SCHEDULED MAINTENANCE
Shape-dependent biological activity of spherical and quasi-spherical silver nanoparticles in E. coli, A549 cells and mice†
Abstract
Silver nanoparticles (AgNPs) of various sizes and shapes are widely used because of their antibacterial properties. However, their bioactivity in mammals is insufficiently investigated. The aim of the present study was to assess the effect of AgNPs' shape on their antibacterial activity, cytotoxicity, and ability to interfere in copper metabolism in mice. For this, AgNPs with the same linear size (75 nm), but different shape (spherical and quasi-spherical), were fabricated by chemical reduction from silver nitrate. The test of the biological activity of AgNPs showed that both types of particles suppressed bacterial (E. coli) and mammalian (A549) cell growth in a time- and dose-dependent manner. Quasi-spherical AgNPs had stronger antibacterial activity (several orders of magnitude) than the spherical AgNPs. In mice, the intake, distribution and accumulation of silver from AgNPs depending on the administration method were compared and intraperitoneal injections were chosen as the most appropriate. Silver concentration in organs of mice and its distribution in the organs did not depend on the shape of AgNPs. During the 7 days of intraperitoneal treatment with AgNPs, the silver concentration in blood serum increased, while the copper concentration and ceruloplasmin (Cp) oxidase activity (measured by the o-dianisidine in-gel assay) decreased. At the same time, the Cp protein concentration determined by immunoblotting did not change. Analysis of the blood serum by gel-filtration has shown that blood serum silver was associated with Cp and with a larger protein, presumably α-2-macroglobulin. After the AgNP injections were cancelled, the organs and the blood serum were cleared from silver through bile, while the copper concentration and Cp oxidase activity of blood serum recovered to their normal levels. So, the correlation between particle shape and their biological activity was observed. Quasi-spherical AgNPs having more edges possessed higher antibacterial activity. At the same time, both types of AgNPs lowered the copper status of blood serum in mice in a similar manner. In the article, the potential danger of AgNP's low doses for mammals, including humans, and the specificity of the nanosilver turnover in the mammalian body, which suggests that AgNPs can be used for safe treatment, are discussed.
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