SYNTHESIS AND CHARACTERIZATION OF TERNARY NANOCOMPOSITES FOR ANTIBACTERIAL ACTIVITY

Abstract

Metal and metal oxide based nanocomposites provide an alternative approach for the development of novel antimicrobial agents. Magnesium oxide nanoparticles are stable, biocompatible and good antimicrobial agents due to their basicity and generation of reactive oxygen species. Silver nanoparticles possess significant antimicrobial activity towards drugresistant bacteria. Aluminium oxide can act as a template for MgO and Ag nanoparticles and thus can provide their sustained release. In the present study, MgO-Al2O3-Ag ternary nanocomposites with varied compositions were synthesized by two different chemical methods; sol-gel and thermal decomposition methods. The as prepared products, obtained from both sol-gel and thermal decomposition methods, were calcined at 500 °C and 300 °C, respectively, to obtain the nanocomposites. The synthesized nanocomposites were characterized by various analytical techniques including X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), thermo-gravimetric analysis (TGA) and diffuse reflectance spectroscopy (DRS). The XRD patterns of nanocomposites show peaks due to MgO, Al2O3 and Ag, indicating the presence of these phases in the nanocomposites. The DRS spectra of nanocomposites, indicate the presence of surface plasmon resonance due to Ag nanoparticles. Morphological analysis and elemental composition of the prepared samples was evaluated using field emission scanning electron microscopy (FE-SEM) and energy dispersive X-ray (EDX) analysis. Transmission electron microscopy (TEM) was performed to measure the particle size in the nanocomposites. The ternary MgO-Al2O3-Ag nanocomposite, synthesized by sol-gel method, was explored as antibacterial agent against Escherichia coli (E. coli), a gram-negative rod shaped bacterium and Staphylococcus aureus (S. aureus), a gram-positive spherical shaped bacterium. II Minimum inhibitory concentration (MIC) of the nanocomposite against these bacterial model systems was evaluated by visual turbidity assay, optical density analysis and disc diffusion method. At very low concentration of the MgO-Al2O3-Ag nanocomposite [MgO:Al2O3:Ag(10:10:5)], good antibacterial activity against both the model systems was observed, suggesting its potential as a wide-range antibacterial agent. Morphological and structural changes in the bacterial cells were observed by atomic force microscopy (AFM), FESEM and TEM studies. The antibacterial activity of the ternary MgO-Al2O3-Ag nanocomposite was also compared with that of binary MgO-Al2O3. The binary nanocomposite shows very less antibacterial activity at the MIC value of the ternary nanocomposite. This indicates the synergistic action of MgO and Ag nanoparticles present in the ternary nanocomposite. The synthesized ternary nanocomposite can be used as an effective antibacterial agent in pharmaceutical, industrial and biomedical field to control microbial infection.