Carboxymethyl cellulose-assisted synthesis of carbon-confined leaf-like zeolite imidazolate framework-derived ZnS@N/C nanodots for enhanced multi-walled carbon nanotube dispersion and real-time neurotransmitter monitoring in PC-12 cells

Dopamine (DA) is a key neurotransmitter required for attention, learning, movement, emotion, and cognition. Imbalance in DA levels is linked to disorders such as depression, addiction, schizophrenia, and neurodegenerative diseases. Therefore, a simple, sensitive, and selective method for DA detection is required. In this study, carbon and nitrogen co-doped zinc sulfide (ZnS@N/C) nanodots combined with multi-walled carbon nanotubes (MWCNT) were developed for DA detection in PC-12 live cells. The ZnS@N/C nanodots were synthesized from a leaf-like zeolite imidazolate framework (ZIF-L), carboxymethyl cellulose (CMC), and sodium diethyldithiocarbamate trihydrate (DEDTC) <i>via</i> thermal annealing. DEDTC acted as a sulfur source, while CMC acted as a carbon source and improved the dispersibility of the MWCNT in the composite. Electrochemical properties were confirmed using cyclic voltammetry, electrochemical impedance spectroscopy, and amperometry (<i>i</i>-<i>t</i>). The ZnS@N/C/MWCNT composite exhibited excellent electrochemical performance due to the synergistic effects of ZnS@N/C (which provided high electrocatalytic activity and more active sites) and MWCNT (which enhanced conductivity). Amperometry (<i>i-t</i>) revealed that the ZnS@N/C/MWCNT/screen-printed electrode (SPCE) showed good linearity in the DA concentration range of 0.0125-1774 µM, with a low detection limit of 3.97 nM. Furthermore, the ZnS@N/C/MWCNT/SPCE successfully monitored the DA levels in PC-12 cells under K⁺ stimulation in a neurological environment. These results demonstrated that the ZnS@N/C/MWCNT/SPCE is an efficient, selective, and sensitive sensor for rapid DA detection, offering potential applications in biomedical research.