Ratiometric Fluorescent Quantification of the Size-Dependent Cellular Toxicity of Silica Nanoparticles

Nanoscale particles are ubiquitous in the atmosphere, and the widespread use of nanoparticles may increase the risks of organ damage. Therefore, it is of great significance to investigate the toxicity of nanoparticles of different sizes toward living cells, especially lung epithelial cells. In this study, the quantitative ratiometric fluorescent detection of intracellular pH changes was utilized to evaluate the cytotoxicity of mesoporous silica nanoparticles of different sizes after the nanoparticles had entered lung epithelial cells. The results showed that, with decreasing nanoparticle size, the intracellular reactive oxygen species (ROS) concentration increased and the intracellular pH value decreased; consequently, this led to the enhanced cytotoxicity of the nanoparticles. Notably, no obvious cytotoxicity was induced by the nanoparticles when the size of the nanoparticles was larger than 135 nm. The presented strategy of using ratiometric fluorescent detection of intracellular pH to quantify the size-dependent cellular toxicity of nanoparticles provides a novel approach for investigating the cytotoxicity of nanomaterials.