Electrochemical marker for metastatic malignant melanoma based on the determination of l-dopa/l-tyrosine ratio

In this paper, we have proposed an electrochemical marker for the metastatic malignant melanoma by determining 3,4-dihydroxy-l-phenylalanine (l-dopa or DOPA) and l-tyrosine (Tyr) ratio using the electropolymerized film of 3-amino-5-mercapto-1,2,4-triazole on glassy carbon (p-AMTa) electrode. Earlier studies suggested that DOPA/Tyr ratio can be used to determine the aggressiveness of malignant melanoma. Based on this report, we attempted to determine the concentrations of DOPA and Tyr simultaneously using p-AMTa electrode by electrochemical method. The voltammetric signals of DOPA and Tyr were not resolved when we use bare GC electrode. However, p-AMTa electrode not only separates the voltammetric signals of DOPA and Tyr but also enhanced their oxidation currents. Using the p-AMTa film, we have successfully determined DOPA and Tyr simultaneously for the first time. To demonstrate the clinical application of the present method, we have successfully determined the concentrations of DOPA and Tyr in human blood plasma samples (n = 4) and estimated DOPA/Tyr ratio. The ratio was found within the prescribed limit, indicating that the blood plasma samples are free from melanoma disease.