Fabrication And Characterization Of NaCS/Chitosan Layer-by-Layer Self Assembly Complex Membrane & Microcapsules

A novel biocompatible layer-by-layer (LbL) self assembly multilayer structure by NaCS-Chitosan was fabricated. This multilayer layer structure had significance in both theotical and application research. On the first part it enriched the means of built multilayer systems; on the other hand, the LbL self assembly microcapsules had potential application in the design drug delivery systems.Firstly, LbL self assembly was carried out on flat plane. The growth of LbL complex membrane was characterized by FITC labeled chitosan. Also the effects of several experimental parameters on LbL membrane growth were studied such as chitosan concentration, chitosan molecular weight, substitution degree of NaCS and NaCl concentration in the system.Then the fabrication and characterization of LbL hollow microcapsules were conducted. In order to control the size of LbL microcapsules, a series of size-controlled poly-lactic acid and calcium carbonate microspheres were prepared as core templates. Surface response experiments were conducted to optimize the various experimental conditions in poly lactic acid microspheres preparation. Also the additive effect on CaCO₃ was investigated and optimized. As the results, the micro-spheres with high spherical degree, good size distribution and negative surface charges were fabricated.Finally, LbL self assembly hollow microcapsules was fabricated and characterized. NaCS and chitosan were deposited on micro-particles templates to form core-shell structures. A novel method for removing the core templates PLA and CaCO₃ from the formed core-shell structure was proposed by addition of N-Methyl pyrrolidone or EDTA-Na. This preparation process was well observed by the microscope-camera system. The hollow microcapsules were tested by SEM, CLSM and SPM to characterize their size, morphology and surface. The results showed that the shell thickness of microcapsules was about 6nm, and the average thickness of one layer of NaCS/chitosan polyelectrolyte complex was 1.5nm. The molecular weight cut-off in SDS-PAGE showed about 70kDa by using of diffusion test with the cell lysate of E.coli.