Visualization of thermosensitive hydroxypropyl chitin with aggregation-induced emission features for sustained-release drug delivery

Hydroxypropyl chitin (HPCH) has been studied as a carrier for drug delivery due to its excellent biocompatibility, biodegradability and reversible thermosensitivity. However, the behaviors of the erosion/degradation of HPCH and release of drug for drug-loaded HPCH in vivo are unclear. Visualization of the drug-loaded HPCH could reveal the location and degradation of the carrier, and the release and distribution of the drug in vivo, which is more beneficial for promoting the clinical translation. Herein, we simultaneously tracked HPCH labeled by aggregation-induced emission fluorogens (AnDA-HPCH) and a model drug (indocyanine green, ICG) in vitro and in vivo without mutual interference. The erosion/degradation rate of AnDA-HPCH and the drug release of ICG from the ICG-loaded AnDA-HPCH sponge implanted in the buttock of mice were slower than those of the injected hydrogel containing the same amounts of drug and polymer. Further, the long-acting local anesthetic ropivacaine-loaded HPCH sponge implanted in the back of rats showed an effective analgesic time of approximately 30 h, which was 3-fold longer than that with the injected RPH@HPCH hydrogel (10 h) and much longer (6 times) than that of the xaracoll-like formulation (5 h). This thermosensitive HPCH sponge may be a promising visible biomedical implant for sustained-release drug carrier and tissue repair.