Facile fabrication of malonic acid capped silver nanoparticles and their antibacterial activity

Abstract

The successful management of infections caused by human pathogenic bacteria is becoming a challenge for clinicians. Therefore, new strategies to circumvent the growth of pathogens need to be developed. The current study was therefore aimed to synthesize silver nanoparticles (AgNPs) through chemical reduction process of silver nitrate by tri sodium citrate or sodium borohydride and evaluated their antibacterial activity. During the synthesis process, AgNPs were capped by malonic acid (a dicarboxylic acid). We have exploited two approaches of cold (reduction by NaBH4) and hot (reduction by trisodium citrate) process for the synthesis of AgNPs which revealed maximum absorbance of AgNPs at 412 nm and 397 nm respectively. The malonic acid (MA) functionalized AgNPs (AgNPs/MA) were systematically characterized for their size, surface changes and morphology. These colloidal AgNPs were stable and polydisperse in nature with an average diameter of 20 nm. The zeta potential (ZP) analysis showed stable AgNPs. The AgNPs synthesis was optimized in a set of different reactions where concentration of metal precursor, concentration of capping agent, temperature, time of stirring and duration of reaction were variable. The AgNPs/MA were found poly-dispersed in nature with predominantly spherical shape. The antibacterial potential of AgNPs was then assessed against both Gram positive (Staphylococcus aureus) and Gram negative bacteria (Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Klebsiella pneumoniae) by antimicrobial disc susceptibility assay with three replicates per treatment which showed promising antibacterial activity of AgNPs. The AgNPs/MA possessing remarkably smaller size exhibited encouraging antibacterial activity against human bacterial pathogens suggesting their potential application in controlling bacterial infections in clinical settings and can be utilized in further biomedical applications.

Keywords

• Silver nanoparticles
• Tri sodium citrate
• Sodium borohydride
• Malonic acid
• Capping