Fabrication And Properties Of Chitosan Hydrogel Filled Multilayer Microcapsules

The Layer-by-Layer (LbL) self-assembly based on electrostatic interaction was initially introduced by Decher and co-workers in 1991. Since then, polyelectrolyte multilayer microcapsules prepared by layer-by-layer adsorption of oppositely charged polyelectrolytes have received considerable attentions. Some microcapsules can spontaneous deposite various substances which meets different applications in the fields like biotechnology, chemical engineering and pharmacy.Chitosan is one kind of polysaccharides with good biocompatibility, non-toxic to human body, with antibacterial and anti-inflammatory effects. Water soluble chitosan derivative(CML) was obtained by grafting methacrylic acid(MAA) and lactic acid(LA) onto chitosan chain, and CaCO₃ microparticles doped with the CML (CaCO₃(CML)) were fabricated. Layer-by-layer assembly of sodium poly(styrene sulfonate) salt (PSS) and poly(allylamine hydrochloride) (PAH) was then conducted on the CaCO₃(CML) microparticles to form core-shell particles. Core removal by disodium ethylenediaminetetraacetate dehydrate(EDTA) yielded the PSS/PAH multilayer microcapsules with CML in their interiors. The CML hydrogel was formed in situ by photoinduced crosslinking. The as-prepared microcapsules preserved the microscopic morphology of their template particles. Unlike the traditional multilayer microcapsules, these CML hydrogel filled microcapsules remained their spherical shape after drying, but their size was decreased from 6.8μm to 4.6μm. The capsule size and shape were recovered after hydration. These microcapsules showed high loading efficiency of fluorescent dyes including negatively charged fluorescein sodium and bovine serum albumin, positively charged rhodamine, and neutral Nile red in both water and organic solutions. The drying stability, hydration property, pH responsive, and controllable degradation of the gel-filled capsules were studied.Loading and release behavior of bioactive substance DNA in the microcapsules were studied. The influence of incubation concentration, temperature, salt concentration and pH value on the loading and release behavior of DNA were systematically investigated.