Green synthesis of copper nanoparticles using aqueous extracts from Hyptis suaveolens (L.)

Abstract

Copper nanoparticles (CuNPs) with antimicrobial and cytotoxic properties were obtained using extracts from Hyptis suaveolens (L.) commonly called wild tulsi. Green synthesis using plant extracts is a preferred means to obtain nanoparticles because of the simplicity, efficiency, and clean process. Plant extracts contain phytochemicals that provide microbial and other medical properties to the nanoparticles. In this study, Hyptis suaveolens (L.) was treated in water and the extracts obtained were used to synthesize copper nanoparticles. Transmission electron microscopy (TEM) images showed that the synthesized copper nanoparticles are spherical in shape with an average diameter of 7.2 nm. X-ray diffraction (XRD) and selected area electron diffraction (SAED) analysis showed that the particles were mostly of copper 92% and about 8% of oxygen indicating partial conversion of the copper sulphate into copper oxide. Plasmonic absorbance also indicated that the nanoparticles were predominantly made of copper. The nanoparticles showed excellent antimicrobial activity against bacteria and fungi in the lowest concentration tested. Both wild tulsi extract (WTE) and wild tulsi nanoparticle (WTN) were non-toxic on NIH 3T3 cells at lower concentrations tested, however, WTN showed cytotoxicity at higher concentrations and with extended incubation times.