Development of a generic microelectrode array biosensing system

Abstract

A new type of electrochemical cell has been developed for use in biosensor applications. Utilising a random array of platinum microdiscs as the working electrode, it incorporates a Ag/AgCl reference electrode and platinum auxiliary electrode into the tip of a polished glassy Teflon probe. Immobilisation of the biochemical moiety onto the surface of the probe is achieved using a mixture of polyurethane (PU) and polyethylene oxide (PEO). Enclosing the tip of the probe within a dialysis membrane completes the electrochemical cell. The hydrophilic nature of the PU–PEO mixture ensures the biochemical moiety is trapped in a stable, hydrophilic environment. The result is an all in one generic electrochemical sensor that can be used in a wide range of biosensor applications in both batch or flow injection modes. The unique features of this system are demonstrated in this paper using the glucose — glucose oxidase (GOD) system. Parameters affecting sensor performance were investigated in both batch and flow injection modes. In terms of sensitivity, reproducibility, equilibration time and linear dynamic range, the performance of the microdisc based sensing system was superior to similar macroelectrode versions. Practical detection limits (0.1 μM) were four–five orders of magnitude better for this system compared with a conventional electrode system. The advantages of using this system in flow injection mode, particularly in terms of increased linear range, were also addressed. The overall linear range of our system (0.1 μM–60 mM) is three–four orders of magnitude greater than the conventional electrode system.