Silver Nanoparticles as a Smart Antimicrobial Agent

In modern medicine the resistance to conventional antibiotics is becoming a serious concern due to high instances of mortality. Several metallic nanoparticles are suggested as promising anti-microbial agents against multidrug-resistant bacteria and some viruses. Among the nanoparticles mentioned, we review the recent finding which demonstrate the impact of silver nanoparticles on antimicrobial activities and recommend them as a potential candidate for restraining infections.

The Effects of Silica Nanoparticles in Macrophage Cells

Silica nanoparticles, which are applicable in many industrial fields, have been reported to induce cellular changes such as cytotoxicity in various cells and fibrosis in lungs. Because the immune system is the primary targeting organ reacting to internalized exogenous nanoparticles, we tried to figure out the immunostimulatory effect of silica nanoparticles in macrophages using differently sized silica nanoparticles. Using U937 cells we assessed cytotoxicity by CCK-8 assay, ROS generation by CM-H2DCFDA, intracellular Ca++ levels by staining with Fluo4-AM and IL-8 production by ELISA. At non-toxic concentration, the intracellular Ca++ level has increased immediately after exposure to 15 nm particles, not to larger particles. ROS generation was detected significantly in response to 15 nm particles. However, all three different sizes of silica nanoparticles induced IL-8 production. 15 nm silica nanoparticles are more stimulatory than larger particles in cytotoxicity, intracellular Ca++ increase and ROS generation. But IL-8 production was induced to same levels with 50 or 100 nm particles. Therefore, IL-8 production induced by silica nanoparticles may be dependent on other mechanisms rather than intracellular Ca++ increase and ROS generation.

Phagocytosis and Endocytosis of Silver Nanoparticles Induce Interleukin-8 Production in Human Macrophages

Phagocytosis or endocytosis by macrophages is critical to the uptake of fine particles, including nanoparticles, in order to initiate toxic effects in cells. Here, our data enhance the understanding of the process of internalization of silver nanoparticles by macrophages. When macrophages were pre-treated with inhibitors to phagocytosis, caveolin-mediated endocytosis, or clathrin-mediated endocytosis, prior to exposure to silver nanoparticles, Interleukin-8 (IL-8) production was inhibited. Although cell death was not reduced, the inflammatory response by macrophages was compromised by phagocytosis and endocytosis inhibitors.