A facile method to classify clinic isolates with a turn-off sensor array based on graphene oxide and antimicrobial peptides

Abstract

Graphene oxide (GO) absorbed aromatic and charged materials due to its high volume-to-surface ratio and unique physical and electrical properties. Antimicrobial peptides can inhibit bacterial growth by intercalating into the bacterial envelope and their antimicrobial efficiencies vary depending on the species and are sensitive to metal cations. Herein, a turn-off sensor array based on graphene oxide and antimicrobial peptide that was fused with a poly-histidine adaptor was described and used for bacterial discrimination. The poly-histidine adaptor prone to binding with graphene oxide helped GO to quench the fluorophore labelled peptides efficiently. As illustrated by the titration assays presented herein, GO quenched the 6-carboxyfluorescein-labelled peptides at a >99.6 % quenching efficiency, ensuring a very low background. A sensor array was established with various antimicrobial peptide types and calcium concentrations under optimized parameters. The 13 most frequently observed clinical species were subjected to the sensor array, and the obtained fluorescent signals ranged from several thousand to several million, with superior resolution between species. The sensor array was evaluated by comparing its accuracy in a blind assay using single or combined parameters. The accuracy reached >70 % for single parameters and >95 % for combinations, and all 155 bacteria were identified using this sensor array. In addition, the interaction between the membrane components and antimicrobial peptides were examined by quartz crystal microbalance with dissipation and the effect of calcium ions was elucidated by monolayer assays.