Phthalocyanines in photodynamic therapy

In photodynamic therapy (PDT), photosensitizers (PSs) allow the transfer and translation of light energy into a type II chemical reaction. Rapid cyto and vascular toxicity due to the reactive end products of this pathway is the result of photochemical reactions. PDT requires a sensitizing agent, light energy, and oxygen, which, when successfully combined, create a photodynamic reaction (Alison et al., 2004a). Metallophthalocyanines (PC) have drawn considerable attention in recent years for their potential use as second-generation PSs for PDT of neoplastic diseases. e major advantage of PCs currently is their strong absorption of red light at approximately 675 nm (extinction coecient 2.5 × 10⁵ mol-1 dm³ cm^-1), which allows light penetration into tissues to almost twice the depth. In addition, PCs have low absorption of light in other parts of the solar spectrum, thus lowering the risk of skin photoreaction that oen occurs in patients aer PDT. Water-soluble sulfonated derivatives were used for demonstrating PC photoecacy in the destruction of in vivo tumors. Numerous lipophilic PC derivatives have proven to be eective PDT agents in vivo, although the success of these agents relies upon their incorporation into carrier vehicles or their formulation in specic reagents, such as liposomes and oil emulsions that circumvent the problem of aggregation in biological uids (Zaidi et al., 1993).