INHIBITION OF ISLET AMYLOID POLYPEPTIDE FIBRILLATION BY OKRA SEED EXTRACT-COATED GOLD-NANOPARTICLES

In recent work, an ethanolic extract of okra seeds was successfully conjugated onto gold nanoparticles (AuNPs) via a reduction reaction that has been developed by our laboratory. Because of eliciting antioxidant activity and the presence of g-sitosterol in the extract, such synthesis methodology could be applied. The resulting okra-AuNPs were physically characterized by different methods, including dynamic light scattering (DLS), Zeta potential measurement, UV-Visible spectrophotometry, Transmission Electron Microscopy (TEM), Helium Ion Microscopy (HIM), and Fourier Transform Infrared (FTIR) spectroscopy. The other two biological characterization techniques, such as thioflavin assay and cell viability test, were also performed. Results indicated that the okra-AuNPs were spherical with a mean diameter of around 35.6 nm. A maximum absorption wavelength (l_max) was at 521 nm. A zeta potential was determined to be around -59.2 ± 2.9 mV. Binding between the okra-AuNPs and islet amyloid polypeptide (IAPP) was observed, resulting in IAPP aggregation and reduction of β-sheet contents of the aggregated polypeptides. It seemed that the okra-AuNPs exhibited cytoprotective activity on pancreatic beta cells by inhibiting IAPP fibrillation. Therefore, the okra-AuNPs would be useful as a delivery system for diseases associating with IAPP assembly and amyloid formation.