fig1

Figure 1. Mechanisms of photosensitization. The photosensitizer (PS), is a molecule capable to absorb energy from light in a specific wavelength. Once excited, the PS transits from its ground state PS(S₀), to its singlet excited PS(S₁) and triplet excited PS(T₁) states. At this point PS(T₁) can react directly with biomolecules, like proteins or lipids (targets), via Type I photochemical reaction, resulting in formation of radicals, like PS^•, capable to initiate radical chain reactions. Otherwise, PS (T₁) can react with molecular oxygen ³O₂, via the Type II photochemical reaction. Both generates diffusive oxidant species like radical superoxide, O₂^.-, and singlet oxygen, ¹O₂, via type I and II respectively, capable to extend the damage