Biosensors & Bioelectronics 17 (2002) 297 – 302 Biosensor arrays for simultaneous measurement of glucose, lactate, glutamate, and glutamine Isabella Moser *, Gerhard Jobst, Gerald A. Urban IMTEK, Albert -Ludwigs Uniersity Freiburg, Georges Koehler Allee 103, D-79110 Freiburg, Germany Received 26 July 2000; received in revised form 18 June 2001; accepted 5 July 2001 Abstract For simultaneous measurement of glucose, lactate, glutamine, and glutamate a biosensor array is implemented in a micro flow-system thus giving a microsystem. The microsystem consists of a glass chip with the integrated biosensor array and a bottom part, which comprises a gold counter electrode, a 300 m thick seal, and electrical interconnection lines. The flow device has a total internal volume of 2.1 or 6 l when integrated with a mixer on chip. The biosensors with no crosstalking and high long term stability were produced by modifying the electrochemical transducers and utilizing photopatternable enzyme membranes. The use of appropriate miniaturization technology leads to mass producable devices for in vivo and ex vivo applications in whole blood and fermentation broth. Due to a novel glutaminase with an activity optimum in the neutral pH range direct and simultaneous monitoring of glutamine together with glucose, lactate, and glutamate could be performed. © 2002 Elsevier Science B.V. All rights reserved. Keywords: BioMEMS; Monitoring; Integration; Microfluidics; Cross talk free; Stability www.elsevier.com/locate/bios 1. Introduction The demand for fast, reliable and continuous mea- surements of chemical species in medicine, biotechnol- ogy and environmental sciences has evolved the need for small, easy to handle and inexpensive analytic devices. In medical application but also for metabolism monitoring of cell cultures small sample consumption by the analytical system is a must. One way to reduce the sample volume is miniaturization of the device, the other possibility is integration of several sensors in a common shared measurement chamber. It is obvious that combining both strategies would give the best results. On the other hand an integration of small dimensioned biosensors causes well known problems like chemical cross talk between adjacent amperometric biosensors (Suzuki and Akaguma, 2000; Palmisano et al., 2000). Suzuki et al. (Suzuki and Akaguma, 2000) compared the chemical cross talk between glucose and lactate biosensors prepared to give three different types of membrane biosensors. The first biosensor prepara- tion was done by glutaraldehyde crosslinking of gelatin and enzymes, the second by enzyme entrapment during electropolymerization of pyrrole, and the third one by using a photolithographic PVA-SbQ method. Palmisano et al. (Palmisano et al., 2000) describe inte- grated glucose/lactate biosensors on dual platinum disk electrodes modified by an electropolymerized polypyrrole film and covered by membranes of glucose oxidase or lactate oxidase crosslinked with glutaralde- hyde. Both authors used relatively large commercial dual electrodes of comparable dimensions (7 mm 2 ) and applied the enzyme solutions manually. While Palmisano describes his system as being cross talk free due to whole design and the flow injection analysis (FIA) measurement method, which would sweep away generated H 2 O 2 Suzuki finds with a similar measure- ment method cross talk for all bi-biosensors. In another approach screen printed disposable ring and split-disk plastic film carbon electrodes were coated with osmium poly(vinylpyridine) redox polymer horseradish peroxidase (Os – gel – HRP) and used for immobilization of glucose oxidase and lactate oxidase * Corresponding author. Fax: +49-761-203-7262. E-mail address: moser@imtek.de (I. Moser). 0956-5663/02/$ - see front matter © 2002 Elsevier Science B.V. All rights reserved. PII:S0956-5663(01)00298-6