A Systematic Study of the Interaction Mechanism between Bovine Serum Albumin and Tio2 Nanoparticles with Various Shapes, Surface Charges, and Hydrophobicity Properties

Abstract

The mechanism of interaction between titanium dioxide (TiO2) nanoparticles with varying structures, surface charges, hydrophobic characteristics and bovine serum albumin (BSA) was explored using a variety of spectroscopic methods and molecular docking simulations. Ultraviolet-visible spectroscopy showed that when BSA was in contact  with TiO2, the absorption peak intensity rose, indicating that TiO2 nanoparticles affected the solvent environment of BSA and exposed BSA aromatic chromogenic groups. The fluorescence spectra results revealed a direct contact between TiO2 nanoparticles and the amino acid residues of BSA in nanoscale distances, the dissociation constants for four different type of TiO2 nanoparticles with BSA were 0.01±0.060, 0.31±0.086, 0.42±0.066 and 0.52±0.270, respectively. Synchronous fluorescence, circular dichroism, and Fourier transform-infrared (FTIR) spectroscopy studies indicated that spherical TiO2 and rod-shaped TiO2 almost had no effect on BSA conformation. Surface positively charged TiO2 of 0.04 and 0.08 mM raised the α-helix content of BSA from 56.08% to 56.19% and 57.27%, respectively; whereas surface hydrophobic modified TiO2 increased content to 60.46% and 62%, respectively. FTIR spectroscopy demonstrates that at greater concentrations of TiO2 nanoparticles and BSA, positive charged and hydrophobic modified TiO2 can enhance the α-helix content of BSA to 69.89% and 77.18%, respectively. The molecular docking results showed that the binding energy of anatase TiO2 and BSA was -0.3 kJ mol-1 while hydroxyl-anatase TiO2 and BSA was -0.54 kJ mol-1. Both experimental evidence and theoretical simulations indicate that the morphology of TiO2 nanoparticles impacts their binding force with BSA and hydroxyl groups play an essential role in the binding process. For positively charged TiO2, it may cause a small perturbation of the BSA structure. Additionally, hydrophilic TiO2 also has a small effect on the conformation of BSA, and this effect can be amplified by increasing the hydrophobicity of TiO2.

Keywords: TiO2, surface modification, BSA, hydroxyl groups, Hydrophobicity, conformational influence