An insight into the comparative binding affinities of chlorogenic acid functionalized gold and silver nanoparticles with ctDNA along with its cytotoxicity analysis

Abstract

The binding mechanism of natural drugs and its functionalized metal nanoparticles with DNA have prime importance in the field of nano-toxicology and nano-medicine. The focus of this study was to describe the comparative binding efficiency, structural conformation, mode of binding and thermodynamic parameters due to the complex formation of chlorogenic acid (CHA) capped gold (CA-AuNPs) and silver (CA-AgNPs) nanoparticles with ctDNA, using a series of biophysical analysis. The gold and silver nanoparticles were successfully synthesized by CHA as both capping and reducing agent. The CA-AuNPs and CA-AgNPs were characterized by UV–Visible spectroscopy, XRD, FTIR, DLS and HR-TEM analysis confirmed the formation of stable AuNPs and AgNPs with an average size of 37 and 20 nm respectively. The strength and mode of interaction of CHA functionalized metal nanoparticles with ctDNA were evaluated on the basis of binding parameters extracted from UV–visible absorption, dye displacement fluorescence studies and ITC. The conformational alterations of ctDNA double helix due to its complexation with CA-AgNPs and CA-AuNPs were monitored by Circular dichroism and Fourier transform infrared spectroscopy. The thermodynamic parameters obtained from ITC established the stabilizing forces responsible for the exothermic binding processes. The binding constants obtained from the spectroscopic and calorimetric studies consistently explained the strong binding efficiency of CA-AgNPs than CA-AuNPs with ctDNA. The DNA detection efficiency of CA-AgNPs was comparatively higher than that of CA-AuNPs executed by LOD and colorimetric alterations. The MTT assay on normal human cell lines revealed that CA-AuNPs exhibited mild dose-response suppression on normal human cell lines when compared with CA-AgNPs. These results based on DNA nanoparticles binding mechanism will help for the designing and synthesis of new CHA functionalized nanoparticles possessing better sensing and therapeutic efficacy with minimal side effects.