Spectroscopic studies of the interaction between tetra-substituted aluminum phthalocyanines and bovine serum albumin

Abstract

Serum albumin, the most abundant plasma protein in mammalian blood, shows significant effects on delivery and therapeutic efficacy of drugs, therefore, the investigation of binding interaction between serum albumin and drugs is vital and necessary. In the present study, the binding interaction of two aluminum (III) phthalocyanine (AlPc) derivatives, tetrasulfonate-and tetra-(p-sulfoazophenyl-4-aminosulfonyl)-substituted AlPc (complexes 1 and 2), with bovine serum albumin (BSA) was investigated by UV-Vis and fluorescence spectroscopy. Adding BSA to the Pc complexes in water caused remarkable changes in the Q-band of the Pc complexes, indicating an altered aggregation behavior. When titrating these AlPcs with BSA in PBS, the intrinsic fluorescence of BSA was significantly quenched through a static quenching process. The binding of Pc complexes to BSA might change its conformation, evidenced by the red shift of maximum emission wavelength. Furthermore, binding constants and binding sites were obtained and binding ability between the Pc complexes and BSA was assessed. Our results suggest that complexes 1 and 2 readily interact with BSA whereas the latter shows more affinity (with higher binding constant value) to BSA, implying the stretched amphiphilic substituents of complex 2 may contribute to their transportation in the blood.

Spectroscopic analysis of the interaction between tetra-(p-sulfoazophenyl-4-aminosulfonyl)-substituted aluminum (III) phthalocyanines and serum albumins

“…In the present study, the Stern-Volmer equation was used to elucidate the mechanism of°uorescence quenching of the BSA and HSA in the presence of di®erent concentration of AlPc as previously reported. 5 For BSA, as shown in the inset of Fig. 3(a), with the increase in AlPc concentration (from 0 to 1:0 Â 10 À5 mol/L), the K sv was determined to be 3:38 Â 10 5 M À1 , which was 1.53 times over that for HSA (2:21 Â 10 5 M À1 , inset of Fig.…”

“…5 The concentration of BSA and HSA was 1:0 Â 10 À5 mol/L, while the concentration of AlPc complex ranged from 0 to 1:2 Â 10 À5 mol/L.…”

“…PDT treatment evolved utilizing an appropriate light wavelength to excite the injected photosensitizers which accumulated in tumor issue and then generates singlet oxygen or/and other reactive oxygen species (ROS). 4,5 Photosensitizers, light, and oxygen are three basic components. Although many photosensitizers have been reported for their potential of application in PDT, such as photofrin, hematoporphyrin derivatives, 5-aminolevulinic acid (ALA) and silicon phthalocyanine (Pc4), [6][7][8] so far there are only a few photosensitizers under clinical applications.…”

“…5,9,10 Pcs have been used in many¯elds including the PDT applications. 9 In PDT applications, photosensitizers are injected directly into the patients' blood vessel, so it is important to investigate the interaction between the photosensitizers and blood proteins.…”

“…The°uorescence of tryptophan residue is sensitive to the surrounding microenvironment, hence it has been a powerful tool to investigate small molecule-or nanoparticle-BSA/ HSA interactions. 5,[12][13][14][15] The solubility of Pcs plays an essential role in their applications, so di®erent kinds of methods have been used to modulate their solubility. Therefore, many substituted Pcs have been synthesized.…”