Effects of gene carrier polyethyleneimines on the structure and binding capability of bovine serum albumin.

Polyethyleneimine (PEI), one of the most effective non-viral gene carriers, is also cytotoxic, however the molecular basis is poorly understood. Little is known about the effects of PEI on the structure and functions of the biomacromolecules. In this work, fluorescence, UV-vis absorption, circular dichroism (CD) spectroscopy and zeta-potential measurement were conducted to reveal the interaction between PEIs (average molecular weight 25, 10 and 1.8kDa) and bovine serum albumin (BSA), and to evaluate the effects on the conformation of BSA as long as its binding capability to the model compounds, 8-anilino-1-naphthalenesulfonic acid (ANS) and quercetin. PEIs were found to complex with BSA and induced a conformational change of the protein by a major reduction of α-helix at PEI concentration <0.2mg·mL-1 and an increase at higher PEI concentration. The binding efficacy of ANS and quercetin to BSA was greatly reduced by the competitive binding by PEI and influenced by the conformational change of BSA, which was found to display a similar trend to the change of the α-helix content of the protein. The polymer size played an important role in PEI-BSA interaction. PEI of higher molecular weight was more favorable to interact with BSA and more efficient to perturb the conformation and binding capability of the protein.