Interaction of food-grade titanium dioxide nanoparticles with pepsin in simulated gastric fluid

With the wide applications of food-grade nanoparticles (NPs) in foods, increasing attention has been focused on the fate of NPs in the gastrointestinal tract. In this study, titanium dioxide nanoparticles (TiO2-NPs) were used as model NPs with the aim to investigate the interaction between NPs and pepsin in simulated gastric fluid. Transmission electron microscopy revealed the possible formation of protein corona, mainly soft corona, between TiO2-NPs and pepsin. With the increase in the TiO2-NP concentration from 0.01 to 0.05, 0.1, and 0.2 mg/mL, the fluorescence of pepsin was quenched, and its ultraviolet-visible intensity was weakened. Results indicated that TiO2-NPs can react with pepsin, leading to changes in the microenvironment of aromatic amino acids and a decrease in the hydrophobicity around tyrosine residues. Circular dichroism spectrum revealed that TiO2-NPs do not exert clear changes to the secondary structure of pepsin. However, the pepsin activity decreased within the measured concentration range.