The Interaction Between Cholesterol-Modified Amino-Pullulan Nanoparticles and Human Serum Albumin: Importance of Nanoparticle Positive Surface Charge

Abstract

To study the interaction of nanoparticles (NPs) and human serum albumin (HSA), we designed three different aminosubstituted hydrophobically cholesterol-modified pullulan NPs (CHPN NPs). Dynamic light scattering (DLS) revealed sizes of 145, 156, and 254 nm and zeta potentials of 0.835, 7.22, and 11.7 mV for CHPN1, CHPN2, and CHPN3 NPs, respectively. Isothermal titration calorimetry (ITC) revealed that the binding constants were (1.59±0.45)×105 M−1, (2.08±0.26)×104 M−1, and (2.71±0.92)×104 M−1, respectively, and HSA coverage was (1.52±0.12), (0.518±0.316), and (0.092±0.015). Fluorescence spectroscopy of HSA revealed that the fluorescence intensity was quenched by CHPN NPs, which was maintained with a long final complexation period. Circular dichroism (CD) revealed a quick decrease in the α-helix content of HSA to 39.1% after the final complexation. NPs with a more positive charge led to a greater decrease in α-helix content than occurred in other NPs, so the NP surface charge played a role in the HSA–NP interaction. After HSA binding, the surface charge was −3.66±0.12 for CHPN1, −2.65±0.06 for CHPN2 and −1.12±0.28 mV for CHPN3 NPs. The NP surface property changed because of HSA binding, which is important for NP applications.