Confined Singlet Oxygen in Mesoporous Silica Nanoparticles: Selective Photochemical Oxidation of Small Molecules in Living Cells.

Chemical conversion of specific bioactive molecules by external stimuli in living cells is a powerful noninvasive tool for clarification of biomolecular interactions and to control cellular functions. However, in chaotic biological environments, it has been difficult to induce arbitrary photochemical reactions on specific molecules because of their poor molecular selectivity. Here we report a selective and nontoxic photochemical reaction system utilizing photoactivated mesoporous silica nanoparticles to control biological functions. Methylene blue modification within nanoparticle pores for photosensitization produced singlet oxygen confined to the pore that could mediate selective oxidation of small molecules without any damage to living cells. This intracellular photochemical system produced bioactive molecules in situ and remotely controlled the cell cycle phase. We also confirmed that this photoreaction could be applied to control cell cycle phase in tumor tissue transplanted in mice. The cell cycle phase in the cells in mice, to which our system was administered, was arrested at the G2/M phase upon photoirradiation. We demonstrate a simple and promising method for the exogenous conversion of an intracellular biomolecule to another functional compound.