title: Antibacterial activity and mechanism of Ag-ZnO nanocomposite on S. aureus and GFP-expressing antibiotic resistant E. coli.
abstract: Emergence of multi-resistant organisms (MROs) leads to ineffective treatment with the currently available medications which pose a great threat to public health and food technology sectors. In this regard, there is an urgent need to strengthen the present therapies or to look over for other potential alternatives like use of "metal nanocomposites". Thus, the present study focuses on synthesis of silver-zinc oxide (Ag-ZnO) nanocomposites which will have a broad-spectrum antibacterial activity against Gram-positive and Gram-negative bacteria. Ag-ZnO nanocomposites of varied molar ratios were synthesized by simple microwave assisted reactions in the absence of surfactants. The crystalline behavior, composition and morphological analysis of the prepared powders were evaluated by X-ray diffraction, infrared spectroscopy, field emission scanning electron microscopy (FE-SEM) and atomic absorption spectrophotometry (AAS). Particle size measurements were carried out by transmission electron microscopy (TEM). Staphylococcus aureus and recombinant green fluorescent protein (GFP) expressing antibiotic resistant Escherichia coli were selected as Gram-positive and Gram-negative model systems respectively and the bactericidal activity of Ag-ZnO nanocomposite was studied. The minimum inhibitory concentration (MIC) and minimum killing concentration (MKC) of the nanocomposite against the model systems were determined by visual turbidity analysis and optical density analysis. Qualitative and quantitative assessments of its antibacterial effects were performed by fluorescent microscopy, fluorescent spectroscopy and Gram staining measurements. Changes in cellular morphology were examined by atomic force microscopy (AFM), FE-SEM and TEM. Finally, on the basis of the present investigation and previously published reports, a plausible antibacterial mechanism of Ag-ZnO nanocomposites was proposed.
authors.affiliation: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India.
authors.forename: Ishita
authors.initials: I
authors.lastname: Matai
authors.affiliation: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India.
authors.forename: Abhay
authors.initials: A
authors.lastname: Sachdev
authors.affiliation: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India.
authors.forename: Poornima
authors.initials: P
authors.lastname: Dubey
authors.affiliation: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India.
authors.forename: S Uday
authors.initials: SU
authors.lastname: Kumar
authors.affiliation: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India.
authors.forename: Bharat
authors.initials: B
authors.lastname: Bhushan
authors.affiliation: Nanobiotechnology Laboratory, Centre for Nanotechnology, Indian Institute of Technology Roorkee, Roorkee, Uttarakhand 247667, India. Electronic address: pgopifnt@iitr.ernet.in.
authors.forename: P
authors.initials: P
authors.lastname: Gopinath
mesh_terms: D000900:Anti-Bacterial Agents / Q000494:pharmacology*; D001422:Bacterial Adhesion / Q000187:drug effects; D004247:DNA / Q000378:metabolism; D004352:Drug Resistance, Microbial / Q000187:drug effects*; D004926:Escherichia coli / Q000187:drug effects* / Q000648:ultrastructure; D049452:Green Fluorescent Proteins / Q000378:metabolism*; D007477:Ions; D008826:Microbial Sensitivity Tests; D053761:Nanocomposites / Q000737:chemistry* / Q000648:ultrastructure; D010316:Particle Size; D010957:Plasmids / Q000378:metabolism; D012834:Silver / Q000494:pharmacology*; D013050:Spectrometry, Fluorescence; D017550:Spectroscopy, Fourier Transform Infrared; D013211:Staphylococcus aureus / Q000187:drug effects* / Q000648:ultrastructure; D014961:X-Ray Diffraction
chemical_list: D000900:Anti-Bacterial Agents; D007477:Ions; D049452:Green Fluorescent Proteins; D012834:Silver; D004247:DNA
keywords: Antibacterial mechanism; Bactericidal; Multi-resistant organisms; Nanocomposites; Nanoparticles