目的研究海藻酸钠-壳聚糖-海藻酸钠微胶囊(ACA)的冻存机制,探索一种ACA微囊低温保存的降温方法。方法ACA微囊随机分为2组,分别加入生理盐水(对照组)与终浓度为10%的低温保护剂二甲基亚砜(DMSO)(DMSO组),每组ACA微囊悬液置于可控低温显微镜载物台中,分别以1、10、30、100℃/min的降温速率降温至-120℃左右时停止降温,在显微镜下观察ACA微囊的形态改变。将2组完全冷冻的ACA微囊以50℃/min复温速率复温至37℃,在倒置显微镜下观察其形态学改变,计算微囊的完好率、皱缩率与破损率。结果对照组以1、10℃/min的降温速率冻存ACA微囊时,生成的冰晶粗大,冰晶的生长可导致微囊发生形变;而DMSO组以30、100℃/min的降温速率冻存ACA微囊时,生成的冰晶较为细小,对微囊的损伤也更小,并且复温后的微囊形态保存良好,与对照组和同组以1、10℃/min降温速率冻存比较,其微囊完好率明显增高(P〈0.05)。结论微囊在低温保存过程中主要受到冰晶生长所导致的机械性损伤,提高降温速率与添加低温保护剂可以有效地抑制冰晶生长。
Objective To investigate the characteristics of alginate-chitosan-alitosan-alginate (ACA) cryopreserved at different solutions and temperatures, and to explore the optimal cryopreservation protocols for ACA microcapsules. Methods The alginate-chitosan-alginate (ACA) microcapsules were randomly divided into 2 groups in physiological saline solution(control group) and the final concentration of 10% DMSO solution (DMSO group) respectively. Each group was frozen at 1 ℃/min, 10 ℃/min, 30 ℃/min and 100 ℃/min to about -120 ℃ then rewarmed at 50 ℃/min to 37 ℃ by the cryomicoscopy system. Observe the forms of the microcapsules and count the integrity rate. the crenation rate and the damage rate. Results The ice crystals grew into big crystals at the freezing process when the cooling rate was 1 or 10 ℃/min(control group). The growth of ice would result in the distortion of microcapsules. The size of the ice crystals would grow down when the cooling rate was 30 or 100 ℃/min (DMSO group). It also could reduce the cryodamage of the microcapsules. Compared with the control group and the same group freezing at 1 and 10 ℃/min, the rates of integrity was significantly higher (P 〈 0.05). Conclusions Mechanical damage occurs mainly during the growing of ice crystals at the time of microcapsules cryopreservation process. The growth of the ice could be restrained effectively by raising the cooling rate and using the cryoprotector.