MoS2 nanostructured materials for electrode modification in the development of a laccase based amperometric biosensor for non-invasive dopamine detection

A novel laccase-based amperometric biosensor was developed through the modification of carbon paper electrodes with layered two-dimensional molybdenum disulfide (MoS2) presented in two different morphologies, flowers (MoS2-F) and ribbons (MoS2-R). Two laccase isoforms from Pycnoporus sanguineus CS43 fungi (LacI and LacII) were evaluated for the first time as a biological recognition element, and their performance was compared with commercial laccase from Trametes versicolor (TvL). The best results were observed with the MoS2-R morphology at a concentration of 2 mg/mL Biosensors modified with MoS2-R and with the three enzymes, showed two linear ranges of detection, from 0.1 to 0.5 mu M and from 1 to 5 mu M. Biosensors modified with LacII exhibited a high sensitivity of 340.3 nA/mu M; and low limit of detection (LOD) of 10 nM, which are the best values reported in the literature for dopamine detection by laccase based biosensor. Optimized electrodes modified with enzymes LacII and TvL were tested in a synthetic urine sample in order to evaluate their practical effectiveness, resulting in LOD of 0.67 and 2.67 mu M respectively, which are below the average concentrations of dopamine normally found in real urine samples (around 2 mu M).