Polyphenol capping on gold nanosurface modulates human serum albumin fibrillation

Different small molecules and nanomaterials have been known as inhibitors of protein misfolding and subsequent fibrillation, which marks the initiation of various degenerative conditions. This work explores the effect of polyphenol capped gold nanoparticles on extent of human serum albumin fibrillation. Silymarin capped (SAuNPs), quercetin capped (QAuNPs) and gallic acid capped gold nanoparticles (GAuNPs) were synthesized in a uniform size range and their relative antioxidant capacity was determined through DPPH assay. The fibrillation of HSA at 65 °C was inhibited by ~15 % in presence of SAuNPs and the process was monitored through a combination of ThioflavinT fluorescence spectroscopy, circular dichroism spectroscopy and microscopic analysis. The inhibitory effect appeared much pronounced in case of QAuNPs (~67 %) and GAuNPs (~60 %). Using SDS PAGE analysis, we demonstrated that differential inhibitory activity of SAuNPs, QAuNPs, GAuNPs was attributed to the antioxidant potential of the individual nanoparticles. Our work revealed that apart from protein-nanoparticle surface interactions, antioxidant capacity has a role in determining the effectiveness of a protein fibrillation inhibitor. Cytotoxic analysis of protein-gold nanoparticles aggregates on HaCaT cell lines further confirmed that the nanoparticles were biosafe and can be considered as active therapeutics for translational use.