SYNTHESIS OF VARIOUS NANOCOMPOSITES AND STUDY OF THEIR BIOMEDICAL APPLICATIONS

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 such as use of "metal nanocomposites" and "herbal drug loaded polymeric nanofibers". 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 energy dispersive X-ray (EDX) analysis. Particle size measurements were carried out by transmission electron microscopy (TEM). Staphylococcus aureus (S. aureus) and recombinant green fluorescent protein (GFP) expressing antibiotic resistant Escherichia coil (E. coil) were selected as Gram-positive and Gram-negative 11 model systems respectively and the bactericidal activity of Ag-ZnO nanocomposite were 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. Excellent bactericidal activity at low concentrations of nanocomposites was observed in both A the bacterial model systems suggesting its potential application as a broad-spectrum antibacterial agent. 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. Also, electrospinning technique was utilized to fabricate chitosan-PEO (Polyethylene oxide) nanofibers loaded with herbal drug. The morphology, homogeneity and diameter of the synthesized nanofibers were determined by FE-SEM analysis. Visual turbidity analysis and fluorescence microscopy were done to determine the MIC and MKC values of herbal drug. Further, the antibacterial activity of drug loaded nanofibers was determined by fluorescence microscopy against GFP E.coii. The fabricated nanofibers exhibited good antibacterial activity at low concentrations of herbal drug suggesting its implications in wound dressings.