In vitro study of simultaneous toxicity of Amorphous Silica Nanoparticles and Formaldehyde in epithelial cells of human lung and toxicological analysis of occupational exposures

Abstract

Human exposure to silica nanoparticles (SNPs) and formaldehyde (FA) is increasing and this has raised some concerns over their possible toxic effects on the exposed working populations. Notwithstanding several studies in this area, the combined toxicological effects of these contaminants have not been yet studied. Therefore, this in vitro study was designed to evaluate the SNPs and FA combined toxicity on human lung epithelial cells (A549 cells). Physicochemical characteristics of SNPs including particle size, morphology, size distribution and zeta potential were determined using Transmission Electron Microscope (TEM) and Dynamic Light Scattering (DLS). Then the cells were exposed to various concentration of SNPs and FA for three period time 24, 48 and 72 h separately and in combined form and the single and combined toxicity of SNPs and FA were evaluated by focusing on cellular viability via MTT assays. TEM analysis of SNPs revealed a primary particle size of 20-30 nm and after dissolving proper amount of SNPs in distilled water and dispersing by sonicator, the particle size increased to 81.6±13.88 nm and zeta potential was -21.2±4.55 mV, as measured by DLS. Also, the MTT assay results showed a significant increase in cytotoxicity in combined treated cells compared with SNPs and FA treated cells for three period time 24, 48 and 72 h (P value < 0.05). Two-factorial analysis showed an additive toxic interaction between SNPs and FA. Eventually, this can be deduced that workers exposed simultaneously to SNPs and FA, may be at high risk compared with exposure to each other