Amorphous aggregation of tau in the presence of titanium dioxide nanoparticles: biophysical, computational, and cellular studies

BACKGROUND: Nanoparticles (NPs) when injected into the body can reach target tissues like nervous system and interact with tau proteins and neurons. This can trigger conformational changes of tau and may affect NP toxicity. METHODS: In this study, we used several biophysical techniques (extrinsic and intrinsic fluorescence spectroscopy, circular dichroism (CD) spectroscopy, ultraviolet (UV)-visible spectroscopy), transmission electron microscopy (TEM) investigations, molecular docking and molecular dynamics studies, and cellular assays [3-(4,5-Dimethylthiazol-2-Yl)-2,5-Diphenyltetrazolium Bromide (MTT) and flow cytometry) to reveal how structural changes of tau protein can change the cytotoxicity of titanium dioxide (TiO(2)) NPs against neuron-like cells (SH-SY5Y) cells. RESULTS: It was shown that TiO(2) NPs result in hydrophilic interactions, secondary and tertiary structural changes, and the formation of amorphous tau aggregates. Conformational changes of tau increased the induced cytotoxicity by TiO(2) NPs. These data revealed that the denatured adsorbed protein on the NP surface may enhance NP cytotoxicity. CONCLUSION: Therefore, this study provides useful insights on the NP–protein interactions and discusses how the protein corona can increase cytotoxicity to determine the efficacy of targeted delivery of nanosystems.