EpiAirway Performs Well in Inhaled Drug Delivery Experiments
- A Rapid, Highly Effective, Low Cost Alternative to Expensive Animal and Human Clinical Screens
- Great Utility as a Primary Screen for Development of Nasal Drug Delivery Vehicles
Evaluation of the Penetration and Cytotoxic Effects of Drug Formulations on an In Vitro Nasal Mucousal Model. J. M. Easow, E. Scotto-Lavino, E. J. Roemer, and S. R. Simon, Department of Pathology, SUNY Stonybrook
The nasal route is an attractive alternative to conventional oral or parenteral drug delivery. The nasal mucosa provides a moist and highly vascularized membrane, crucial to rapid absorption into the blood stream, thus facilitating faster transport to the site of action.
The two main disadvantages of nasal delivery are the limited maximum dose per spray and the rapidity of clearance from the nasal cavity. These difficulties can best be addressed early in drug development. In vitro screening of drug formulations can provide an efficient and cost-effective method of identifying lead candidates prior to in vivo testing.
We have evaluated the ability of a large number of drug formulations to penetrate mucous membranes using MatTek's EpiAirway™ System. The EpiAirway System consists of human derived tracheal/bronchial epithelial cells grown on a collagen coated membrane to form a highly differentiated, organotypic model with many of the same features of nasal mucosa. The cells produce tight junctions that inhibit the passage of low molecular weight solutes, as well as the flow of electric current, permitting the use of trans-epithelial resistance (TER) as a correlate of permeability. Concurrent evaluation of formulation cytotoxicity is important in order to evaluate whether drug permeation is due to a significant loss of viability or if it is occurring on viable tissue constructs. For these studies two complementary systems: lactate dehydrogenase (LDH) release, to measure the accumulation of dead cells, and reduction of tetrazolium salt (MTT), to evaluate the metabolic activity of living cells; were used.
EpiAirway cultures are obtained in phenol red and hydrocortisone free medium and are cultured at 37oC for 48 hours to allow the tissues to equilibrate and begin secreting mucin. Test formulations are applied to the apical surface at the air-tissue interface of quadruplicate tissues. Samples are drawn from the underlying culture medium at 15, 30, 60 and 120 minutes for assay of drug concentration and lactate dehydrogenase (LDH) evaluation of cell death. Following harvest of the final time points, TER of the cell constructs is measured to evaluate tissue integrity. Finally, the viability and relative metabolic activity of each sample tissue is evaluated by cell uptake and transformation of the formazan dye, MTT.
To date we have studied and evaluated the effects of multiple nasal delivery test formulations for a variety of drugs. During the course of screening studies, several of the test articles were run more than once. In each case, the tissue responses were remarkably reliable and reproducible in samples run using different tissue lots. If test formulations incurred any cytotoxic effects, results were consistent across the multiple tissues dosed. Those formulations with evidence of cytotoxic results from LDH and MTT assay data also had significant reduction or loss of tissue resistance. However there were a number of test articles with reduced TER values and increased permeation presenting no cytoxic response.
Overall, this model exhibited a consistent profile of reliability, responding with appropriate sensitivity to test conditions while retaining the characteristics expected of normal tissue and yielding reproducible data, which allowed for the rapid identification of lead candidates for pharmaceutical development.
This study was supported by a NSF-RAIRE grant, No.STI9620074.
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(This abstract originally appeared in the SUNY Stonybrook publication "URECA News", May 2002. Reprinted with permission of E. Roemer, Dept. of Pathology. Bolded text by MatTek Corp. to highlight key points.)
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