Investigation of amyloid formation inhibition of chemically and biogenically from Citrus aurantium L. blossoms and Rose damascena oils of gold nanoparticles: Toxicity evaluation in rat pheochromocytoma PC12 cells

Fibrillation inhibition effects of chemically and biogenically gold nanoparticles (GNPs) were investigated in vitro using human insulin as a model for fibrillation of protein. This inspection was followed using the Congo red assay, thioflavin T fluorescence measurements, transmission electron microscopy, and evaluation of cytotoxicity effects on rat pheochromocytoma PC12 cells. Biogenic GNPs were synthesized using oil extracts of Citrus aurantium L. blossoms and Rose damascena blossoms as reducing and concomitant agents. Congo red assay showed development of fibril formation of insulin at acidic media at 60 °C over a period of 48 h. In these circumstances, transmission electron micrographs confirmed the progress of fibril state from globular chains to amyloid. However, the results of ThT fluorescence measurements indicated a concentration-dependent inhibiting effect of chemically synthesized GNPs on insulin fibrillation in vitro, simultaneously by conversion of the formed fibrils into amorphous aggregates. Furthermore, biogenic GNPs were found to more effectively inhibit the fibril formation, compared to chemically synthesized GNPs. Accordingly, just 0.05 nmol L−1 of the biogenic GNPs showed similar inhibition property of chemically synthesized GNPs with a concentration of 10 nmol L−1. Both types of GNPs diminished toxicity of insulin fibrils in rat pheochromocytoma PC12 cells viability.