Protection of photoactivity of photosensitizers by amphiphilic polysaccharide micelles

Photosensitizer (photosan)-encapsulated micelles were prepared by self-assembly of Photosan with two amphiphilic polysaccharide derivatives, including the cholesteryl conjugated sodium alginate derivative (CSAD) and the deoxycholic acid group conjugated chitosan derivative (DA-Chit). The results of UV-Vis and fluorescence spectroscopy indicated that the hydrogen bonding strength dominated the micelle formation. Methyl viologen was used as a model quencher of photosan. Using the steady-state fluorescence technology, the quenching constants were determined to be 2.05, 1.88 and 0.30 L/mmol for the free photosan, the photosan-CSAD micelle and the photosan-DA-Chit micelle, respectively. This suggested that photosan was protected from quenching of methyl viologen by the polysaccharide micelles. In addition, the protection effect of the photosan-DA-Chit micelle was significantly stronger than that of the photosan-CSAD micelle. The photosan-DA-Chit micelle is thus anticipated for protection of photoactivity of photosan during the blood circulation process in vivo .