Multi-analyte determination of dopamine and catechol at single-walled carbon nanotubes – Conducting polymer – Tyrosinase based electrochemical biosensors

• Sinusoidal voltages were successfully applied in the preparation of biosensors.
• Sinusoidal voltages of low frequencies produced coatings with higher porosity.
• The simultaneous determination of analytes was performed by bipotentiostatic measurements.
• A two-analyte detection protocol was elaborated.
• The analytes concentrations were determined with good accuracy and precision.

Simultaneous electrochemical determination of dopamine and catechol was achieved at gold (Au) disk microelectrode arrays (MEAs) and interdigitated microband electrode arrays (IDEs), modified with a bio-composite material consisting of single-walled carbon nanotubes (CNT), functionalized with carboxylic groups, poly(3,4-ethylenedioxythiophene) (PEDOT), and tyrosinase (Ty). The bio-composite material was electrodeposited onto these devices using a novel preparation procedure based on application of sinusoidal voltages (SV) of various frequencies over a dc potential. The influence of SV frequency on the porosity of the bio-composite coatings was investigated by assessing the morphology and chemical structure of the nanostructured bio-composite materials. This was carried out by scanning electron microscopy, profilometry, and infrared reflection absorption spectroscopy. The analytical devices used in this work contain two arrays separated by an insulating gap. One array from the chip was modified with a PEDOT–CNT–Ty layer, while the second one was modified with a PEDOT-only layer. Target analytes were determined via bipotentiostatic measurements at both PEDOT–CNT–Ty and PEDOT modified electrodes using cyclic voltammetry. The figures of merit of the analytical performance, i.e. sensitivity, linear response range, limits of detection and quantification, repeatability, re-usability and operational stability, were also investigated. The IDE based biosensor prepared at low frequency range displayed the lowest limit of detection of 2.4 μM dopamine, the best repeatability of 4.9%, and a recovery of 100.9% for dopamine determination in the presence of catechol.

Cyclic voltammograms recorded simultaneously in bipotentiostatic mode at a device including a Au-IDE/PEDOT–CNT–Ty–GAD biosensor (solid line) and a Au-IDE/PEDOT sensor (dotted line) in phosphate buffer solution containing different dopamine concentrations.Figure optionsDownload as PowerPoint slide