On-chip electrochemical sensing of neurotransmitter in nerve cells by functionalized graphene fiber microelectrode

The rapid and precise in situ analysis of biomarkers in controllable microenvironment is of great importance for biological and biomedical researches. In this work, we have developed an on-chip electrochemical sensor integrating with a functionalized graphene fiber microelectrode, i.e., electroactive cobalt tetroxide nanowire arrays (Co3O4-NWAs) modified phosphor-doped graphene fiber (PGF) microelectrode, and explored its application in sensitive and accurate detection of neurotransmitter dopamine (DA) in human nerve cells. Herein, PGF microelectrode was synthesized using graphene oxide nanosheets as the building block and phytic acid as green phosphor source, which not only exhibits excellent electrochemical properties and provides a large specific surface area for the growth of high-density Co3O4-NWAs on it, but also possesses good mechanical flexibility and miniaturized size that enable it to be integrated into a microfluidic chip to construct an on-chip electrochemical sensor. The resultant sensing system exhibits good performances for DA detection, with a high sensitivity of 17.5 μA μM-1 cm-2, a linear range of 100 nM–25 μM, and a detection limit as low as 50 nΜ (S/N = 3), and has been used in real-time tracking DA released by human neuronally differentiated SHSY-5Y cells on chip, which holds great promise for its wider application in analytical chemistry and clinic medicine.