Cell Permeability Assay
Creative Animodel provides several cell models to evaluate absorption and permeability of drugs. We are committed to offering professional and high-efficiency cell permeability assay to screen the most favorable compounds. Creative Animodel is a leading biotech company offering a range of DMPK services. Our scientists strictly follow the industry standards to guarantee the accuracy and reliability of assay results.
Figure 1. Cell permeability assay
Cell permeability assay is one of the most common in vitro permeability assays. The major application of the cell permeability assay is to screen chemical libraries for compounds that have favorable permeability characteristics. The most common cell culture based models are Caco-2, MDCK, LLC-PK1 and HT29 cell models. The characteristics and applications of these models are as follows:
Caco-2 cell model
The Caco-2 cell model is a good characterized and widely used in vitro cell model in the field of drug permeability research. It has been considered the gold standard technique and has been used to standardize other absorption assessment techniques. Caco-2 cells are cultured on a filter support in a multiple well format. The permeability is measured by the movement of molecules from one side of the cell monolayer to another. Caco-2 cells are from a human colon adenocarcinoma and they exhibit many in vivo intestinal cell characteristics by expressing intestinal enzymes and transporters and having tight intercellular junctions and microvilli. Due to these similarities, the permeation characteristics of drugs across Caco-2 cell lines correlate with their human intestinal permeation characteristics. Therefore, the Caco-2 model can be used to predict the permeability and absorption of drugs in humans.
MDCK cell model
MDCK (Madin-Darby Canine Kidney) cells are derived from dog kidney cells. When the MDCK cells are cultured under standard circumstances, they develop into polarized columnar epithelial cells and form tight cellular junctions. The main advantage of MDCK cells is short culture time, which can be 24 hours or so. The permeability coefficients of hydrophilic compounds are usually lower in Caco-2 cells than in MDCK cells. Due to the different origins, the expression levels of intestinal transporters would be different in Caco-2 and MDCK cell lines. Hence, the MDCK model has to be widely characterized to confirm the correlation of transport mediated drug permeability to human absorption.
LLC-PK1 cell model
LLC-PK1 (Lewis Lung Carcinoma-Porcine Kidney) cells are derived from normal pig kidneys. When cultured, LLC-PK1 cells rapidly differentiate into a well formed monolayer with microvilli on their apical cell surface and bush boarders. It is reported that these cells are used in passive cellular diffusion assay. As with Caco-2 and MDCK cells, these cells also have different transporters on their surface. A study has shown that uracil was transported by both sodium-dependent and sodium-independent pathways in LLC-PK1 cells; but in Caco-2 cells, uracil was transported only by sodium-independently pathway. These different transport mechanism can be attributed to differences in the origin of the cells types and the transporters that are expressed on these cells.
HT29 cell model
The role of mucus on drug permeability is important. Certain strains of HT29 cells produce mucus. The wild-type HT29 cells grown on media containing galactose lead to the selection of a subclone. Then HT29 cells form polarized cell monolayers and secrete mucus. A study has shown that the presence of the mucus layer in HT29-H resulted in lower permeability coefficients than Caco-2 monolayers in a testosterone permeability study. It indicates that the mucus layer accounts for most of the permeability resistance to testosterone. An attempt has been made to co-culture the Caco-2 cells with HT29-MTX or HT29-H cells in order to provide representative characteristics of intestinal mucosa.
Creative Animodel has rich experience and has provided a range of services in the field of pharmacokinetics and biopharmaceutical for more than ten years. Our company also has experienced experts to solve your problems during drug research and development process. We are glad to establish long-term cooperation with our customers. If you have any questions, please feel free to contact us.
1. Gad, S.C. Preclinical Development Handbook: ADME and Biopharmaceutical Properties. A John Wiley and Sons. Inc, Hoboken, New Jersey, 2008.