Fluorescence turn-on sensing and imaging of kinetin using tetralactam macrocycle-based supramolecular probe

Kinetin (KT) is a crucial and widely used cytokinin; therefore, its dynamic detection and visualization are of significant importance. In this work, a water-soluble tetralactam macrocycle (TM)-based supramolecular probe was constructed for the in vitro detection and in vivo imaging of KT. Leveraging the excellent recognition of biomimetic TM toward KT, the sensitive and selective "turn-on" fluorescence detection of KT was realized in the range 2-200 μM with a limit of detection of 0.27 μM. The in vitro detection capacity of this supramolecular probe was validated in complex matrices, including potato extract and pesticides. Moreover, a portable visual sensing platform was further developed by integrating the supramolecular probe with hydrogel. Importantly, this supramolecular probe enables monitoring of the concentration distribution of KT through in situ fluorescence imaging, which may provide valuable insights into the physiopathological processes and action mechanisms of KT in plants. Furthermore, a sensor array was developed for discriminating between KT and other structure-similar cytokinins. This method holds great significance for cytokinin-related research.