Gold nanoparticle-modified ultramicroelectrode arrays for biosensing: a comparative assessment.

Gold ultramicroelectrode arrays (UMEAs) modified with gold nanoparticles (GNP) are shown to be a highly suitable transducer platform for the fabrication of biosensors. Comparative studies were carried out with microelectrodes and UMEAs, the latter being either bare or modified with GNPs. GNPs could be electrodeposited on to the UMEA surface, thereby increasing its active area up to one hundred times but without affecting its inherent electrodic properties. Horseradish peroxidase enzyme (HRP) was covalently immobilized over the three different transducer platforms by means of a thiol self-assembled monolayer (SAM). The resulting biosensors were applied to the amperometric detection of catechol, selected as a target analyte, at a set potential of -0.1 V vs. Ag/AgCl. The use of GNP-modified UMEAs increased the sensitivity of the developed biosensor 3-fold and 80-fold compared with the values achieved with bare UMEA and microelectrode based biosensors, respectively. The GNP-modified UMEA based biosensor showed a linear response to catechol in the concentration range from 0.1 mM to 0.4 mM, with a limit of detection of 0.05 mM.