The Effect of Particle Size on the Cytotoxicity of Amorphous Silicon Dioxide: An in Vitro Toxicological Study

INTRODUCTION: Amorphous silicon dioxide (A-SiO(2)) is abundant in the Earth’s crust, the A-SiO(2) nano and microparticles are released into the air through industrial and manufacturing activities. Due to the limited available toxicological information, the objective of the present study was to evaluate the toxicity of different sizes of A-SiO(2) particles on the A549 cell-lines in an in vitro study. MATERIALS AND METHODS: The A-SiO(2) particles in two categories of nano (10-100 nm) and micro (< 5um) were used in this study. The human lung A549 cell-line was exposed to either nano- or micro-sized A-SiO(2) particles at 10, 50, 100, and 250 μg/ml, and the effects were investigated. RESULTS: The cytotoxicity of A-SiO(2) nano and microparticles in both 24- and 72-hour exposure times resulted in decreased cell survival, mitochondrial membrane potential, and increased ROS generation which was concentration-time dependent (P <0.05) but glutathione content was not affected in a time-dependent manner. Cytotoxicity of nanoparticles, contrary to the previous study, was not higher than microparticles in the comparable dose and exposure times. CONCLUSION: The rate of ROS generation in the A549 cell-line exposed to A-SiO(2) nanoparticles was higher than microparticles. And at the same time, cell survival for exposed cells to A-SiO(2) nano and microparticles were higher for nanoparticles in shorter exposure periods and was inversely concentration- and time-dependent. Further studies on exploring the effect of size and its possible toxic mechanism are recommended to achieve a more credible risk assessment.