GMB is a common anticancer drug that needs careful monitoring because of its variable and toxic effects. Detecting GMB in biological samples can help adjust the dosage and enhance the treatment outcomes. In this study, a novel electrochemical sensor was developed based on a carbon paste electrode modified with single stranded DNA, gold nanoparticles and multi-walled carbon nanotubes. We characterized the unmodified (bare CPE) and modified (ss-DNA/AuNPs/MWCNTs/CPE) electrodes using scanning electron microscopy (SEM), EDX analysis and cyclic voltammetry (CV) techniques. The oxidation peak current was linearly proportional to the GMB concentration in two linear ranges: 1-10 μM and 10-50 µM, with a detection limit of 0.52 µM and a limit of quantification (LOQ) of 1.75 µM. The lower linear concentration range (1-10 µM) showed a sensitivity of 5.68 A.M-1.cm-2, while the higher range (10-50 µM) showed a sensitivity of 1.34 A.M-1.cm-2. We also investigated the repeatability, applicability and reproducibility of this method for human serum samples. We tested the selectivity and practical ability of the ss-DNA/AuNPs/MWCNTs/CPE for the determination of GMB in the presence of various interfering species and human serum samples. The results indicated that the ss-DNA/AuNPs/MWCNTs/CPE was a selective, reliable and accurate electrochemical sensor for GMB.
