Interfacial Engineering of Bimetallic Ag/Pt Nanoparticles on Reduced Graphene Oxide Matrix for Enhanced Antimicrobial Activity

Nanoarchitectonics of Bimetallic Cu-/Co-Doped Nitrogen-Carbon Nanozyme-Functionalized Hydrogel with NIR-Responsive Phototherapy for Synergistic Mitigation of Drug-Resistant Bacterial Infections

Superbug infections and transmission have become major challenges in the contemporary medical field. The development of novel antibacterial strategies to efficiently treat bacterial infections and conquer the problem of antimicrobial resistance (AMR) is extremely important. In this paper, a bimetallic CuCo-doped nitrogen-carbon nanozyme-functionalized hydrogel (CuCo/NC-HG) has been successfully constructed. It exhibits photoresponsive-enhanced enzymatic effects under near-infrared (NIR) irradiation (808 nm) with strong peroxidase (POD)-like and oxidase (OXD)-like activities. Upon NIR irradiation, CuCo/NC-HG possesses photodynamic activity for producing singlet oxygen(1O2), and it also has a high photothermal conversion effect, which not only facilitates the elimination of bacteria but also improves the efficiency of reactive oxygen species (ROS) production and accelerates the consumption of GSH. CuCo/NC-HG shows a lower hemolytic rate and better cytocompatibility than CuCo/NC and possesses a positive charge and macroporous skeleton for restricting negatively charged bacteria in the range of ROS destruction, strengthening the antibacterial efficiency. Comparatively, CuCo/NC and CuCo/NC-HG have stronger bactericidal ability against methicillin-resistant Staphylococcus aureus (MRSA) and ampicillin-resistant Escherichia coli (AmprE. coli) through destroying the cell membranes with a negligible occurrence of AMR. More importantly, CuCo/NC-HG plus NIR irradiation can exhibit satisfactory bactericidal performance in the absence of H2O2, avoiding the toxicity from high-concentration H2O2. In vivo evaluation has been conducted using a mouse wound infection model and histological analyses, and the results show that CuCo/NC-HG upon NIR irradiation can efficiently suppress bacterial infections and promote wound healing, without causing inflammation and tissue adhesions.

Ag+-Adsorbing Semiconducting Polymer Nanosponge for Smart Local Treatment of Wound Infection

Nanoplatform combined with photothermal therapy (PTT) and silver nanoparticles have been widely used to combat bacterial infections. However, the development of environmentally benign antibacterial nanoplatforms with controllable and long-term antibacterial activity is still challenging. Herein, we synthesized an Ag+-adsorbing organic semiconducting polymeric nanosponge (PDPP3T NPe@Ag+) to realize Ag+ enhanced photothermal anti-infective therapy. Furthermore, the PDPP3T NPe@Ag+ sponge can also spatiotemporally release silver ions in a pH/NIR light-responsive manner for controllable and long-term antimicrobial therapy. Owing to good biocompatibility and controlled release of silver ions, PDPP3T NPe@Ag+ can effectively kill bacteria in vitro and promote wound healing in vivo. We expect that this antimicrobial platform could be utilized as a robust antibacterial agent for infective therapy.

Abrading-Induced Breakdown of Ag Nanoparticles into Atomically Dispersed Ag for Enhancing Antimicrobial Performance

Silver is among the most essential antimicrobial agents. Increasing the efficacy of silver-based antimicrobial materials will reduce operating costs. Herein, we show that mechanical abrading causes atomization of Ag nanoparticles (AgNPs) into atomically dispersed Ag (AgSAs) on the surfaces of an oxide-mineral support, which eventually boosts the antibacterial efficacy considerably. This approach is straightforward, scalable, and applicable to a wide range of oxide-mineral supports; additionally, it does not require any chemical additives and operates under ambient conditions. The obtained AgSAs-loaded γ-Al₂O₃ inactivated Escherichia coli (E. coli) five times as fast as the original AgNPs-loaded γ-Al₂O₃. It can be utilized over 10 runs with minimal efficiency loss. The structural characterizations indicate that AgSAs exhibit a nominal charge of 0 and are anchored at the doubly bridging OH on the γ-Al₂O₃ surfaces. Mechanism studies demonstrate that AgSAs, like AgNPs, damage bacterial cell wall integrity, but they release Ag⁺ and superoxide substantially faster. This work not only provides a simple method for manufacturing AgSAs-based materials but also shows that AgSAs have better antibacterial properties than the AgNPs counterpart.

Synthesis of a Ag/rGO nanocomposite using Bos taurus indicus urine for nitroarene reduction and biological activity

The present study develops a unique in situ synthesis of a catalytically and biologically active Ag/reduced graphene oxide (rGO) nanocomposite. Herein, we employed Bos taurus indicus urine to synthesize a Ag/rGO nanocomposite in an environmentally benign, facile, economical, and sustainable manner. The elemental composition analysis reveals the presence of Ag, O and C elements. The scanning electron micrograph shows the formation of spherical silver in nanoform whereas rGO is found to be flake shaped with a wrinkled nature. The synthesized nanomaterial and its composite shows a positive catalytic effect in simple organic transformation for the reduction of nitroarene compounds. Investigations were conducted into the catalytic effectiveness of the prepared nanomaterials for diverse nitroarene reduction. Then, using NaBH₄ at 25 °C, the catalytic roles of Ag and the Ag/rGO nano-catalyst were assessed towards the catalytic reduction of several environmental pollutants such as 2-, 3- and 4-nitroaniline and 4-nitrophenol into their respective amino compounds. To test their catalytic performance, bio-mimetically synthesized Ag NPs were thermally treated at 200 °C and compared with the Ag/rGO nanocomposite. Furthermore, biomedical applications such as the antibacterial and antioxidant properties of the as-prepared nanomaterials were investigated in this study.

Phytochemical-Stabilized Platinum-Decorated Silver Nanocubes INHIBIT Adenocarcinoma Cells and Enhance Antioxidant Effects by Promoting Apoptosis via Cell Cycle Arrest

(1) Background: The increasing use of silver and platinum bimetallic nanoparticles in the diagnosis and treatment of cancer presents significant advances in biomedical applications due to their extraordinary physicochemical properties. This study investigated the role of aqueous phytochemical extract in stabilizing platinum nanodots-decorated silver nanocubes (w-Pt@AgNPs) for enhancing antioxidant activities and their mechanism. (2) Methods: UV-Vis, Fourier transform infrared (FTIR) spectroscopy, and transmission electron microscopy (TEM) were used to characterize the formed w-Pt@AgNPs. LC-QToF-MS/MS was used to analyze the bioactive compounds, while DPPH, ABTS, and FRAP were used to detect the scavenging potential. Flow cytometric assays were performed to investigate the cytotoxicity and the mechanism of cell death. (3) Results: Morphological studies indicated that w-Pt@AgNPs were cube in shape, decorated by platinum nanodots on the surfaces. Compared to ethanolic extract-synthesized e-Pt@AgNPs, w-Pt@AgNPs exhibited the strongest antioxidant and cytotoxic activity, as data from Annexin V and Dead cell labeling indicated higher induction of apoptosis. Despite the high proportion of early apoptotic cells, the w-Pt@AgNPs triggered a decrease in G1/G0 cell cycle phase distribution, thereby initiating a G2/M arrest. (4) Conclusions: By enhancing the antioxidant properties and promoting apoptosis, w-Pt@AgNPs exhibited remarkable potential for improved cancer therapy outcomes.

Recent Progress on Bioinspired Antibacterial Surfaces for Biomedical Application

Surface bacterial fouling has become an urgent global challenge that calls for resilient solutions. Despite the effectiveness in combating bacterial invasion, antibiotics are susceptible to causing microbial antibiotic resistance that threatens human health and compromises the medication efficacy. In nature, many organisms have evolved a myriad of surfaces with specific physicochemical properties to combat bacteria in diverse environments, providing important inspirations for implementing bioinspired approaches. This review highlights representative natural antibacterial surfaces and discusses their corresponding mechanisms, including repelling adherent bacteria through tailoring surface wettability and mechanically killing bacteria via engineering surface textures. Following this, we present the recent progress in bioinspired active and passive antibacterial strategies. Finally, the biomedical applications and the prospects of these antibacterial surfaces are discussed.

A review of recent and emerging antimicrobial nanomaterials in wastewater treatment applications

In this paper, we present a critical review on antimicrobial nanomaterials with demonstrated potential for application as a disinfection technology in wastewater treatment. Studies involving fabrication and testing of antimicrobial nanomaterials for wastewater treatment were gathered, critically reviewed, and analyzed. Our review shows that there are only a few eligible candidate nanoparticles (NPs) (metal and metal oxide) that can adequately serve as an antimicrobial agent. Nanosilver (nAg) was the most studied and moderately understood metal NPs with proven antimicrobial activity followed by ZnO (among antimicrobial metal oxide NPs) which outperformed titania (in the absence of light) in efficacy due to its better solubility in aqueous condition. The direction of future work was found to be in the development of antimicrobial nanocomposites, since they provide more stability for antimicrobial metal and metal oxides NPs in water, thereby increasing their activity. This review will serve as an updated survey, yet touching also the fundamentals of the antimicrobial activity, with vital information for researchers planning to embark on the development of superior antimicrobial nanomaterials for wastewater treatment applications.

Therapeutic nanodendrites: current applications and prospects

Multidisciplinary efforts in the field of nanomedicine for cancer therapy to provide solutions to common limitations of traditional drug administration such as poor bioaccumulation, hydrophobicity, and nonspecific biodistribution and targeting have registered very promising progress thus far. Currently, a new class of metal nanostructures possessing a unique dendritic-shaped morphology has been designed for improved therapeutic efficiency. Branched metal nanoparticles or metal nanodendrites are credited to present promising characteristics for biomedical applications owing to their unique physicochemical, optical, and electronic properties. Nanodendrites can enhance the loading efficiency of bioactive molecules due to their three-dimensional (3D) high surface area and can selectively deliver their cargo to tumor cells using their stimuli-responsive properties. With the ability to accumulate sufficiently within cells, nanodendrites can overcome the detection and clearance by glycoproteins. Moreover, active targeting ligands such as antibodies and proteins can as well be attached to these therapeutic nanodendrites to enhance specific tumor targeting, thereby presenting a multifunctional nanoplatform with tunable strategies. This mini-review focuses on recent developments in the understanding of metallic nanodendrite synthesis, formation mechanism, and their therapeutic capabilities for next-generation cancer therapy. Finally, the challenges and future opportunities of these fascinating materials to facilitate extensive research endeavors towards the design and application were discussed.

Antimicrobial efficacy of platinum-doped silver nanoparticles

Silver nanoparticles (AgNPs) have been proposed to combat oral infection due to their efficient ionic silver (Ag+ ) release. However, concentrations required for antimicrobial efficacy may not be therapeutically viable. In this work, platinum-doped silver nanoparticles (Pt-AgNPs) were explored to evaluate their potential for enhanced Ag+ release, which could lead to enhanced antimicrobial efficacy against S. aureus, P. aeruginosa, and E. coli. AgNPs doped with 0.5, 1, and 2 mol% platinum (Pt0.5 -AgNPs, Pt1 -AgNPs, and Pt2 -AgNPs) were synthesized by a chemical reduction method. Transmission electron microscopy revealed mixed morphologies of spherical, oval, and ribbon-like nanostructures. Surface-enhanced Raman scattering revealed that the surface of Pt-AgNPs was covered with up to 93% Pt. The amount of Ag+ released increased 16.3-fold for Pt2 -AgNPs, compared to AgNPs. The initial lag phase in bacterial growth curve was prolonged for Pt-AgNPs. This is consistent with a Ag+ release profile that exhibited an initial burst followed by sustained release. Doping AgNPs with platinum significantly increased the antimicrobial efficacy against all species. Pt2 -AgNPs exhibited the lowest minimum inhibitory concentrations, followed by Pt1 -AgNPs, Pt0.5 -AgNPs, and AgNPs, respectively. Doping AgNPs with a small amount of platinum promoted the release of Ag+ , based on the sacrificial anodic effect, and subsequently enhanced their antimicrobial efficacy.

Layered double hydroxide nanostructures and nanocomposites for biomedical applications

Layered double hydroxide (LDH) nanostructures and related nanocomposites have attracted significant interest in biomedical applications including cancer therapy, bioimaging and antibacterial treatment. These materials hold great advantages including low cost and facile preparation, convenient drug loading, high drug incorporation capacity, good biocompatibility, efficient intracellular uptake and endosome/lysosome escape, and natural biodegradability in an acidic environment. In this review, we summarize the development of three types of LDH nanostructures including pristine LDH, surface modified LDH, and LDH nanocomposites for a range of biomedical applications. The advantages and disadvantages of LDH nanostructures and insights into the future development are also discussed.

Bimetallic Nanoparticles for Antimicrobial Applications

Highly effective antimicrobial agents are needed to control the emergence of new bacterial strains, their increased proliferation capability, and antibacterial resistance that severely impact public health, and several industries including water, food, textiles, and oil and gas. Recently, bimetallic nanoparticles, formed via integration of two different metals, have appeared particularly promising with antibacterial efficiencies surpassing that of monometallic counterparts due to synergistic effects, broad range of physiochemical properties, and diverse mechanisms of action. This work aims to provide a review on developed bimetallic and supported bimetallic systems emphasizing in particular on the relation between synthesis routes, properties, and resulting efficiency. Bimetallic nanostructures on graphene, zeolites, clays, fibers, polymers, as well as non-supported bimetallic nanoparticles are reviewed, their synthesis methods and resulting properties are illustrated, along with their antimicrobial activity and potential against different strains of microbes.

Green synthesis of allicin based hybrid nanoflowers with evaluation of their catalytic and antimicrobial activities

OBJECTIVE

Although organic-inorganic hybrid nanoflowers (hNFs) with much enhanced catalytic activity and stability were fabricated using proteins and enzymes, in this study, for the first time, we report synthesis of allicin and copper ion (Cu²⁺) coordinated NFs and investigate their peroxidase-like and antimicrobial activities.

RESULTS

The allicin (active ingredient of Allium sativum) and Cu²⁺ was acted as an organic and inorganic part, respectively for synthesis of the Cu-hNFs. The hNFs were characterized by various techniques. Spherical, uniform, mono-dispersed and flower-like-shaped morphology of the hNFs (synthesized at pH 5) were imaged by scanning electron microscopy. The presence of Cu metal in the hNFs was detected by energy dispersive X-ray spectroscopy. Characteristic bonds stretching and bending for structural analysis of the hNFs were carried out by Fourier transform infrared spectrometry. In terms of applications, the hNFs showed quite effective peroxidase-like activity towards to guaiacol (used as a model substrate) in the presence of hydrogen peroxide (H₂O₂) through Fenton reaction. We demonstrated that the NFs exhibited ~ 200% and ~ 500% higher catalytic activities in 1 h (hr) and 3 h (hrs) than their initial catalytic activity measured in 5 minute (min). Additionally, effective antibacterial properties of the Cu-hNFs were observed against fish pathogen bacteria (Aeromonas hydrophila, Vibrio parahaemolyticus, and Lactococcus garvieae).

CONCLUSIONS

We finally demonsrated that allicin based hybrid nanomaterial can be prepared by a relatively cheap, one step, easy and eco-friendly method. The allicin hNFs can be considered as novel Fenton agent for peroxidase like activity and bactericidal.

Enhanced dissolution of silver nanoparticles in a physical mixture with platinum nanoparticles based on the sacrificial anode effect

A strategy to reduce implant-related infections is the inhibition of the initial bacterial implant colonization by biomaterials containing silver (Ag). The antimicrobial efficacy of such biomaterials can be increased by surface enhancement (nanosilver) or by creating a sacrificial anode system for Ag. Such a system will lead to an electrochemically driven enhanced Ag ion release due to the presence of a more noble metal. Here we combined the enlarged surface of nanoparticles (NP) with a possible sacrificial anode effect for Ag induced by the presence of the electrochemically more noble platinum (Pt) in physical mixtures of Ag NP and Pt NP dispersions. These Ag NP/Pt NP mixtures were compared to the same amounts of pure Ag NP in terms of cell biological responses, i.e. the antimicrobial activity against Staphylococcus aureus and Escherichia coli as well as the viability of human mesenchymal stem cells (hMSC). In addition, Ag NP was analyzed by ultraviolet-visible (UV-vis) spectroscopy, cyclic voltammetry, and atomic absorption spectroscopy. It was found that the dissolution rate of Ag NP was enhanced in the presence of Pt NP within the physical mixture compared to a dispersion of pure Ag NP. Dissolution experiments revealed a fourfold increased Ag ion release from physical mixtures due to enhanced electrochemical activity, which resulted in a significantly increased toxicity towards both bacteria and hMSC. Thus, our results provide evidence for an underlying sacrificial anode mechanism induced by the presence of Pt NP within physical mixtures with Ag NP. Such physical mixtures have a high potential for various applications, for example as antimicrobial implant coatings in the biomedicine or as bactericidal systems for water and surface purification in the technical area.

Bimetallic nanoparticles against multi-drug resistant bacteria

Bimetallic nanoparticles can fight multi-drug resistant (MDR) bacteria and treat wound infections caused by MDR bacteria.

Optimization of Antibacterial Efficacy of Noble-Metal-Based Core-Shell Nanostructures and Effect of Natural Organic Matter

Noble-metal-based nanomaterials made of less toxic metals have been utilized as potential antibacterial agents due to their distinctive oxidase-like activity. In this study, we fabricated core-shell structured Pd@Ir bimetallic nanomaterials with an ultrathin shell. Pd@Ir nanostructures show morphology-dependent bactericidal activity, in which Pd@Ir octahedra possessing higher oxidase-like activity exert bactericidal activity stronger than that of Pd@Ir cubes. Furthermore, our results reveal that the presence of natural organic matter influences the antibacterial behaviors of nanomaterials. Upon interaction with humic acid (HA), the Pd@Ir nanostructures induce an elevated level of reactive oxygen species, resulting in significantly enhanced bactericidal activity of the nanostructures. Mechanism analysis shows that the presence of HA efficiently enhances the oxidase-like activity of nanomaterials and promotes the cellular internalization of nanomaterials. We believe that the present study will not only demonstrate an effective strategy for improving the bactericidal activity of noble-metal-based nanomaterials but also provide an understanding of the antibacterial behavior of nanomaterials in the natural environment.

Comparing the microbial inhibition of nanofibres with multi-metal ion exchanged nano-zeolite Y in air sampling

AIMS

Fibre membranes containing metals have attracted great attention because of their high antibacterial efficiency. However, comparison of antibacterial activity of fibres with multi-metals in air samples has remained understudied.

METHODS AND RESULTS

Different ion exchanged nano-zeolite Y (IE-NZY) of Ag, Zn and Cu was studied. Polyvinylpyrrolidine/polyvinylidene fluoride nanofibres containing various IE-NZY were synthesized according to electrospinning technique. The presence of metal ions was confirmed using XRF. The morphological properties of nanofibres were characterized by SEM. Zone of inhibition was seen between 10·1 and 12 mm against Staphylococcus aureus and 11·5-14·57 for Escherichia coli. IE-NZY containing Ag, Zn and Cu had the highest antibacterial efficiency. In the air samples, there were any colonies on the media under the Ag/Cu-NZY and Zn/Cu/Ag-NZY nanofibres.

CONCLUSIONS

The bacterial inhibition for nanofibres containing a three metal nano-zeolite Y (TM-NZY) is higher than bimetals (BM-NZY) types while for monometals nano-zeolite Y (MM-NZY), it was lower compared to the others.

SIGNIFICANCE AND IMPACT OF THE STUDY

The results indicate significant antibacterial activity of ion-exchanged NZY in air sampling.

A review of the antimicrobial potential of precious metal derived nanoparticle constructs

The field of nanotechnology is rapidly growing. The promise of pharmacotherapeutics emerging from this vast field has drawn the attention of many researchers. However, with the increase in the prevalence of antibiotic resistant microorganisms, the manifestations of these promises are needed now more than ever. Many have postulated the antimicrobial potential of nanoparticle constructs derived from precious metals/noble metals nanoparticles (NMNPs), such as silver nanoparticles that show activity against multidrug resistant bacteria. In this review we will evaluate the current studies and explore the data to obtain a clear picture of the potential of these particles and the validity of the claims of drug resistant treatments with NMNPs.

Antimicrobial Synergistic Effect Between Ag and Zn in Ag-ZnO·mSiO2 Silicate Composite with High Specific Surface Area

Antimicrobial materials are widely used for inhibition of microorganisms in the environment. It has been established that bacterial growth can be restrained by silver nanoparticles. Combining these with other antimicrobial agents, such as ZnO, may increase the antimicrobial activity and the use of carrier substrate makes the material easier to handle. In the paper, we present an antimicrobial nanocomposite based on silver nanoparticles nucleated in general silicate nanostructure ZnO·mSiO₂. First, we prepared the silicate fine net nanostructure ZnO·mSiO₂ with zinc content up to 30 wt% by precipitation of sodium water glass in zinc acetate solution. Silver nanoparticles were then formed within the material by photoreduction of AgNO₃ on photoactive ZnO. This resulted into an Ag-ZnO·mSiO₂ composite with silica gel-like morphology and the specific surface area of 250 m²/g. The composite, alongside with pure AgNO₃ and clear ZnO·mSiO₂, were successfully tested for antimicrobial activity on both gram-positive and gram-negative bacterial strains and yeast Candida albicans. With respect to the silver content, the minimal inhibition concentration of Ag-ZnO·mSiO₂ was worse than AgNO₃ only for gram-negative strains. Moreover, we found a positive synergistic antimicrobial effect between Ag and Zn agents. These properties create an efficient and easily applicable antimicrobial material in the form of powder.

Bimetallic silver-platinum nanoparticles with combined osteo-promotive and antimicrobial activity

Bimetallic alloyed silver-platinum nanoparticles (AgPt NP) with different metal composition from Ag₁₀Pt₉₀ to Ag₉₀Pt₁₀ in steps of 20 mol% were synthesized. The biological effects of AgPt NP, including cellular uptake, cell viability, osteogenic differentiation and osteoclastogenesis as well as the antimicrobial activity towards Staphylococcus aureus and Escherichia coli were analyzed in comparison to pure Ag NP and pure Pt NP. The uptake of NP into human mesenchymal stem cells was confirmed by cross-sectional focused-ion beam preparation and observation by scanning and transmission electron microscopy in combination with energy-dispersive x-ray analysis. Lower cytotoxicity and antimicrobial activity were observed for AgPt NP compared to pure Ag NP. Thus, an enhanced Ag ion release due to a possible sacrificial anode effect was not achieved. Nevertheless, a Ag content of at least 50 mol% was sufficient to induce bactericidal effects against both Staphylococcus aureus and Escherichia coli. In addition, a Pt-related (≥50 mol% Pt) osteo-promotive activity on human mesenchymal stem cells was observed by enhanced cell calcification and alkaline phosphatase activity. In contrast, the osteoclastogenesis of rat primary precursor osteoclasts was inhibited. In summary, these results demonstrate a combinatory osteo-promotive and antimicrobial activity of bimetallic Ag₅₀Pt₅₀ NP.

Upshift of the d Band Center toward the Fermi Level for Promoting Silver Ion Release, Bacteria Inactivation, and Wound Healing of Alloy Silver Nanoparticles

Silver (Ag)-based nanoparticles (NPs) with a high potential of Ag⁺ release have been known to be capable of promoting bacteria inactivation and the wound healing process; however, keeping a steady flux of high levels of Ag⁺ in Ag-based NPs is still challenging. Herein, a novel strategy in terms of altering the intrinsic electronic structure of Ag NPs was attempted to facilitate Ag oxidation and boost the Ag⁺ flux, as results of improved antibacterial and wound healing performance of Ag NPs. Gold (Au), platinum (Pt), and palladium (Pd) were doped into Ag NPs to tune their d band centers to upshift toward the Fermi level, and the formed Pd-Ag alloy NPs showed the largest shift, followed by Pt-Ag and Au-Ag NPs, as determined by density function theory calculation and ultraviolet photoemission spectroscopy measurement. Further X-ray photoelectron spectroscopy analysis indicates that a larger upshift could induce less electron filling in the antibonding orbital and a higher Ag oxidation level, leading to the more remarkable Ag⁺ release as determined by inductively coupled plasma optical emission spectrometry. All these alloy Ag NPs could more efficiently inhibit bacterial growth and accelerate the wound healing process than pure Ag NPs, and their antibacterial activity and wound healing performance were progressively proportional to the upshift values of the d band center. Taken together, tuning the d band center to upshift toward the Fermi level becomes a feasible strategy for designing therapeutic Ag-based NPs with a promising antibacterial and wound healing performance.

Inhibitory effect of reduced graphene oxide-silver nanocomposite on progression of artificial enamel caries

The use of antimicrobial agents is an efficient method to prevent dental caries. Also, nanometric antibacterial agents with wide antibacterial spectrum and strong antibacterial effects can be applied for prevention of dental caries.

Novel Candy-like Cu4O3 Microstructure: Facile Wet Chemical Synthesis, Formation Mechanism, and Good Long-Term Antibacterial Activities

The novel candy-like Cu₄O₃ microstructure has been synthesized successfully for the first time by a facile wet chemical method, and the formation mechanism was studied based on series of control experiments. The antibacterial activities of the candy-like Cu₄O₃ were evaluated by means of Gram-negative Escherichia coli ( E. coli) and Gram-positive Staphylococcus saureus ( S. aureus). The antibacterial mechanism was investigated by tracing the morphology evolution of the bacteria. The results show that the candy-like Cu₄O₃ microstructure was formed underwent the route of Cu(NH₃)₄²⁺ → Cu(OH)₄^2- → Cu(OH)₂ → CuO → Cu₄O₃ nuclei → Cu₄O₃ crystal growth → candy-like Cu₄O₃, and optimal reaction conditions are required to obtain the candy-like Cu₄O₃. The candy-like Cu₄O₃ microstructure exhibits good long-term antibacterial activities to both E. coli and S. aureus bacteria. Critical concentration of Cu²⁺ ions released from the candy-like Cu₄O₃ was found responsible for the sudden increase beyond 90% in antibacterial activity.

CuO Nanoparticles-Containing Highly Transparent and Superhydrophobic Coatings with Extremely Low Bacterial Adhesion and Excellent Bactericidal Property

Human health and industrial instruments have been suffering from bacterial colonization on the surface of materials for a long time. Recently, antibacterial coatings are regarded as the new strategy to resist bacterial pathogens. In this work, novel highly transparent and superhydrophobic coatings with extremely low bacterial adhesion and bactericidal performance were prepared by spray-coating hydrophobic silica sol and CuO nanoparticles. The coated glass showed high transmittance in 300-2500 nm with a maximum value of 96.6%. Compared with bare glass, its superhydrophobic characteristics resulted in a reduction in adhesion of bacteria ( Escherichia coli, E. coli) by up to 3.2 log cells/cm². Additionally, the live/dead staining test indicated that the as-prepared coating exhibited excellent bactericidal performance against E. coli. Moreover, the as-prepared coating could maintain their superhydrophobicity after the sand impact test. The proposed method to fabricate such coatings could be applied on various substrates. Therefore, this novel hybrid surface with the abilities to reduce bacterial adhesion and kill attached bacteria make it a promising candidate for biosensors, microfluidics, bio-optical devices, household facilities, lab-on-chips, and touchscreen devices.

Green synthesis of catalytic gold/bismuth oxyiodide nanocomposites with oxygen vacancies for treatment of bacterial infections

We have developed a simple and green solution for the synthesis of catalytic gold-doped bismuth oxyiodide (Au/BiOI) nanocomposites at room temperature from an aqueous mixture of gold ions, bismuth ions, and iodide ions. Au nanoparticles (NPs) were formed in situ and doped into BiOI nanosheets. The oxygen vacancies generated in BiOI give rise to its oxidase-like activity, and Au doping facilitated the reaction leading to a 4-fold higher oxidase-like activity of the Au/BiOI nanocomposite. The Au/BiOI nanocomposites showed wide spectrum antimicrobial activity not only against non-multidrug-resistant E. coli, K. pneumoniae, S. enteritidis, S. aureus, and B. subtilis bacteria, but also against multidrug-resistant bacteria, methicillin-resistant S. aureus (MRSA). The gold doping reduced the minimal inhibitory concentration value by ∼2000-fold for the Au/BiOI nanocomposite, in comparison with only BiOI nanoparticles. The bactericidal property of the Au/BiOI nanocomposite arose from the combined effect of the disruption of the bacterial membrane through a strong interaction of the nanocomposite with the bacteria and the generation of reactive oxygen species. Also, the Au/BiOI nanocomposite is highly biocompatible, which has been demonstrated in vitro by analysis of cytotoxicity and hemolysis, and in vivo by evaluating ocular tissue responses. Furthermore, intrastromal administration of Au/BiOI nanocomposites can effectively alleviate S. aureus-induced bacterial keratitis in rabbits, suggesting a significant disinfectant benefit in preclinical studies. The Au/BiOI nanocomposites show great potential for the inactivation of bacterial pathogens in an aqueous environment and treatment of bacterial infection-induced diseases.

Surface Modified with a Host Defense Peptide-Mimicking β-Peptide Polymer Kills Bacteria on Contact with High Efficacy

Methicillin-resistant Staphylococcus aureus (MRSA) has been one of the major nosocomial pathogens to cause frequent and serious infections that are associated with various biomedical surfaces. This study demonstrated that surface modified with host defense peptide-mimicking β-peptide polymer, has surprisingly high bactericidal activities against Escherichia coli ( E. coli) and MRSA. As surface-tethered β-peptide polymers cannot move freely to adopt the collaborative interactions with bacterial membrane and are too short to penetrate the cell envelop, we proposed a mode of action by diffusing away the cell membrane-stabilizing divalent ions, Ca²⁺ and Mg²⁺. This hypothesis was supported by our study that Ca²⁺ and Mg²⁺ supplementation in the assay medium causes up to 80% loss of bacterial killing efficacy and that the addition of divalent ion chelating ethylenediaminetetraacetic acid into the above assay medium leads to significant recovery of the bacterial killing efficacy. In addition to its potent bacterial killing efficacy, the surface-tethered β-peptide polymer also demonstrated excellent biocompatibility by displaying no hemolysis and supporting mammalian cell adhesion and growth. In conclusion, this study demonstrated the potential of β-peptide polymer-modified surface in addressing nosocomial infections that are associated with various surfaces in biomedical applications.

Novel Antimicrobial Titanium Dioxide Nanotubes Obtained through a Combination of Atomic Layer Deposition and Electrospinning Technologies

The search for new antimicrobial substances has increased in recent years. Antimicrobial nanostructures are one of the most promising alternatives. In this work, titanium dioxide nanotubes were obtained by an atomic layer deposition (ALD) process over electrospun polyvinyl alcohol nanofibers (PVN) at different temperatures with the purpose of obtaining antimicrobial nanostructures with a high specific area. Electrospinning and ALD parameters were studied in order to obtain PVN with smallest diameter and highest deposition rate, respectively. Chamber temperature was a key factor during ALD process and an appropriate titanium dioxide deposition performance was achieved at 200 °C. Subsequently, thermal and morphological analysis by SEM and TEM microscopies revealed hollow nanotubes were obtained after calcination process at 600 °C. This temperature allowed complete polymer removal and influenced the resulting anatase crystallographic structure of titanium dioxide that positively affected their antimicrobial activities. X-ray analysis confirmed the change of titanium dioxide crystallographic structure from amorphous phase of deposited PVN to anatase crystalline structure of nanotubes. These new nanostructures with very large surface areas resulted in interesting antimicrobial properties against Gram-positive and Gram-negative bacteria. Titanium dioxide nanotubes presented the highest activity against Escherichia coli with 5 log cycles reduction at 200 μg/mL concentration.

Synthesis and biological characterization of alloyed silver–platinum nanoparticles: from compact core–shell nanoparticles to hollow nanoalloys

Bimetallic nanoparticles consisting of silver and platinum were prepared by a modified seeded-growth process in water in the full composition range in steps of 10 mol%. The particles had diameters between 15–25 nm as determined by disc centrifugal sedimentation (DCS) and transmission electron microscopy (TEM). Whereas particles with high platinum content were mostly spherical with a solid silver core/platinum shell structure, mostly hollow alloyed nanoparticles were observed with increasing silver content. The internal structure and the elemental distribution within the particles were elucidated by high-resolution transmission electron microscopy (HRTEM) in combination with energy-dispersive X-ray spectroscopy (EDX). The particles were cytotoxic for human mesenchymal stem cells (hMSC) above 50 mol% silver. This was explained by dissolution experiments where silver was only released at and above 50 mol% silver. In contrast, platinum-rich particles (less than 50 mol% silver) did not release any silver ions. This indicates that the presence of platinum inhibits the oxidative dissolution of silver.

Bimetallic nanoparticles consisting of silver and platinum were prepared by a modified seeded-growth process in water in the full composition range in steps of 10 mol%.

Synthesis and functionalization of ordered mesoporous carbons supported Pt nanoparticles for hydroconversion of n-heptane

Reaction pathway of n-heptane hydroconversion.

Enhanced Antimicrobial Efficacy of Bimetallic Porous CuO Microspheres Decorated with Ag Nanoparticles

The antimicrobial action of porous CuO microspheres (μCuO), Ag nanoparticles (nAg), and bimetallic porous CuO microspheres decorated with Ag nanoparticles (μCuO/nAg) was evaluated against surrogate microorganisms representative of pathogens commonly implicated in foodborne and healthcare-associated human infections. This work addressed the Gram-negative bacteria E. coli (Escherichia coli O157:H7-GFP B6-914), Salmonella (Salmonella enterica serovar enteritidis phage-type PT21), and the Gram-positive bacteria Listeria (Listeria innocua), as well as environmental microorganisms derived from local river water. Compared to particles composed only of CuO or Ag, the bimetallic porous μCuO/nAg particle exhibits enhanced antimicrobial efficacy. The antimicrobial action of bimetallic porous μCuO/nAg particles is dose-dependent, with 50 μg/mL particle concentration completely inhibiting the growth of both the Gram-negative (Salmonella) and the Gram-positive (Listeria) bacteria after 6 h. To assess the mechanism of antimicrobial action, the changes in surface morphologies of bacteria treated with the particles were observed using scanning electron microscopy. In the case of the Gram-negative bacteria, the bacterial cell membrane is damaged, likely due to the release of metal ions from the particles; however, particle-induced cell membrane damage is not observed for Gram-positive bacteria. Collectively, results from this work shed further light on possible mechanisms of antimicrobial action of micro-/nanoparticles and highlight the potential for bimetallic particle-based inhibition of microbial infections.

Aortic Graft Infection: Graphene Shows the Way to an Infection-Resistant Vascular Graft

Aortic graft infection is a potentially lethal complication of open and endovascular repair of aortic aneurysms. Graphene is the only existing two-dimensional material, and its unique structure gives graphene and its derivatives a plethora of original characteristics. Among other characteristics, graphene demonstrates bacteriostatic and bactericidal effects that could potentially resolve the problem of graft infection in the future. Data already exist in literature supporting this antibacterial effect of graphene oxide and reduced graphene oxide. Combining these materials with other substances enhances the antibacterial effect. Additionally, it looks feasible to expect antibiotic-delivering graphene-based graft materials in the future. Based on already published data, we could conclude that regarding graphene and its derivatives, the blessing of bactericidal effect comes with the curse of human cells toxicity. Therefore, it is important to find a fine balance between the desired antibacterial and the adverse cytotoxic effect before graphene is used in graft materials for humans.

Antibacterial mechanisms of graphene-based composite nanomaterials

Pathogenic bacteria are gaining resistance to conventional antibiotics at an alarming rate due to overuse and rapid transfer of resistance genes between bacterial populations. As bacterial resistance to antibiotics causes millions of fatalities worldwide, it is of urgent importance to develop a new class of antibiotic materials with both broad-spectrum bactericidal activity and suitable biocompatibility. Graphene derivatives are rapidly emerging as an extremely promising class of antimicrobial materials due to their diverse bactericidal mechanisms and relatively low cytotoxicity towards mammalian cells. By combining graphene derivatives with currently utilized antibacterial metal and metal-oxide nanostructures, composite materials with exceptional bactericidal activity can be achieved. In this review, the antibacterial activities of graphene derivatives as well as their metal and metal-oxide composite nanostructures will be presented. The synthetic methodology for these various materials will be briefly mentioned, and emphasis will be placed on the evaluation of their mechanisms of action. This information will provide a valuable insight into the current understanding of the interactions governing the microbial toxicity of graphene-based composite nanostructures.

Functional Graphene Nanomaterials Based Architectures: Biointeractions, Fabrications, and Emerging Biological Applications

Functional graphene nanomaterials (FGNs) are fast emerging materials with extremely unique physical and chemical properties and physiological ability to interfere and/or interact with bioorganisms; as a result, FGNs present manifold possibilities for diverse biological applications. Beyond their use in drug/gene delivery, phototherapy, and bioimaging, recent studies have revealed that FGNs can significantly promote interfacial biointeractions, in particular, with proteins, mammalian cells/stem cells, and microbials. FGNs can adsorb and concentrate nutrition factors including proteins from physiological media. This accelerates the formation of extracellular matrix, which eventually promotes cell colonization by providing a more beneficial microenvironment for cell adhesion and growth. Furthermore, FGNs can also interact with cocultured cells by physical or chemical stimulation, which significantly mediate their cellular signaling and biological performance. In this review, we elucidate FGNs-bioorganism interactions and summarize recent advancements on designing FGN-based two-dimensional and three-dimensional architectures as multifunctional biological platforms. We have also discussed the representative biological applications regarding these FGN-based bioactive architectures. Furthermore, the future perspectives and emerging challenges will also be highlighted. Due to the lack of comprehensive reviews in this emerging field, this review may catch great interest and inspire many new opportunities across a broad range of disciplines.

Highly sensitive pressure switch sensors and enhanced near ultraviolet photodetectors based on 3D hybrid film of graphene sheets decorated with silver nanoparticles

Highly sensitive pressure switch sensors and enhanced near ultraviolet photodetectors based on 3D Ag/GNs hybrid film were proposed and fabricated, and this work presented a simple route to obtain high performance devices.

In situ reduction of silver nanoparticles on hybrid polydopamine–copper phosphate nanoflowers with enhanced antimicrobial activity

Polydopamine hybrid copper phosphate nanoflowers are synthesized using a biomineralization process. The polydopamine on the nanoflowers can reduce Ag⁺in situ.

Size-controlled growth and antibacterial mechanism for Cu:C nanocomposite thin films

Plasma energy induced size reduction of Cu nanoparticles (at fixed volume fraction) in C matrix demonstrated effective antibacterial activity.

Silver Nanocoating Technology in the Prevention of Prosthetic Joint Infection

Prosthetic joint infection (PJI) is a feared complication of total joint arthroplasty associated with increased morbidity and mortality. There is a growing body of evidence that bacterial colonization and biofilm formation are critical pathogenic events in PJI. Thus, the choice of biomaterials for implanted prostheses and their surface modifications may significantly influence the development of PJI. Currently, silver nanoparticle (AgNP) technology is receiving much interest in the field of orthopaedics for its antimicrobial properties and a strong anti-biofilm potential. The great advantage of AgNP surface modification is a minimal release of active substances into the surrounding tissue and a long period of effectiveness. As a result, a controlled release of AgNPs could ensure antibacterial protection throughout the life of the implant. Moreover, the antibacterial effect of AgNPs may be strengthened in combination with conventional antibiotics and other antimicrobial agents. Here, our main attention is devoted to general guidelines for the design of antibacterial biomaterials protected by AgNPs, its benefits, side effects and future perspectives in PJI prevention.