High sensitive electrochemical lable free DNA biosensor for determination of Levodopa with Fe3O4 nanoparticle decorated reduced graphene oxide modified electrode

Levodopa (Lev) is an unusual amino acid that is used for the treatment of Parkinson,s disease to provide symptomatic relief to most patients at the early stages of disease[1]. In the present work, an electrochemical biosensor was developed for Levodopa (LD) detection using label-free double strand DNA (ds-DNA) and graphene (Gr) decorated with Fe3O4 magnetic nanoparticles on a carbon paste electrode (CPE). Electrochemical studies revealed that modification of the electrode surface with ds- DNA and Gr- Fe3O4 nanocomposite significantly increases the oxidation peak currents but reduces the peak potentials of Levodopa. After the optimization of operational parameters, calibration curve was linear in the range of 5.0×10-8- 1100×10-6 M with a detection limit of 1.7×10-8 M. The relative standard deviations for 20μM was 3.20% (n=5).The proposed biosensor was successfully applied to the analysis of Levodopa in human serum. A suitable selectivity was achieved for determination of Levodopa in real samples.