| In recent years, the method of using biological microcapsule technology to obtain cell immobilization has been widely used. Microcapsules prepared by taking natural polysaccharide sodium alginate and chitosan as raw materials、calcium chloride as ionic cross-linking agent have become the most unique work in biological microcapsule research field for their good biocompatibility、easy to be molded and the character of transmission of controlled substance. However, due to the acid dissociation constant of phosphoric acid, glutamic acid, citric acid is bigger than alginate acid, when using calcium ion to crosslink sodium alginate, the formed calcium ion in calcium alginate gel has a metathetic function with phosphoric acid, glutamic acid and citric acid, which result in calcium alginate/chitin microcapsule’s excessive swelling, mechanical strength drop, easy to be damaged, reduction of the application effect of biological microcapsules. Aiming at these problems, this paper adopts the technology of pulse electric field, takes four different ionic cross-linking agents: calcium chloride, barium chloride, zinc chloride, manganese sulfate to react with sodium alginate solution droplets to prepare four kinds of alginate/chitosan microcapsule. By comparing the effect of different cross-linking agents on the stable mechanical properties^material disperse properties to study the function between cross-linking agents and sodium alginate and explore more stable ionic crosslinking agent, thus, expand the application of alginate/chitosan in biology, medicine, food, environment and other fields.The main results were as follows:1. Microcapsules formed by cross-linking agents with four different ions:Ca2+, Ba2+, Zn2+, Mn2+all have good sphericity, smooth surface, uniform diameter distribution and good dispersion. The stability of the four kinds of microcapsule in physiological saline is as follows: barium alginate microcapsule> zinc alginate microcapsule> calcium alginate microcapsule> manganese alginate microcapsule. Microcapsule stability and ionic crosslinking agent concentration was positively correlated.2. Experiment investigates the effect of chitosan molecular weight on microcapsule stability with different ionic crosslinking. Using chitosan molecular weight as60kDa,100kDa,200kDa respectively reacts with alginate gel beads of four ionic crosslinking:Ca2+、 Ba2+、Zn2+、Mn2+to form membrane. The results show that chitosan molecular weight had a little effects on the stability of microcapsule in physiological saline. Compared with crosslinking sample Mn2+, alginate gel beads formed by ion crosslinking agents: Ca2+、 Ba2+、Zn2+, when react with different molecular weight, the formed microcapsules can stably exist in physiological saline.3. With bovine serum albumin、egg albumin、papain and insulin as model proteins, by taking chitosan with molecular weight is60kDa、deacetylation degree is95%to react with alginate gel beads to form membrane, examining the diffusion properties of microcapsules formed by Ca2+、Ba2+、Zn2+、Mn2+on protein molecules. The results show that bovine serum albumin molecules with the molecular weight of67kDa can partly diffuse into calcium alginate and zinc alginate microcapsule; molecular weight of44kDa ovalbumin molecule may diffuse into barium alginate microcapsule. Manganese alginate microcapsule appear a worst permeability performance on protein, only makes molecular weight of21kDa papain diffuse into microcapsules.4. Film forming conditions have a significant impact on the permeability of microcapsules prepared by four different cross-linking agents:Ca2+、Ba2+、Zn2+、Mn2+Within the scope of20kDa to100kDa, with the increase of chitosan molecular weight, permeability of microcapsules on protein molecule decreases, which reveals the degree of microcapsule membrane density increases; with expansion of film forming time, increase of the thickness and density of microcapsule, which can decrease the permeability of protein molecule. Therefore, adjusting the polysaccharide molecular weight and mulching time can regulate permeability of microcapsule in a certain range.In short, using four different ions:Ca2+, Ba2+, Zn2+, Mn2+as cross-linking agents shows a regulating effect on the stability and permeability of microcapsules, which provides more choices for alginate/chitosan microcapsules in the field of cell immobilization controlled drug release and immobilized enzyme reactor. |
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