Investigations into the Use of a Thionine/PEDOT Layer as an NADH Electrocatalyst with Applications in Glutamate Sensing

Abstract

The electrochemical properties of a poly(3,4-ethylenedioxythiophene) film doped with the organic dye, thionine are investigated. It is proposed that an interaction is occurring between the Thionine and PEDOT film due to the positive shift of the thionine couple, improved film retention, and the lack of reactive amino groups. The electrocatalytic oxidation of NADH by this modified electrode was also investigated, together with glutamate sensing.

Scanning electrochemical microscopy imaging of poly (3,4-ethylendioxythiophene)/thionine electrodes for lactate detection via NADH electrocatalysis

“…Thionine has a tendency to form aggregates in solution if the concentration is too high (Nicotra et al, 2008), which can influence film reproducibility and performance. This approach (a) is based on prior work in our group (Warren et al, 2010) which generated an NADH electrocatalytic layer with subsequent glutamate detection (at glutamate dehydrogenase modified electrodes). Further optimisation of this immobilisation approach was deemed necessary in order to improve thionine loading and uniformity (hence approach (b) as outlined below).…”

“…Previous work in our group (Warren et al, 2010) demonstrated that incorporation of nanotubes into the sensor design enhanced performance of the resulting glutamate dehydrogenase biosensor. By modifying MWNT with thionine using an approach similar to that of Wang et al (2007), and then by incorporating them into a preformed PEDOT film (0.1 M sodium p-toluene sulphonate), successful immobilisation of Th-fMWNT onto the electrode surface was achieved.…”

“…Thionine-PEDOT and PEDOT/Thionine films. Thionine-PEDOT films were prepared as described previously (Warren et al, 2010). Briefly, films were formed from 10 mM thionine acetate, 15 mM EDOT in 10 mM LiClO 4 via chronocoulometry (5 mC charge passed at E APP 1.2 V vs. Ag/AgCl).…”

“…Fig. 1 (a, b) shows SECM images of the redox films formed by the two different immobilisation methods, (a) where thionine was incorporated during PEDOT polymerisation (Warren et al, 2010) and (b) where the thionine was incorporated following PEDOT formation (as described above). It was apparent that method (b) produces a more uniformly reactive film with almost an order of magnitude higher (3.95 × 10 −10 A) anodic response relative to that of (a) (5.55 × 10 −11 A).…”

“…Prior work in our group has reported a Thionine/PEDOT catalytic layer for NADH oxidation (Warren et al, 2010). Here we advance the work with exploitation of thionine functionalised carbon nanotubes (MWNTs) using Gum Arabic as suspension reagent, in order to limit leaching of thionine from the electrode surface and to further exploit amine functionalities as a linker group for enzyme attachment.…”