[Non-covalent albumin conjugates of silicon (IV) phthalocyanines axially substituted with nucleoside: preparation and in vitro photodynamic activities]

Abstract

The interactions of bovine serum albumin (BSA) with five novel silicon (N) phthalocyanines(SiPcl-5) axially modified by nucleosides (cytidine, 5-N-cytidine, methyl cytidine, uridine and methyl uridine) derivatives were studied by fluorescence spectroscopy. The results show that there are strong interactions between these silicon phthalocyanines and BSA with a binding constant of (4.90-83.18) x 10(5) mol(-1) x L. Therefore, the non-covalent BSA conjugate of bis(2', 3'-O-isopropyl-cytidine-oxy) phthalocyaninatosilicon(IV) (SiPc1) was further been prepared. The molar ratio of phthalocyanine to albumin was found to be 1:1 for the obtained SiPcl-BSA conjugate. The absorption spectra of SiPc1 and SiPc1-BSA in the visible region have no significant difference, both showing an Q-band maximum at about 686 nm. It indicates that the spectroscopic characteristics of SiPc1 are not affected by binding to albumin. The SiPcl-BSA conjugate exhibits high photodynamic activity against human hepatoma cell line HepG2 with an IC50 value of 3.0 x 10(-7) mol x L(-1). By comparsion, SiPc1-BSA has a higher photodynamic activity than SiPc1 (in PBS formation, IC50 = 7.0 x 10(-7) mol x L(-1)), which can be attributed to its higher cellular uptake.