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

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 mu M 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.