Preparation of self-assembled platinum nanoclusters to combat Salmonella typhi infection and inhibit biofilm formation

In this work, phytoprotein functionalized platinum nanoparticles (PtNCs) were synthesized using the proteins from fresh green spinach leaves. Transmission electron microscopy showed that PtNCs were spherical shape with size ∼5 nm, which self assembled into spherical platinum nanoclustures (PtNCs) with size within the range of 100–250 nm. The presence of elemental platinum was confirmed by EDX analysis. FTIR studies confirm that the PtNCs were stabilized by the protein. As prepared PtNCs inhibits the growth of the food borne pathogen, Salmonella typhi with minimum inhibitory concentration (MIC) of 12.5 μM. Light microscopy evidenced that the PtNCs can damage the established biofilms. Antibacterial mechanistic study revealed that PtNCs damages the S. typhi membranes, which was confirmed by scanning electron microscopy and further by fluorescence microscopy using acridine orange/propidium iodide dual staining assay. Besides membrane damage, PtNCs also triggered the intracellular ROS-mediated oxidative damage over the antioxidant defense and kills S. typhi. The hemolytic test showed low cytotoxicity of PtNCs at 100 μM (four times higher the MIC). Finally, the therapeutic efficacy of PtNCs was validated in S. typhi infected zebrafish animal model and the obtained results are discussed.