Highly Selective and Quantitative Point-of-Care Diagnostic Method for Adrenaline.

Adrenaline, also known as epinephrine, is a neurotransmitter/hormone that is an important target in diagnostics. Development of an effective method for detecting it in the presence of other neurotransmitters is a challenging task. The electrochemical and fluorescent techniques commonly used have low selectivity in distinguishing among catecholamines. Herein, a small-molecule organic probe with an activated furfural moiety is reported to exploit the nucleophilicity of epinephrine to generate a bright-colored donor-acceptor Stenhouse adduct. Among nine common neurotransmitters or their analogues, only epinephrine was found to generate a unique colour change discernible with the naked eye, whereas the other ones remain unaffected. Under various in-field detection conditions, including solution, droplet, and paper strip-based detection, the colour change were also noticeable. The low detection limit of 1.37 nM and a limit of quantitation of 4.37 nM were achieved with simple UV/Vis methods in addition to the sub-ppm level sensing under visual conditions with naked eyes. The probe could be used for practical colorimetric measurements as a point-of-care tool without any complex and expensive machinery, making this approach accessible to all. In addition, using a simple smartphone, the determination of epinephrine concentrations is possible by using machine-learning techniques.