Highly sensitive and selective glutamate microbiosensor based on cast polyurethane/AC-electrophoresis deposited multiwalled carbon nanotubes and then glutamate oxidase/electrosynthesized polypyrrole/Pt electrode

A highly sensitive and selective glutamate microbiosensor based on polypyrrole (PPy), multiwalled carbon nanotubes (MWCNT) and glutamate oxidase (GluOx) deposited on the transducer platinum electrode (Pt) is described. The sensor consists of a permselective membrane of polypyrrole for the rejection of interferences, followed by a layer of multiwalled carbon nanotubes and glutamate oxidase deposited by asymmetrical alternating current electrophoretic deposition (AC-EPD). The biosensor has a high sensitivity (3.84 nA/(μM mm2)), low response to interferences such as ascorbic acid, uric acid and acetaminophen, a fast response time (7 s), low detection limit (∼0.3 μM), a linear range of 140 μM and a satisfactory stability. In order to improve the linear range and the stability, a thin layer of polyurethane (PU) was applied to the Pt/PPy/MWCNT/GluOx sensor. The resulting sensor with the PU outer membrane showed an increase in the linear range up to ∼500 μM glutamate and has a better stability at the expense of a decrease in sensitivity (2.5 nA/(μM mm2)) and an increase in the response time (15 s).