Aggregation-induced emission luminogen based self-healing hydrogels fluorescent sensors for α-amylase

The development of self-healing hydrogels with an adjustable fluorescence still remains a challenge, owing to the water-induced aggregation-caused quenching nature of traditional organic luminogens. In this work, a fluorescent self-healing hydrogel with a dual network was designed, in which the host–guest recognition of tetraphenylethylene (TPE) modified poly(l-glutamic acid) (PLGA–TPE) with acrylate γ-cyclodextrin (Ac-γ-CD) was strengthened by the second chemical crosslinking of Ac-γ-CD with acrylamide. Taking advantage of the host–guest recognition, the fluorescence of the TPE moieties has been suppressed in the hydrogel, and then the dual-network architecture of the hydrogel can be degraded by α-amylase cutting the α-1,4 glycosidic bonds of Ac-γ-CD, enabling the hydrogel to fluoresce. The fluorescence of the hydrogel increases gradually, and the mechanical properties decrease simultaneously, indicating a relationship between the degree of hydrolysis of Ac-γ-CD and the disruption of the stable network architecture of the hydrogel. This dual-network hydrogel possesses a fast self-healing ability and the recovery ratio reached almost 100% in 3 min owing to the dynamic nature of the host–guest recognition. Furthermore, by altering the temperature of the system, the fluorescence intensity of the hydrogel can be changed reversibly. Thus, through host–guest recognition, both the network architecture and the fluorescence behavior of this fluorescent self-healing hydrogel could be modulated, and it can therefore potentially be used as an α-amylase sensor or an indicator of the viscoelastic behavior of the hydrogel.