Fabrication of ferrocene modified microsensors for the sensitive detection of glutamate

A sensitive and selective amperometric glutamate microsensor with fast response time (<; 5 s) was developed by fabricating a ferrocene/ glutamate oxidase/ Nafion/ polypyrrol (Fc/GlutOx/Nf/Ppy) composite on the micromachined platinum (Pt) microelectrode. The ferrocene-bovine serum albumin (Fc-BSA) conjugate was immobilized on the GlutOx/Nf/Ppy composite of the sensor by physical adsorption. The sensor sensitivity of the Fc-modified glutamate sensor was more than two times higher than that of the control sensor (glutamate sensor without Fc). The Fc modified glutamate microsensor was able to detect glutamate with a wide detection range (up to 540 μM) with a low detection limit at 1.35 μM. The sensor selectivity towards glutamate against interferents increased significantly after the modification of Pt microelectrodes with Ppy and Nf. The interferent responses from ascorbic acid (AA) and dopamine (DA) were <;4% of that detected on the bare Pt electrode. No decrease in sensor sensitivity was observed during repetitive operations in 10 days. While the enhancement of the sensing signal by the immobilized Fc has been demonstrated, its mechanism is still under investigation at the present stage; additional fundamental study to further elucidate the mechanism of the improved sensing signal contributed from the immobilized Fc will be focused on these directions: the preferential electrocatalytic activity contributed from the immobilized Fc or the increasing surface area of the transducer extended by the immobilized Fc.