Electrochemical determination of levodopa on a reduced graphene oxide paste electrode modified with a metal-organic framework

Developing easy-to-use sensors for monitoring of biomarkers which are related to human health is essential. Levodopa (L-DOPA) is a critical neurotransmitter that mainly uses for effective therapy of Parkinson's disease. This study introduces a novel reduced graphene oxide (RGO) paste electrode (PE), RGOPE, which is modified with a microporous metal-organic framework (MOF) as a sensing interface in the electrochemical determination of the L-DOPA. The electrochemical behavior of the modified RGOPE was studied by cyclic voltammetry (CV), square wave voltammetry (SWV), electrochemical impedance spectroscopy (EIS) and chronoamperometry techniques. The influence of parameters such as the scan rate and pH value on the peak current were investigated. Under the optimal condition, the modified RGOPE as a sensor presented a capability in highly sensitive sensing of the L-DOPA at a typical working potential of 0.56 V vs. Ag/AgCl. The sensitivity, linear dynamic range and detection limit of the sensor for detection of the L-DOPA were calculated to be 0.58 mu A mu M-1, 100 nM-85 mu M and 25 nM, respectively. To compare the effect of the RGO in the modification process, the electrode was modified with the carbon paste electrode and the result shows the RGO has some admirable properties in the sensing strategy of the L-DOPA.