Nanomaterials for Enhanced Photodynamic Therapy

Photodynamic therapy is a non-invasive option for eliminating superficial tumors and to control infections. However, despite some protocols are already approved for the clinic, PDT applications could be much broader if some of its main hindrances were overcome. For instance, the most efficient photosensitizers are hydrophobic, so if one injects them intravenously they tend to aggregate and to be internalized by phagocytes in the blood, impairing the delivery to the target site. In addition, visible light has a limited penetration in tissues, therefore the main applications of PDT are limited to superficial tumors unless an invasive procedure is used for the light to reach deeper sites. Another setback is the hypoxia that commonly happens in tumors, hindering the full potential of PDT as it depends on a constant oxygen supply. In this chapter the reader will find some strategies based on Nanotechnology to overcome these and other obstacles for PDT to reach its full clinical potential, i.e. hypoxia-reverting protocols, X-ray-driven PDT, Cherenkov radiation-driven PDT, and active tumor-targeting.