Antibacterial Activity Stability Research Articles

Prevalence and Antibiotic Resistance of Ureaplasma urealyticum in Sperm Cultures: A Retrospective Analysis", Abidjan, Côte d’Ivoire

Aims: Mycoplasmas are bacteria of the urogenital tract often associated with various infections and infertility. In terms of treatment, acquired resistance to antibiotics has been reported. The aim of this study was to investigate changes in the prevalence and antibiotic resistance of Ureaplasma urealyticum strains isolated during sperm culture, in order to help update therapeutic protocols for the treatment of U. urealyticum-associated infections Place and Duration of Study: These were men received at the INHP from January 2018 to December 2021 for sperm culture Methodology: This is a retrospective study in which the culture results of 907 semen samples received in the laboratory between 2018 and 2021 were analysed. Identification, indicative counts and antibiotic susceptibility testing of U. urealyticum were performed using the Biosynex Mycoplasma kit. Results: 283 strains of U. urealyticum were isolated between 2018 and 2021, with an average prevalence of 31.2%. In 2018, only minocycline, josamycin and roxithromycin were active on all the strains tested, while fluoroquinolones and clindamycin showed high levels of resistance, with rates of 75.9% and 86.1% respectively. From 2019 onwards, resistance spread to all antibiotics, with increasing levels of resistance, with the exception of minocycline, which remained active on all strains. The highest resistance rates were observed in 2021 and were 74.6% and 96.6% for pristinamycin and clindamycin respectively. Conclusion: Despite the high level of resistance, minocycline and josamycin have shown relatively stable antibacterial activity and could be proposed as the molecules of choice for the treatment of U. urealyticum infections. Closer monitoring of the development of antibiotic resistance in these bacteria is therefore necessary.

Bacillus subtilis 2118 exhibits bactericidal activity due to an inserted fish cDNA library

The probiotic Bacillus subtilis represents an efficient, environmentally friendly biocontrol agent to address the problem of evolving, mutation, and dissemination of multidrug-resistant bacteria. In the current study, B. subtilis 2118 strain was screened based on an insert fragment from a large yellow croaker cDNA library damage effect on the B. subtilis host. The supernatant of B. subtilis 2118 displayed a wide-spectrum antibacterial activity against one Gram+ and five Gram- bacteria, including Staphylococcus aureus, Aeromonas hydrophila, A. veronii, Escherichia coli, Vibrio alginolyticus, and V. parahemolyticus. It was further found that B. subtilis 2118 crude protein displayed bactericidal activity against indicator bacteria S. aureus and A. hydrophila with MIC of 187.50 μg/mL and 375.00 μg/mL, and MBC of both 375.00 μg/mL. The mechanism studies indicated that B. subtilis 2118 crude protein was mainly involved in collapse of cell membrane, cytoplasm agglutinating and outflow, and increasing membrane permeability. Besides these, the crude protein has potential of binding bacterial DNA, and probably interfering protein synthesis or degrading protein. Furthermore, B. subtilis 2118 crude protein maintains stable antibacterial activity even when pH 3–11, temperature 25–100 °C, UV radiation 0–60 min, and different proteases handling. In addition, B. subtilis 2118 crude protein has scarce hemolysis and less cytotoxicity towards 293 T and PCK cells. Taken together, B. subtilis 2118 strain and its crude protein have strong potential as alternative agents for antibiotics in aquaculture.

Lysozyme Peptides as a Novel Nutra-Preservative to Control Some Food Poisoning and Food Spoilage Microorganisms.

Foodborne illnesses and microbial food contamination are crucial concerns and still issues of great worldwide concern. Additionally, the serious health hazards associated with the use of chemical preservatives in food technology. Lysozyme (Lz) is an active protein against Gram-positive bacterial cell wall through its muramidase lytic activity; however, several authors could identify some antimicrobial peptides derived from Lz that have an exaggerated and broad-spectrum antibacterial activity. Therefore, a lysozyme peptides preparation (LzP) is developed to broaden the Lz spectrum. In this work, we investigated the potential efficacy of LzP as a novel Nutra-preservative (food origin) agent against some pathogenic and spoilage bacteria. Our results showed that LzP demonstrated only 11% of the lysozyme lytic activity. However, LzP exhibited strong antibacterial activity against Escherichia coli, Salmonella enteritidis, and Pseudomonas species, while Salmonella typhi and Aeromonas hydrophila exhibited slight resistance. Despite the lowest LzP concentration (0.1%) employed, it performs stronger antibacterial activity than weak organic acids (0.3%). Interestingly, the synergistic multi-component formulation (LzP, glycine, and citric acid) could inhibit 6 log10 cfu/ml of E. coli survival growth. The effect of heat treatment on LzP showed a decrease in its antibacterial activity at 5 and 67% by boiling at 100 °C/30 min, and autoclaving at 121 °C/15 min; respectively. On the other hand, LzP acquired stable antibacterial activity at different pH values (4-7). In conclusion, LzP would be an innovative, natural, and food origin preservative to control the growth of food poisoning and spoilage bacteria in food instead chemical one.

Streptomyces enissocaesilis L-82 has broad-spectrum antibacterial activity and promotes growth for Carassius auratus.

Aeromonas is the main pathogen causing bacterial diseases in fish. The disadvantages of chemical drugs to control fish diseases have been highlighted, and it is urgent to find an eco-friendly control method. In this study, an actinomycete strain with antibacterial activity against fish pathogenic bacteria was screened from soil samples. Combined with morphological characteristics, physiological and biochemical characteristics, and gyrB gene and whole genome comparison analysis, it was identified as a new strain of Streptomyces enissocaesilis, named Streptomyces enissocaesilis L-82. The strain has broad-spectrum antibacterial activity against fish pathogens. A substance with a mass-to-charge ratio of 227.20 [M + H] + was isolated and purified by high-performance liquid chromatography and mass spectrometry. It was presumed to be a derivative of 5-dimethylallylindole-3-acetonitrile. The strain is safe and non-toxic to crucian carp, and can stably colonize crucian carp and inhibit the proliferation of A. hydrophila. After feeding the feed containing 1 × 108CFU/mL strain concentration, the weight growth rate and specific growth rate of crucian carp increased, the activity of ACP and SOD in serum increased, and the survival rate of crucian carp increased after challenge. Genome-wide analysis showed that the strain had strong ability to metabolize and tolerate extreme environments. And has a strong potential for disease resistance. Therefore, the strain is expected to be developed as a feed additive for fish farming. KEY POINTS: • The new Streptomyces enissocaesilis L-82 has a broad spectrum and stable antibacterial activity and meets the safety standards of feed additives. • Strain L-82 can colonize crucian carp, improve the growth, antioxidant, and immune performance of the host, and improve the survival rate after being infected with A. hydrophila. • Genome-wide analysis suggests that the strain has great disease resistance potential and is expected to be developed as a feed additive for fish culture.

Antibacterial activity and synergistic antibiotic mechanism of trialdehyde phloroglucinol against methicillin-resistant Staphylococcus aureus.

The emergence of methicillin-resistant Staphylococcus aureus (MRSA) has become a critical global concern. Identifying new anti-S. aureus agents or therapeutic strategies are urgently needed to treat S. aureus infection. The present study investigated the antibacterial activity of 16 phenolic compounds against MRSA, four of which exhibited antibacterial activity. Their antibacterial activities increased in a dose-dependent manner but showed different responses with the extension of treatment time. Trialdehyde phloroglucinol (TPG) and 2-nitrophloroglucinol (NPG) maintained stable antibacterial activity; however, that of dichlorophenol and myricetin decreased rapidly over 24 hr of treatment. Checkerboard and time-kill assays indicated that TPG and NPG exhibited strong synergistic antibacterial activities with penicillin or bacitracin. Microscopic observation and membrane integrity analysis showed that the combination of TPG and penicillin destroyed the MRSA cell membrane, resulting in the leakage of intracellular biomacromolecules, marked changes in surface zeta potential, and the collapse of membrane potential. Moreover, the combination significantly decreased penicillinase activity and penicillin-binding protein 2a mRNA expression, inhibiting MRSA growth. Taken together, these results demonstrated that the combination of the phloroglucinol derivative TPG and penicillin has significant synergistic anti-MRSA activity and can serve as a potential therapeutic strategy to treat MRSA infections.

The isolation of a novel Streptomyces termitum and identification its active substance against fish pathogens

The emerging outbreak of bacterial diseases poses a major threat to the aquaculture industry, and the abuse of antibiotics leads to the emergence of drug-resistant pathogens; hence, the development of antibacterial agents from natural resources to control and manage fish bacterial diseases has become a promising strategy. In this study, seven potential Streptomyces spp. with antimicrobial activity against fish pathogenic bacteria were isolated from the soils of different regions in China. Streptomyces termitum N-15, which showed the strongest and most stable antibacterial activity, was selected for the fish disease control experiment. Then, we investigated the effect of a basal diet and N-15 supplementation (108 ​CFU/mg diet) on growth performance, blood immune parameters (ACP and AKP), and the expression of immune genes. The results demonstrated that the ACP and AKP activities of serum were significantly increased in the N-15-supplemented group. Moreover, N-15 upregulated the expression level of Toll-like receptor 4 (TLR-4) in the kidney, liver, spleen and head kidney. The challenge test showed that supplementation with N-15 could significantly improve the survival rates of grass carp infected with A. veronii. Chalcomycin A was purified from Streptomyces termitum N-15 and found to have antimicrobial activity against fish pathogenic bacteria for the first time. Furthermore, the complete genome of S. termitum N-15 was found to consist of an 8,887,222 bp circular chromosome with 72.89% GC content and a plasmid genome, including 7744 protein-coding sequences (CDSs). The genome of S. termitum N-15 contained gene clusters for the synthesis of multiple secondary metabolites, including melingomycin, sulforaphane, oromycin, chlortetracycline, isomycin, and primycin, by antiSMASH online software. Gene cluster 1.5 revealed a chalcomycin A biosynthesis gene cluster (chmGⅠ, chmGⅡ, chmGⅢ, chmGⅣ, chmGⅤ). In summary, S. termitum N-15 and its secondary metabolites are expected to be developed into inoculants for promoting fish health in aquacultural systems.

Tri‐functional unit groups contained polyurethane composites with excellent antibacterial property and biocompatibility

AbstractAs biomaterials, it is essential for polyurethane (PU) to have excellent antibacterial activity and biocompatibility at the same time. Herein, quaternary ammonium groups, sulfonic groups, and alkyl groups simultaneously introduced hyperbranched poly(amidoamine) (HPA‐QSA) was synthesized, which was further used to blend with PU and prepared as films. HPA‐QSA/PU blend films showed strong antibacterial activity to kill more than 99.99% of both Gram‐positive and Gram‐negative bacteria due to the quaternary ammonium groups and long alkyl groups, as well as good biocompatibility through protein‐resistance, cytotoxicity, hemolysis assays under the combined action of cations and anions. Moreover, they exhibited stable antibacterial activity and low cytotoxicity in aquatic solutions. Overall, HPA‐QSA/PU films prepared by facile blending process exhibit great promise as low‐cost, effective antibacterial, good biocompatible materials, indicating an appealing prospect in biomedical fields.

Biocompatible tellurium nanoneedles with long-term stable antibacterial activity for accelerated wound healing

Tellurium (Te) nanomaterials (NMs) have emerged as a new antibacterial candidate to respond to the complex global health challenge of bacterial resistance. Herein, Te nanoneedles (NNs) that act both chemically and physically on bacteria are synthesized by a facile method using Na2TeO3, urea and glucose. It is found that the prepared Te NNs have a strong affinity to the cell membrane of bacteria and subsequently promote the generation of reactive oxygen species (ROS) in bacteria, resulting in an excellent antibacterial effect toward Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). What's more, this needle-like morphology also can physically damage the bacterial cell membranes. The Te NNs per se are inert in mammalian cells to produce ROS at a proper concentration, indicating considerable biocompatibility of this material. As a proof-of-concept, the antibacterial Te NNs were used as an anti-inflammatory reagent for promoting bacteria-infected wound healing in vivo, during which Te NNs caused no evident side effects to major organs in mice. Additionally, the antibacterial activity is maintained in the presence of surface oxidation of Te NNs after long-term dispersion in phosphate buffered saline solution. The needle-like Te NMs with long-term antibacterial stability and good biocompatibility have great potential for the treatment of associated infectious diseases.

Preservative effects of a novel bacteriocin from Lactobacillus panis C-M2 combined with dielectric barrier discharged cold plasma (DBD-CP) on acquatic foods.

In this study, a novel bacteriocin Lactocin C-M2 produced by Lactobacillus panis C-M2, combined with dielectric barrier discharged cold plasma (DBD-CP), was used to evaluate the antibacterial effect on aquatic foods. After the purification procedures of ethyl acetate extraction, cation exchange chromatography and semi-preparative liquid phase, the stability of Lactocin C-M2 under DBD-CP environment was determined, and the preservation effect of these two joint treatments was investigated on fresh white fish samples. As revealed by LC-MS/MS and BLAST analysis, Lactocin C-M2 is a new type of class II bacteriocin, with a molecular weight of 863.52 Da and the N-terminal sequence MVKKTSAV. Application of Lactocin C-M2 showed significantly stronger inhibitory effect on bacteria than on yeasts and mold. All the tested 10 Gram positive bacteria and 3 Gram-negative bacteria, including Staphylococcus aureus, Shigella flexneri, Bacillus spp, Lactobacillus spp, Escherichia coli, Pseudomonas aeruginosa, and so on, were inhibited. Lactocin C-M2 also presented stable antibacterial activity after exposure to DBD-CP, with the 95% residual activity against Staphylococcus aureus under the 40∼80 kV voltage for 30∼180 s, indicating the possibility of synergistic application. Combined with addition of 0.9 mg/g Lactocin C-M2, the treatment of DBD-CP with voltage at 60 kV for 90 s on fresh white fish (Culter alburnus) could significantly inhibit the microbial growth, the accumulation of volatile nitrogen and histamine during the storage. Therefore, the Lactocin C-M2, used together with the DBD-CP, is effective in food preservation.

In Vitro & In Vivo Studies on Identifying and Designing Temporin-1CEh from the Skin Secretion of Rana chensinensis as the Optimised Antibacterial Prototype Drug.

Amphibian skin secretion is an ideal source of antimicrobial peptides that are difficult to induce drug resistance to due to their membrane-targeting mechanism as a new treatment scheme. In this study, a natural antimicrobial peptide Temporin-1CEh was identified by molecular cloning and mass spectrometry from the skin secretions of the Chinese forest frog (Rana chensinensis). Through the study of the structure and biological activity, it was found that Temporin-1CEh was a helical peptide from the Temporin family, and possessed good anti-Gram-positive bacteria activity through the mechanism of membrane destruction. Seven analogues were further designed to obtain broad-spectrum antimicrobial activity and higher stability in different physiological conditions. The results showed that T1CEh-KKPWW showed potent antibacterial activity with significantly increasing the activity against Gram-negative bacteria in vitro and in vivo with low haemolysis. In addition, T1CEh-KKPWW2 showed high sensitivity to the pH, serum or salts conditions, which applied a branched structure to allow the active units of the peptide to accumulate. Even though the haemolytic activity was increased, the stable antibacterial activity made this novel analogue meet the conditions to become a potential candidate in future antimicrobial and antibiofilm applications.

Antibacterial activity and cytotoxicity of bioinspired poly(L-DOPA)-mediated silver nanostructure-decorated titanium dioxide nanowires

The combination of silver (Ag) and titanium dioxide (TiO2) nanostructures offer unique advantages in terms of elimination of infection and enhanced antibacterial activity with relatively higher biocompatibility and lower cytotoxicity. Although there have been numerous attempts for the fabrication of these nanocomposite systems, novel, flexible, low-cost, simple, effective, reducing, and stabilizing agent-free strategies are highly required for biomedical applications. Within this context, we report the employment of silver nanostructure decorated TiO2 nanowires (TiO2 NWs) as an ideal antibacterial agent against antibiotic-resistant Gram-negative (Escherichia coli) and Gram-positive bacteria (Staphylococcus aureus). Firstly, TiO2 NWs were fabricated via the hydrothermal procedure. Afterward, by utilizing the oxidative polymerization of 3,4-dihydroxyphenyl-L-alanine (L-DOPA), a conformal and thin polymer layer of L-DOPA (PLDP) was created onto the TiO2 NWs (TiO2/PLDP). Lastly, Ag nanostructures were deposited onto the TiO2/PLDP (TiO2/PLDP/Ag NP) via simply reduction of silver ions. Herein, PLDP with its abundant catechol and amine groups played an important role in the reduction of silver ions and the adsorption of Ag nanostructures with high affinity and resultant stability. The size, density, and morphology of Ag nanostructures were manipulated by tuning the initial amount of Ag ions in a well-controlled manner. The resultant colloidal TiO2/PLDP/Ag composite nanosystem provided remarkably high and stable antibacterial activity against both antibiotic-resistant bacteria strains. Minimum Inhibitory Concentration (MIC) values were found to be 125, 250, and > 500 ppm for high, medium and, low deposition of Ag nanostructures, respectively. Similarly, Minimum Bactericidal Concentration (MBC) for these NP systems, MBC values were found to be 250, 500, and > 1000 ppm, respectively. Also, relatively lower cytotoxicity in human lung healthy (MRC5) and cancer (A549) cell lines was detected in a dose-dependent manner in comparison to the citrate-stabilized Ag nanoparticles. The proposed novel TiO2/PLDP/Ag nanosystem will provide unique opportunities in terms of flexibility, low-cost, simplicity with reducing, and stabilizing agent-free strategy and be employed in the removal of biofilms and anti-inflammatory effects.

Antibacterial functionalization of nylon monofilament surgical sutures through in situ deposition of biogenic silver nanoparticles

Antibacterial coating of nylon monofilament sutures presents difficulties unlike non-absorbable braided sutures due to the nature of nylon material and absence of interstices. To solve these problems, a new technique using in situ deposition of biogenic silver nanoparticles (AgNPs) has been developed to coat nylon surgical sutures. The effect of AgNPs deposition on the surface roughness was observed, with significant reduction in average roughness (9.41 ± 0.96 nm), compared with uncoated sutures (12.35 ± 0.20 nm) (P < 0.05). The ICP-OES analysis of coated sutures revealed total Ag+ concentration of 11.25 ± 0.14 μg/mL, with an AgNPs release of 11.25, 11.27, 19.94, and 24.03% at 1, 3, 5, and 7 days, respectively. The sutures demonstrated bactericidal effects on Gram-positive (Staphylococcus aureus) and Gram-negative (Escherichia coli, Pseudomonas aeruginosa, Acinetobacter baumannii, and Klebsiella pneumoniae) wound pathogens with more than 99.9% reduction. The coated sutures indicated stable antibacterial activity against representative Gram-positive and Gram-negative isolates after 12-week storage. Haemolytic evaluation of coated sutures showed less than 1% lysis of human erythrocytes. In addition, coated sutures inhibited lipopolysaccharide-induced nitric oxide generation by 15.46 μM reduction. Cytocompatibility test on L929 fibroblast cells revealed approximately 81% cell viability and promoted cell migration by 51% after 24 h treatment. The study revealed that in situ deposition of AgNPs on nylon monofilament sutures did not alter the mechanical properties of the sutures, but conferred antibacterial and wound healing properties.

The effects of low-temperature storage on the viability of Lactobacillus casei and the stability of antibacterial activity in green grass jelly synbiotic drinks

Abstract. Rizal S, Suharyono, Nurainy F, Amela JR. 2020. The effects of low-temperature storage on the viability of Lactobacillus casei and the stability of antibacterial activity in green grass jelly synbiotic drinks. Biodiversitas 21: 3826-3831. Synbiotic drinks from green grass jelly have shown antibacterial activity against pathogenic bacteria. These are usually stored at low temperatures to maintain their characteristics. The aim of this study was to determine the effect of storage at low temperature of 10°C on the viability of lactic acid bacteria (Lactobacillus casei) and the stability of the antibacterial activity in synbiotic drinks made of green grass jelly. Antibacterial activity of green grass jelly synbiotic drink was conducted against pathogenic bacteria (Staphylococcus aureus, Salmonella sp., Bacillus cereus, and Escherichia coli). The products were stored for 28 days at 10°C temperature. Observations on the antibacterial activity, pH value, total acid, and total lactic acid bacteria were carried out every 7 days. Antibacterial activity was evaluated using agar well diffusion method. The results showed that storage at low temperature (10 ± 2°C) for 28 days decreased the antibacterial activity and pH value but sharply increased total lactic acid bacteria (at 0 to 7 days of storage) in green grass jelly synbiotic drinks. Salmonella sp. showed the highest inhibition caused by the antibacterial agents in green grass jelly synbiotic drinks while the lowest inhibition was found on Staphylococcus aureus. During storage at low temperature, green grass jelly synbiotic drinks had a total of lactic acid bacteria that ranged from 9.51 to 10.10 (Log CFU/mL) or equal to 3.24x109-1.26x1010 CFU/mL; a total of lactic acid that ranged from 0.48% to 0.87%; and pH values that ranged from 3.78 to 4.08.

Therapeutic potential of a designed CSαβ peptide ID13 in Staphylococcus aureus-induced endometritis of mice.

Staphylococcus aureus is a common pathogen that can cause clinical and subclinical endometritis in humans and animals. In this study, a designed CSαβ peptide ID13 from DLP4 exhibited high stable antibacterial activity in simulated gastric fluid (90.79%), serum (99.54%), and different pH buffers (> 99%) against S. aureus CVCC 546 and lower cytotoxicity (89.62% viability) than its parent peptide DLP4 (74.14% viability) toward mouse endometrial epithelial cells (MEECs). ID13 caused a depolarization of bacterial membrane and downregulation of the expression of genes involved in membrane potential maintenance and biofilm formation. The in vitro efficacy analysis of ID13 showed a synergistic effect with vancomycin, ampicillin, rifampin, and ciprofloxacin; intracellular antimicrobial activity against S. aureus CVCC 546 in MEECs; and the ability to inhibit lipoteichoic acid-induced pro-inflammatory cytokines from RAW 264.7. In the S. aureus-induced endometritis of mice, similar to vancomycin, ID13 remarkably alleviated pathological conditions, inhibited the production of cytokines (TNF-α, IL-1ß, IL-6, and IL-10), and suppressed the TLR2-NF-κB signal pathway. Collectively, these results suggest that ID13 could be a potential candidate peptide for therapeutic application in S. aureus-induced endometritis.Key Points•Higher antibacterial activity and lower hemolysis of ID13 than DLP4.•ID13 could downregulate the genes of bacterial survival and infection.•ID13 could alleviate the S. aureus-induced endometritis of mice.•ID13 could regulate the cytokines and suppress the TLR2-NF-κB signal pathway.Electronic supplementary materialThe online version of this article (10.1007/s00253-020-10685-x) contains supplementary material, which is available to authorized users.

Antimicrobial peptide PMAP-37 analogs: Increasing the positive charge to enhance the antibacterial activity of PMAP-37.

Bacterial resistance induced by the use of antibiotics has provided a chance for the development of antimicrobial peptides (AMPs), and modification of AMPs to enhance the antibacterial activity or stability has become a research focus. PMAP-37 is an AMP isolated from porcine myeloid marrow, and studies on its modification have not yet been reported. In this study, three PMAP-37 analogs named PMAP-37(F9-R), PMAP-37(F34-R), and PMAP-37(F9/34-R) were designed by residue substitution to enhance the positive charge. The antimicrobial activity of PMAP-37 and its analogs in vitro and in vivo were detected. The results showed that compared with PMAP-37, PMAP-37(F9-R) and PMAP-37(F9/34-R) exhibited antibacterial activity against S. flexneri CICC21534. Although PMAP-37(F34-R) had no antibacterial activity against S. flexneri CICC21534, its minimal inhibitory concentrations (MICs) were significantly lower than those of PMAP-37 against most bacterial strains. Besides, all PMAP-37 analogs were pH stable, retaining stable antibacterial activity after treatment with solution from pH 2 to pH 8/9. In addition, the PMAP-37 analogs displayed increased thermal stability, and PMAP-37(F34-R) retained >60% antibacterial activity after boiling for 2 hours. Furthermore, the PMAP-37 analogs exhibited impressive therapeutic efficacy in bacterial infections by reducing bacterial burden and inflammatory damage in the lung and liver, resulting in a reduction in mortality. Notably, the therapeutic effect of PMAP-37(F34-R) was comparable to that of ceftiofur sodium, and even superior to antibiotics in L. monocytogenes CICC21533 infection model. In conclusion, the PMAP-37(F34-R) may be a candidate for the treatment of bacterial infections in the clinic.

Antibacterial durability and biocompatibility of antibacterial-passivated 316L stainless steel in simulated physiological environment

Stainless steel (SS) has been widely applied as one of the most efficient implant metal materials, although corrosion and infection in body environment are still challenging. Herein, an antibacterial passivation method was employed to enhance the antibacterial performance and corrosion resistance of the medical 316L SS. The result proved that the antibacterial-passivated 316L SS exhibited stable antibacterial activity and effectively inhibited the formation of bacterial biofilm. Electrochemical measurements combined with X-ray photoelectron spectroscopy technique were used to study the corrosion resistance and semiconductor behavior of passivated 316L SS immersed in simulated physiological environment. The results indicated that the 316L SS after antibacterial passivation treatment for 1 h, soaking in the medium for 10 days, showed satisfactory corrosion resistance attributing to proper Cu deposition in the passive film. The anodic stripping voltammetry measurement further confirmed that the Cu-bearing passive film could continuously release Cu ions into medium. The zebrafish test demonstrated an excellent in vivo biocompatibility for the 316L SS with antibacterial passivation for 0.5 and 1 h, respectively. In addition, changes of surface roughness, contact angle and chemical composition after antibacterial passivation played an important role in explaining the antibacterial mechanism, which could be clearly divided into contact killing and ionic release killing. Hence, the antibacterial passivation treatment was preliminarily proved as a potential way for enhancing the persistent antibacterial activity and corrosion resistance of 316L SS.

Ag-Introduced Antibacterial Ability and Corrosion Resistance for Bio-Mg Alloys.

Bone implants are expected to possess antibacterial ability and favorable biodegradability. Ag possesses broad-spectrum antibacterial effects through destroying the respiration and substance transport of bacteria. In this study, Ag was introduced into Mg-3Zn-0.5Zr (ZK30) via selective laser melting technology. Results showed that ZK30-Ag exhibited a strong and stable antibacterial activity against the bacterium Escherichia coli. Moreover, the degradation resistance was enhanced due to the comprehensive effect of positive shifted corrosion potential (from -1.64 to -1.53 V) and grains refinement. The positive shifted corrosion potential reduced the severe galvanic corrosion by lowering the corrosion potential difference between the matrix and the second phase. Meanwhile, the introduction of Ag caused the grain refinement strengthening and precipitated-phase strengthening, resulting in improved compressive yield strength and hardness. Furthermore, ZK30-0.5Ag exhibited good biocompatibility. It was suggested that Ag-modified ZK30 was potential candidate for bone implants.

Antibacterial and bioactive properties of stabilized silver on titanium with a nanostructured surface for dental applications

Titanium (Ti) is used in dental applications owing to their excellent mechanical properties, corrosion resistance, and biocompatibility. However, postoperative bacterial infection may cause serious complications and remains one of the most difficult challenges hindering the development of long term Ti dental implants. Therefore, the desire for high quality dental care has led to significant interest in designing implant surfaces that offer stable antibacterial activity with excellent cellular response. In this study, we propose a simple and efficient approach for fabricating an antibacterial stabilized Ag nanostructure on a Ti surface, which is based on a two-step process involving target-ion induced plasma sputtering (TIPS) and Ag sputtering. The TIPS process generates a nanostructured Ti surface that provides a nanotemplate on which the Ag nanostructure may be deposited through Ag sputtering. The Ag nanoclusters adhere tightly to the TIPS-treated Ti (TIPS-Ti) nanostructured surface with no noticeable defects, and the amount of stabilized Ag deposited may be controlled by simply adjusting the Ag-sputtering time. The silver ion is released continuously from the Ag-TIPS-Ti surface for 7 d. The Ag nanostructured TIPS-Ti (Ag-TIPS-Ti) surface not only offers outstanding antibacterial activity toward Escherichia coli and Staphylococcus aureus over 12 h of culturing but also exhibits no severe cytotoxicity for fibroblast cells for up to 10 days. In particular, Ag stabilization by 10 s Ag-sputtering on TIPS-Ti provides the best balance between antibacterial activity and cellular performances, and the resulting fibroblast cell-attachment morphology and proliferation level are similar to those for a polished Ti surface. Therefore, the controllable antibacterial activity and fibroblast tissue affinity of the Ag-TIPS-Ti present a promising avenue for producing reliable, long term dental implants.

Opto-electronic and antibacterial activity investigations of mono-dispersed nanostructure copper oxide prepared by a novel method: reduction of reactive oxygen species (ROS)

A novel approach for synthesis of copper oxide nanoparticles is reported by separation of nucleation and growth. The nano-material was characterized by X-ray diffraction, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, and UV–Vis diffuse reflectance spectroscopy, transmission electron microscopy, atomic force microscopy, and Brunauer–Emmett–Teller analyses. Optical analysis of mono-dispersed nanostructure copper oxide by UV–Vis diffused reflectance spectroscopy showed the band gap value of 1.47 eV with a blue-shift in the optical band gap due to quantum confinement effect. The dynamic light scattering and zeta potential results showed fairly narrow size distribution and colloidal stability. The results showed that nano-particles were mono-dispersed spheres of 8 nm with no aggregation. Cell viability of treated murine fibroblast cell line (L-929) treated by different concentrations of nanoparticles showed significant viability up to 96% at concentrations 15 and 30 μg ml−1. The nanoparticles exhibited outstanding and stable antibacterial activity against Staphylococcus aureus ATCC 6538 at 30 µg ml−1. The viability and reactive oxygen species (ROS) generation in the L-929 cell line indicated that the nanoparticles were not toxic at the concentrations which were effective on bacteria. ROS analysis using DCFH-DA probe on L-929 were exposed to 7.5–60 μg ml−1 of copper oxide nanoparticles in 6 h revealed ROS generation was decreased dramatically compare to the untreated cells and positive control.

Microstructure, mechanical properties, bio-corrosion properties and antibacterial properties of Ti–Ag sintered alloys

In this research, Ag element was selected as an antibacterial agent to develop an antibacterial Ti–Ag alloy by a powder metallurgy. The microstructure, phase constitution, mechanical properties, corrosion resistance and antibacterial properties of the Ti–Ag sintered alloys have been systematically studied by X-ray diffraction (XRD), scanning electron microscope (SEM), compressive test, electrochemical measurements and antibacterial test. The effects of the Ag powder size and the Ag content on the antibacterial property and mechanical property as well as the anticorrosion property have been investigated. The microstructure results have shown that Ti–Ag phase, residual pure Ag and Ti were the mainly phases in Ti–Ag(S75) sintered alloy while Ti2Ag was synthesized in Ti–Ag(S10) sintered alloy. The mechanical test indicated that Ti–Ag sintered alloy showed a much higher hardness and the compressive yield strength than cp-Ti but the mechanical properties were slightly reduced with the increase of Ag content. Electrochemical results showed that Ag powder size had a significant effect on the corrosion resistance of Ti–Ag sintered alloy. Ag content increased the corrosion resistance in a dose dependent way under a homogeneous microstructure. Antibacterial tests have demonstrated that antibacterial Ti–Ag alloy was successfully prepared. It was also shown that the Ag powder particle size and the Ag content influenced the antibacterial activity seriously. The reduction in the Ag powder size was benefit to the improvement in the antibacterial property and the Ag content has to be at least 3wt.% in order to obtain a strong and stable antibacterial activity against Staphylococcus aureus bacteria. The bacterial mechanism was thought to be related to the Ti2Ag and its distribution.