Penetration can occur into the membrane without necessarily diffusing, or passing through, the membrane. Permeation is the movement of the permeant through the membrane that encompasses first partitioning the membrane and then diffusion through the membrane. Penetration and permeation tests are used to profile the permeation behavior of pharmaceutical compounds that can cross cell membranes by passive diffusion, active transport, and pinocytosis to reach the systemic circulation. Penetration and permeability can depend on a variety of factors, such as pH, hydrophilicity and other physico-chemical properties of drugs, and tissue species. As bioparticles are formulated to increase drug penetration and absorption, especially for transdermal drugs, it is important to measure their penetration and permeation abilities to assess drug effectiveness. https://www.cd-bioparticle...