Novel Electron Transfer Mediators for Amperometric Bioelectrodes: Introduction of Methylsquarate and Phenylsquarate

• Published in: Electroanalysis (New York, N.Y.) Vol. 14; no. 17; pp. 1177 - 1184
• Main Authors: Iwuoha, Emmanuel I., Williams, Avril R., Hall, Lincoln A.
• Format: Journal Article
• Language: English
• Published: Weinheim WILEY-VCH Verlag 01.09.2002; WILEY‐VCH Verlag
• Subjects: Amperometric glucose biosensor; Cyclobutene-mediated bioelectrochemistry; Electrosynthetic poly(phenol) biosensor; Methylsquarate electrochemistry; Phenylsquarate electrochemistry
• ISSN: 1040-0397; 1521-4109
• DOI: 10.1002/1521-4109(200209)14:17<1177::AID-ELAN1177>3.0.CO;2-E

Electrochemical characteristics of substituted cyclobutenes, 3‐methyl‐4‐hydroxycyclobut‐3‐ene‐1,2‐dione (methylsquarate, OHME) and 3‐phenyl‐4‐hydroxycyclobut‐3‐ene‐1,2‐dione (phenylsquarate, OHPH), were studied to determine their suitability as electron transfer mediators for amperometric biosensors. Voltammetric experiments performed with a Pt disk electrode show that the squarates exhibit reversible electrochemistry in 0.1 M phosphate buffer (pH 7.0). The squarate redox systems behaved like surface‐bound species and have formal potential, E°′, values of about +185 mV and +285 mV (vs. Ag/AgCl) at pH 7.0 for OHME and OHPH, respectively. The squarates were tested as mediators in metabolic biosensors by performing cyclic voltammetry with Pt disk electrodes in argon‐purged 10 mL buffer solutions containing 3 mM of OHME (or OHPH) and 50 μM glucose oxidase (GOx) in the absence or presence of glucose. Voltammograms are presented for the OHME‐ and OHPH‐mediated electrocatalytic oxidation of glucose with all the reagents in solution. The mediator was also used with an electrosynthetic poly(phenol)‐GOx/Pt bioelectrode. The poly(phenol)‐based biosensor was sensitive to very low concentrations of glucose when OHME or OHPH was used as soluble electron transfer mediator for the electrocatalytic reaction. Experimental results indicate that the cyclobutene mediators have good storage stability and have no adverse effect on GOx when stored in buffer medium at 4 °C.