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Three simple fluorescence turn-on sensors have been designed for the selective detection of adenosine (AD) based on a boronic acid receptor and a coumarin fluorophore (NLC, NJC, NDC). In the absence of AD, the fluorescence emission intensity of the sensors was relatively weak due to the effective electronic transfer from the to the coumarin to the boronic acid moiety. When the AD was introduced into the system, an obvious fluorescence enhancement was observed. It was attributed to the boronic acid covalently binding to the cis -diol unit of the AD resulting in the electronic transfer process being inhibited. Under the optimal conditions, these fluorescent sensors not only could perform good selectivity and fast response (< 30 s), but also show good water solubility. Finally, the proposed sensor NLC has been utilized for the AD determination in urine without any complicated pretreatment and the recovery was in the range of 95–103%. As a result, it is promising for application on the AD detection in complex biological samples. Moreover, there are no small molecular sensors detecting AD have been reported, yet, it is promising for providing a new platform to detect AD by small molecular sensor. [Display omitted] • Fluorescence turn on sensors for specific detection of adenosine (AD) in urine. • The first synthesized small molecular sensor for detecting AD. • The sensors operated by phenylboronic acid as the recognition group and coumarin as the luminescent group. • Sensor NLC has a low detection limit when detecting AD (6.87 μM). [ABSTRACT FROM AUTHOR]

Small-molecule reactive species, such as reactive oxygen species, catecholamines, ions, sialic acid and gas signal molecules, are involved in many important biological events. For example, abnormal reactive oxygen species levels can lead to a range of cell dysfunctions and eventually cancer and neurodegenerative diseases. Therefore, the development of sensors for detecting small-molecule reactive species is of great significance for disease prevention, diagnosis and treatment. Boronic acid has been widely used for the selective recognition of sugars due to their obvious fluorescence change after combining with sugar, easily structure modification and good light stability. In recent years, a large number of boronic acid-based sensors that can selectively recognize small-molecule reactive species have been reported, however, there are few systematic reviews in this field, and lack of in-depth understanding of the identification mechanism and structure-activity relationship. In this review, boronic acid-based sensors detecting small-molecule reactive species (such as reactive oxygen species (H 2 O 2 , ONOO−, CLO−), catecholamines (dopamine, norepinephrine), sialic acid and sialic acid derivatives (sialic acid, sialic Lewis X, sialic Lewis Y) and ions (F−, Fe3+, Cu2+)) over the recent years (2015–2020) will be discussed, focusing on the fluorescence characteristics of the sensors and their potential in disease detection, and we are aiming to provide researchers with better inspiration. • Small-molecule reactive species are involved in many important biological events. • Boronic acid-based fluorescent sensors are widely used to detect small-molecule reactive species in organisms. • We review boronic acid-based sensors for small-molecule reactive species imaging. • We discuss the characteristic and response mechanism of the sensors. [ABSTRACT FROM AUTHOR]