Department of Chemistry and Chemical Biology, McMaster University, 1280 Main Street West, Hamilton, Ontario L8S 4M1,Canada.
Mater Sci Eng C Mater Biol Appl. 2013 Oct;33(7):4295-304. doi: 10.1016/j.msec.2013.06.033. Epub 2013 Jun 28.
Micropipette aspiration and confocal fluorescence microscopy were used to study the structure and mechanical properties of calcium alginate hydrogel beads (A beads), as well as A beads that were additionally coated with poly-L-lysine (P) and sodium alginate (A) to form, respectively, AP and APA hydrogels. A beads were found to continue curing for up to 500 h during storage in saline, due to residual calcium chloride carried over from the gelling bath. In subsequent saline washes, micropipette aspiration proved to be a sensitive indicator of gel weakening and calcium loss. Aspiration tests were used to compare capsule stiffness before and after citrate extraction of calcium. They showed that the initial gel strength is largely due to the calcium alginate gel cores, while the long term strength is solely due to the poly-L-lysine-alginate polyelectrolyte complex (PEC) shells. Confocal fluorescence microscopy showed that calcium chloride exposure after PLL deposition led to PLL redistribution into the hydrogel bead, resulting in thicker but more diffuse and weaker PEC shells. Adding a final alginate coating to form APA capsules did not significantly change the PEC membrane thickness and stiffness, but did speed the loss of calcium from the bead core.
微管吸吮和共聚焦荧光显微镜用于研究钙海藻酸钠水凝胶珠（A 珠）的结构和机械性能，以及另外用聚-L-赖氨酸（P）和海藻酸钠（A）涂覆的 A 珠，分别形成 AP 和 APA 水凝胶。在盐水中储存时，由于凝胶浴中残留的氯化钙，A 珠在长达 500 小时的时间内继续固化。在随后的盐水冲洗中，微管吸吮被证明是凝胶弱化和钙损失的敏感指标。抽吸测试用于比较柠檬酸提取钙前后胶囊的刚度。结果表明，初始凝胶强度主要归因于钙海藻酸钠凝胶核，而长期强度仅归因于聚-L-赖氨酸-海藻酸钠聚电解质复合物（PEC）壳。共聚焦荧光显微镜显示，PLL 沉积后暴露于氯化钙会导致 PLL 重新分布到水凝胶珠中，从而形成更厚但更弥散和更弱的 PEC 壳。最后添加海藻酸钠涂层形成 APA 胶囊不会显著改变 PEC 膜的厚度和刚度，但会加速珠核中钙的流失。
