Biological Effects Of Silver Nanoparticle On Cells

Silver nanoparticles(Ag NPs) have been widely used in textiles, medical equipments, packaging materials, cosmetics and many other fields owing to their broad-spectrum antimicrobial properties. Thus human beings may exposed to them through various pathways. The thorough understanding of the toxicity of Ag NPs is pre-requirement and foundation for the broad and sustained applications of Ag NPs in future. Although there are a huge amount of data on the bioeffects of Ag NPs, studies under real environmental conditions, such as low-dose long-term exposure, are still scattered. It is urgent to conduct comprehensive and systematical research. Based on aforementioned background, we conducted cytotoxicity studies of Ag NPs under simulated environmental conditions.Firstly, we studied the short-term(24 h) and long-term(21 d) toxicity of Ag NPs to cells. We chose three kinds of Ag NPs with different surface coating and particle size between 20 to 40 nm: Ag NPs with citrate as surface coating(Ag-CIT), Ag NPs with polyvinylpyrrolidone as surface coating(Ag-PVP) and bare Ag NPs without any coating(Ag-B). After comprehensive characterization, a systematic short-term toxicity study was performed on the human colorectal adenocarcinoma cell Caco-2 and the normal human gastric epithelial cell GES-1, and a long-term one was performed on Caco-2 cells. Results show that the surface coating predominated the toxicity of Ag NPs in a descending order of Ag-CIT>Ag-B>Ag-PVP. Ag NPs affected cell viabilities in a dose-dependent manner after short-term exposure, namely the cell viability decreased along with the dose increased, and caused different degrees of apoptosis and necrosis. But Caco-2 cells were more sensitive than GES-1 cells to these Ag NPs. Ag NPs can induce the ROS generation and inhibit the cell growth by blocking cells in G1 ans S phase in Caco-2 and GES-1 cells. The long-term exposure of Ag NPs to Caco-2 cells only inhibited the cell proliferation inhibition. After long-term exposure to 0.4 μg/mL Ag-CIT, the cell viability dropped down to less than 50%. Generally, 0.3 μg/mL is the non-toxic dose for the long-term exposure of Caco-2 cells to Ag NPs in this study. However, cells presents the inflammation after exposed to Ag NPs with non-toxic dose in the long-term exposure.Secondly, considering Ag NPs are widely used in medical and agricultural fields as antimicrobial agent, the possibility of co-existence of Ag NPs with antibiotics greatly increases. Thus, it is important to pay attention to their combined action. The combined cytotoxicity and mechanism of three Ag NPs and antibiotic gentamicin were preliminarily explored. Results indicate that only Ag-PVP showed slight synegistic cytotoxicity when combined with gentamicin.The findings provide basic and important data for the the biomedical applications and safety assessment of Ag NPs.