Silver nanoparticles: characterization and antibacterial properties

In this study, two aqueous suspensions of silver nanoparticles, nano silver powder (Sigma Ag-NPs) and nano silver ink (Ink Ag-NPs), were characterized for studying their antibacterial activity. The X-ray diffraction (XRD) and high resolution transmission electron microscopy (HRTEM) were used to determine the crystal structure, shape and size of Ag-NPs. The bactericidal effects of these nanoparticles were investigated against gram positive and gram negative bacteria at two different concentrations, 10 and 50 mu g/disc, by the disk diffusion method using Mueller-Hinton Agar to display good microbial culture growth. Antibacterial experiments results revealed that Escherichia coli (ATCC25922) and Bacillus subtilis (ATCC6633) inhibited by Ink Ag-NPs more than Sigma Ag-NPs. Both Salmonella typhimurium (ATCC14028) and Staphylococcus aureus (ATCC25923) were resistant to both sources of Ag-NPs, while Pseudomonas aeruginosa (ATCC27853) was resistant to Ink Ag-NPs and inhibited by Sigma Ag-NPs. This experiment showed that characteristics and suspension stability of Ag-NPs affect its antibacterial activity against some pathogenic bacterial strains.