An ATP/ATPase responsive supramolecular fluorescent hydrogel constructed via electrostatic interactions between poly(sodium p-styrenesulfonate) and a tetraphenylethene derivative

By electrostatic interactions between poly(sodium p-styrenesulfonate) 1 and the tetraphenylethene (TPE) derivative 2 containing two quaternary ammonium cations, a novel bioresponsive supramolecular fluorescent hydrogel 3 was constructed. This self-assembly process led to the aggregation of TPE, a typical chromophore with aggregation-induced emission (AIE) properties, thereby endowing this hydrogel with AIE fluorescence properties. Moreover, this supramolecular fluorescent hydrogel was responsive to biomolecules. When ATP was added to this system, it interacted with 2 more strongly than 1. Correspondingly, the network structure of the hydrogel was destroyed and the aggregation extent of 2 was decreased, which induced the transition from gel to sol and decreased the fluorescence intensity of the hydrogel at the same time. Subsequently, after phosphatase ATPase was added to the solution, ATP was decomposed and the electrostatic interactions between 1 and 2 were rebuilt, transforming sol into gel and recovering the fluorescence intensity of the hydrogel. Therefore, the fluorescent supramolecular hydrogel 3 was bioresponsive. Simultaneously, this fluorescent supramolecular hydrogel 3 could cross over the cell membrane and enter the cytoplasm, which could be applied in cell imaging.