Interference-free multimodal biosensing of adrenaline over other neurotransmitters: Role of 2-iminomethylenephenylboronic acid as the signal transduction unit of fluorescence and impedance

Aberrant levels of the neurotransmitters adrenaline, noradrenaline, and dopamine are linked to various diseases. Therefore, interference-free biosensing of neurotransmitters has become an important area of research. However, structural similarity (presence of diol/amine functionalities), small size, and neutral charge of the catecholamines add complexity to designing recognition systems and make the detection non-specific. Here we report a recognition unit 2-iminomethylenephenylboronic acid (2-IMPBA), which appears to be a remarkable transduction unit for the tailor-made development of biosensors for interference-free detection of the neurotransmitter adrenaline (AD) via multiple techniques. Integrating a signaling unit 4-methylbenzothiazole-2-amine to 2- formylphenylboronic acid (2-FPBA), yielded a novel fluorosensor, which showed 38- fold fluorescence enhancement selectively with AD without any competition from other bioanalytes, including noradrenaline and dopamine. The attachment of 2-FPBA on the homemade plastic chip electrode surface afforded an impedimetric sensor that detects AD in the picomolar range without any challenge from its competitors. Both optical and electrochemical sensors have been tested for AD measurement in human plasma samples. We are not aware of any report describing the selective discrimination of adrenaline from noradrenaline or other biomolecules commonly found in humanbiofluids.