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[Display omitted] • The enzymatic cascade increased the selectivity of the sensor and reduced the reaction time. • Gold nanoclusters were synthesized for internal calibration to improve the accuracy of the sensor. • The constructed ratiometric fluorescence sensor for choline detection has two linear ranges of 0.5–20 μM and 20–100 μM and low LOD of 0.27 μM. • The fluorescent sensor was successfully applied to the detection of choline in human serum. Choline (ChO) is a biomarker of many diseases. Its accurate and sensitive detection is of great significance for the diseases diagnosis. Gold nanoclusters with bovine serum albumin as template (BSA-AuNCs) were synthesized by microwave-assisted method. A ratiometric fluorescence sensor was constructed based on BSA-AuNCs and 2,3-diaminophenazine, which was the oxidation product of o-phenylenediamine. Combined with cascade enzymatic reaction, it was used for the detection of choline. In the detection system, choline oxidase improved the selectivity of detection, and the peroxidase-like activity of molybdenum disulfide nanosheets shortened the detection time. The linear ranges of choline detection by ratiometric fluorescence sensor were 0.5–20 μM and 20–100 μM. The detection limit was 0.27 μM. The ratiometric fluorescence sensor was easy to operate and had good selectivity. Compared with single signal sensor, it can effectively reduce the error interference such as environmental change, and the detection result was more accurate. [ABSTRACT FROM AUTHOR]

• A novel fluorescence switching aptasensor for ultrasensitive detection of Kana was developed. • Aptamer as fluorescence switching was simple to fabricate. • The constructed aptasensor showed high selectivity and accuracy. • The limit of detection, accuracy and recovery rate of the developed fluorescence aptasensor were satisfied. We developed a fluorescent switching based on bovine serum albumin stabilized gold nanoclusters (BSA-AuNCs) and kanamycin (Kana) aptamer to detect Kana. Red fluorescence of BSA-AuNCs was turn off when Kana aptamer was assembled on the surface of BSA-AuNCs. However, after adding Kana, the specific aptamer detached from the surface of the BSA-AuNCs and formed the complex of aptamer-kanamycin, then the red fluorescence of BSA-AuNCs was turn on. The fluorescence intensity of BSA-AuNCs can be mediated by the amount of Kana aptamer. A good linear response for Kana was obtained in the concentration range 0.04 nM to 7.0 nM. The assay was used to detect Kana in milk matrix, and the accuracy and recovery of the method were satisfied. It is worth noting that the aptamer mediated BSA-AuNCs fluorescent switching was simple and easy to fabricate, which can provide a novel assay for the detection of small molecules. [ABSTRACT FROM AUTHOR]