Influence of Spinacia oleracea leaf extract concentration on silver nanoparticle formation and evaluation of antimicrobial properties

Abstract

Plant mediated nanofabrication is a sustainable strategy for generating biocompatible nanomaterials with diverse industrial applications. Despite growing interest, there remain notable gaps in the understanding of the influence of plant extract concentration on the physiochemical properties of silver nanoparticles (AgNPs), particularly regarding their size. Conflicting reports suggest an increase in AgNP size with increased extract concentration, and others suggest the opposite. To address this, this study explores the influence of varying Spinacia oleracea (S. oleracea) leaf extract concentrations on the physiochemical properties of AgNPs and their antimicrobial activity against Gram negative (Escherichia coli), Gram positive (Staphylococcus aureus, Streptococcus pyogenes) bacteria and Fungi (Candida albicans). Hence, our investigation encompasses persistent infection-causing microorganisms currently plagued with drug resistance issues. This study's findings will enhance understanding of this sustainable nanofabrication approach, highlighting AgNP's potential application as novel antimicrobial agents. Results confirmed spherical nanoranged AgNPs were synthesised, obtaining AgNP-2%, AgNP-3%, AgNP-4%, AgNP-7%, and AgNP-10% v/v S. oleracea leaf extract. Our analysis revealed a consistent trend of size reduction with increasing extract concentration: AgNP-2% (173 nm), AgNP-3% (211 nm), AgNP-4% (148 nm), AgNP-7% (120 nm), and AgNP-10% (109 nm). Regarding antimicrobial activity, the lower concentration AgNPs (AgNP-2% and AgNP-3%) showed no activity, while all the higher concentrations AgNPs displayed full inhibition of all tested microbes. In summary, our research emphasises the significance of plant extract concentration in optimising AgNP synthesis and size reduction. The demonstrated antimicrobial properties suggest promising applications in industries such as environmental (water purification), biomedical (wound healing, drug delivery), and agricultural (pesticides, water remediation).