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Fig. 2 The recognition mechanism of sensor 9b and gallic acid. [Display omitted] • Gallic acid is involved in many important biological events and has a variety of biological properties. • Boronic acid-based fluorescence sensors can specifically recognize compounds with 1, 2-diol structure. • Guanidine group synergizes with boronic acid group to enhance the binding affinity, selectivity and water solubility of sensor 9b. • We discussed the fluorescence response characteristics of sensor 9b with gallic acid and its application in actual samples. As one of the widespread phenols in nature, gallic acid (GA) has attracted a subject of attention due to its extensive biological properties. It is very important and significant to develop a sensitive and selective gallic acid sensor. In recent years, owing to their reversible covalent binding with Lewis bases and polyols, boronic acid compounds have been widely reported as fluorescence sensors for the identification of carbohydrates, ions and hydrogen peroxide, etc. However, boronic acid sensors for specific recognition of gallic acid have not been reported. Herein, a novel water-soluble boronic acid sensor with double recognition sites is reported. When the concentration of gallic acid added was 1.1 × 10−4 M, the fluorescence intensity of sensor 9b decreased by 80%, followed by pyrogallic acid and dopamine. However, the fluorescence of the sensor 9b combined with other analytes such as ATP, sialic acid, and uridine was basically unchanged, indicating that the sensor 9b had no ability to recognize these analytes. Also, sensor 9b has a fast response time to gallic acid at room temperature, and has a high binding constant (12355.9 ± 156.89 M−1) and low LOD (7.30 × 10−7 M). Moreover, gallic acid content of real samples was also determined, and the results showed that this method has a higher recovery rate. Therefore, sensor 9b can be used as a potential tool for detecting biologically significant gallic acid in actual samples such as food, medicine, and environmental analysis samples. [ABSTRACT FROM AUTHOR]

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]