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"Nejsmutnějším aspektem života v současné době je to, že věda shromažďuje poznatky rychleji, než společnost shromažďuje moudrost."

Isaac Asimov

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THE EFFECT OF SILVER PHOSPHATE NANOPARTICLES (SPNPS) AND SELENIUM NANOPARTICLES (SENPS) ON S. AUREUS

Our main objective was to study the interactions of silver and selenium nanoparticles with bacterial culture Staphylococcus aureus on the cellular, molecular and protein level. Silver phosphate nanoparticles (SPNPs) and selenium nanoparticles (SeNPs). Significant antibacterial effect of both SPNPs and SeNPs on the bacterial culture of S. aureus was observed, particularly after the addition of selenium nanoparticles. 300µM SPNPs caused 37.5% inhibition of the bacterial growth, the effect of SeNPs in the same concentration was even much larger and caused total bacterial growth inhibition. The observed effect may be related with the interactions of nanoparticles with DNA and proteins. For this reason we have studied the interaction of SPNPs or SeNPs nanoparticles with amplified zntR gene, which caused the decrease in melting temperatures of the nanoparticle complexes with zntR gene (by 23 % for SeNPs and by 12 % for SNPS) in comparison with the control value. The concentration of bacterial metallothionein (MT) was significantly 87% lower in bacterial cells after application of SPNPs (6.3 µg/mg of protein) and increased by 29% after addition of SeNPs (63 µg/mg of protein) when compared to the S.aureus control (49 µg/mg of protein). We observed the significant antimicrobial effects of the nanoparticles on bacterial growth and DNA integrity, which may be used to reduce the risk of bacterial infections, uncontrollable with normal antibiotic treatment.

Staphylococcus aureus is a very serious and frequently agent of complications, emerging after transplantation of implants such as vascular grafts, caused by the entry of these bacteria from the patient´s skin or the environment into the wound [1, 2]. The incidence of infections is resumable with appropriate antibiotics. However, most of the bacterial strains has developed resistance to these antibiotics, and the trend of resistance formation even for new antibiotics is growing steadily [3]. A very effective option to suppression of these infections is application of metals, especially the nanoparticles [4-6]. The synthesized silver and selenium nanoparticles have been found to be bactericidal and have been proved as a good alternative for the development of antimicrobial agents [2, 6, 7]. Metalic nanoparticles interact with cellular components (DNA, RNA and ribosomes), deactivate and effectively suspend cellular processes[8]. It was found that silver nanoparticles (SPNPs) can penetrate the cell membrane to cytosol thanks to the slow dissolution and release abilities of Ag+ ions. For achieving of the antimicrobial activity is an important the option of dimension of nanoparticles, which prevent the aggregation of nanoparticles in larger units [9, 10]. Mechanism of antimicrobial action of SPNPs remains unclear. However, the possibilities of SPNPs action based on enzyme inhibition, change of membrane integrity, penetration into the bacterial cytoplasm and accumulation in the periplasmic space or formation of reactive oxygen species are proposed. It was found, that G+ bacteria react significantly later to the SPNPs effect, than G- bacteria, probably due to the cell wall and membrane composition [8]. In previous studies, selenium was researched for various medical applications and as a potential material for orthopaedic implants [11]. There are also studies that point to the ability of selenium compounds to inhibit the growth of bacteria and the formation of bacterial biofilms [11]. For a number of selenium compounds (such as 2,4,6-tri-para-methoxyphenylselenopyrylium chloride, 9-para-chlorophenyloctahydroselenoxanthene and perhydroselenoxanthene) has been demonstrated antibacterial activity in vitro, especially against S. aureus. However, the effects of elemental selenium nanoparticles remain largely unknown [2, 12]. Ramos et al. confirmed in their study on effects of selenium nanoparticles on S. aureus, considerable inhibition of the bacterium in the presence of SeNPs after 24 hours [12]. Vision of use of silver and selenium nanoparticles in the transplantation sector appears to be in the future a very practical and effective alternative [13].

The aim of this study was observation of the effect of selenium and silver nanoparticles on growth and biochemical characteristics of S. aureus using the array of microbiological, biochemical, electrochemical and mass-spectroscopy methods.

Práce je spojená s projektem SIX CZ.1.05/2.1.00/03.0072

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