Photodynamic Therapy (PDT) of Cancer:

(In collaboration with Prof. Allan Oseroff and Ravindra Pandey at RPCI)

 

Photodynamic therapy (PDT) is based on the concept that when certain photoactive molecules called photosensitizers (PS) are irradiated with light, they generate highly reactive oxygen species (ROS) upon energy exchange with molecular oxygen. Since these PS molecules have an inherent avidity of tumor sites, PDT is used as a robust anti-cancer approach where the photo-generated ROS bring about irreversible damage to tumor cells. PDT, which originated at Roswell Park Cancer Institute, Buffalo, is now routinely used in the clinical setting for combating various types of cancers as well as dermatological and several other diseases.

  Here, we are probing organically modified silica (ORMOSIL) nanoparticles as a tumor-specific delivery vehicle for the PS drugs. We have found that the spectroscopic and functional properties of the PS are preserved following encapsulation/conjugation with the nanoparticles. Figure 1a, schematically shows the generation of ROS (singlet oxygen) following photo-excitation of nano-encapsulated/conjugated photosensitizer.Preliminary experiments with cultured cells (in vitro) and experimental animals (in vivo) have demonstrated robust tumor-specific accumulation of the photosensitizer/nanoparticles composite, as shown in Fig. 1b. At present, we are analyzing the photodynamic anti-tumor effect of these nanoparticles in various mouse models of cancer.