| We prepared two kinds of spherical CaCO3 microparticles without any organic additives and applied them for successful construction of biocompatible microcapsules by deposition of biomolecules of chitosan(CHI)[or its derivative hydroxyl propyl chitosan(HPCHI) or quaternary ammonium chitosan(QACHI)]and sodium alginate(SA).After removal of the carbonate cores by disodium ethylenediaminetetraacetic acid(EDTA),CHI-SA,HPCHI-SA and QACHI-SA hollow microcapsules with good biocompatibility were fabricated.The characterization results indicate their excellent integrity.The self-made spherical pure calcium carbonate particles have very good monodispersity and there are massive pores on the surfaces of the particles,therefore during the process of layer by layer assembly,much more polyelectrolytes(PEs) can be adsorbed on the rough surface.Calcium carbonate particles from the calcium chloride and disodium carbonate have a high specific surface area of 11.297 m2g-1 and the pore diameter is from 5 to 15 nm,which makes it facilitate much more effective adsorption of biomolecules and have an important application in the process of immobilization such as proteins.After the decomposition of pure CaCO3 core made of CaCl2 and Na2CO3,the specific pancake-patterned microcapsules were obtained.The calcium element exists in the(CHI-SA)4 and(HPCHI-SA)4 microcapsules,as demonstrated by energy dispersive X-ray spectroscopy(EDS) and inductively coupled plasma(ICP).The calcium content is determined to be 2.290×10-10,1.201×10-10 mg in each(CHI-SA)4, (HPCHI-SA)4 microcapsule,respectively.No CaCO3 residue exist in the microcapsules,because the characteristic adsorption bands of CO32- bonded with Ca2+ are absent in the FT-IR spectra of the microcapsules.Moreover,the FT-IR spectra and ICP measurement confirm the formation of self-organized pancake-patterned microcapsules.Namely,during the process of core decomposition,dissolved water-soluble Ca2+ in the form of Ca2+-EDTA coordinates with SA in the shell,leading to the gel-like Ca2+-SA in the microcapsules.So such containers have promising application for Ca2+ storage in organic matrix in the biomedical fields.After core removal,the biocompatible hollow microcapsules(HPCHI-SA)5 and (QACHI-SA)5 with a diameter about 5μm and intact structures were successfully fabricated by sequential deposition of PEs on the pure CaCO3 particles made of Ca(NO3)2 and Na2CO3.The microcapsules were characterized by SEM,transmission electron microscope(TEM),atomic force microscope(AFM) and confocal laser scanning microscopy(CLSM),indicating good integrity and stability.The adhesion of microcapsules is also confirmed by CLSM technique.In summary,we demonstrate that four kinds of biocompatible microcapsules with diverse structures have been successfully fabricated with pure CaCO3 particles without any organic additives as cores by the LbL technique. |
