Membrane filtration for microencapsulation and microcapsules fabrication by layer-by-layer polyelectrolyte adsorption

Layer-by-layer polyelectrolyte adsorption at colloid particle surfaces as w ell as the removal of the core latex to obtain multilayer microcapsules is conducted by means of membrane filtration. As target particles for adsorpti on we use nonsoluble polystyrene sulfate latex, soluble melamine formaldehy de resin latex, and decomposable glutaraldehyde fixed human red blood cells . The materials adsorbed are poly(allylamine hydrochloride), poly(styrenesu lfonate), poly(dialyldimethylammonium chloride), chitosan, and chitosansulf ate. The coating process is carried out under different membrane filtration conditions with respect to the pressure regime, the filter materials, and the stirring conditions. We characterize the prepared multilayers at the pa rticle surface or in the microcapsule (shell) form by atomic force microsco py, confocal laser scanning microscopy, transmission electron microscopy, s ingle-particle light scattering, and-electrophoresis. The quality, performa nce, and yield of the presented method are compared with the results obtain ed by centrifugation and sequential adsorption as alternative preparation s trategies. Membrane filtration surpasses all other methods, so far establis hed, with respect to the above criteria.