Colon-specific microspheres loaded with puerarin reduce tumorigenesis and metastasis in colitis-associated colorectal cancer

Colitis-associated colorectal cancer (CAC) is a common malignancy that develops in chronically inflamed mucosa and is usually accompanied by metastases at other sites. Puerarin, a natural isoflavone isolated from the root of the Pueraria lobata (Willd.) Ohwi, has potential anti-colon cancer activity. However, the poor solubility and low bioavailability of puerarin has restricted its application in the pharmaceutical industry. In the present study, pH-responsive alginate microspheres loaded with puerarin were prepared by emulsification/internal gelation for targeted treatment of colitis-associated colorectal cancer. Herein, puerarin, as an active drug, could participate in the construction of alginate microspheres with hydrogen bonding. The microspheres exhibited pH-responsive release behavior with little release of puerarin in simulated gastric fluid and high amounts (approximately 55%) of release in simulated colonic fluid. A fluorescence tracer indicated microspheres had high retention time of more than 20 h in the colon. Meanwhile, puerarin-loaded alginate microspheres not only significantly decreased the inflammatory response by downregulating the levels of pro-tumorigenic cytokines, but they reduced tumorigenesis and metastasis by inhibiting epithelial-mesenchymal transitions in AOM/DSS-induced colitis-associated colorectal cancer in mice. The overall results suggested that puerarin-loaded alginate microspheres could effectively inhibit development of colonic tumors, which could be developed as a promising therapeutic strategy for colitis-associated colorectal cancer.