Gåserød O, Smidsrød O, Skjåk-Braek G
Department of Biotechnology, Norwegian University of Science and Technology, Trondheim.
Biomaterials. 1998 Oct;19(20):1815-25. doi: 10.1016/s0142-9612(98)00073-8.
The binding of chitosan to alginate beads was studied quantitatively by using radioactive labelled fractions of chitosan. The alginate-chitosan capsules were made either by dropping a solution of sodium alginate into a solution containing chitosan or by incubating calcium alginate beads in a solution of chitosan. The first procedure yielded a binding of 0.015 microg chitosan per mm2 of capsule surface, while the latter procedure yielded over 2 microg mm(-2). The maximum obtained weight ratio of chitosan to alginate in a microcapsule after 24 h was 0.40. The binding of chitosan was markedly increased by reducing the number average molecular weight of chitosan below 20000 Da and by increasing the porosity of the alginate gel. The porosity was increased by producing homogeneous gels, and by adding calcium chloride to the chitosan solution during the membrane forming stage. The effect of calcium ions on the porosity of the gel was studied by experiments involving release of blue dextran from calcium alginate beads. The binding of chitosan was also found to increase with decreasing fraction of N-acetylations, FA, on chitosan in the range of FA = 0.3 to FA = 0, and with increasing pH in the range from pH 4 to 6. Capsules with a diameter of 500 microm had a higher weight ratio of chitosan to alginate after 24 h of binding than the capsules with the larger diameter of 1500 microm.
通过使用放射性标记的壳聚糖馏分，对壳聚糖与海藻酸盐珠粒的结合进行了定量研究。海藻酸盐 - 壳聚糖胶囊的制备方法有两种：一是将海藻酸钠溶液滴入含有壳聚糖的溶液中，二是将海藻酸钙珠粒在壳聚糖溶液中孵育。第一种方法得到的胶囊表面每平方毫米结合0.015微克壳聚糖，而第二种方法得到的结合量超过2微克/平方毫米。24小时后，微胶囊中壳聚糖与海藻酸盐的最大重量比为0.40。将壳聚糖的数均分子量降低到20000 Da以下以及增加海藻酸盐凝胶的孔隙率，可显著提高壳聚糖的结合量。通过制备均匀凝胶以及在成膜阶段向壳聚糖溶液中添加氯化钙来增加孔隙率。通过涉及从海藻酸钙珠粒中释放蓝色葡聚糖的实验研究了钙离子对凝胶孔隙率的影响。还发现，在FA = 0.3至FA = 0的范围内，随着壳聚糖上N - 乙酰化分数FA的降低，以及在pH值从4至6的范围内pH值的升高，壳聚糖的结合量增加。直径为500微米的胶囊在结合24小时后，壳聚糖与海藻酸盐的重量比高于直径为1500微米的较大胶囊。
