如图 2 所示,采用乳液交联法制备了间充质干细胞微球。实验步骤包括将 0.125 g 磁性纳米二氧化硅(MS)均匀分散到 10 mL 壳聚糖溶液中,壳聚糖溶于体积分数为 5.0% 的醋酸溶液中制备的壳聚糖溶液的质量分数为 2.5%,然后将壳聚糖溶液逐滴加入到含有 60 mL 液体石蜡和 1.8 mL 吐温 80 的乳液中。在 40 ℃ 水浴和 800 r-min 条件下搅拌 30 分钟后,将壳聚糖溶液滴加到含有 60 mL 液体石蜡和 1.8 mL 吐温 80 的乳液中。-1加入 2.0 mL 戊二醛,反应 1 小时。-1 产物用石油醚、乙醇和蒸馏水多次洗涤,得到 MSC 微球,真空干燥备用。
图 2 磁性硅基壳聚糖微球的制备示意图
5.环氧基磁性硅基壳聚糖微球(MSCE)的制备
0.5 g of dried MSC microspheres prepared by the method of 4 were weighed and added into a conical flask of 50 mL. Then 2.0 mL of of NaOH solution, epichrolohydrin solution and NaBH4 solution were added into the flask with a certain concentration, respectively. And the reaction was carried out by constant temperature oscillation for a certain time. The reaction mechanism of preparation of MSCE is shown in Figure 3.
Figure 3 The principle of preparation of epoxy-based magnetic silicon-based chitosan microspheres
After activation, the activated microspheres are washed repeatedly with distilled water until there are no free OH- and epoxy groups on the surface to obtain epoxy based magnetic silicon based chitosan microspheres ( MSCE). The detection method is as follows: take 3.0 mL of the washing supernatant and add 1~2 drops of phenolphthalein. After shaking, if it didn’t turn red, it means there have no free OH- with MSCE; take 3.0 mL of the washing supernatant and add 3.0 mL of 1.3 mol·L-1 sodium thiosulfate and 1 ~2 drops of phenolphthalein, if the solution did not turning red after shaking, it means there have no free epoxy groups with MSCE. The reaction equation of the detection of epoxy group is as follows:
6 Preparation of MSCE immobilized naringinase enzyme
5.0 g of MSCE prepared by method 5 was added to 50 mL of naringinase enzyme solution with a certain pH, and the reaction was oscillated under a constant temperature water bath, as shown in Figure 4. After the reaction, the microspheres were washed with buffer solution for several times until no free naringinase was found on the surface of the microspheres. The microspheres were drained by a Brinella funnel to obtain MSCE immobilized naringinase enzyme, which was refrigerated at 4 ℃ for later use.
Figure 4 The principle of preparation of MSCE immobilized naringinase enzyme