Spermine induced in-situ synthesis of polychromatic carbon nanodots towards smartphone-readable ratiometric fluorescence sensing of multiple catecholamines.

Abnormal levels of catecholamines can indicate underlying health issues, such as Parkinson's disease, hypertension, and pheochromocytoma. However, it is difficult to accurately differentiate multiple catecholamines using traditional detection methods due to their highly similar structures. Herein, we proposed a carbon-based fluorescent probe with adaptability named spermine that can react with multiple catecholamines to generate polymer carbon dots with distinct fluorescence colors, enabling visual differentiation and quantitative detection of epinephrine, norepinephrine and levodopa. Spermine does not requires synthesis and exhibits excellent biocompatibility, as it naturally exists in bacteria and most animal cells. Additionally, ratiometric fluorescent probes with high sensitivity was constructed to eliminate nonspecific factors in the sample detection process. Furthermore, due to the simplicity of the designed fluorescence detection steps, a convenient paper-based biosensor for visual detection of multiple catecholamines was formed by pre-dropping the probe on the detection layer, which can be integrated into the portable platform and the detection value can directly display on the smartphone. Therefore, the integrated portable platform of the biosensor can differentiate catecholamines types through fluorescent color and intelligently detect the content of catecholamine in the sample.