Porous Silicon Nanoparticle Photosensitizers for Singlet Oxygen and Their Phototoxicity against Cancer Cells

Porous Si nanoparticles, prepared from electrochemically etched single crystal Si wafers, function as photosensitizers to generate 102 in ethanol and in aqueous media. The preparation conditions for the porous Si nanoparticles were optimized to maximize (1) the yield of material; (2) its quantum yield of 102 production; and (3) its in vitro degradation properties. The optimal formulation was determined to consist of nanoparticles 146 +/- 7 nm in diameter, with nominal pore sizes of 12 +/- 4 nm. The quantum yield for O-1(2) production is 0.10 +/- 0.02 in ethanol and 0.17 +/- 0.01 in H2O. HeLa or NIH-3T3 cells treated with 100 mu g/mL porous Si nanoparticles and exposed to 60J/cm(2) white light (infrared filtered, 100 mW/cm(2) for 10 min) exhibit similar to 45% cell death, while controls containing no nanoparticles show 10% or 25% cell death, respectively. The dark control experiment: yields <10% cytotoxicity for either cell type.