Heteroassociation of antitumor agent doxorubicin with bovine serum albumin in the presence of gold nanoparticles

Optical density spectra were obtained for aqueous solutions of doxorubicin (DOX) antitumor agent and bovine serum albumin (BSA) with different concentrations, as well as upon addition of insignificant amount of gold nanoparticles (AuNPs, C-AuNPs = 0.658 x 10(-10) M) to them. For the region of optical density saturation at the maximum of the DOX optical absorption band (lambda(max) = 481 nm) for C-DOX/C-BSA = 0.46, the concentration of complexes equal to 1.09 x 10(-5) M at the concentration of free molecules of DOX [D] = 1.72 x 10(-4) M and BSA [B] = 7.79 x 10(-5) M was determined. The use of the isomolar series method shows that the structure of the complexes corresponds to a ratio of 2:1, in accordance with the DOX and BSA molecules at an equilibrium binding constant K = 4.79 x 10(6) M-1. The addition of AuNPs does not affect the stoichiometry of complexes, but significantly changes their formation dynamics. Thus, in the presence of AuNPs, the concentration of DOX-BSA-AuNPs heteroassociates increases significantly due to the adsorption of DOX on AuNPs and the high ability of BSA to bind to AuNPs, and the equilibrium binding constant decreases to K = 2.99 x 10(6) M-1. (C) 2019 Elsevier B.V. All rights reserved.