Figure 1. General methodology of integrative, cell based transport modeling.

A) For computational simulations at the cellular level, a monobasic compound diffuses across a phospholipid bilayer and undergoes ionization and partition/binding in each compartment. The neutral form of the monobasic molecule is indicated as [M], and the protonated, cationic form of the molecule is indicated as [MH⁺]. B) For computational simulations at the histological level, each airway generation is modeled as a tube lined by epithelial cells; as molecules are absorbed over time, the drug concentration in the lumen decreases accompanied by an increase in drug concentration in the circulation C) For computational simulations at the organ level, the lung is modeled as a branching tree, with airway generation modeled as a cylinder, from the trachea to the alveoli. D) Experimental design of insert system with patterned pore arrays on membrane support for viewing lateral transport of fluorescent molecules along the plane of a cell monolayer, away from a point source. E) Transmitted light image of a 5×5, 3 µm diameter pore array (20 µm spacing) on a polyester membrane. F) Transmitted light image of an MDCK cell monolayer above a membrane support with 3×3, 3 µm diameter pore array (40 µm spacing). Scale bar: 40 µm. G) 3D reconstruction of confocal images of the distribution of three fluorescent probes added to the uppermost surface of NHBE cell multilayers grown on air-liquid interface cultures on porous membrane support. Each 3D plane is composed of the image with the fluorescent channel; red (MTR), blue (Hoe), and green (LTG). H) Illustration of the tiling algorithm used to visualize and quantify the distribution of Hoe and MTR in lung cryosections, after IT and IV coadministration of the probes.