Preparation of different sized nano-silver loaded on functionalized graphene oxide with highly effective antibacterial properties.

Graphene oxide (GO) has attracted great interest in many different areas, as a delivery vehicle for antibacterial agents, and has shown high potential. Although silver nanoparticles (AgNPs) have a strong antibacterial effect, the biological application of AgNPs is often hindered by their aggregation and low stability. In this study, we developed an approach of polyoxyethylene bis(amine) (PEG) directed AgNPs grown on GO, then we combined the two materials to prepare a series of functionalized GO bearing different sized AgNPs, and studied the size effects of AgNPs on growth inhibition of Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). We evaluated the antibacterial effect of GO@PEG@AgNPs on E. coli and S. aureus by various methods such as minimum inhibitory concentration (MIC) experiment, cell wall/membrane integrity assay and scanning electron microscopy (SEM) characterisation of bacterial morphology. The GO@PEG@AgNPs composites exhibited markedly higher antibacterial efficacy than AgNPs alone. The smallest GO@PEG@AgNPs (10 nm) particularly demonstrated higher antibacterial activity than other sizes (30, 50, and 80 nm). We believe that these findings contribute to great potential application as a regulated graphene-based antibacterial solution.