Enzyme Immobilization and Direct Electrochemistry Based on a New Matrix of Phospholipid-Monolayer-Functionalized Graphene

A new nanocomposite material for enzyme immobilization and subsequent direct electrochemistry and electrocatalysis was developed by using 1,2-dimyristoyl-sn-glycero-3-phospho-(1-rac-glycerol)-phospholipid-monolayer-membrane-modified graphene (DMPG-G). Microperoxidase-11 (MP11) was chosen as a model enzyme to investigate the composite system. Owing to the improved conductivity and biocompatible microenvironment, MP11 that was immobilized in the matrix of the DMPG-G nanocomposite (DMPG-G-MP11) effectively retained its native structure and bioactivity. DMPG-G-MP11-modified glassy carbon electrode (DMPG-G-MP11/GCE) exhibited a pair of well-defined quasi-reversible redox peaks of MP11 and showed high electrocatalytic activity towards hydrogen peroxide (H2O2). The linear response of the developed biosensor for the determination of H2O2 ranged from 2.0x10-6 to 4.5x10-4?M with a detection limit of 7.2x10-7 M. This biosensor exhibited high reproducibility and long-term storage stability. The promising features of this biosensor indicate that these lipidgraphene nanocomposites are ideal candidate materials for the direct electrochemistry of redox proteins and that they could serve as a versatile platform for the construction of a third-generation biosensor.