Photosensitizer encapsulated organically modified silica nanoparticles for direct two-photon photodynamic therapy and in vivo functional imaging.

Nanoparticle-assisted two-photon imaging and near infrared (NIR) imaging are two important technologies in biophotonics research. In the present paper, organically modified silica (ORMOSIL) nanoparticles encapsulated with either PpIX (protoporphyrin IX) photosensitizers or IR-820 NIR fluorophores were synthesized and optically characterized. Using the former ORMOSIL nanoparticles, we showed: (i) direct excitation of the fluorescence of PpIX through its efficient two-photon absorption in the intracellular environment of tumor cells, and (ii) cytotoxicity towards tumor cells by PpIX under two-photon irradiation. The latter ORMOSIL nanoparticles can be used as efficient NIR fluorescent contrast agents for various types in vivo animal imaging. We applied IR-820 doped ORMOSIL nanoparticles in in vivo brain imaging of mice. We also demonstrated the applications of them to sentinel lymph node (SLN) mapping of mice. Finally, we showed that the nanoprobes could target the subcutaneously xenografted tumor of a mouse for long time observations. ORMOSIL nanoparticles have great potentials for disease diagnosis and clinical therapies.