Antibacterial Platform Research Articles

Magnetically Guided Nanoworms for Precise Delivery to Enhance In Situ Production of Nitric Oxide to Combat Focal Bacterial Infection In Vivo.

Overexploitation of antibiotics increases the emergence of multidrug-resistant agents (MDRAs), which may potentially cause a global crisis with severe health consequences. Hence, there is great demand for next-generation antibacterial platforms based on antibiotic-free strategies or targeted therapies to mitigate the emergence of MDRAs. Herein, an all-in-one hollow nanoworm (A-Fe/AuAg@PDA) is developed with a core comprising citrate-capped Au-Ag nanoparticles (Cit-AuAg NPs) loaded with Fe2O3 and an l-arginine (L-Arg)-modified polydopamine (PDA) outer shell, possessing exceptional magnetic-targeting ability and a photothermal therapeutic effect. Following intravenous injection, A-Fe/AuAg@PDA can be precisely delivered to the targeted infection sites by an externally applied magnetic field. The in situ produced NO, together with Ag ions and reactive oxygen species, synergistically results in the highly effective elimination of in vivo bacterial infection. With the aid of functional worm-like A-Fe/AuAg@PDA nanocarriers possessing superior biocompatibility, the combination of magnetic guidance therapy and near-infrared-triggered in situ generation of NO may provide a novel approach for eradicating abscesses in the body. To our knowledge, this is the first study highlighting the magnetically guided delivery of worm-like nanocarriers for the antibiotic-free therapy of bacterial infections using in situ generated NO gas, which demonstrates high potential for application in clinical gas therapy.

A photothermal and self-induced Fenton dual-modal antibacterial platform for synergistic enhanced bacterial elimination

Although the single-modal antibacterial technology has received widespread attention, it has limitations because of challenges associated with the complete eradication of bacteria. Herein, we present a synergistic antibacterial strategy based on copper peroxide loaded-tungsten disulfide nanoflowers (CP@WS2 NFs). In this system, copper peroxide can self-supply H2O2 to activate the Fenton reaction, which causes the destruction of some bacteria under acidic condition. Under near-infrared laser irradiation, WS2 NFs transform light-to-localized heat to eliminate the remaining bacteria. The system can cause serious leakage of cell components, reduce the amount of adenosine triphosphate and destroy the bacterial membrane. In vitro experiments indicated a predominant synergistic antibacterial effect on Escherichia coli and Staphylococcus aureus. In vivo experiments of wound healing confirmed that the system can enhance bacterial elimination, concurrently promoting wound healing with high biocompatibility. In addition, our study reveals a promising dimension for the rational design of a synergistic antibacterial system.

Mechanism Insight into Rapid Photodriven Sterilization Based on Silver Bismuth Sulfide Quantum Dots.

Microbial contamination and the prevalence of resistant bacteria is considered a worldwide public health problem. Therefore, recently, great efforts have been made to develop photoresponsive platforms for the simultaneous photodynamic antibacterial (PDA) and photothermal antibacterial (PTA) therapy processes as mediated by specific light. However, owing to the absorption mismatches of the photothermal agents and photodynamic photosensitizers, it has been discovered that many synergistic photoresponsive antibacterial platforms cannot be excited by a single-wavelength light. In this study, silver bismuth sulfide quantum dots (AgBiS2 QDs) identified from the literature as a near-infrared light (NIR) that triggers bifunctional materials with simultaneous photodynamic and photothermal effects for photoresponsive bacterial killing were used. Specifically, AgBiS2 QDs were successfully synthesized via a bottom-up approach, using polyethylenimine (PEI) as an assistant molecule. With PEI wrapping, the attachment between the negatively charged membrane surfaces of the bacterial cells and AgBiS2 QDs was enhanced via the electrostatic interactions. The photodriven antibacterial activity of AgBiS2 QDs was then investigated against both S. aureus and E. coli. The results revealed a significant reduction in bacterial survival. The killing effect was found to be independent of the AgBiS2 QDs, and redox potentials controlled the photogenerated electrons that thermodynamically favored the formation of multiple reactive oxygen species (ROS). A possible phototriggered antibacterial mechanism was then proposed in which the AgBiS2 QDs are anchored first to the bacterial surface and then induce breaking on its outer membrane by high local heat and ROS under single 808 nm NIR laser illumination to finally induce bacterial death.

Protein-Inorganic Hybrid Nanoflowers as Efficient Biomimetic Antibiotics in the Treatment of Bacterial Infection.

Nanozymes have been developed as new generation of biomimetic antibiotics against wound infection. However, most of new-developed nanozymes based on inorganic particles or hybrid ones usually originate from incompatible raw materials or unwanted metal salts, highly limiting their further biomedical usages. To overcome above drawbacks, it is highly required to develop novel nanozymes with great antibacterial activity by using biocompatible reagents and endogenous metal species as raw materials. Here, we demonstrated that bovine serum albumin enwrapped copper phosphate-based protein-inorganic hybrid nanoflowers possessed intrinsic peroxidase-like activity, which could be used as efficient biomimetic antibiotics against bacterial infection via the nanozyme-mediated generation of high toxic reactive oxygen species (ROS). With the admirable peroxidase-like activity, our nanoflowers could efficiently kill drug-resistance bacteria under physiological conditions, improve the wound healing after pathogen-induced infection, as well as avoid the potential tissue injury in time. Comprehensive toxicity exploration of these nanoflowers indicated their high biocompatibility and excellent biosafety. Our current strategy toward the design of protein-inorganic hybrid nanozymes with high biosafety and few side effects could provide a new paradigm for the development of nanozyme-based antibacterial platform in future.

Synergistic and On-Demand Release of Ag-AMPs Loaded on Porous Silicon Nanocarriers for Antibacteria and Wound Healing.

Due to the abuse of antibiotics, antimicrobial resistance is rapidly emerging and becoming a major global risk for public health. Thus, there is an urgent need for reducing the use of antibiotics, finding novel treatment approaches, and developing controllable release systems. In this work, a dual synergistic antibacterial platform with on-demand release ability based on silver nanoparticles (AgNPs) and antimicrobial peptide (AMP) coloaded porous silicon (PSi) was developed. The combination of AgNPs and AMPs (Tet-213, KRWWKWWRRC) exhibited an excellent synergistic antibacterial effect. As a carrier, porous silicon can efficiently load AgNPs and AMP under mild conditions and give the platform an on-demand release ability and a synergistic release effect. The AgNPs and AMP coloaded porous silicon microparticles (AgNPs-AMP@PSiMPs) exhibited an acid pH and reactive oxygen species (ROS)-stimulated release of silver ions (Ag+) and AMPs under bacterial infection conditions because of oxidation and desorption effects. Moreover, the release of the bactericide could be promoted by each other due to the interplay between AgNPs and Tet-213. In vitro antibacterial tests demonstrated that AgNPs-AMP@PSiMPs inherited the intrinsic properties and synergistic antibacterial efficiency of both bactericides. In addition, wound dressing loaded with AgNPs-AMP@PSiMPs showed outstanding in vivo bacteria-killing activity, accelerating wound-healing, and low biotoxicity in aStaphylococcus aureus-infected rat wound model. The present work demonstrated that PSiMPS might be an efficient platform for loading the antibiotic-free bactericide, which could synergistically and on-demand release to fight wound infection and promote wound healing.

Shining light on transition metal sulfides: New choices as highly efficient antibacterial agents.

Globally, millions of people die of microbial infection-related diseases every year. The more terrible situation is that due to the overuse of antibiotics, especially in developing countries, people are struggling to fight with the bacteria variation. The emergence of super-bacteria will be an intractable environmental and health hazard in the future unless novel bactericidal weapons are mounted. Consequently, it is critical to develop viable antibacterial approaches to sustain the prosperous development of human society. Recent researches indicate that transition metal sulfides (TMSs) represent prominent bactericidal application potential owing to the meritorious antibacterial performance, acceptable biocompatibility, high solar energy utilization efficiency, and excellent photo-to-thermal conversion characteristics, and thus, a comprehensive review on the recent advances in this area would be beneficial for the future development. In this review article, we start with the antibacterial mechanisms of TMSs to provide a preliminary understanding. Thereafter, the state-of-the-art research progresses on the strategies for TMSs materials engineering so as to promote their antibacterial properties are systematically surveyed and summarized, followed by a summary of the practical application scenarios of TMSs-based antibacterial platforms. Finally, based on the thorough survey and analysis, we emphasize the challenges and future development trends in this area.

Near-infrared carbon dot-based platform for bioimaging and photothermal/photodynamic/quaternary ammonium triple synergistic sterilization triggered by single NIR light source

The design of efficient synergistic therapeutic strategies for bacterial infection is highly desirable due to their high therapeutic efficiency and less side effects. In this study, a rapid and effective multi-mode antibacterial platform that integrates quaternary ammonium compounds (QACs), photothermal therapy (PTT) and photodynamic therapy (PDT) was developed. QACs can induce initial damage to the bacterial cell membrane and render it more sensitive to heat. During 808 nm laser irradiation, the generation of hyperthermia and reactive oxygen species (ROS) can induce the death of damaged Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus), and the corresponding bacterial killing efficiencies are approximately 99.36% and 99.98%, which exceed single-mode therapy. In vivo antibacterial and anti-infective assays proved that effective sterilization could accelerate the infected wound healing process, and the traumas healed well within 14 days after treatment with Cu-RCDs-C35 and 808 nm irradiation. The wound healing area ratio was calculated to be 96%, which substantially exceeds the PBS + Laser, Cu-RCDs, and RCDs-C35+Laser groups. In addition, the cellular imaging experiment showed that Cu-RCDs-C35 could also serve as a fluorescence probe in bioimaging due to its inherent luminescence. Therefore, the present study provides high-efficiency and multifunctional carbon nanomaterials as antibacterial and bioimaging agents.

Au-ZnO Conjugated Black Phosphorus as a Near-Infrared Light-Triggering and Recurrence-Suppressing Nanoantibiotic Platform against Staphylococcus aureus.

Antibiotic therapy is the gold standard for bacterial infections treatment. However, the rapid increase in multidrug-resistant (MDR) bacterial infections and its recent use for secondary bacterial infections in many COVID-19 patients has considerably weakened its treatment efficacy. These shortcomings motivated researchers to develop new antibacterial materials, such as nanoparticle-based antibacterial platform with the ability to increase the chances of killing MDR strains and prevent their drug resistance. Herein, we report a new black phosphorus (BP)-based non-damaging near-infrared light-responsive platform conjugated with ZnO and Au nanoparticles as a synergistic antibacterial agent against Staphylococcus aureus species. First, BP nanosheets containing Au nanoparticles were assembled in situ with the ZnO nanoparticles prepared by a low-temperature solution synthesis method. Subsequently, the antibacterial activities of the resulting Au–ZnO–BP nanocomposite against the non-resistant, methicillin-resistant, and erythromycin-resistant S. aureus species were determined, after its photothermal efficacy was assessed. The synthesized nanocomposite exhibited excellent anti-S. aureus activity and good photothermal characteristics. The non-resistant S. aureus species did not produce drug-resistant bacteria after the treatment of multiple consecutive passages under the pressure of the proposed nanoantibiotic, but rapidly developed resistance to erythromycin. This work clearly demonstrates the excellent photothermal antibacterial properties of Au–ZnO–BP nanocomposite against the MDR S. aureus species.

Glucose oxidase and Fe3O4/TiO2/Ag3PO4 co-embedded biomimetic mineralization hydrogels as controllable ROS generators for accelerating diabetic wound healing.

The hyperglycemic environment and the presence of bacterial infections delay the healing of diabetic wounds. Herein, glucose oxidase (GOx) and Fe3O4/TiO2/Ag3PO4 were embedded in a polyacrylic acid-calcium phosphate (PAA-CaPs@Nps@GOx) hydrogel through an in situ biomimetic mineralization approach. The GOx encapsulation efficiency was 96.75% and exhibited exceptional enzyme activity stability. Moreover, the co-immobilization of GOx and Fe3O4/TiO2/Ag3PO4 nanoparticles generated a simple and multifunctional antibacterial platform with the advantages of decreasing blood glucose concentration and efficiently producing reactive oxygen species (ROS). In addition, the degradation rate of the hydrogel was controlled by regulating the concentration of phosphate thus controlling the release of Fe3O4/TiO2/Ag3PO4 and GOx. As a result, both the potential toxicity and oxidative stress associated with the antimicrobial biomaterial can be controlled within the body therefore potentially preventing detriment. In vivo results indicated that the PAA-CaPs@Nps@GOx hydrogel effectively promoted diabetic wound healing and showed great potential for clinical applications of chronic wound management.

Near-infrared light II - assisted rapid biofilm elimination platform for bone implants at mild temperature

Light-triggered therapy is a prospective method to combat implant-associated infection but near-infrared I (NIR-I) light has insufficient penetrating ability in tissues and local hyperthermia induced by the photothermal treatment may destroy surrounding healthy tissues. Herein, a near-infrared II (NIR-II) phototherapy system composed of upconversion elements doped titanium dioxide nanorods (TiO2 NRs)/curcumin (Cur)/hyaluronic acid (HA)/bone morphogenetic protein-2 (BMP-2) is designed for biomedical titanium and demonstrated to overcome the above hurdles simultaneously. Incorporation of F, Yb, and Ho not only improves the photocatalytic ability, but also renders the implants with the upconversion capability, so that the NRs can generate enough reactive oxygen species (ROS) when irradiated by the NIR-II laser. Furthermore, the combined actions of quorum sensing inhibitors, ROS, and physical puncture by NRs eliminate Staphylococcus aureus biofilms on titanium rapidly at a mild temperature of 45 °C by only requiring irradiation with the 1060 nm laser for only 15 min in vitro and in vivo. The presence of Cur mitigates the immune response and BMP-2 improves osteogenic differentiation, thus accelerating new bone formation. This low-temperature NIR-II light-triggered antibacterial platform has large potential in combating deep-tissue infection in clinical applications.

Photothermally triggered nitric oxide nanogenerator targeting type IV pili for precise therapy of bacterial infections

Nitric oxide (NO) is an important biological messenger involved in the treatment of bacterial infections, but its controlled and targeted release in bacterial infections remains a major challenge. Herein, an intelligent NO nanogenerator triggered by near-infrared (NIR) light is constructed for targeted treatment of P. aeruginosa bacterial infection. Since maleimide can recognize and attach to the pilus of T4P of P. aeruginosa, we adopt this strategy to achieve the accurate release of therapeutic drugs at the infection site, i.e., after maleimide targets Gram-negative bacteria, the SNP@MOF@Au-Mal nanogenerator will release NO and generate ROS in situ from the inorganic photosensitizer gold nanoparticles under NIR irradiation to achieve synergistic antibacterial effect. In vivo experiments proved that the bacterial burden on the wound was reduced by 97.7%. Additionally, the nanogenerator was shown to promote the secretion of growth factors, which play a key role in regulating inflammation and inducing angiogenesis. This strategy has the advantage of generating a high concentration of NO in situ to promote the transfer of more NO and its derivatives (N2O3, ONOO−) to bacteria, thereby significantly improving the antibacterial effect. The multifunctional antibacterial platform has been demonstrated as a good carrier for gas therapy because of its simple and efficient gas release performance, indicating its great potential for the treatment of drug-resistant bacterial infections.

A synergistic antibacterial platform: combining mechanical and photothermal effects based on Van-MoS2–Au nanocomposites

Herein, we successfully developed a new multifunctional antibacterial system, which combined mechano-bactericidal (Au-nanostars) and photothermal (MoS2) mechanism. Meanwhile, the targeting molecule of vancomycin was modified on the surface of MoS2–Au nanocomposites (Van-MoS2–Au), that generally yield high efficiency in antibacterial performance due to their effective working radii. Van-MoS2–Au nanocomposites were capable of completely destroying both gram-negative (E. coli) and gram-positive (B. subtilis) bacteria under 808 NIR laser irradiation for 20 min, and nearly no bacterial growth was detected after 12 h incubation. Moreover, these nanocomposites could destruct the refractory biofilm as well, which was a much more difficult medical challenge. The new antibacterial nanomaterials might offer many biomedical applications because of the biocompatibility and strong antibacterial ability.

An antiadhesion and antibacterial platform based on parylene F coatings

As an excellent barrier material, parylene has been widely used in plenty of fields. However, conventional parylenes cannot endure medical sterilization procedures, including high-temperature sterilization and ultraviolet disinfection, which restrict their medical applications. A new parylene member, Parylene F, overcomes the above drawbacks and shows potential in medical applications. In this work, parylene F (type AF4) was deposited on two polydimethylsiloxane (PDMS) substrates through chemical vapor deposition (CVD) method, and the thickness of parylene F was 1 μm (PDMS-PF-1) and 5 μm (PDMS-PF-5), respectively. For the first time, we investigated the antifouling property and biocompatibility of parylene F. We found an interesting phenomenon that parylene F demonstrated dual-action antifouling activities—antiadhesion and antibacterial. For gram-negative bacteria Escherichia coli, the fouled area to the total area ratios on PDMS-PF-1 (0.69 ± 0.25 %) and PDMS-PF-5 (0.5 ± 0.1 %) were significantly lower than that on the pristine PDMS (6 ± 0.77 %). The antibacterial ratios (dead/total bacteria) of PDMS-PF-1 (45.49 ± 9.58 %) and PDMS-PF-5 (45.3 ± 8.8 %) were higher than that of the pristine PDMS (28.12 ± 3.26 %). Similar results were also observed in the tests against gram-positive bacteria Bacillus subtilis. The synergistic effect of antiadhesion and antibacterial characteristics endowed the surface with excellent antifouling properties. These results indicated that the thickness of parylene F had a close relationship to its antiadhesion performance, while not affecting the antibacterial activity. Additionally, this study revealed that parylene F exhibited good light transmittance (PDMS-PF-1 > 83 % and PDMS-PF-5 > 81 % in the visible wavelength) and excellent biocompatibility (relative cell viability > 86 %). These excellent properties mean that parylene F can act as a potential candidate for medical and related applications.

An intelligent platform based on acidity-triggered aggregation of gold nanoparticles for precise photothermal ablation of focal bacterial infection

Precisely striking the bacterially infected site and avoiding damage to healthy tissues is vital for bacterial infection therapy. Herein, an intelligent antibacterial platform that triggers the aggregation of gold nanoparticles (AuNPs) on bacterial surface based on the acidic environment of bacterial infection was developed. Also, the AuNPs functionalized with an acidity-triggered moiety (Pep-DA) exhibited a charge-convertible properties to target bacterial infection sites. The positively charged acidity-triggered AuNPs endowed the AuNPs aggregate on negatively charged bacterial surface in the infected site rather than in healthy tissues, achieving the threshold to interparticle plasmonic coupling effect among AuNPs, and killing bacteria accurately under NIR irradiation light. This acidity-triggered aggregation strategy provides an excellent therapeutic mode for treating focal bacterial infections with no critical damage to healthy tissues.

Ultrasmall AgNP-Impregnated Biocompatible Hydrogel with Highly Effective Biofilm Elimination Properties.

Ultrasmall silver nanoparticles (AgNPs; size < 3 nm) have attracted a great deal of interest as an alternative to commercially available antibiotics due to their ability to eliminate a wide range of microbial pathogens. However, most of these ultrasmall AgNPs are highly reactive and unstable, as well as susceptible to fast oxidation. Therefore, both the stability and toxicity remain major shortcomings for their clinical application and uptake. To circumvent these problems, we present a novel strategy to impregnate ultrasmall AgNPs into a biocompatible thermosensitive hydrogel that enables controlled release of silver alongside long-term storage stability and highly potent antibacterial activity. The advantage of this strategy lies in the combination of a homogenous dispersion of AgNPs in a hydrogel network, which serves as a sustained-release reservoir, and the unique feature of ultrasmall AgNP size, which provides an improved biofilm eradication capacity. The superior biofilm dispersion properties of the AgNP hydrogel is demonstrated in both single-species and multispecies biofilms, eradicating ∼80% of established biofilms compared to untreated controls. Notably, the effective antibacterial concentration of the formulation shows minimal toxicity to human fibroblasts and keratinocytes. These findings present a promising novel strategy for the development of AgNP hydrogels as an efficient antibacterial platform to combat resistant bacterial biofilms associated with wound infections.

Super-repellent photodynamic bactericidal hybrid membrane

Biomaterial-associated infections caused by pathogenic bacteria have become an urgent threat to public health. Efficient bactericidal strategies that can inactivate bacteria without triggering antimicrobial resistance (AR) are highly desired. Herein, we present a synergistic antibacterial membrane with superhydrophobic and photodynamic bactericidal properties via a facile non-solvent induced phase separation process (NIPS). Benefiting from the excellent liquid-repellence, the synergistic antibacterial hybrid membrane resists most of bacterial adhesion at the initial stage. Subsequently, few of adhered bacteria can be easily eliminated by photodynamical therapy (PDT), in which the bactericidal activity is mediated by cytotoxic reactive oxygen species (ROS) under the visible light illumination, avoiding the risk of AR. This synergistic membrane exhibits highly effective antibacterial performances, as demonstrated by the total kill against Gram-positive S. aureus, and Gram-negative E. coli and P. aeruginosa. Moreover, the membranes also display essential non-fouling performances, as testified by both whole blood adhesion as well as self-cleaning test. Due to its simplification and high-efficiency, this type of membrane may find potential applications as an antibacterial platform for bacterial infection-resistant areas.

Photothermal Antibacterial and Antibiofilm Activity of Black Phosphorus/Gold Nanocomposites against Pathogenic Bacteria

Black phosphorus (BP) as a layered two-dimensional (2D) semiconductor material with a tunable band gap has attracted growing attention for promising applications in diverse fields including biotechnology owing to its excellent physical and chemical properties. In this study, BP crystals were synthesized using a chemical vapor transport method and exfoliated into BP nanosheets in deoxygenated water or hexane. Next, monodisperse Au nanoparticles that were synthesized using a surfactant-assisted chemical reduction method were assembled on exfoliated BP nanosheets hexane to yield BP/Au nanocomposites. The photothermal antibacterial and antibiofilm activities of BP nanosheets and BP/Au nanocomposites were investigated against Enterococcus faecalis, a pathogenic biofilm-forming bacterium, by studying the photothermal effect and bacterial growth curve and using colony counting and live/dead fluorescence staining methods under near-infrared (NIR) light irradiation. Thanks to the higher photothermal conversion efficiency of BP/Au nanocomposites than that of bare BP nanosheets under NIR light irradiation, they destructed the bacterial cell membrane more efficiently than bare BP with the biofilm inhibition rate of 58%. It should be noted that this is the first study on the antibacterial and antibiofilm activity of BP/Au nanocomposites via a photothermal process under NIR light irradiation. This work shows the potential of BP/Au nanocomposites in fighting against pathogenic bacteria and paves the way for the exploration of antibacterial platforms based on the biocompatible 2D semiconductor BP.

Mesoporous Silica Supported Silver-Bismuth Nanoparticles as Photothermal Agents for Skin Infection Synergistic Antibacterial Therapy.

The emergence of multidrug resistant bacteria has resulted in plenty of stubborn nosocomial infections and severely threatens human health. Developing novel bactericide and therapeutic strategy is urgently needed. Herein, mesoporous silica supported silver-bismuth nanoparticles (Ag-Bi@SiO2 NPs) are constructed for synergistic antibacterial therapy. In vitro experiments indicate that the hyperthermia originating from Bi NPs can disrupt cell integrity and accelerate the Ag ions release, further exhibiting an excellent antibacterial performance toward methicillin-resistant Staphylococcus aureus (MRSA). Besides, under laser irradiation, Ag-Bi@SiO2 NPs at 100 µg mL-1 can effectively obliterate mature MRSA biofilm and cause a 69.5% decrease in the biomass, showing a better therapeutic effect than Bi@SiO2 NPs with laser (26.8%) or Ag-Bi@SiO2 NPs without laser treatment (30.8%) groups. More importantly, in vivo results confirm that ≈95.4% of bacteria in abscess are killed and the abscess ablation is accelerated using the Ag-Bi@SiO2 NPs antibacterial platform. Therefore, Ag-Bi@SiO2 NPs with photothermal-enhanced antibacterial activity are a potential nano-antibacterial agent for the treatment of skin infections.

TEM Studies on Antibacterial Mechanisms of Black Phosphorous Nanosheets.

PurposeRecently, two-dimensional (2D) nanomaterials are gaining tremendous attention as novel antibacterial platforms to combat against continuously evolving antimicrobial resistance levels. Among the family of 2D nanomaterials, black phosphorus (BP) nanosheets have demonstrated promising potential for biomedical applications. However, there is a need to gain nanoscale insights of the antibacterial activity of BP nanosheets which lies at the center of technical challenges.MethodsUltra-large BP nanosheets were synthesized by liquid-exfoliation method in the eco-friendly deoxygenated water. Synthesized BP nanosheets were characterized by TEM, AFM, and Raman spectroscopy techniques and their chemical stability was evaluated by EDS and EELS elemental analysis. The antibacterial activity of BP nanosheets was evaluated at nanoscale by the ultramicrotome TEM technique. Further, HAADF-STEM image and EDS elemental line map of the damaged bacterium were utilized to analyze the presence of diagnostic ions. Supportive SEM and ATR-FTIR studies were carried out to confirm the bacterial cell wall damage. In vitro colony counting method was utilized to evaluate the antibacterial performance of ultra-large BP nanosheets.ResultsElemental EELS and EDS analysis of BP nanosheets stored in deoxygenated water confirmed the absence of oxygen peak. TEM studies indicate the various events of bacterial cell damage with the lost cellular metabolism and structural integrity. Colony counting test results show that as-synthesized BP nanosheets (100 μg/mL) can kill ~95% bacteria within 12 hours.ConclusionTEM studies demonstrate the various events of E. coli membrane damage and the loss of structural integrity. These events include the BP nanosheets interaction with the bacterial cell wall, cytoplasmic leakage, detachment of cytoplasm from the cell membrane, reduced density of lipid bilayer and agglomerated DNA structure. The EDS elemental line mapping of the damaged bacterium confirms the disrupted cell membrane permeability and the lost cellular metabolism. SEM micrographs and ATR-FTIR supportive results confirm the bacterial cell wall damage.

Tailoring H2O2 generation kinetics with magnesium alloys for efficient disinfection on titanium surface

A new antibacterial strategy for Ti has been developed without the use of any external antibacterial agents and surface treatments. By combining Mg alloys with Ti, H2O2, which is an oxidizing agent that kills bacteria, was spontaneously generated near the surface of Ti. Importantly, the H2O2 formation kinetics can be precisely controlled by tailoring the degradation rates of Mg alloys connected to Ti. Through microstructural and electrochemical modification of Mg with alloying elements (Ca, Zn), the degradation rates of Mg alloys were controlled, and the H2O2 release kinetics was accelerated when the degradation rate of Mg alloys increased. With the introduction of an in vivo assessment platform comprised of Escherichia coli (E. coli) and transgenic zebrafish embryos, we are able to design optimized antibacterial systems (Ti-Mg and Ti-Mg-3wt% Zn) that can selectively eradicate E. coli while not harming the survival rate, development, and biological functions of zebrafish embryos. We envision that our antibacterial strategy based on utilization of sacrificial Mg alloys could broaden the current palette of antibacterial platforms for metals.