A promising electrochemical sensor based on gold nanoparticles decorated cysteic acid film for sensitive detection of methadone

Methadone is a synthetic analgesic drug, which has been widely used for the treatment of opioid dependence since the mid-1960s [1]. The treatment has been controversial as it replaces a short-acting opioid with a long-acting one [2]. The mechanism of action by which MET can alleviate opioid dependence and diminishing symptoms in affected individuals, have been discussed thoroughly [3]. Accordingly, accurate analytical method for MET is necessary. In this paper, a sensitive and convenient electrochemical sensor based on stacked cysteic acid film and gold nanoparticles composite modified glassy carbon electrode was developed for the determination of methadone. Electrochemical investigation of the modified electrode is achieved using cyclic voltammetry, differential pulse voltammograms and field emission scanning electron microscopy. The effective surface areas of AuNPs/cysteic acid/GCE increased for about 4-fold larger than that of the unmodified GCE. The kinetic parameters of the electron transfer coefficient (α) and number of electrons involved in the rate determining step (nα) for the oxidation of methadone were determined utilizing CV. The designed modified electrode was revealed linear responses in the ranges of 0.024 to 4.45 μM and 4.45 to 12.67 μM with a limit of detection of 0.014 μM. Excellent recovery results were obtained for determination of methadone in spiked human blood plasma and urine samples at the modified electrode.