The "Nano" World in Photodynamic Therapy.

Photodynamic Therapy (PDT) is an externally activated, photochemistry-based approach that generates cytotoxic reactive molecular species (RMS), which kill or modulate biological targets. PDT provides unique opportunities for applications of nanotechnology where light activation can trigger both direct RMS-mediated cytotoxic activity and the release of contents within the nanoconstructs (Figure 1). This process allows several species, working via different mechanisms and molecular targets to be activated or released in the right place and time, thus providing a distinctive approach to combination therapy. With advances in the development of miniaturized, even biodegradable, light sources and delivery systems, exciting possibilities of anatomical reach with PDT are being made possible. This brief article introduces aspects of interfaces of PDT and nanotechnology but, due to space constraints, makes no attempt to be a comprehensive review.