Antimicrobial activity, cytotoxicity and inflammatory response of novel plastics embedded with silver nanoparticles.

AIM: Infections associated with medical devices are an important cause of morbidity and mortality. Microorganisms are responsible for catheter infections that may then result in the local or systemic dissemination of the microorganism into the bloodstream. The aim of this study was to evaluate the antimicrobial activity of silver nanoparticles (AgNPs) embedded in polyurethane plastics, commonly used for catheter fabrication. MATERIALS & METHODS: AgNPs in the range of 25-30 nm were synthesized and embedded in polyurethane plastics at different concentrations. The antimicrobial activities of these plastics were tested against the three pathogenic microorganisms, Escherichia coli, Staphylococcus epidermidis and Candida albicans, frequently associated with catheter infections. The cytotoxicity of the plastics was evaluated on human-derived macrophages using propidium iodide and the secretion of the pro- and anti-inflammatory cytokines IL-6, IL-10 and TNF-a was measured using ELISA. RESULTS: A significant reduction of 6- to 7-log in the number of bacteria was measured, while a reduction of 90% was measured in the case of C. albicans. Neither cytotoxic effect on macrophages nor immunological response was observed. CONCLUSION: Plastics embedded with AgNPs have great potential to limit microbial colonization of implanted medical devices.

Antibacterial activity, inflammatory response, coagulation and cytotoxicity effects of silver nanoparticles.

The incorporation of nanoparticles (NPs) in industrial and biomedical applications has increased significantly in recent years, yet their hazardous and toxic effects have not been studied extensively. Here, we studied the effects of 24 nm silver NPs (AgNPs) on a panel of bacteria isolated from medical devices used in a hospital intensive care unit. The cytotoxic effects were evaluated in macrophages and the expression of the inflammatory cytokines IL-6, IL-10 and TNF-α were quantified. The effects of NPs on coagulation were tested in vitro in plasma-based assays. We demonstrated that 24 nm AgNPs were effective in suppressing the growth of clinically relevant bacteria with moderate to high levels of antibiotic resistance. The NPs had a moderate inhibitory effect when coagulation was initiated through the intrinsic pathway. However, these NPs are cytotoxic to macrophages and are able to elicit an inflammatory response. Thus, beneficial and potential harmful effects of 24 nm AgNPs on biomedical devices must be weighed in further studies in vivo. From the Clinical Editor: The authors of this study demonstrate that gallic acid reduced 24 nm Ag NPs are effective in suppressing growth of clinically relevant antibiotic resistant bacteria. However, these NPs also exhibit cytotoxic properties to macrophages and may trigger an inflammatory response. Thus, the balance of beneficial and potential harmful effects must be weighed carefully in further studies.

Synthesis, characterization, and evaluation of antimicrobial and cytotoxic effect of silver and titanium nanoparticles.

Microbial resistance represents a challenge for the scientific community to develop new bioactive compounds. Nosocomial infections represent an enormous emerging problem, especially in patients with ambulatory treatment, which requires that they wear medical devices for an extended period of time. In this work, an evaluation of the antimicrobial activity of both silver and titanium nanoparticles was carried out against a panel of selected pathogenic and opportunistic microorganisms, some of them commonly associated with device-associated infections. Cytotoxicity assays monitoring DNA damage and cell viability were evaluated using human-derived monocyte cell lines. We show that silver-coated nanoparticles having a size of 20-25 nm were the most effective among all the nanoparticles assayed against the tested microorganisms. In addition, these nanoparticles showed no significant cytotoxicity, suggesting their use as antimicrobial additives in the process of fabrication of ambulatory and nonambulatory medical devices. FROM THE CLINICAL EDITOR: In this study, antimicrobial activity of silver and titanium nanoparticles was evaluated against a panel of selected pathogenic and opportunistic microorganisms. Silver-coated nanoparticles of 20-25 nm size were the most effective among all the nanoparticles without significant cytotoxicity, suggesting their use as antimicrobial additives in the process of fabrication of ambulatory and nonambulatory medical devices.

Reduction of arsenic content in a complex galena concentrate by Acidithiobacillus ferrooxidans.

BACKGROUND: Bioleaching is a process that has been used in the past in mineral pretreatment of refractory sulfides, mainly in the gold, copper and uranium benefit. This technology has been proved to be cheaper, more efficient and environmentally friendly than roasting and high pressure moisture heating processes. So far the most studied microorganism in bioleaching is Acidithiobacillus ferrooxidans. There are a few studies about the benefit of metals of low value through bioleaching. From all of these, there are almost no studies dealing with complex minerals containing arsenopyrite (FeAsS). Reduction and/or elimination of arsenic in these ores increase their value and allows the exploitation of a vast variety of minerals that today are being underexploited. RESULTS: Arsenopyrite was totally oxidized. The sum of arsenic remaining in solution and removed by sampling represents from 22 to 33% in weight (yield) of the original content in the mineral. The rest of the biooxidized arsenic form amorphous compounds that precipitate. Galena (PbS) was totally oxidized too, anglesite (PbSO4) formed is virtually insoluble and remains in the solids. The influence of seven factors in a batch process was studied. The maximum rate of arsenic dissolution in the concentrate was found using the following levels of factors: small surface area of particle exposure, low pulp density, injecting air and adding 9 K medium to the system. It was also found that ferric chloride and carbon dioxide decreased the arsenic dissolution rate. Bioleaching kinetic data of arsenic solubilization were used to estimate the dilution rate for a continuous culture. Calculated dilution rates were relatively small (0.088-0.103 day(-1)). CONCLUSION: Proper conditions of solubilization of arsenic during bioleaching are key features to improve the percentage (22 to 33% in weight) of arsenic removal. Further studies are needed to determine other factors that influence specifically the solubilization of arsenic in the bioleaching system such as: pH, dissolved oxygen concentration, redox potentials, nature of concentrate and temperature among others. At. ferrooxidans was able to completely oxidize the minerals present during the arsenic bioleaching. Other elements present originally in the concentrate such as Zn, Sb, and Cu were also solubilized. The process of bioleaching is expected to be influenced by mechanisms that still need to be established due to the diversity of the minerals involved and by the presence of traces of metals in the concentrate. The increase in pulp density generates a decrease in the dissolved arsenic concentration. This decrease is greater in runs where air was not injected to the system. The maximum rate of arsenic dissolution in the concentrate was found using; small surface area of particle exposure, low pulp density, injecting air and adding 9 K medium to the system. The effect of addition of ferric chloride during the arsenic bioleaching resulted in a decrease of the solubilized arsenic in the system. The presence of CO2 is associated to the decrease in arsenic dissolution.