soft Tissue Response and Antibacterial Function at the Transmucosal Region of Titanium Implant.

Metallic dental implants have been extensively used in clinical practice due to their superior mechanical properties, biocompatibility, and aesthetic outcomes. However, their integration with the surrounding soft tissue at the mucosal region remains challenging and can cause implant failure due to the peri-implant immune microenvironment. The soft tissue integration of dental implants can be ameliorated through different surface modifications. This review discussed and summarized the current knowledge of topography-mediated immune response and topography-mediated antibacterial activity in Ti dental implants which enhance soft tissue integration and their clinical performance. For example, nanopillar-like topographies such as spinules, and spikes showed effective antibacterial activity in human salivary biofilm which was due to the lethal stretching of bacterial membrane between the nanopillars. The key findings of this review were (I) cross-talk between surface nanotopography and soft tissue integration in which the surface nanotopography can guide the perpendicular orientation of collagen fibers into connective tissue which leads to the stability of soft tissue, (II) nanotubular array could shift the macrophage phenotype from pro-inflammatory (M1) to anti-inflammatory (M2) and manipulate the balance of osteogenesis/osteoclasia, and (III) surface nanotopography can provide specific sites for the loading of antibacterial agents and metallic nanoparticles of clinical interest functionalizing the implant surface. Silver-containing nanotubular topography significantly decreased the formation of fibrous encapsulation in per-implant soft tissue and showed synergistic antifungal and antibacterial properties. Although the Ti implants with surface nanotopography have shown promising in targeting soft tissue healing in vitro and in vivo through their immunomodulatory and antibacterial properties, however, long-term in vivo studies need to be conducted particularly in osteoporotic, and diabetic patients to ensure their desired performance with immunomodulatory and antibacterial properties. The optimization of product development is another challenging issue for its clinical translation, as the dental implant with surface nanotopography must endure implantation and operation inside the dental microenvironment. Finally, the sustainable release of metallic nanoparticles could be challenging to reduce cytotoxicity while augmenting the therapeutic effects.

Antibacterial Test Of Ethanol Extract Gel Preparation Kencur Rhizome (Kaempferia Galanga) Against Staphylococcus Epidermidis

Staphylococcus epidermidis is one of the bacteria that causes acne. infections can be treated by using natural antibiotics. galangal rhizome (Kaempferia galanga L.) contains chemical compounds including flavonoids, saponins, tannins, alkaloids and terpenoids/steroids where these active compounds have an antibacterial function that can overcome acne problems on the surface of the skin. Galangal rhizome ethanol extract gel preparations were made with 3 variations of concentration (10%, 15% and 20%). The aim of this research was to determine whether the ethanol extract gel preparation of kencur rhizome (Kaempferia galanga L.) had antibacterial activity against Staphylococcus epidermidis and to determine the physical quality of the gel preparation. The method used is an experimental laboratory which is useful for determining the effect of ethanol extract of kencur rhizomes with concentrations of 10%, 15% and 20% on Staphylococcus epidermidis bacteria in gel preparations. The antibacterial test was carried out using the well diffusion method. The antibacterial test results with concentrations of 10%, 15% and 20% respectively were 13.68; 13.60 ; 14.24 mm has an influence on the inhibition zone of Staphylococcus epidermidis bacteria. The research results showed that a concentration of 20% had the highest bacterial inhibitory power.

Akirin2 enhances antibacterial ability via interacting with 14-3-3ζ in V. splendidus-challenged Apostichopus japonicus

Akirin2 is pivotal for regulating host immunological responses in vertebrates, including antibacterial immunity and inflammation. However, the functional significance of Akirin2 in invertebrates remains largely unexplored. In this study, we cloned the complete cDNA sequence of Akirin2 from A. japonicus (AjAkirin2) and elucidated its immunological mechanism upon pathogen infection. The whole AjAkirin2 cDNA sequence spanned 1014 bp, which comprised a 630 bp open reading frame encoding 209 amino acids, a 230 bp 5′-untranslated region (UTR), and a 154 bp 3′-UTR. Spatial expression analysis displayed constitutive expression of AjAkirin2 in all examined tissues. Both mRNA and protein expression abundance of the AjAkirin2 showed considerably high in coelomocytes of sea cucumbers challenged with Vibrio splendidus or stimulated with lipopolysaccharide. In addition, we found that sea cucumbers with 107 CFU/mL V. splendidus infection had a lower survival rate upon AjAkirin2 knockdown. Mechanistically, the result of GST-pull down and co-IP assays indicated that AjAkirin2 directly interacted with Aj14-3-3ζ. Moreover, we also detected that AjAkirin2 positively regulated Aj14-3-3ζ expression in sea cucumber coelomocytes. Furthermore, the knockdown of AjAkirin2 or Aj14-3-3ζ resulted in increasing intracellular bacteria load and suppressed the expression of key genes of the NF-κB signaling pathway (p65 and p105) and inflammatory cytokines including IL-17, VEGF, and MMP-1. In summary, these results confirmed the critical role of AjAkirin2 in mediating innate immune responses against V. splendidus infection via interaction with Aj14-3-3ζ and thereby exerting antibacterial function.

Polydopamine-Coated Copper-Doped Co3O4 Nanosheets Rich in Oxygen Vacancy on Titanium and Multimodal Synergistic Antibacterial Study.

Medical titanium-based (Ti-based) implants in the human body are prone to infection by pathogenic bacteria, leading to implantation failure. Constructing antibacterial nanocoatings on Ti-based implants is one of the most effective strategies to solve bacterial contamination. However, single antibacterial function was not sufficient to efficiently kill bacteria, and it is necessary to develop multifunctional antibacterial methods. This study modifies medical Ti foils with Cu-doped Co3O4 rich in oxygen vacancies, and improves their biocompatibility by polydopamine (PDA/Cu-Ov-Co3O4). Under near-infrared (NIR) irradiation, nanocoatings can generate •OH and 1O2 due to Cu+ Fenton-like activity and a photodynamic effect of Cu-Ov-Co3O4, and the total reactive oxygen species (ROS) content inside bacteria significantly increases, causing oxidative stress of bacteria. Further experiments prove that the photothermal process enhances the bacterial membrane permeability, allowing the invasion of ROS and metal ions, as well as the protein leakage. Moreover, PDA/Cu-Ov-Co3O4 can downregulate ATP levels and further reduce bacterial metabolic activity after irradiation. This coating exhibits sterilization ability against both Escherichia coli and Staphylococcus aureus with an antibacterial rate of ca. 100%, significantly higher than that of bare medical Ti foils (ca. 0%). Therefore, multifunctional synergistic antibacterial nanocoating will be a promising strategy for preventing bacterial contamination on medical Ti-based implants.

Ultra-small gold nanoparticles embedded cyclodextrin metal-organic framework composite membrane to achieve antibacterial and humidity-responsive functions

Cyclodextrin metal-organic framework (CD-MOF) is an edible and porous material that can serve as a template for synthesizing small-sized metal nanoparticles. However, its highly hydrophilic nature has limited its wider application. Herein, ultra-small gold nanoparticles (U-AuNPs) were loaded into CD-MOF to produce a composite material Au@CD-MOF. The CD-MOF was utilized as a template to control the size of the AuNPs. The synthesized Au@CD-MOF was easily dispersible in aqueous medium and its released U-AuNPs exhibited effective water dispersion stability within 120 days. Additionally, compared to gold nanoparticles prepared using traditional methods (T-AuNPs), the U-AuNPs exhibited superior antibacterial properties. Furthermore, hydrophilic Au@CD-MOF was incorporated into a hydrophobic polydimethylsiloxane (PDMS) matrix (Au@CD-MOF/PDMS) to achieve a humidity-responsive antibacterial function. The composite membrane exhibited remarkable responsiveness to humidity, showing almost no release of U-AuNPs at 0 % humidity. However, it exhibited approximately 89 % release within 1 h, and complete release of U-AuNPs was observed within 4 h under 100 % humidity. These findings highlight the successful preparation of a humidity-responsive antibacterial composite membrane, which has great potential applications in various scenarios, particularly in the field of antibacterial food packaging.