Self-assembled Supra-Plate from Gold Nanoparticle with Zn(II) and 1H-pyrazole-3,5-dicarboxylic Acid for Antibacterial Studies.

Interactions of aromatic nitrogen and carboxylate group of 1H-pyrazole-3,5-dicarboxylic acid (PDC) with bivalent Zn(II) metal ions and gold nanoparticle (AuNP, average diameter ~16 nm) surface has been targeted in this current study. The time-dependent absorption and structural analysis experimentally demonstrate the combined role of PDC and metal ion towards the self-assembly of AuNP. The collective interaction in solution triggers self-assembly, which results in the synthesis of unique Au/Zn@PDC supra-plates at room temperature. The Zn(II) induced supra-plates have been further characterized by X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The selectivity of the self-assembly for supra-plate architectures has been verified with handful of other metal ions such as Mn(II), Fe(II), Co(II), Ni(II), Cu(II), Mg(II) and Pb(II). Among these studied metal ions, Pb(II) only provides the self-assembled supra-sphere formation under identical conditions. Pb(II) being a toxic metal ion, antibacterial properties have been explored for Au/Zn@PDC supra-plates with four significant human pathogens: Methicillin-resistant Staphylococcus aureus (MRSA) ATCC BAA-44, Methicillin-sensitive Staphylococcus aureus (MSSA) S18 (clinical isolate), Klebsiella pneumoniae ATCC BAA-1706, and Klebsiella pneumoniae MDR 36 (clinical isolate). Compared to the parent constituents, these bacterial cells experience greater damage to the cell wall, when treated with Au/Zn@PDC supra-plates with a minimum inhibitory concentration (MIC) of 0.2-0.8 ng/mL.