Metal/polyoxometallate and metal/polyoxometallate/amino acid nanocomposites for surface charge dependant antibacterial activity

Tyrosine amino acid was used as a reducing and stabilizing agent to synthesise gold and silver nanoparticles. These gold and silver nanoparticles were functionalised with two polyoxometallates (POMs) namely phosphotungstic acid (PTA) and phosphomolybdic acid (PMA) to impart antibacterial properties on the nanoparticles surface. Further these nanoconjugates were modified with cationic amino acid lysine to enhance antibacterial effects. UV-vis, TEM, AAS, ICPMA and Zeta potential measurements were carried out to characterize these gold, silver nanoparticles and their respective nanoconjugates. The antibacterial effects of these nanomaterials with different metals composition, doses (concentrations) and surface functionalisation were evaluated by colony counting method. Escherichia coli was used as a model Gram negative microorganism. Antibacterial activity of these gold or silver nanoparticles and their respective nanoconjugates were found to be dependent on the concentration of dose, metal composition and their functionalisation. Silver nanoparticles and nanoconjugates were found to have more antibacterial activity compare to gold nanoparticles and nanoconjugates. The increasing amount of the doses enhanced bactericidal action. Short incubation time (15-20 minutes) was sufficient to exhibit antibacterial activity. Lysine amino acid modified nanoconjugates exhibited excellent antibacterial activity. Application of these materials can be further expanded towards anticancer applications by non-specific or selective targeting of these materials towards cancer cells