Self-containing reactant biochips for the electrochemiluminescent determination of glucose, lactate and choline

A multi-parametric biochip for glucose, lactate and choline has been developed based on luminol/hydrogen peroxide electrochemiluminescence (ECL). The sensing layers developed were composed of enzyme-bound beads co-entrapped in a photopolymer with luminol-charged beads and spotted at the surface of a glassy carbon electrode (GCE). Lactate oxidase, choline oxidase and luminol were immobilised via electrostatic interactions with DEAE (diethylaminoethyl)-Sepharose whereas glucose oxidase was immobilised, after modification with histidine, by chelation on nickel-charged IDA (imidodiacetic acid)-Sepharose. The luminol immobilisation enabled the achievement of micro-biosensors, present at the surface of the same GCE and free of lateral contamination between each spot by the other’s reaction product. After optimisation of the applied potential, the integration time and the luminol charge in the sensing layer, the electrochemiluminescent H2O2 sensor exhibited a detection limit of 2 μM and a working range from 2 μM to 0.5 mM. lti-biosensor enabled the concomitant detection of glucose, lactate and choline in the ranges 20 μM–2 mM, 2 μM–0.2 mM and 2 μM–0.2 mM, respectively. Glucose and lactate measurements in complex matrix such as human serum, were in good agreement with the reference methods, without internal calibration of the sample, demonstrating the absence of matrix interference with the present analytical system.