Absorption and fluorescence spectral properties of hematoporphyrin in liposomes, micelles, and nanoparticles

A model photosensitizer, hematoporphyrin (Hp), encapsulated in various nanocarriers was investigated for both absorption and fluorescence properties. The generation of singlet oxygen upon light activation was also studied. The absorption intensity of nanoencapsulated hematoporphyrin was stronger and exhibited a red-shift of the Soret and Q absorption bands compared to the non-encapsulated hematoporphyrin. The fluorescence spectral changes were similar to the absorption spectral pattern. The generation of singlet oxygen for encapsulated hematoporphyrin upon light activation differed significantly from the free form hematoporphyrin, and the yield of singlet oxygen production was found in the following order: liposomes > micelles ≈ nanoparticles > free Hp. Under the current studied conditions, the use of nanocarriers significantly improve the photophysical properties of hematoporphyrin in aqueous solutions, and the liposome was the optimum system than either the micelle or the nanoparticle.