Enhancement of Photocatalytic Cancer Cell-Killing Activity by Using Ag@TiO2 Core-Shell Composite Nanoclusters

The photocatalytic cancer cell-killing activity of the Ag metal core-TiO2 shell (Ag@TiO2) composite colloidal nanoclusters has been investigated on HeLa cells under the UV-visible light irradiation. The Ag@TiO2 composite nanocluster photocatalyst with the uniform size and shape was successfully synthesized by a simple citrate reduction method. The photocatalytic cell-killing activity of the Ag@TiO2 nanoclusters was found to vary with the molar ratio of Ag to TiO2. The direct involvement of the metal particles in mediating the electron transfer from the photoexcited TiO2 under the band gap excitation is considered to carry out the efficient photocatalytic reaction on the cells. The charge separation and the interfacial charge-transfer promote the photocatalytic cancer-cell killing more than the TiO2 semiconductor alone. It was found that the Ag@TiO2 nanoclusters under the low concentrations kill HeLa cells by 100%, whereas TiO2 nanoparticles alone kill only ca. 25% under the same concentrations.