Polyethylenimine-Modified Graphene Oxide as a Novel Antibacterial Agent and Its Synergistic Effect with Daptomycin for Methicillin-Resistant <i>Staphylococcus aureus</i>

An aqueous dispersion of polyethylenimine-modified graphene oxide (PEI-GO) was prepared via a one-step synthesis through an epoxy ring-opening reaction. PEI-GO exhibited bacterial growth inhibition activity on methicillin-resistant <i>Staphylococcus aureus</i> (MRSA) with a minimum inhibitory concentration as low as 8 μg mL^–1. Time–kill curve assay and SYTOX Green assay showed the antibacterial activity and bacteria cell membrane permeability of PEI-GO, respectively. Most importantly, when PEI-GO was employed at 1–2 μg mL^–1, a synergistic effect with daptomycin to resensitize daptomycin-resistant MRSA was revealed. A synergistic effect between PEI-GO and daptomycin provides a possible way to increase bacterial killing and reduce the development of daptomycin resistance. The antibacterial activity of PEI-GO is attributed to the damaged cell membrane caused by the sharp edge and chain structure of the PEI-GO nanosheets as well as the high density of amine groups present in the PEI chains. Our results indicate that PEI-GO dispersion has a great potential for clinical pathogenic bacteria treatment