Spectroscopic study on interaction of Nymphaea nouchali leaf extract mediated bactericidal gold nanoparticles with human serum albumin

We have reported the eco-friendly gold nanoparticles (AuNPs) from 15% aqueous leaf extract of therapeutic plant Nymphaea nouchali where leaf extract acts as both reducing and stabilizing agents. The generation of AuNPs was confirmed by UV-visible spectroscopy, FTIR, FE-SEM, DLS, and the size and morphology were further confirmed via TEM analysis (average d = 54.7 nm). The existence of gold signal in EDX spectrum and measurement of zeta potential reveals a negative value (-21.7 mV) clearly indicates its stability. This synthesized AuNPs shows strong in vitro bactericidal effect against E. coli (DH5-Alpha) with 0.12 nM minimum inhibitory concentration, suggests its progress in therapeutic efficacy. The interaction of this AuNPs with human serum albumin (HSA) was investigated by UV-visible, FTIR, fluorescence, circular dichroism spectroscopies and zeta potential evaluation at 25 degrees C. It has been observed that the interaction mechanism is a static quenching process with the slightest change in the HSA secondary conformation because of HSA-AuNPs conjugate formation, but the primary structure remains unaffected. Negative free energy change indicates, the HSA-AuNPs formation is a thermodynamically favourable process. This analysis may offer a valuable information on the healthier antibacterial AuNPs synthesized from a medicinal plant extract. (C) 2018 Elsevier B.V. All rights reserved.