A programmable paper-based microfluidic chip based on multicolor fluorescence carbon dots for visual sensing of multiple catecholamines in human serum.

Catecholamines (epinephrine, norepinephrine, and levodopa) are a kind of neurotransmitter with similar structure, which orchestrates the regulation of emotional balance, stress adaptation, cardiovascular system optimization, and energy metabolism coordination. To satisfy the actual requirements for rapid, accurate, and on-site detection of multiple catecholamines, we propose a programmable paper-based microfluidic chip, which is loaded with diethanolamine as a multifunctional and efficient non-fluorescent detection probe. Specifically, diethanolamine reacts with epinephrine, norepinephrine, and levodopa to generate polymer carbon dots with yellow, green, and blue fluorescence. On this basis, the integration of paper-based microfluidics with smartphone-assisted technology enables the intelligent visual fluorescence detection of multiple catecholamines. The analytical device exhibits a good linear relationship in the detection of epinephrine (0.008 ~ 0.5 mM), norepinephrine (0 ~ 0.2 mM), and levodopa (0.004 ~ 0.06 mM), with lower limits of detection of 7.4, 19.6, and 1.6 μM, respectively. The practicability and efficiency of the analytical detection device were further demonstrated through the analysis of human serum samples. The intelligent analytical device for the individual quantitative detection and visual differentiation of epinephrine, norepinephrine, and levodopa provides a novel and exciting avenue for accurate detection of multiple catecholamines.