A pH/Time/Pectinase-Dependent Oral Colon-Targeted System Containing Isoliquiritigenin: Pharmacokinetics and Colon Targeting Evaluation in Mice

Background and Objectives Oral colon-targeted gel beads containing isoliquiritigenin (ISL) were successfully designed in our study. In order to further explore the targeting of the colon by the gel beads, a systematic study of their in vivo pharmacokinetics and colon targeting was performed in mice. Methods Eighteen male mice were included in this study. The mice were separated into six groups at random. We collected blood, stomach, duodenum, jejunum, ileum, and colon tissues at 2, 4, 6, 8, 12, and 24 h after oral administration of gel beads containing isoliquiritigenin at a dose of 20 mg/kg. Gel beads in tissues were recorded and taken out to observe their swelling and erosion. The total ISL concentrations in different tissues and gel beads were analyzed by high-performance liquid chromatography. Results All gel beads reached the upper part of the stomach at 2 h with no obvious swelling. Most of the gel beads were still in the lower part of stomach, while a small amount had reached the small intestine at 4 h. A few gel beads reached the colon and swelled at 6 h. Furthermore, the gel beads in the colon were swollen and erosive at 8 h. Meanwhile, the plasma ISL concentration could be detected, which indicated that the ISL in the gel beads was absorbed. At 12 h, the gel beads were almost dissolved and the plasma concentration was 8.33 times that at 8 h. At 24 h, the gel beads had completely disappeared, and the plasma concentration was 2.55 times that at 12 h. Conclusion The gel beads containing ISL are a sustained, controlled, and colon-targeting delivery system that can alter the ISL distribution in the gastrointestinal tract.