Synthesis and Spectroscopic Properties of Covalent Albumin Conjugates of Phthalocyanine Zincs Substituted with Metadicarboxyphenoxyl Groups

Four kinds of covalent serum albumin (BSA or HSA) conjugates of beta-tetrakis[(3,5-dicarboxy)phenoxy]-phthalocyaninatozinc (1) and beta-octakis [(3, 5-dicarboxy)phenoxy]-phthalocyaninatozinc (2) were synthesized by the approach of amide bond. The molar ratio of phthalocyanine to albumin in conjugates were found to be 6 similar to 7 : 1. Their absorption spectra were measured in PBS solution. When conjugated to albumin, compound 1 displays more distinct monomer absorption characteristics (with the maximum absorption at 677 nm) than its free form. Compound 2 in albumin framework exists mostly in monomer form, which is beneficial to photodynamic therapy in aqueous solution. Both 2-BSA and 2-HSA show a sharp and intense Q-band at 681 nm and 682 nm with the molar extinction coefficient of 2.01 X 10(5) and 2.05 X 10(5) mol(-1) . L . cm(-1) respectively. The Q-band absorption spectra and existent state of phthalocyanine 1 or 2 in conjugates were not affected by the pH value of aqueous solution, which are obviously different from that of the corresponding free phthalocyanine.