Passive film patches

Absorption through the oral mucosa can take place in two ways i) inter- or paracellular pathway, which is a passive transport through the lipid matrix between the cells and ii) trans- or intracellular pathway through the cell walls, which can be either passive or active transport. The following dosage forms may be used i) polymer-coated nanoparticles, ii) special tablets, iii) pol)mtier films, and iv) gels (patches) [112-119]. 

The formation of thick biofilms could in principle be beneficial if a compact film would uniformly cover a metal, preventing access of oxygen to the surface. However, biofilms usually do not form uniformly over a metal surface but usually in patches. Therefore they stimulate the formation of corrosion cells between covered and non-covered areas. The phenomenon is further enhanced if anaerobic conditions prevail at the metal surface in the areas covered by the biofUm, creating conditions for the development of anaerobic bacteria such as SRB that inhibit passivation. The following two examples illustrate the corrosive effect of microorganisms. 

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