Microfluidic neurotransmitters sensor in blood plasma with mediator-immobilized conducting polymer/N, S-doped porous carbon composite

A novel electrochemical microfluidic separation and sensing (EMSS) device was fabricated for monitoring neurotransmitters (NTs) in human blood plasma. Initially, the neurotransmitter separation was achieved with the AC field perturbation in a microfluidic channel followed by the successive detection using a sensor at the end of channel. The sensor performances using some of electron transfer mediators were demonstrated for sensing of seven NTs (5-hydroxytryptamine, dopamine, norepinephrine, epinephrine, 5-hydroxyindoleacetic acid, 5-hydroxytryptophan, and 3, 4-dihydroxy-l-phenylalanine). The sensor probe was fabricated by electropolymerization of 2, 2´:5´, 5″-terthiophene-3´-p-benzoic acid (TBA) with heteroatoms (N and S) doped porous carbon (HPC) to form a composite layer onto the screen printed carbon electrode, followed by covalent immobilization of a redox mediator. Among the tested mediators, Evans blue revealed the most superior performance. The parameters affecting the sensing performance were optimized, in terms of pH, temperature, fluid flow rate and AC parameters (i.e., frequency, amplitude, etc). The calibration plots for the seven NTs standard samples were found to be linear within the range of 0.05−130 nM with the detection limits between 0.034 (±0.005) and 0.044 (±0.004) nM. Finally, the reliability of the proposed device was assessed by detecting six NTs and two NTs derivatives in a human plasma sample.