Phospholipid-graphene nanoassembly as a fluorescence biosensor for sensitive detection of phospholipase D activity

A novel phospholipid-graphene nanoassembly is developed based on self-assembly of phospholipids on nonoxidative graphene surfaces. The nanoassembly can be prepared easily through noncovalent hydrophobic interactions between the lipid tails and the graphene without destroying the electronic conjugation within the graphene sheet. This imparts the nanoassembly with desired electrical and optical properties with nonoxidative graphene. The phospholipid coating offers excellent biocompatibility, facile solubilization, and controlled surface modification for graphene, making the nanoassembly a useful platform for biofunctionalization of graphene. The nanoassembly is revealed to comprise a bilayer of phospholipids with a reduced graphene oxide sheet hosting in the hydrophobic interior, thus affording a unique planar mimic of the cellular membrane. By using a fluorescein-labeled phospholipid in this nanoassembly, a fluorescence biosensor is developed for activity assay of phospholipase D. The developed biosensor is demonstrated to have high sensitivity, wide dynamic range, and very low detection limit of 0.010 U/L. Moreover, because of its single-step homogeneous assay format it displays excellent robustness, improved assay simplicity and throughput, as well as intrinsic ability to real-time monitor the reaction kinetics.