Photodynamic therapy (PDT) is a promising noninvasive treatment of cancers and other diseases. Two-photon excitation PDT (2P-PDT) is advantageous over the traditional one-photon counterpart by offering unique advantages of deeper penetration into body tissues, more confined treatment area and 3-dimensional spatial selectivity to reduce adverse effects to nearby healthy tissues. However, clinical applications of 2P-PDT are limited by the small two-photon absorption capability of current photosensitizers. A lot of research efforts have been devoted to the development of novel two-photon photosensitizers with improved two-photon light harvesting capability. 

Here I will present our recent efforts on development of various nanophotosensitizersthat allow simultaneous two-photon imaging and photodynamic therapy with enhanced efficiency. We used two strategies to develop composite nanomaterials with enhanced two-photon optical properties. One is based on energy transfer from conjugated polymers which acted as two-photon light harvesting materials to transfer the absorbed energy to photosensitizers. We have developed photosensitizers doped conjugated polymer nanoparticles that display strong two-photon absorption capability, high emission yield and singlet oxygen generation capability, selectively cancer cell targeting and killing capability at the same time. The second approach is based on plasmon resonance enhancement. We have developed various plasmonengineered nanocomposites with enhanced two-photon properties for simultaneous two-photon imaging and phototherapy. The exceptional properties of these nano-photosensitizers render them great potentials for high spatial resolution imaging-guided two-photon phototherapy.