A novel competitive capacitive glucose biosensor based on concanavalin A-labeled nanogold colloids assembled on a polytyramine-modified gold electrode

A highly sensitive competitive capacitive glucose biosensor was constructed based on gold nanoparticles, which were employed as a platform to immobilize concanavalin A (Con A). Gold nanoparticles were fixed on a gold electrode, on which a layer of polytyramine was preformed via electrochemical polymerization. The sensing mechanism is based on the competitive dissociation of a glucose polymer or a glycoconjugate from the glycoligand binding sites of immobilized Con A by the added glucose. To further improve the sensor response, several glucose polymers as well as a synthesized glycoconjugate using the periodate method, were screened. Consequently, dextran (MW 39 kDa) was selected and the feasibility of the proposed biosensor was evaluated for a competitive assay of glucose. Experimental results show that the biosensor responded linearly to glucose in the range from 1.0 × 10^-6 to 1.0 × 10^-2 M, corresponding to 0.18 μg mL^-1 to 1.8 mg mL^-1 of glucose with a detection limit of 1.0 × 10^-6 M under optimized conditions. The studied biosensor exhibited a response time of about 15 min and a neglectable loss in sensitivity after 10 repeated analytical cycles.