pH controlled permeability of lipid/protein biomimetic microcapsules.

The permeability of lipid and protein microcapsules fabricated by alternating adsorption of human serum albumin (HSA) and L-alpha-dimyristoylphosphatidic acid (DMPA) on a template and subsequent removal of the core is studied as a function of pH value and supplementary layers. The capsules were permeable for macromolecules (FITC-labeled dextran, M(w) 40 kDa) at pH < 4.8 and impermeable at pH > 7.4. The assembly of supplementary DMPA bilayers rendered the capsules impermeable for small hydrophilic molecules such as 6-carboxyfluorescein (6-CF). Hence DMPA/HSA capsules can be resealed after fabrication by supplementary layers. This provides the opportunity of applying such biomimetic membrane capsules as drug carriers or model systems to study biological processes at membranes.