Synthesis and characterization of Cu/Ag nanoparticle loaded mullite nanocomposite system: A potential candidate for antimicrobial and therapeutic applications

Antibacterial and Antifungal Properties of Polyester, Polylactide, and Cotton Nonwovens and Fabrics, by Means of Stable Aqueous Dispersions Containing Copper Silicate and Some Metal Oxides

Literature reviews have described the applications of silver, copper, and zinc ions and metallic particles of Cu, Ti, and Zn oxides, which have been found to be useful antimicrobial reagents for the biofunctionalization of various materials and their surfaces. For this purpose, compositions of water dispersions containing emulsions of synthetic copolymers based on acrylic and vinyl monomers, polysaccharides (hydroxyethyl cellulose and starch), and various additives with wetting and stabilizing properties were used. Many stable water dispersions of different chemical compositions containing bioactive chemical compounds (copper silicate hydrate, titanium dioxide, and zinc oxide (and other auxiliary substances)) were developed. They were used for the preparation of thin hybrid coatings having good antimicrobial properties against Gram-negative bacteria (Escherichia coli), Gram-positive bacteria (Staphylococcus aureus), and yeast fungus (Candida albicans). Polyester (PES) and polylactide (PLA) nonwovens were modified using the dip-coating method, while PES and cotton fabrics were biofunctionalized by means of dip-coating and coating methods. The antimicrobial (antibacterial and antifungal) properties of the textile materials (nonwovens and fabrics) biofunctionalized with the above-mentioned bioactive agents exhibiting antimicrobial properties (CuSiO3, TiO2, ZnO, or ZnO∙SiO2) were strongly dependent on the agents' content in the water dispersions. The PES and PLA nonwovens, modified on the surface with water compositions containing copper silicate hydrate, showed good antibacterial properties against the Gram-negative bacteria Escherichia coli, even at a content of 1 wt.% CuSiO3∙xH2O, and against the Gram-positive bacteria Staphylococcus aureus, at the content of at least 5 wt.% CuSiO3∙xH2O. The bacterial growth reduction factor (R) was greater than 99% for most of the samples tested. Good antifungal properties against the fungus Candida albicans were found for the PES and PLA nonwoven fabrics modified with dispersions containing 5-7 wt.% CuSiO3∙xH2O and 4.2-5.0 wt.% TiO2. The addition of TiO2 led to a significant improvement in the antifungal properties of the PES and PLA nonwovens modified in this way. For the samples of PES WIFP-270 and FS F-5 nonwovens, modified with water dispersions containing 5.0 wt.% CuSiO3∙xH2O and 4.2-5.0 wt.% TiO2, the growth reduction factor for the fungus Candida albicans (R) reached values in the range of 80.9-98.0%. These new biofunctionalized polymeric nonwoven textile materials can find practical applications in the manufacture of filters for hospital air-conditioning systems and for the automotive industry, as well as in air purification devices. Moreover, similar antimicrobial modification of fabrics with the dip-coating or coating methods can be applied, for example, in the fabrication of fungi- and mold-resistant garden furniture.

Zinc-modified phosphate-based glass micro-filler improves Candida albicans resistance of auto-polymerized acrylic resin without altering mechanical performance

Colonization of auto-polymerized acrylic resin by pathogenic Candida albicans is a common problem for denture users. In this study, zinc-modified phosphate-based glass was introduced into an auto-polymerized acrylic resin at concentrations of 3, 5, and 7 wt.%. The mechanical or physical properties (flexural strength, elastic modulus, microhardness, and contact angle), surface morphology of the resultant materials, and the antimicrobial effect on C. albicans were investigated. There were no statistical differences in the mechanical properties between the control and the zinc-modified phosphate-based glass samples (p > 0.05); however, the number of C. albicans colony-forming units was significantly lower in the control group (p < 0.05). Scanning electron microscopy revealed that C. albicans tended not to adhere to the zinc-modified-phosphate-based glass samples. Thus, the zinc-modified materials retained the advantageous mechanical properties of unaltered acrylic resins, while simultaneously exhibiting a strong antimicrobial effect in vitro.

Colorful Conductive Threads for Wearable Electronics: Transparent Cu-Ag Nanonets

Electronic textiles have been regarded as the basic building blocks for constructing a new generation of wearable electronics. However, the electronization of textiles often changes their original properties such as color, softness, glossiness, or flexibility. Here a rapid room-temperature fabrication method toward conductive colorful threads and fabrics with Ag-coated Cu (Cu-Ag) nanonets is demonstrated. Cu-Ag core-shell nanowires are produced through a one-pot synthesis followed by electroless deposition. According to the balance of draining and entraining forces, a fast dip-withdraw process in a volatile solution is developed to tightly wrap Cu-Ag nanonets onto the fibers of thread. The modified threads are not only conductive, but they also retain their original features with enhanced mechanical stability and dry-wash durability. Furthermore, various e-textile devices are fabricated such as a fabric heater, touch screen gloves, a wearable real-time temperature sensor, and warm fabrics against infrared thermal dissipation. These high quality and colorful conductive textiles will provide powerful materials for promoting next-generation applications in wearable electronics.

Surface-Decorated Graphene Oxide Sheets with Copper Nanoderivatives for Bone Regeneration: An In Vitro and In Vivo Study Regarding Molecular Mechanisms, Osteogenesis, and Anti-infection Potential

It has been previously reported that graphene oxide/copper nanoderivative (GO/Cu)-incorporated chitosan/hyaluronic acid scaffolds might be promising wound dressings for the management of infected wound healing. The aim of the present research is to deeply explore the potential antimicrobial mechanisms and synergistic osteogenic activity, as well as the in vivo anti-infective behavior of GO/Cu nanocomposites, making them possible candidates for establishing implantable biomaterials for the repair of infected bone defects. The antibacterial mechanisms of the nanocomposites were explored through the examination of membrane integrity, oxidative stress, and metabolic enzyme activities. Then, the cytocompatibility with bone mesenchymal stem cells (rBMSCs) and osteogenic potential were confirmed, and a subcutaneous bacterial infection model in rats was also established to verify the in vivo anti-infective property and biosafety of the nanocomposites. It was found that leakage of adenosine triphosphate, proteins, and reducing sugars from the bacterial cells, indicative of damaged permeability of bacterial membranes, and promoted production of reactive oxygen species and disordered metabolic enzyme activities in response to oxidative stress were possible molecular mechanisms responsible for the synergistic antibacterial effects of the GO/Cu nanocomposites. Additionally, good cytocompatibility with rBMSCs and promoted osteogenic differentiation were found in GO/Cu nanocomposites (mass ratio = 2:1), which also demonstrated satisfactory in vivo anti-infective performance, reduced inflammation, and acceptable biosafety. Based on our results, damaged bacterial membranes, increased ROS production, and disorders of crucial enzyme metabolism were the main antibacterial mechanisms involved in the bacterium-killing events caused by the GO/Cu nanocomposites, which also showed enhanced osteogenic activity, in vivo anti-infective capability, and acceptable cytocompatibility and biosafety. Therefore, GO/Cu (2:1) nanocomposites are a potential strategy for improving the biological performance of current bone substitutes used for combating bacterial-contaminated bone defects.

Heavy metal ions and particulate pollutants can be effectively removed by a gravity-driven ceramic foam filter optimized by carbon nanotube implantation

It is of great significance to develop a new gravity-driven filter to remove water pollutants, but it is still challenging. Here, a novel and simple strategy is demonstrated to manufacture fly ash (FA) ceramic foams showing a three-dimensional interconnected porous structure, with multiwalled carbon nanotubes (MWCNTs) implanted by combining carbamate grafting and polydimethylsiloxane coating. The polydimethylsiloxane formed a physical coating on the carbamate group, generating an effective thermal insulating layer on the outer side of the entire MWCNT. The FA foam, which shows a sufficient adsorption capacity for Pb(II) (51.67 ± 1.17 mg g^-1) and Cd(II) (30.12 ± 0.37 mg g^-1) at pH = 5, T = 25 °C, has a 96.33%, 95.12%, 89.50% removal efficiency for Cd(II), Pb(II), and particulate pollutants, and exhibits excellent recycling performance. This paper provides new opportunities to fabricate gravity-driven filters with low energy consumption for wastewater treatment.

Catalytic Use toward the Redox Reaction of Toxic Industrial Wastes in Innocuous Aqueous Medium and Antibacterial Activity of Novel Cu x Ag x Zn1-2x O Nanocomposites

In this work, we report the redox properties in organic catalytic transformation and antibacterial activity of novel Cu x Ag x Zn1-2x O nanocomposites. Cu- and Ag-doped ZnO [Cu x Ag x Zn1-2x O (x = 0.1)] (CAZ), Cu-doped ZnO [Cu x Zn1-x O (x = 0.1)] (CZ), and Ag-doped ZnO [Ag x Zn1-x O (x = 0.1)] (AZ) were prepared via a chemical co-precipitation method. The synthesized nanocomposites were characterized using different spectroscopic techniques. The catalytic activity of CAZ, CZ, and AZ was examined for the reduction of 4-nitrophenol (4-NP) and 4-nitroaniline (4-NA) in the presence of NaBH4 in an aqueous medium. The photocatalytic oxidation efficiency of these catalysts was also observed against naphthol orange (NO) under ultraviolet light. It was found that the catalytic reduction and oxidation efficiency of CAZ is higher than that of CZ and AZ in 4-NP/4-NA and NO in a water solvent, respectively. The antibacterial property of CAZ was also studied against Gram-positive and Gram-negative bacteria by agar well diffusion and the minimum inhibitory concentration methods. It was found that CAZ shows better antimicrobial activity compared to its parental Cu(NO3)2·3H2O, AgNO3, and ZnO. Therefore, the incorporation of Cu and Ag into ZnO increases its catalytic and antimicrobial activity remarkably. Fourier-transform infrared and X-ray diffraction (XRD) studies of CAZ indicate the incorporation of Cu and Ag into the lattice of ZnO. The phase structure of CAZ was wurtzite hexagonal, and the average crystallite size was 93 ± 1 nm measured from XRD. The average grain size and particle size of CAZ were found to be 200 and 100 ± 5 nm originating from SEM and transmission electron microscopy studies, respectively. The optical energy band gap of CAZ is 3.15 eV, which supports the excellent photocatalyst under UV light. CAZ also exhibits good agreement for photoluminescence properties with a high intensity peak at 571 nm, indicating surface oxygen vacancies and defects which might be responsible for higher photocatalytic activity compared to others. The nanocomposite shows excellent reusability without any significant loss of activity.

Comparison of Antibacterial Mode of Action of Silver Ions and Silver Nanoformulations With Different Physico-Chemical Properties: Experimental and Computational Studies

The aim of this study was to compare the antibacterial mode of action of silver ions (Ag⁺) and selected silver nanoformulations against E. coli strains (E. coli J53, Escherichia coli BW25113 and its derivatives: Δ ompA, Δ ompC, Δ ompF, Δ ompR, ompRG596AcusSG1130A, cusSG1130A). In this research we used various experimental methods and techniques such as determination of the minimal inhibitory concentration, flow cytometry, scanning electron microscopy, circular dichroism as well as computational methods of theoretical chemistry. Thanks to the processing of bacteria and silver samples (ions and nanoformulations), we were able to determine the bacterial sensitivity to silver samples, detect reactive oxygen species (ROS) in the bacterial cells, visualize the interaction of silver samples with the bacterial cells, and identify their interactions with proteins. Differences between the mode of action of silver ions and nanoformulations and the action of nanoformulations themselves were revealed. Based on the results of computational methods, we proposed an explanation of the differences in silver-outer protein interaction between silver ions and metallic silver; in general, the Ag⁰ complexes exhibit weaker interaction than Ag⁺ ones. Moreover, we identified two gutter-like areas of the inner layer of the ion channel: one more effective, with oxygen-rich side chains; and another one less effective, with nitrogen-rich side chains.

Selective antifungal and antibacterial activities of Ag-Cu and Cu-Ag core-shell nanostructures synthesized in-situ PVA

A simple chemical reduction method was employed to synthesize Cu-Ag and Ag-Cu core-shell nanostructures inside polyvinyl alcohol (PVA) matrix at room temperature. The core-shell nanostructures have been synthesized by varying the two different concentrations (i.e. 0.1 and 0.01 M) of the respective metal ions in equimolar ratios using successive reduction with hydrazine hydrate (HH) as a reducing agent. The core-shell nanostructures have been further characterized by different characterization techniques. The UV-visible spectroscopy exhibit the respective shift in the band positions suggesting the formation of core-shell nanostructures, which was further confirmed by field emission transmission electron microscopy-high-angle-annular dark field elemental mapping. The effect of metal ion concentration of the core-shell nanostructure on various Gram positive and Gram negative bacteria like Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, Pseudomonas aeruginosa and one fungal species Aspergillus fumigatus was observed by performing MIC and MBC/MFC study. Cu-Ag core-shell nanostructures were found to be effective antibacterial agent against all tested Gram-positive and Gram-negative bacteria, whereas Ag-Cu core-shell nanostructures were more efficient against a particular fungal species known as A. fumigatus. The highest value of MIC (75 µg ml^-1) for Ag-Cu 0.1M core shell nanostructures (D1) was noted against S. aureus and E. coli whereas the lowest value (20 µg ml^-1) was observed with P. aeruginosa. While in case of Cu-Ag 0.1M core shell nanostructures (E1) the highest value of MIC (100 µg ml^-1) was noted against S. aureus and P. aeruginosa whereas the lowest value (15 µg ml^-1) was observed with A. fumigatus. Also, field effect scanning electron microscope (FESEM) images of untreated and core-shell nanoparticles treated micro-organisms showed that 0.1 M Ag-Cu and 0.1 M Cu-Ag core-shell nanostructure can successfully break the cell wall of the fungi A. fumigatus and bacteria P. aeruginosa, respectively. Thus the present study concludes that, Cu-Ag & Ag-Cu core-shell nanostructures damage the cell structure of micro-organisms and inhibits their growth. Hence, the present Cu-Ag & Ag-Cu core-shell nanostructure acts as good antimicrobial agent against the bacteria and fungi, respectively.

Essential oil impregnated luminescent hydroxyapatite: Antibacterial and cytotoxicity studies

In this study, porous fluorescent nanocrystalline erbium doped hydroxyapatite (eHAp) was synthesized via hydrothermal assisted co-precipitation method. Eucalyptus oil (EU), frankincense oil (FO), Tea tree oil (TTO), wintergreen oil (WO) were successfully absorbed into eHAp pellet by vacuum filtration technique using Buckner funnel. Phase crystallization, fluorescence property and microstructure of eHAp were confirmed by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), Photoluminiscence spectroscopy (PL) and Field emission scanning electron microscopy (FESEM). Strong antimicrobial activity was observed for EU, TTO and WO on both E. coli and S. aureus mediated by cell membrane damage and leakage of cytoplasmic components. The oil absorbed eHAp nanocomposites were found to be moderately biocompatible with normal WI-38 cells up to MIC concentration various time scale. The nanocomposites showed significant cytotoxic activity on breast cancer cell line MDA-MB 468 and the fluorescent property of the eHAp was utilized to visualize internalization of particles in the cells. The release profile of the oils from the eHAp matrix showed pH dependent release indicated that the porous matrix can be used as a suitable carrier for modulated and sustained release of bioactive components. Thus, given the multifunctional attributes these natural essential oil-based nanocomposites show great promise as an alternative to conventional therapeutic treatments.

Natural Inorganic Ingredients in Wound Healing

Background:

One of the major clinical challenges is to achieve a rapid and efficient treatment of complex chronic wounds. Nowadays, most wound dressings currently available are unable to find a solution the challenges of resistance to bacterial infection, protein adsorption and increased levels of exudates. Natural inorganic ingredients (clay minerals, metal cations, zeolites, etc) could be the key to solve the problem satisfactorily. Some of these materials have shown biocompatibility and ability to enhance cell adhesion, proliferation and cellular differentiation and uptake. Besides, some natural inorganic ingredients effectively retain drugs, allowing the design of drug delivery matrices.

Objective:

possibilities of natural inorganic ingredients in wound healing treatments have been reviewed, the following sections have been included: 1. Introduction 2. Functions of Inorganic Ingredients in wound healing 2.1. Antimicrobial effects 2.2. Hemostatic effects 3. Clay minerals for wound healing 3.1. Clay minerals 3.2. Clay mineral semisolid formulations 3.3. Clay/polymer composites and nanocomposites 3.4. Clay minerals in wound dressings 4. Other inorganic materials for wound healing 4.1. Zeolites 4.2. Silica and other silicates 4.3. Other minerals 4.4. Transition metals 5. Conclusion

Conclusion:

inorganic ingredients possess useful features in the development of chronic wounds advanced treatments. They improve physical (mechanical resistance and water vapor transmission), chemical (release of drugs, hemostasis and/or adsorption of exudates and moisture) and biological (antimicrobial effects and improvement of healing) properties of wound dressings. In summary, inorganic ingredients have proved to be a promising and easily accessible products in the treatment of wounds and, more importantly, chronic wounds.

Ta-Coated Titanium Surface With Superior Bacteriostasis And Osseointegration

Background

Although tantalum (Ta)-based coatings have been proven to have good antibacterial activity, the underlying mechanism and in vivo biological performance remain unclear, which are essential for the clinical application of Ta-coated biomaterials as dental implants.

Purpose

The main objective of this study is to investigate the antibacterial activity of Ta-modified titanium (Ti) implants against peri-implantitis-related microbes and the potential molecular mechanisms.

Methods

Fusobacterium nucleatum and Porphyromonas gingivalis were selected to evaluate the antibacterial activity and potential antibacterial mechanism of Ta modification. The in vivo biocompatibility of Ta-modified implants was also evaluated.

Results

The results showed that Ta-modified surface performed excellent antimicrobial activity against Fusobacterium nucleatum and Porphyromonas gingivalis. Micro galvanic might be formed between the incorporated Ta and the Ti base, which could consume the protons and result in decreased ATP synthesis and increased ROS generation. The gene expression of bacterial virulence factors associated with cellular attachment, invasion and viability as the target of ROS was downregulated. Importantly, in vivo biological studies showed that Ta modification significantly promoted the osseointegration of implants by stimulating the expression of bone-forming proteins.

Conclusion

This study may provide some insights into clinical applications of Ta-coated Ti implants, especially in possibly infected situations.

Development of an antibacterial nanobiomaterial for wound-care based on the absorption of AgNPs on the eggshell membrane

To develop a promising antibacterial agent for wound-care dressing, a series of silver nanoparticles (AgNPs) and eggshell membrane (ESM) composites (AgNPs/ESM) were prepared. AgNPs were prepared using a chemical reduction method and their characteristics were determined. Various pH and processing time combinations were tested to find the optimal conditions for preparing AgNPs/ESM composites. To obtain the optimal nontoxic-level silver release, the AgNPs stock solution was diluted to 2 times, 4 times, 6 times, 8 times and 10 times with water and the concentration of silver released by the composites was also tested. All the prepared composites showed antibacterial activity, but the activity was the strongest when the stock AgNPs solution was diluted to four times (a concentration of silver was 2.41 mg/L). The addition of AgNPs changed the ESM from hydrophobic to hydrophilic by lowering the water contact angles from 105° to 75°, which is important for the wound-healing process. And the AgNPs/ESM composites had a higher surface area (159.08 m²/g) than the natural ESM (24.32 m²/g) and a suitable pore size (10.92 nm) as well, endowing with better absorption and antibacterial abilities. These findings suggested that the AgNPs/ESM composites are promising candidates for the development of antimicrobial agent for biomedical devices and therapeutic applications, such as wound-healing agent.

Application and modification of polysulfone membranes

Polysulfone (PSf) is a favorite polymer for the production of membrane due to its excellent physicochemical properties, including thermal stability; good chemical resistance to different materials such as different bases, acids, and chlorine; sufficient mechanical strength; and good processability. The present study offers an overview of the recent development in the application and modification of PSf membranes, focusing on some applications such as water and wastewater treatment, membrane distillation, pollutant removal, gas separation, separator for lithium ion battery, and support of composite membranes. In general, there are two major difficulties in the use of membranes made of PSf: membrane fouling and membrane wetting. Therefore, PSf membrane with good anticompaction and antifouling properties is reviewed. Finally, important issues related to the modification of PSf membranes for real applications are discussed. This article provides an intelligent direction for the progress of PSf membranes in the future.

Regium-π bonds: An Unexplored Link between Noble Metal Nanoparticles and Aromatic Surfaces

The ability of metal clusters involving elements from group 11 (Ag, Cu, Au) to favorably interact with π systems of different size and electronic nature was evaluated at the PBE0-D3/def2-TZVPP//PBE0-D3/def2-TZVP level of theory. The M₉ clusters (M=Cu, Ag, Au) were used as σ-hole and σ-lump donors, and benzene, trifluorobenzene, and hexafluorobenzene as aromatic rings. In addition, the study was expanded to the analysis of extended π systems by using naphthalene and anthracene as well as their corresponding perfluorinated derivatives. Furthermore, Bader's theory of Atoms in Molecules as well as natural bonding orbital and spin-density calculations were used to further investigate and characterize the regium-π and σ-lump complexes described herein. Apparently, regium-π bonds have not previously been described in the literature and may be of great importance in the understanding of organocatalytic processes involving aromatic substrates as well as in the design of new materials based on this novel subclass of σ-hole bonding.

Cytotoxicity, genotoxicity and antibacterial activity of poly(vinyl alcohol)-coated silver nanoparticles and farnesol as irrigating solutions

OBJECTIVE

To evaluate the cytotoxicity, genotoxicity and antibacterial activity of poly(vinyl alcohol)-coated silver nanoparticles (AgNPs-PVA) and farnesol (FAR).

DESIGN

The cytotoxicity (% of cell viability) was evaluated by MTT assay and the genotoxicity (% of DNA in the tail) was evaluated by Comet assay. Root canal disinfection with different irrigating protocols was evaluated ex vivo in human teeth contaminated with Enterococcus faecalis for 21days. Three microbiological samples were collected: initial (after contamination); post-irrigation (after irrigation); and final (after 7days). After each sample, the number of log 10 CFU mL^-1 was determined. Statistical analyses was performed using two-way ANOVA and Bonferroni post-hoc tests for MTT assay, Kruskal-Wallis and Dunn post-hoc tests for Cometa and antibacterial assays (α=0.05).

RESULTS

The MTT assay showed that AgNPs and FAR were less cytotoxic that sodium hypochlorite (NaOCl) and showed a lower% of DNA in the tail, in comparison with H₂O₂ (positive control - C+). In the post-irrigation microbiological sample, all the irrigating protocols were more effective than C+ (without irrigation). NaOCl/saline, NaOCl/saline/AgNPs-PVA and NaOCl/saline/FAR led to complete bacterial elimination (p >0.05). In comparison with the initial sample, both the post-irrigation and the final samples showed microbial reduction (p < 0.05).

CONCLUSIONS

AgNPs-PVA and FAR showed low cytotoxicity and genotoxicity, and exhibit potential for use as a final endodontic irrigation protocols.

Development of Nano-Antimicrobial Biomaterials for Biomedical Applications

Around the globe, there is a great concern about controlling growth of pathogenic microorganisms for the prevention of infectious diseases. Moreover, the greater incidences of cross contamination and overuse of drugs has contributed towards the development of drug resistant microbial strains making conditions even worse. Hospital acquired infections pose one of the leading complications associated with implantation of any biomaterial after surgery and critical care. In this regard, developing non-conventional antimicrobial agents which would prevent the aforementioned causes is under the quest. The rapid development in nanoscience and nanotechnology has shown promising potential for developing novel biocidal agents that would integrate with a biomaterial to prevent bacterial colonization and biofilm formation. Metals with inherent antimicrobial properties such as silver, copper, zinc at nano scale constitute a special class of antimicrobials which have broad spectrum antimicrobial nature and pose minimum toxicity to humans. Hence, novel biomaterials that inhibit microbial growth would be of great significance to eliminate medical device/instruments associated infections. This chapter comprises the state-of-art advancements in the development of nano-antimicrobial biomaterials for biomedical applications. Several strategies have been targeted to satisfy few important concern such as enhanced long term antimicrobial activity and stability, minimize leaching of antimicrobial material and promote reuse. The proposed strategies to develop new hybrid antimicrobial biomaterials would offer a potent antibacterial solution in healthcare sector such as wound healing applications, tissue scaffolds, medical implants, surgical devices and instruments.

Phenolic compound-mediated single-step fabrication of copper oxide nanoparticles for elucidating their influence on anti-bacterial and catalytic activity

A single-step synthesis of copper oxide nanoparticles (CuO NPs) from a phenolic compound (rosmarinic acid) at ambient temperature was developed in this study.

Toward a Molecular Understanding of the Antibacterial Mechanism of Copper-Bearing Titanium Alloys against Staphylococcus aureus

The antibacterial mechanism of the Cu-containing materials has not been fully understood although such understanding is crucial for the sustained clinical use of Cu-containing antibacterial materials such as bone implants. The aim of this study is to investigate the molecular mechanisms by which the Gram-positive Staphylococcus aureus is inactivated through Cu-bearing titanium alloys (Ti6Al4V5Cu). Cu ions released from the alloys are found to contribute to lethal damage of bacteria. They destroy the permeability of the bacterial membranes, resulting in the leakage of reducing sugars and proteins from the cells. They also promote the generation of bacteria-killing reactive oxygen species (ROS). The ROS production is confirmed by several assays including fluorescent staining of intracellular oxidative stress, detection of respiratory chain activity, and measurement of the levels of lipid peroxidation, catalase, and glutathione. Furthermore, the released Cu ions show obvious genetic toxicity by interfering the replication of nuc (species-specific) and 16SrRNA genes, but with no effect on the genome integrity. All of these effects lead to the antibacterial effect of Ti6Al4V5Cu. Collectively, our work reconciles the conflicting antibacterial mechanisms of Cu-bearing metallic materials or nanoparticles reported in the literature and highlights the potential use of Ti6Al4V5Cu alloys in inhibiting bacterial infections.