Synthesis and characterization of biocompatible gymnemic acid–gold nanoparticles: a study on glucose uptake stimulatory effect in 3T3-L1 adipocytes

Abstract

Biosynthesized gold nanoparticles using gymnemic acid (GA), a secondary metabolite of Gymnema sylvestre, are studied. The gymnemic acid reduced gold nanoparticles (GA–AuNPs) were primarily confirmed from the colour change and UV absorption. The reducing potential of GA was computed and free GA was quantified after the biosynthesis of GA–AuNPs using HPLC. The size, charge, shape, crystalline nature and functional groups of GA–AuNPs were studied by TEM, DLS, XRD and FT-IR analysis respectively. The stability of GA–AuNPs in various physiological buffers and pH was examined. The cytotoxicity of GA–AuNPs and the comparative glucose utilization effect of GA and GA–AuNPs were analysed. The GA–AuNPs appeared ruby red in colour and showed UV absorption at 540 nm. The reducing efficiency of GA was found to be 98%. The complete utilization of GA (100%) after the biosynthesis of GA–AuNPs was observed in the HPLC chromatogram. The GA–AuNPs displayed a spherical morphology under TEM analysis. The DLS analysis of GA–AuNPs revealed an average size of 62.93 nm and a zeta potential of −14.9 mV. The XRD data confirmed the nature of GA–AuNPs to be face centered cubic (fcc) crystals and their stability was identified from the FT-IR spectra. The GA–AuNPs showed remarkable stability in the various media and displayed 56.67% cell viability at 1000 μM concentration in 3T3-L1 adipocytes. The adipocytes treated with GA and GA–AuNPs displayed a minimal and a dose-dependent rise in glucose uptake respectively, demonstrating enhanced bioavailability mediated glucose utilization. The study suggests that GA–AuNPs might serve as an effective plant-based oral formulation for the treatment of hyperglycemia.