[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 - 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.

[Influence of albumin on the spectroscopic properties and existence state of mono-substituted phthalocyanine zinc (II)].

Interaction between 1-[4-(2-carboxyl-ethyl-)phenoxy] phthalocyanine Zinc(II) (ZnPcC1) and albumin (human serum albumin or bovine serum albumin) was studied. ZnPcC1 can be covalently bound to albumin through amide bond formation. The molar ratios of ZnPcC1 to albumins are found to be about 7 : 1 in the covalent bioconjugates. On the other hand, there are strong non-covalent interactions between ZnPcC1 and albumins with a binding constant of ca. 1.0 x 10(5) mol(-1) x L. Binding sites competition experiments suggest that the binding site locates in subdomain I B of human serum albumin. When conjugated to albumin, no matter covalent conjugation or non-covalent conjugation, the ZnPcC1 exhibit more distinctive characteristic monomer absorption than the free ZnPcC1, which is a property beneficial to photodynamic therapy. Covalent conjugation results in the Q-band of ZnPcC1 red-shifting about 5 nm, whereas non-covalent conjugation does not lead to red-shift.