Mechanism-based pharmacokinetics and biopharmaceutics; investigation of the mechanisms of intestinal transport and metabolism and oral delivery of pharmaceutical macromolecules (carbohydrate- and protein-derivatives, genes, and vaccines) and drug analogues of natural compounds such as organic cations/anions, peptides and nucleosides; predictive and correlative physiologically-based pharmacokinetic modeling; physicochemical and biological mechanisms of enhancing adjuvancy of polymeric vaccine delivery vehicles