Site-directed capture of laccase at edge-rich graphene via an interfacial hydrophobicity effect for direct electrochemistry study

Abstract

Direct electrochemistry of oxidoreductase on electrode plays critical roles in the development of enzymatic biosensing and biofuel cells. Herein, a free-standing edge-rich graphene (ERG) film in-situ fabricated on a porous and conductive Si3N4 nanowires template with hydrophobic surface was directly used as a self-supporting electrode for site-directed capture of laccase from Agaricus bisporus. The ERG film possessed abundant edge-rich active sites, high conductivity, and especially hydrophobic surface, which realized the direct electron transfer of the immobilized laccase and its bioelectrocatalysis towards the O2 reduction. With the comprehensive comparison to hydrophilic ERG, we found that the interfacial hydrophobicity played an important role for the orientated immobilization of laccase. Thereafter a faster electron transfer kinetic (1.32 vs. 0.74 s−1) and a higher bioelectrocatalytic activity towards O2 with over 10 times’ enhancement in reductive current were achieved. This is probably because the hydrophobic region of laccase tends to specifically interact with the hydrophobic surface, allowing the site-directed capture of laccase on the hydrophobic ERG electrode. With an emphasis of the interfacial hydrophobicity effect, these results would not only contribute to an in-depth understanding of the nano-bio interface electron transfer, but also provide a new insight to design high-efficient bioelectrodes for biosensors and biofuel cells applications.