Synergistic Antimicrobial Capability of Magnetically Oriented Graphene Oxide Conjugated with Gold Nanoclusters

Bacterial resistance toward antibiotics has been a worldwide threat; one way to fight against the resistance is to develop a multimechanism antibacterial agent to achieve synergistic performance. Graphene oxide (GO) is an emerging antibacterial agent combining multiple mechanisms (physical insertion and chemical disruption), and its rich functional groups enable the complexation/conjugation of nanomaterials to further improve antibacterial performance. Herein, a synergistic antimicrobial agent is established through the assembly of paramagnetic holmium ions and gold nanoclusters (AuNCs) onto GO nanosheets. The assembled nanosheets can be vertically aligned under weak and practical magnetic fields (T ), providing high-density sharp edges with preferential orientation to effectively pierce the bacterial membrane. Also, the conjugated AuNCs are efficiently delivered into bacteria to induce high oxidative stress, which strongly disturbs bacterial metabolism, leading to the death of both Gram-positive and Gram-negative bacteria. The antibacterial agent uses both physical (via oriented GO) and chemical (via GO and AuNCs) mechanisms to achieve synergistic antimicrobial performance with low IC50 values of 9.8 mu g mL(-1) on the basis of GO and 0.39 x 10(-6) m on the basis of AuNCs. This multicomponent agent with dual antimicrobial mechanisms is expected to be a promising multifunctional-antimicrobial agent with high biosafety.