Surface functionality driven antimicrobial activity: Case study of amino acid reduced nanoparticles with different bacterial strains

Size and shape-controlled synthesis of metal and metal alloy nanoparticles has gained significant attention due to unique physico-chemical properties imparted in these nanomaterials. Most of these synthesis routes have thus far explored use of noxious chemicals such as borohydride etc for their synthesis. With the increasing focus on more eco-friendly routes towards nanomaterials synthesis, we demonstrate that metal (Au, Ag) and metal alloy (Au/Ag) nanoparticles with controlled composition can be synthesized using amino acids such as tyrosine and tryptophan. The formation of sub-10 nm metal and metal alloy nanoparticles, surface charge and their composition were confirmed by UV-Vis, TEM, zeta potential and AAS measurements. Our investigations further explored the utility of amino acids-reduced metal alloy nanoparticles for antimicrobial applications against Gram positive (e.g. Staphylococcus aureus) and Gram negative (Escherichia coli) bacteria. Our studies confirm that by controlling the surface charge and composition of bimetallic nanoparticles using amino acids, a control over specificity towards a particular group of bacteria (Gram positive vs Gram negative) can be achieved. We are currently exploring the mechanism for the specific mode of action for the bimetallic nanoparticles.