Electrochemical sensor integrated microfluidic device for sensitive and simultaneous quantification of dopamine and 5-hydroxytryptamine

Inspired by the trend of device miniaturization for quick and sensitive detection with small amount of samples in biomedical and forensic fields. An electrochemical sensor based on poly (diallyl dimethylammonium) chloride reduced graphene oxide (PDDA-RGO) modified mull-walled carbon nanotubes - carbon paste electrode (MWCNT-CPE), abbreviated as MWCNT-CPE/PDDA-RGO, was fabricated and integrated with microfluidic device for microliter sample detection. Detailed characterizations reveal that hybrid nanomaterials of PDDA-RGO and MWCNT have a synergistic effect for the electrocatalytic reaction of dopamine and 5-hydroxytryptamine, enabling detection with high sensitivity. Such an integrated microfluidic device exhibits excellent sensitivity, wide linear range, and good stability and repeatability for 20 mu L sample detection. The calibration curves obtained by voltammetry show the linear range of 0.05-120.0 mu M with limit of detection (LOD) of 0.016 mu M (S/N = 3) for dopamine, and 0.05-50.0 mu M with LOD of 0.0098 mu M (S/N = 3) for 5-hydroxytryptamine. Its capability of sensitively and selectively quantify dopamine and 5-hydroxytryptamine in microliter volume rat's plasma, suggests that, it can be potentially applied in monitoring bioactive substances both in vivo and in vitro.