Single-chirality single-walled carbon nanotubes for electrochemical co-detection of serotonin and dopamine

Dopamine (DA) and serotonin (5-HT) are neurotransmitters whose dysregulation is associated with neurodegenerative diseases. The influence of single-walled carbon nanotube (SWCNT) chirality on sensing remains underexplored. Mixed-chirality SWC- NTs can limit sensor reproducibility and accuracy. Precise control of electrode material structure may promote more specific surface-analyte interactions, enhancing selectivity. Here, screen-printed carbon electrodes (SPCE) were modified with four SWCNT types: mixed-chirality metallic/semiconducting (m/s), metallic (m), or semiconducting (s) SWCNT, and single-chirality semiconducting (6,5)-SWCNT isolated by aqueous two-phase extraction. Vacuum filtration produced surfactant-free SWCNT layers. Codetection of 5-HT and DA was evaluated using differential pulse voltammetry (DPV). The (6,5)-SWCNT/SPCE gave the largest potential difference (∆E = Ep(5-HT)− Ep(DA)) of 151 ± 4 mV and a peak current ratio (Ip(DA)/Ip(5-HT)) of 0.99 ± 0.23. Corresponding values for unmodified SPCE, m/s-SWCNT/SPCE, m-SWCNT/SPCE, and s-SWCNT/SPCE were 139±10, 145±3, 143±6, and 147±3 mV, and 0.60±0.23, 0.63±0.12, 0.63±0.11, and 0.69±0.01, respectively. The (6,5)-SWCNT/SPCE detected both analytes even when one analyte was present in excess. Between 0.04 and 1 µM, linear responses were obtained for 5-HT alone, DA in the presence of 1 µM 5-HT, and 5-HT in the presence of 1 µM DA, with sensitivities of 0.024 ± 0.002, 0.011 ± 0.001, and 0.024± 0.001 nA/nM, respectively. These results show that SWCNT chirality control improves the electrochemical co-detection of 5-HT and DA.