Improved DET communication between cellobiose dehydrogenase and a gold electrode modified with a rigid self-assembled monolayer and green metal nanoparticles: The role of an ordered nanostructuration

Efficient direct electron transfer (DET) between cellobiose dehydrogenase from Corynascus thermophilus (CtCDH) and a novel gold electrode platform, obtained by covalent linking of green AuNPs and AgNPs modified with a dithiol self-assembled monolayer, consisting of biphenyl-4,4'-dithiol (BPDT), was presented. The green AuNPs and AgNPs were synthesized using quercetin as reducing agent at room temperature. TEM experiments showed that the AuNPs and AgNPs were circular in shape with an average diameter of 5 and 8 nm, respectively. Cyclic voltammetry of CtCDH immobilized onto the AuNPs/BPDT/AuE and the AgNPs/BPDT/AuE electrode platforms were carried out and compared with naked AuE, BPDT/AuE, AuNPs/AuE, and AgNPs/AuE. A pair of well-defined redox waves in neutral pH solution due to efficient DET of CtCDH was present with both MNPs/ BPDT/AuE platforms. No DET communication was found with platforms without MNPs linked to BPDT. The apparent heterogeneous electron transfer rate constants (k(s)) of CtCDH were calculated to be 21.5 +/- 0.8 s(-1) and 10.3 +/- 0.7 s(-1), for the AuNPs/BPDT/AuE and the AgNPs/BPDT/AuE platforms, respectively. The modified electrodes were successively used to develop an eco-friendly biosensor for lactose detection. The CtCDH/AuNPs/BPDT/AuE based biosensor showed the best analytical performances with an excellent stability, a detection limit of 3 mu M, a linear range between 5 and 400 mu M and a sensitivity of 27.5 +/- 2.5 mu A cm(-2) mM(-1). Such performances were favorably compared with other lactose biosensors reported in literature. The biosensor was successively tested to quantify lactose content in real milk and cream samples. No significant interference present in the sample matrices was observed.