Novel Synthesis of Maltol Capped Copper Nanoparticles and Their Synergistic Antibacterial Activity with Antibiotics

This study is the first-ever reported synthesis of maltol capped copper nanoparticles (McCuNPs) using maltol as a capping agent by chemical reduction scheme. Suitable surface plasmon resonance (SPR) band was achieved by optimizing parameters such as variable concentrations of copper sulfate, maltol, and sodium borohydride. McCuNPs were characterized by visible spectroscopy, Fourier transform infrared (FTIR) spectroscopy, atomic force microscopy (AFM), and dynamic light scattering (DLS) techniques. Results revealed that the black-colored McCuNPs exhibited surface plasmon resonance band at 576 nm, and –OH, C–O, and C = O functional groups took part in the reduction of Cu+2 to Cu0. Synthesized McCuNPs were found to be monodispersed and spherical in shaped, with an average size of 50 nm (size range of 50–60 nm). Moreover, McCuNPs remained stable at 4 °C in an aqueous phase for 1 week in a tightly capped vial. The antimicrobial activity of McCuNPs (alone) and in combination with ciprofloxacin⋅HCl (Cip⋅HCl) and streptomycin sulfate (STR⋅SO4) was also investigated against clinical isolates of pathogenic bacterial strains by disc diffusion method. The McCuNPs alone showed zone of inhibitions against all tested strains, whereas its combination with Cip⋅HCl and STR⋅SO4 showed enhanced synergistic effect. However, Cip⋅HCl adsorbed McCuNPs revealed improved inhibition as compared to STR⋅SO4 adsorbed McCuNPs due to its active mode of action against these bacteria.