Inactivation of Foodborne Pathogens by NiO/TiO2 Composite Nanofibers: A Novel Biomaterial System

Abstract

This study presents the fabrication and characterization of novel NiO/TiO2 composite nanofibers and their antibacterial activity. The utilized NiO/TiO2 composite nanofibers were prepared by electrospinning of a sol–gel composed of nickel nitrate hexahydrate, titanium isopropoxide and poly(vinyl acetate). The obtained electrospun nanofiberous mat was vacuum dried at 80 °C and then calcined at 600 °C in air for 2 h. The physicochemical properties of the synthesized nanofibers were determined by X-ray diffraction pattern, field emission scanning electron microscopy, energy-dispersive X-ray spectroscopy, electron probe microanalysis and transmission electron microscopy. The antibacterial activity was tested against four common foodborne pathogenic bacteria viz., Staphylococcus aureus, Escherichia coli, Salmonella typhimurium and Klebsiella pneumoniae by minimum inhibitory concentration (MIC) method taking five different concentrations (5–45 μg/ml). Our investigation reveals that the lowest concentration of NiO/TiO2 composite solution inhibiting the growth of tested strains was found to be 5 μg/ml. TEM analysis demonstrated that the exposure of the selected microbial strains to the composite nanofibers led to disruption of cell membranes and depressed the activity of some membranous enzymes, which caused bacteria to die eventually. Furthermore, the results illustrate that the combination of NiO and TiO2 can be synergistic and resulted in superior antimicrobial activity of NiO/TiO2 composite nanofibers. To sum up, novel NiO/TiO2 composite nanofibers that possess large surface-to-volume ratio with excellent antimicrobial activity were fabricated that can be used to inhibit the microbial growth associated with food stuff.