Development of label-free electrochemical lactose biosensor based on graphene/poly(1,5-diaminonaphthalene) film

• The combination of graphene and conductive P(1,5-DAN) for a novel sensing platform.
• The synthesized electrode applied for electrochemical label free detection of lactose.
• Potential application for other electrochemical biosensors with superior sensitivity.

In this work, a lactose biosensor was developed by co-immobilizing β-galactosidase (β-Gal) and glucose oxidase (GOx) on microelectrodes pre-modified with Pt/graphene/P(1,5-DAN) for estimation of lactose in dairy products to prevent lactose intolerance. The Pt microelectrode was modified with graphene and 1,5-polydiaminonaphthalene film. Graphene was synthesized by chemical vapor deposition on copper tape and manually transferred to the electrode surface. Polymeric P(1,5-DAN) was grafted on top of the graphene film by electropolymerization. Modified surface of the electrode was characterized by Raman spectra analysis, FE-SEM, AFM and cyclic voltammetry. The results indicated that deposition graphene film on electrode surface induced considerable enhancement in current signal, over 20 times as high as the uncoated electrode surface. The developed sensor was successfully used to determine lactose in model samples with sensitivity, correlation coefficient (R2) and limit of detection (LOD) estimated to be 1.33 μA/(μgml−1), 0.995 and 1.3 μg/ml, respectively. The combined graphene and conductive P(1,5-DAN) could serve as a novel sensing platform on electrochemical sensors with superior sensitivity.

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