Ion sensitive field-effect transistor (ISFET) based urease biosensors with solid state reference systems for single-ended and two-ended differential readout electronics were investigated. The sensing membranes of the biosensors were fabricated with urease immobilized in a conducting polymer-based matrix. The responses of 12.9~198.1 mV for the urea concentrations of 8~240 mg/dL reveal that the activity of the enzyme was not significantly decreased. Biosensors combined with solid state reference systems were fabricated, and the evaluation results demonstrated the feasibility of miniaturization. For the differential system, the optimal transconductance match for biosensor and reference field-effect transistors (REFET) pair was determined through the modification of the membranes of the REFETs and enzyme field-effect transistors (EnFETs). The results show that the transconductance curve of polymer based REFET can match with that of the EnFET by adjusting the photoresist/NafionTM ratio. The match of the transconductance curves for the differential pairs provides a wide dynamic operating measurement range. Accordingly, the miniaturized quasi-reference electrode (QRE)/REFET/EnFET combination with differential arrangement achieved similar urea response curves as those measured by a conventional large sized discrete sensor.
References
[1]
Covington, A.K.; Valdes-Perezgasga, F.; Weeks, P.A.; Brown, A.H. pH ISFETs for intramyocardial pH monitoring in man. Analusis？1993, 21, 43–46.
[2]
Osaka, T.; Komaba, S.; Seyama, M.; Tanabe, K. High-sensitivity urea sensor based on the composite film of electroinactive polypyrrole with polyion complex. Sens. Actuat. B-Chem？1996, 35–36, 463–469.
[3]
Pijanowska, D.G.; Torbicz, W. pH-ISFET based urea biosensor. Sens. Actuat. B–Chem？1997, 44, 370–376.
[4]
Puig-Lleixa, C.; Jimenez, C.; Alonso, J.; Bartroli, J. Polyurethane-acrylate photocurable polymeric membrane for ion-sensitive field-effect transistor based urea biosensors. Anal. Chimica Acta？1999, 389, 179–188.
[5]
Soldatkin, A.P.; Montoriol, J.; Sant, W.; Martelet, C.; Jaffrezic-Renault, N. A novel urea sensitive biosensor with extended dynamic range based on recombinant urease and ISFETs. Biosens. Bioelectron？2003, 19, 131–135.
[6]
Jaffrezic-Renault, N.; Wan, K.; Senillou, A.; Chovelon, J.M.; Martelet, C. Development of new polymeric membranes for ENFETs for biomedical and environmental applications. Analusis？1999, 27, 578–586.
[7]
Evtugyn, G.A.; Budnikov, H.C.; Nikolskava, E.B. Sensitivity and selectivity of electrochemical enzyme sensors for inhibitor determination. Talanta？1998, 46, 465–484.
[8]
Gerard, M.; Chaubey, A.; Malhotra, B.D. Application of conducting polymers to biosensors. Biosens. Bioelectron？2002, 17, 345–359.
[9]
Kinlen, P.J.; Heider, J.E.; Hubbard, D.E. A solid-state pH sensor based on a Nafion-coated iridium oxide indicator electrode and a polymer-based silver chloride reference electrode. Sens. Actuat. B？1994, 22, 13–25.
[10]
Volotovsky, V.; Nam, Y.J.; Kim, N. Urease-based biosensor for mercuric ions determination. Sens. Actuat. B？1997, 42, 233–237.
[11]
Chang, K.M.; Chang, C.T.; Chao, K.Y.; Chen, J.L. Development of FET-Type Reference Electrodes for pH-ISFET Applications. J. Electrochem. Soc？2010, 157, J143–J148.
[12]
Sone, Y.; Ekdunge, P.; Simonsson, D. Proton Conductivity of Nafion 117 as Measured by a Four-Electrode AC Impedance Method. J. Electrochem. Soc？1996, 143, 1254–1259.
[13]
Bergveld, P. Development of an ion-sensitive solid-state device for neuro-physiological measurements. IEEE Trans. Biomed. BME？1970, 17, 70–71.
Ravezzi, L.; Conci, P. ISFET sensor coupled with CMOS read-out circuit microsystem. Electron. Lett？1998, 34, 2234–2235.
[16]
Khanna, V.K.; Kumar, A.; Jain, Y.K.; Ahmad, S. Design and development of a novel high-transconductance pH-ISFET (ion-sensitive field-effect transistor)-based glucose biosensor. Int. J. Electron？2006, 93, 81–96.
[17]
Rocher, V.; Chovelon, J.M.; Jaffrezic-Renault, N.; Cros, Y.; Birot, D. An Oxynitride ISFET Modified for Working in a Differential Mode for pH Detection. J. Electrochem. Soc？1994, 141, 535–539.
[18]
Ravezzi, L.; Stoppa, D.; Corra, M.; Soncini, G.; Dalla Betta, F.; Lorenzelli, L. A CMOS ASIC for differential read-out of ISFET sensors. Electron. Circuits. Syst？2001, 3, 1513–1516.
[19]
Hammond, P.A.; Ali, D.; Cumming, D.R.S. Design of a Single-Chip pH sensor using a conventional 0.6-μm CMOS process. IEEE Sens. J？2004, 4, 706–712.
Shimada, K.; Yano, M.; Shibatani, K.; Komoto, Y.; Esashi, M.; Matsuo, T. Application of catheter-tip ISFET for continuous in-vivo measurement. Med. Biol. Eng. Comput？1980, 18, 741–745.
[22]
Smith, R.L.; Scott, D.C. A solid state miniature reference electrode. Proceedings of the IEEE/VSF Symposium on Biosensors, Los Angeles, CA, USA, 15–17 September 1984; pp. 61–62.
[23]
Huang, I.Y.; Huang, R.S. Fabrication and characterization of a new planar solid-state reference electrode for ISFET sensors. Thin Solid Films？2002, 406, 255–261.
[24]
Maminska, R.; Dybko, A.; Wr′oblewski, W. All-solid-state miniaturised planar reference electrodes based on ionic liquids. Sens. Actuat. B？2006, 115, 552–557.
[25]
Suzuki, H.; Hiratsuka, A.; Sasaki, S.; Karube, I. Problems associated with the thin-film Ag/AgCl reference electrode and a novel structure with improved durability. Sens. Actuat. B？1998, 46, 104–113.
[26]
Suzuki, H.; Ozawa, H.; Sasaki, S.; Karube, I. A novel thin-film Ag/AgCl anode structure for microfabricated Clark-type oxygen electrodes. Sens. Actuat. B？1998, 53, 140–146.
Grattarola, M.; Massobrio, G. Bioelectronics Handbook: MOSFETs, Biosensors, and Neurons; McGraw-Hill: New York, NY, USA, 1998.
[29]
van der Schoot, B.H.; Bergveld, P. ISFET based enzyme sensors. Biosensors？1988, 3, 161–186.
[30]
Boubriak, O.A.; Soldatkin, A.P.; Starodub, N.F.; Sandrovsky, A.K.; El’skaya, A.K. Determination of urea in blood serum by a urease biosensor based on an ion-sensitive field-effect transistor. Sens. Actuat. B？1995, 26, 429–431.
