Z-scan optical method complements the Thioflavin T assay for investigation of anti-Alzheimer's impact of polyphenols.

Polyphenols are effective in eliminating amyloid-beta aggregations, the main hallmark of Alzheimer's disease. Various nano drugs and biomaterials based on polyphenolic compounds have been synthetized to treat or prevent Alzheimer's disease, and the main in-vitro approach to investigate the anti-Alzheimer's properties of materials, is the Thioflavin T assay. While useful it has drawbacks and in particular cannot always guarantee the accuracy of data, specifically in cases of polyphenolic compounds; thus, in this situation accurate results requires utilizing other assays along with Thioflavin T. In this experiment, we introduced the Z-scan technique as a complementary test for Thioflavin T assay. In this study, the anti-Alzheimer's properties of two polyphenols quercetin and fulvic acid were assessed in the presence and absences of silver nanoparticles at various concentrations, both via Z-scan technique and Thioflavin T assay, after which the two tests were aligned with each other. The polyphenols' non-linear refractive indices obtained by the Z-scan technique correlated well with their related fluorescence intensities from the Thioflavin T assay in such a way that, the smaller the magnitude of the non-linear refractive indices, the stronger the anti-amyloidogenic impact. Our work shows that Z-scan could be used along with Thioflavin T for enhanced investigation of polyphenols' anti-Alzheimer's properties.