In Vitro ADME

       In the process of developing small molecule drugs, it is necessary to evaluate the bioavailability of compounds as early as possible, in order to lay the foundation for subsequent pharmacological experiments and later development. In addition to using experimental animals to evaluate bioavailability, various in vitro analysis methods have been developed to evaluate the ability of compounds to penetrate the intestinal wall. These in vitro experiments not only have lower costs, but also higher flux and shorter experimental period. The permeability analysis of Caco-2 monolayer cells has become one of the standard in vitro methods.  

       CaCO-2 permeability assays can help researchers estimate the ability of candidate drugs to penetrate the small intestine epithelium. Specific applications of the CaCO-2 cell model include studying whether orally administered drugs are transported from A to B direction or from B to A direction, and clarifying whether drug absorption is a result of passive diffusion or active transport, providing a basis for drug administration protocols.  

       The CaCO-2 cell line is derived from human colon cancer and has typical features of intestinal epithelial cells, such as the ability to form polarized monolayers of columnar epithelium with well-differentiated and dense microvilli on the apical surface of the cells neatly arranged to form a striated edge as well as intercellular connections. Incubation of Caco-2 cells on porous permeable polycarbonate membranes resulted in fusion and spontaneous differentiation into intestinal epithelial cells, forming a continuous monolayer. After 21 days of incubation, a dense cell monolayer is formed that is structurally and biochemically similar to small intestinal epithelial cells.  

       The Caco-2 cell permeability assay not only helps to determine intestinal permeability, but also identifies specific transporter or efflux proteins as well as intestinal phase II drug metabolism enzymes. Thus, this cell-based assay provides valuable information for drug development in a validated and reproducible manner that is not available from nonbiological models, or even from many other biological models.