An Arrayed Micro-glutamate Sensor Probe Integrated with On-probe Ag/AgCl Reference and Counter Electrodes

Complete all-in-one multi-arrayed glutamate (Glut) sensors have been constructed on a silicon-based micromachined probe composed of micro-platinum (Pt) working electrodes, a micro-silver/silver chloride (Ag/AgCl) reference electrode (RE), and a micro-Pt counter electrode (CE). The OCP shift of the electrodeposited Ag/AgCl on-probe micro-reference electrode compared with a Ag/AgCl wire is <0.1mV/h. The composition ratio of Ag, Cl, and Pt on the electrodeposited on-probe micro-reference electrode is observed to be 1.00:0.48:0.02 analyzed by EDS. The miniaturized amperometric Glut biosensors were constructed on working electrode sites (electrode area: approximate to 8.5x10(-5)cm(2)) of the microprobe modified with glutamate oxidase (GlutOx) enzyme layers for the selective, fast, and continuous detection of L-glutamate. The sensor selectivity towards common electroactive interferents has been improved significantly by coating the electrode surface with perm-selective polymer layers, overoxidized polypyrrole (PPY) and Nafion (R). The sensitivity, detection range, and response time of the proposed all-in-one Glut biosensors are 204.7 +/- 5.8nAM(-1)cm(-2) (N=5), 4.99-109M, and 2.7 +/- 0.3sec, respectively and no interferent signals of AA and DA were observed. The sensor can be reused over 19times of continuous repetitive operation (total measurement time: approximate to 4hours) and the sensor sensitivity can retain up to fourweeks of storage.