Preparation Of Mutilayer NaCS-PDMDAAC Biocapsules Templated On Spherical Calcium Carbonate Particles

The capsules system composed of cellulose sulfate sodium and Poly-dimethyl-diallyl-ammonium chloride (NaCS-PDMDAAC) was an interesting polyelectrolytes capsules system with high mechanical properties and biocompatibility. In the past, these PDMDAAC-NaCS capsules were prepared by dropping a solution of NaCS into a solution of PDMDAAC. In fact, their size was almost over 1 mm, which was limited for microscope application. In this work, we will prepare homogeneous micrometer-sized hollow capsules using alternate adsorption of PDMDAAC and NaCS on CaCO3 template particles by layer-by-layer self-assembly technique.Firstly, the CaCO3 particles with various shapes were prepared by the reaction of potassium carbonate (K2CO3) with calcium chloride (CaCl2) in the presence of carboxylmethyl cellulose sodium (CMC).The influence of CMC concentration, the stirring rate, temperature and time on the morphology and size of the CaCO3 particles were studied. The results showed that at a CMC concentration of 0.5 g/L, the smooth spherical CaCO3 particles were obtained at the room temperature.Secondly, the CaCO3 particles were characterized by scanning electron microscopy, particle-size analyzer, XRD, thermogravime tric analysis and Zeta-sizer. The results showed that at a CMC concentration of 0.5 g/L, the smooth spherical CaCO3 particles with size around 6-8μm were obtained. The CMC content was 5.12%and theξ-potential of CaCO3 was-37.3 mV. And these CaCO3 particles could be used as core templates. And the crystallization process of spherical CaCO3 particles was also discussed.Thirdly, four bilayers of PDMDAAC and NaCS polymer film were deposited on the CaCO3 cores by layer-by-layer self-assembly technique. The film buildup was characterized by (ⅰ) microelectrophoresis; (ⅱ) scanning electron microscopy (SEM); and (ⅲ) thermogravimetric analysis (TGA). Hollow capsules were then prepared by exposing the coated CaCO3 particles to EDTA-Na.Finally the molecular weight cut-off (MWCO) of the microcapsules was determined by exposing the microcapsules to the E.coli cell lysate.