Porous CaCO3 microparticles were fabricated by colloidal crystallization. Two oppositely charged polyelectrolytes, poly (styrene sulfonate, PSS) and poly (allylamine hydrochloride, PAH) were adsorbed layer-by-layer on the CaCO3 templates. Polyelectrolyte microcapsules were then obtained by removing the CaCO3 core. Scanning electron microscopy (SEM), energy-dispersion X-ray analysis (EDX), laser diffraction particle sizing and Raman spectroscopy were employed to characterize the physico-chemical properties of the constructed microcapsules. In vitro drug release studies were conducted using the model water-soluble drug Rhodamine B. Factors such as the number of polyelectrolyte layers and pH were investigated. SEM micrographs revealed uniform CaCO3 microparticles, nearly spherical in shape with pronounced surface roughness, and highly developed interior porous structure. The surface of polyelectrolyte coated particles became rougher than the initial CaCO3 microparticles. The acquired SEM micrographs of the (PSS/PAH)n microcapsules indicated that the number of layers affected the morphology of the microcapsules. The (PSS/PAH)3 microcapsules revealed a very porous network with many holes resembling the initial morphology of CaCO3 microparticles. Raman spectra showed peaks at 1125 cm-1 (S=O bond) and 1600 cm-1 (aromatic ring stretching) which represented the PSS molecule. The thickness of each layer was about 10 to 20 nm and it can be tailored to such nanometer level by controlling the number of adsorbed layers. The in vitro release of Rhodamine B was dependent on both the number of wall bilayers as well as the pH of the release media. These systems provide an opportunity for the development of controlled release dosage forms with greater effectiveness in the treatment of chronic conditions.
Keywords: CaCO3 microparticles, layer-by-layer, polyelectrolyte microcapsules, colloidal crystallization
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