Real-time and noninvasive tracking of injectable hydrogel degradation using functionalized AIE nanoparticles

Visually monitoring of the residual morphology and quantitatively determining the degradation degree of hydrogels applied in tissue repair therapy in a real-time and noninvasive manner were a crucial technological mean. Despite conventional organic fluorescent molecules commonly used as probe to capture the real-time clues of the labeled hydrogels, they still encounter obstacles, including intrinsic photobleaching, cytotoxicity, and unknown interference factor of degradation caused by the change from polymer structure of hydrogels, thus making it difficult to accurately obtain the information of the hydrogels in vivo. To address the hard nut, we designed the multifunctional hydrogel system with a real-time quantitative aggregation-induced emission fluorescent detection and photoacoustic imaging tracking based on tetraphenylethene (TPE) that possesses the trait of aggregation-induced emission and low photobleaching, bound on the surface of mesoporous dopamine microspheres (MPDAs), and subsequently loaded into the photo-crosslinked injectable hydrogels. In vitro results showed that MPDA-TPE had good compatibility, emitted strong fluorescence when embedded in hydrogels, and maintained stable fluorescence property unless the hydrogels were degraded. Meanwhile, a mathematical formula for the kinetic degradation of hydrogels was established between gravitational and visual degradation in vitro, which can be used to predict in vivo degradation. Furthermore, MPDA possessed the clear photoacoustic imaging effect to provide more accurate clues. The designed hydrogel system holds a potential role in prediction of the in vivo degradation of implanted materials in an accurate, convenient, and real-time noninvasive manner and is a meaningful treatment aid in tissue engineering.