Micromechanical Properties of Newly Developed Polyelectrolyte Microcapsules (PEMC)

Abstract

Microcapsules fabricated from polyelectrolytes offer advantages in that they are permeable to polar molecules and are extremely stable against chemical and physical influences as compared with liposomes. Polyelectrolyte microcapsules (PEMC) were prepared by consecutive multiple adsorption of different polyanions and polycations on decomposable/dissolvable biological templates like red blood cells. Poly(styrene sulfonate) [PSS], dextransulfate and human serum albumin were adsorbed alternately with poly(allylamine hydrochloride) [PAH] onto glutardialdehyde treated red blood cells as template, which was decomposed after completing the coating by a hypochlorite solution. Deformability properties of PEMC were studied by means of micropipette technique and confocal laser scanning imaging. The morphological properties of the PEMC were characterised by atomic force microscopy, confocal laser scanning microscopy and electrophoretic mobility. Rheological properties were investigated by viscosimetry as well aggregometry (light backscattering). The detectable surface charge was always negative. The wall thickness as well as the bending modulus (BM) of the PEMC was dependent on the number of layers and the used polyelectrolytes. The thicknesses were in the range between 7 and 28 nm and the BM was 4 to 5 magnitudes larger than the BM of red blood cells, which results in a slightly increased apparent blood viscosity and an increased aggregation time of a mixture of PEMC and blood (1 : 1).