Determination of glutamate pyruvate transaminase activity in clinical specimens using a biosensor composed of immobilized L-glutamate oxidase in a photo-crosslinkable polymer membrane on a palladium-deposited screen-printed carbon electrode

The determination of glutamate pyruvate activity (GPT) is of particular clinical importance. A portable GPT sensor for both diagnostic and home-care purpose is highly expected. A highly sensitive and stable L-glutamate sensor was fabricated for the rapid detection of the GPT activity in serum. The sensor is composed of immobilized L-glutamate oxidase in a photo-crosslinkable polymer (PVA-SbQ) membrane on a palladium-deposited screen-printed carbon electrode. The sensor exhibited high sensitivity (detection limit of 50 nM for monosodium glutamate), remarkable long-term stability in storage (5 months in the dry dark state and 1 month in buffer solution) and good reproducibility (R.S.D. = 2.6%, n = 100). The electrode-to-electrode reproducibility was found to depend on the composition of the polymeric matrix. The optimal substrate composition for the detection of GPT activity was 1 mM alpha-ketoglutarate and 100 mM L-alanine. The GPT activity in serum can be determined within 3 min. The response of the sensor to GPT activity is linear over the range of 8-250 U/l. Good correlation between the sensor and the Sigma GPT assay kit was achieved (R-2 = 0.9958). The sensor is potentially applicable to a home-care purpose when a portable measuring device is adapted. (C) 2003 Elsevier Science B.V. All rights reserved.