Size-dependent in vitro toxicity of porous silicon micro- and nanoparticles
H.A. Santos, J. Salonen, J. Riikonen, T. Heikkilä, L. Peltonen, V-P Lehto, J. Hirvonen
University of Turku, FI
Keywords: Nanoparticles, cytotoxicity, porous silicon, drug carriers
Abstract:Biomedical applications of inorganic nanomaterials have been actively investigated during the last years. Due to the new functionalities, which may arise from the reduced size, the safety issues need to be assessed for each nanomaterial before they can be implemented in human therapeutics. The aim of the present study was to evaluate how the size reduction of porous silicon PSi) particles from micro- to nano-size affects in vitro cytotoxicity and the biochemical mechanisms of the toxicity caused by exposing human intestinal carcinoma-derived cells (Caco-2) to PSi particles. For this purpose, several methods were used: fluorescence- and luminescence-based assays, flow cytometry, and confocal laser scanning microscopy. The study was performed as a function of particle size fractions, particle concentration and surface chemistry, and incubation times using PSi particles with various sizes (70 nm – 75 µm). The effects of the surface chemistry were also studied. Four different surface chemistries, two hydrophilic and two hydrophobic, were prepared. PSi nano- and micro-particles reduced cell viability in a dose- and time-dependent manner. Cytotoxicity of PSi was also found to be due to the combined effects of the particle size and the surface chemistry of the PSi particles and it increases as the size reduces.