Sequential Surface Functionalization by Polyoxometalates and Lysine Renders Non-toxic Gold Nanoparticles Strong Antibacterial Agents

H.K. Daima, P.R. Selvakannan, S.K. Bhargava, V. Bansal
RMIT University, AU

Keywords: gold nanoparticles, functionalization, antibacterial agents, polyoxometalates

Summary:

Gold nanoparticles (AuNPs)are considered as biocompatible and important component for biomedical applications. In current study, AuNPs were synthesised using tyrosine amino acid mediated reduction of gold ions. These nanoparticles were functionalised with two polyoxometalates (POMs) such as phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) which induce oxidative stress. Subsequently part of these POMs modified nanomaterials were functionalized with lysine which direct the nanoparticles to negatively charged bacterial cell and induce rupture of the bacterial cell membrane. Antibacterial activities were evaluated toward Gram negative bacteria Escherichia coli. AuNPs were not toxic to E. coli cells but after their functionalization with POMs they showed antibacterial activity and lysine modified gold-POMs nanoconjugates exhibited significant antibacterial activity. By varying the surface functionlization of non-toxic AuNPs with POMs and lysine, we have shown the different levels of antibacterial action and their mode of action. Major advantage of this approach is that very less requirement of the toxic material used for surface modification and the AuNPs act as carrier. UV vis, FTIR, XPS, Zeta potential, AAS, ICPMA, and TEM studies were carried out to characterize these AuNPs and their nanoconjugates. Nano SEM was used to reveal morphological changes in bacterial cells after treatments.