Implications of Photophysical and Physicochemical Factors on Successful Application of Photodynamic Therapy

Photodynamic therapy is an evolving treatment modality for cancer owing to its non-invasive approach. This mode of therapy depends on the dynamic interaction of light, oxygen and a photoactive drug to induce oxidative damage to affected cells. This apparently simple technique could be complicated by several factors, mainly contributed by the nature of the physicochemical properties of the photoactive drug, variation in light source and exposure time, as well as tumor physiological environment. This review covers a brief history on the use of various fluorophores in photodynamic therapy, successful marketed formulations and the factors affecting the treatment modalities. The potential of nanostructures as effective delivery carriers with improved photodynamic efficacy is also elaborated. A thorough understanding of the chemistry of photoactive drugs, characteristics of the delivery carriers and light irradiation parameters will enable optimal efficacy of photodynamic therapy.