Salt-responsive Self-assembly Of Luminescent Hydrogel With Intrinsic Gelation-enhanced Emission

Tetraphenylethylene (TPE), an archetypal luminogen with aggregation-inducedemission (AIE), was grafted to a salt responsive peptide to yield a yet luminescenthydrogelator. The gelator is specifically responsive to salt factor, while other factors,such as temperature, pH and the solvents could not trigger the gelation process.Moreover, the TPE-Q19hydrogel has a novel property of gelation-enhanced emission.The gelator was not fluorescent under mono-dispersed solution, whereas efficientlyemitted with the gelation proceeding and reached the maximum when the solution-geltransformation completed. Different with traditional fluorescent hydrogels, theinduced luminescence was a dynamic change and enabled real time monitoring ofhydrogel formation. Experiment results showed that the TPE-Q19hydrogel hassatisfied mechanism properties and biodegradability. The gel could return back tosolution under hydrolysis of trypsin.The morphology and assembly mechanism of TPE-Q19hydrogel were alsostudied. The results showed that Q19is the leading part of assembly. Inmono-dispersed solution, Q19dominated the gelator self-assemble into β-sheetnanofibers under stimulation of salt. As result, TPE was encapsulated into thehydrophobic inner of fiber structure, which would restrict the IMR of peripheralphenyl rings and ultimately lead to enhanced emission of TPE.The designed gelator is composed with polypeptide, a kind of materials withhigh biological compatibility and low toxicity. The gelation condition is mildcontrollable. Most importantly, its novel gelation-induced emission enabled the realtime monitoring of hydrogel formation, which is promising for the development ofself-revealing soft materials for biological applications.