Construction of protein-modified TiO2 nanoparticles for use with ultrasound irradiation in a novel cell injuring method.

Recently, our group discovered an alternative titanium dioxide (TiO(2)) activation method that uses ultrasound irradiation (US/TiO(2)) instead of ultraviolet irradiation. The pre-S1/S2 protein from hepatitis B virus, which recognizes liver cells, was immobilized to the surface of TiO(2) nanoparticles using an amino-coupling method. The ability of the protein-modified TiO(2) nanoparticles to recognize liver cells was confirmed by surface plasmon resonance analysis and immuno-staining analyses. After uptake of TiO(2) nanoparticles by HepG2 cancer cells, the cells were injured using this US/TiO(2) method; significant cell injury was observed at an ultrasound irradiation intensity of 0.4 W/cm(2). Together with these results, this strategy could be applied to new cell injuring systems that use ultrasound irradiation in place of photodynamic therapy in the near future.