Electroanalytical Characterisation of Dopa Decarboxylase Inhibitors Carbidopa and Benserazide on Multiwalled Carbon Nanotube and Poly(Nile blue A) Modified Glassy Carbon Electrodes

Dilek Kul,Christopher M A Brett

doi:10.4061/2011/185864

Abstract

Modified glassy carbon electrodes have been made by deposition of functionalised multiwalled carbon nanotubes (MWCNTs) followed by formation of poly(Nile blue) (PNB) films by electropolymerisation, using potential cycling in 0.1 M phosphate buffer solution (PBS) at pH 6.0. The electrochemical oxidation of carbidopa (CD) and benserazide (BS) on these MWCNTs/PNB-modified electrodes was investigated using cyclic and differential pulse voltammetry in 0.1 M PBS at different values of pH between 5.0 and 8.0; both CD and BS gave one diffusion-controlled irreversible oxidation peak in cyclic voltammetry. Analytical characterisation of CD and BS was carried out in 0.1 M PBS, pH 5.0. Peak currents in differential pulse voltammetry were linear over the concentration range of1×10−5to1×10−4 M for CD and4×10−6to4×10−5 M for BS. The repeatability, precision, and accuracy of the method were also investigated. Higher sensitivities and lower detection limits, of 1.17 μM for CD and 0.50 μM for BS, were obtained with this new modified electrode compared with previous studies reported in the literature.

Highlights

Dopa decarboxylase inhibitors are used as part of the treatment for Parkinson’s disease
Five cycles were used for the polymerisation of Nile blue A (NB), since thicker poly(Nile blue) (PNB) films, obtained with more than 5 cycles, onto multiwalled carbon nanotubes (MWCNTs) coatings, led to unstable surface modifier films [24]
Peak currents for the electropolymerisation of NB onto MWCNT coatings were much higher than those of on the surface of the glassy carbon (GC) electrode, since modification by MWCNT leads to a larger electroactive surface area [15, 24, 25]

Summary

Introduction

Dopa decarboxylase inhibitors are used as part of the treatment for Parkinson’s disease. Parkinson’s disease (PD) is a degenerative disorder of the central nervous system that affects movement, muscle control, balance, and other functions. The most obvious symptoms are motor related such as tremor, rigidity, slowness of movement, and postural instability [1, 2]. There is currently no cure for Parkinson’s disease. Medications are used to increase levels of dopamine in the brain of patients with PD and in this way slow down the progression of the disease, since motor symptoms are produced by a lack of dopamine. The main drugs used for Parkinson’s disease are levodopa, dopamine agonists, and MAO-B inhibitors [3]

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