Plasmid DNA linearization in the antibacterial action of a new fluorescent Ag nanoparticle–paracetamol dimer composite

Abstract

Herein, we report the generation of a composite comprised of p-hydroxyacetanilide dimer and Ag nanoparticles (NPs) by reaction of AgNO₃ and ρ-hydroxyacetanilide. The formation of the composite was established by UV-vis, FTIR and NMR spectroscopy, transmission electron microscopy and X-ray diffraction along with substantiation by mass spectrometry. Interestingly, the composite exhibited an emission spectrum with a peak at 435 nm when excited by light of wavelength 320 nm. The composite showed superior antimicrobial activity with respect to its individual components against a wide range of Gram positive and Gram negative bacteria at relatively low concentrations of Ag NPs and at which there was no apparent cytotoxicity against mammalian cells. Our results suggest that the composite strongly interacted with the bacterial cell walls leading to cell bursting. Interestingly, enhancement in the reactive oxygen species (ROS) generation in bacteria was observed in the presence of the composite. It is proposed that the ROS generation led to oxidation of the dimer to N-acetyl-ρ-benzoquinone imine (NAPQI). The generated NAPQI acted as a DNA gyrase inhibitor causing cell death following linearization of DNA.