Prussian blue-glutamate oxidase modified glassy carbon electrode: A sensitive L-glutamate and beta-N-oxalyl-alpha-beta-diaminopropionic acid (beta-ODAP) sensor

A sensitive biosensor has been developed for the neurotoxin beta-N-oxalyl-alpha,beta-diaminopropionic acid (beta-ODAP) contained in the seeds of grass pea (Lathyrus sativus) and for L-glutamate based on glutamate oxidase (GlOx) and a Prussian blue (PB) modified glassy carbon (GC) electrode. The configuration of the system is so as to detect the hydrogen peroxide released during the enzymatic cycle at a low applied potential, -50 mV versus Ag vertical bar AgCl, in the flow injection mode. For this purpose GlOx was coupled to PB electrodeposited onto a glassy carbon electrode and stabilised by treatment with tetrabutylammonium toluene-4-sulfonate (TTS) during one of the steps in the electrodeposition. GlOx was cross-linked with glutaraldehyde (GA), bovine serum albumin (BSA) and Tween-20 on the surface of the PB modified GC electrodes. Addition of 0.01% and 0.001% polyethyleneimine (PEI) to the immobilisation mixture resulted in an enhancement of the response signal with about 35% and 62% for glutamate and P-ODAP, respectively, when using 0.01% PEI and with 164% and 200% for glutamate and P-ODAP, respectively, when using 0.001% PEI. The linear response range for P-ODAP was extended from 0.05-0.5 mM to 0.01-1 mM, when 0.001% PEI was used. However, a higher concentration of PEI, 0.1%, caused a decrease in the sensitivity of the biosensor. (c) 2005 Elsevier B.V. All rights reserved.