Physiochemical Surface Properties of Lung Tissues for Modeling Drug Deposition

Michael Lamb, Mathew D. Rowe, and Keisha B. Walters. Swalm School of Chemical Engineering, Mississippi State University, 330 Swalm Chemical Engineering Building, Mississippi State, MS 39759

The objectives of this research are to investigate and model the physical and chemical surface properties of lung tissues and model the interaction of these tissues with inhalation drugs. By studying the contact angles of saliva and drug doped saliva on lung tissue and mucin layer samples, appropriate deposition and adsorption boundary conditions can be developed with eventual implementation in fluid dynamic simulations. In order to measure the contact angle between these surfaces and the probe liquids, a contact angle goniometer was used to take digital images of the sessile drops and software was used to determine surface contact angle using several different models. Static contact angles of three probe liquids, pH 7 phosphate buffer solution, HPLC water, and artificial saliva doped with potassium iodide, salbutamol, or theophyiline, have been measured on bovine lung tissue samples. The contact angle of artificial saliva doped with potassium iodide was found to change rapidly (~ 40 to 25) within the first 120 seconds of contact with bovine lung tissue, and the contact angle of artificial saliva doped with theophyiline demonstrated a similar behavior in the first 120 seconds (~33 to 22). At low drug concentrations, the saliva composition was found to have a stronger influence on the contact angle than the dopant. Investigation will continue using the saliva and drug-doped saliva as the probe liquids on both lung tissue and mucin layers and development will begin on a model to account for the relationship between drug chemistry, molecular weight and shape, and concentration and the degree of deposition on lung tissues.