Development and characterization of temperature-sensitive hydrogels embedded with sodium alginate-chitosan microspheres

Ulcerative colitis (UC) is a chronic intestinal disorder characterized by severe intestinal inflammation and superficial mucosal ulcers. Ramulus mori alkaloids (SZ-A) were approved by the National Medical Products Administration of China in 2020 for the treatment of type 2 diabetes mellitus. Later studies confirmed that SZ-A act on multiple inflammatory pathways to exert anti-inflammatory effects, suggesting that SZ-A has the potential to alleviate UC. A temperature-sensitive hydrogel embedded with sodium alginate (SA)-chitosan (CS) microspheres was constructed for colon-targeted delivery of SZ-A. The results showed that the microspheres prepared by exogenous emulsification had rounded and smooth surfaces with high drug-loading capacity. The optimum preparation conditions were as follows: 600 rpm stirring speed; a 1:4 ratio of water-to-oil phase; and a 5% Span80 emulsifier. The temperature-sensitive hydrogels embedded with SA-CS microspheres (TMH) had a moderate gelling temperature of 31.8 ± 0.74°C. The rheologic results showed that the internal structure of TMH was stable with viscoelasticity, and the in vitro release results indicated that the TMH exhibited slow-release performance. The findings suggest that TMH has suitable gelling temperature and viscoelasticity, and may be a promising targeted delivery vector for UC treatment.