Investigation of the Effects of Zinc Oxide Nanoparticles on Membrane Damage of Human Neuroblastoma Cell Lineage (SH-SY5Y) and Change of Tau Protein Structure by Spectroscopic Methods

The use of nanoparticles in biological applications and cancer treatment has increased dramatically in the recent decade. Metal oxides of nanoparticles are among the most significant nanoparticles. Due to its suitable physical and chemical properties, zinc oxide is utilized in various fields, especially biomedicine and cancer treatment. This has raised a great deal of concern about the effects of nanoparticles on the body's biomolecules. The current study was set out to investigate zinc oxide nanoparticle's effects on neuroblastoma cells and their interaction with Tau protein. MTT and LDH tests were performed according to the instructions to evaluate the toxicity of zinc oxide nanoparticles on human neuroblastoma cells. Afterward, UV spectroscopy, CD spectroscopy, and fluorescence spectroscopy were performed according to the guidelines to investigate the interaction of zinc oxide nanoparticles with Tau protein. The results of the MTT assay showed a decrease in the survival rate of human neuroblastoma cells in a dose-dependent manner. The results of the Lactate dehydrogenase evaluation indicated an increase in LDH enzyme leakage from human neuroblastoma cells. Furthermore, zinc oxide nanoparticles form complexes with Tau-P through spontaneous and electrostatic interactions. The interaction of zinc oxide nanoparticles with Tau-P caused the accumulation of this protein and showed a significant change in the Tau-P structure. CD spectroscopy results showed that zinc oxide nanoparticles changed the α-helix and β-sheet structure of the Tau protein. Besides, the results of the Stern-Volmer equation revealed that the type of interaction of zinc nanoparticles with Tau-P is static quenching interaction. In summary, these results demonstrated the safety aspect of zinc oxide nanoparticles in proteins and natural cells and their biological applications, which emphasizes further investigation on zinc oxide nanoparticles usage. Zinc oxide nanoparticles can manipulate the structure of Tau-P that can lead to Alzheimer's disease. Consequently, more studies on the use of zinc oxide nanoparticles are required.