Does Surface Chirality of Gold Nanoparticles Affect Fibrillation of HSA?

In order to demonstrate the influence of the surface chirality of the nanoparticles on amyloid fibrillation, the inhibiting effectiveness of the chiral gold nanoparticles, synthesized using the two enantiomeric forms (i.e., d - and l -) of glutamic acid, toward the fibrillation of human serum albumin (HSA) has been investigated. Here the enantiomers of glutamic acid are used as both reducing and stabilizing/capping agents. It is found that the surface chirality is the only major difference between the d -glutamic acid mediated gold (DGAu) and l -glutamic acid mediated gold (LGAu) nanoparticles. The fibrillation process has been monitored using various biophysical techniques, e.g., turbidity assay, Thioflavin T fluorescence kinetics, Congo red binding study, circular dichroism spectroscopy, fluorescence microscopy, and transmission electron microscopy. The experimental results illustrate that DGAu is more effective in inhibiting the formation of HSA fibrils than LGAu. Furthermore, the differential inhibiting effect of DGAu and LGAu toward HSA fibrillation has been described on the basis of the dissimilar interaction behavior of the nanoparticles with the HSA molecules, as revealed by the Trp fluorescence quenching, and the isothermal titration calorimetry. It is suggested that the surface chirality of the gold nanoparticles strongly influences the protein adsorption dynamics including the modes of orientation of adsorbed HSA molecules, causing the inhibition of fibrillation to different extents.