Gastroretentive core–shell hydrogel assembly for sustained release of metformin hydrochloride

The core–shell hydrogel assembly can be ingested into the stomach. The shell rapidly swells to prevent the expelling from the pylorus, and the core serves as a drug reservoir for loading highly water-soluble metformin hydrochloride. The hydrogel assembly can release metformin hydrochloride for 72 h in vitro, and blood drug concentrations maintain relatively constant for nearly 80 h in vivo. After use, the hydrogel assembly can be degraded naturally. [Display omitted] •A core–shell assembly is developed for the delivery of highly water-soluble drugs.•The assembly has a stable structure and can reside in the stomach for 3 days.•The assembly can release metformin hydrochloride sustainedly for 72 h in vitro.•Blood drug concentrations maintain relatively constant for nearly 80 h in vivo. The metformin hydrochloride is the only oral guanidine anti glycemic agent and is used as the first-line drug for the treatment of type II diabetes. Owing to its high water solubility and short half-life, however, this drug is difficult to be released sustainedly. Here, a core–shell structured hydrogel assembly as gastroretentive carrier is proposed for the sustained release of metformin hydrochloride. The hydrogel assembly can be ingested orally into the stomach. On contact with the gastric juice, the shell rapidly swells to prevent the hydrogel to be expelled from the pylorus, and the core serves as a drug reservoir for loading metformin hydrochloride. The core–shell structure can decrease the driving force of drug release and extend the drug diffusion pathway. As a result, the hydrogel assembly can release metformin hydrochloride sustainedly for 72 h in vitro and maintain stable blood drug concentration for nearly 80 h in vivo. Moreover, the hydrogel assembly can be biodegraded by the gastric environment.