Abstract Wrinkled microcapsules have attracted great interest due to their distinguished features, including enhanced adhesion propensity and release profiles. These features could be beneficial for food-related applications and improve the bioavailability of encapsulated compounds by promoting their attachment to epithelium. However, the fabrication of such microcapsules with food-grade materials has been met with limited success. In this study, a facile approach to produce wrinkled microcapsules using a food-grade protein, zein, is proposed. Internal phase separation was used to form zein microcapsules and three acids (phytic acid, citric acid, and succinic acid) were incorporated at two concentration levels (10 mM and 20 mM) to modify the secondary structure of zein in the microcapsules. The results showed that the mechanical properties of the microcapsules, which were characterized by nanoindentation, were greatly dependent on the protein secondary structure, particularly the α-helix structure. The morphology of the microcapsules was evaluated by image analysis. An extensive wrinkle was observed on the surfaces of the microcapsules with high viscoplasticity. Among the three acids used in this study, phytic acid significantly increased the degree of wrinkling and viscoplasticity of the microcapsules. Further characterization with circular dichroism and wide-angle X-ray scattering suggested that a less ordered zein secondary structure was formed in the samples prepared using phytic acid than in those prepared using other acids or without acid, which further supports the hypothesis that the nanomechanical properties and degree of wrinkling are associated with the protein secondary structures.

中文翻译：

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皱纹蛋白质微胶囊的微流体制备及其受蛋白质二级结构影响的纳米力学性能

摘要 褶皱微胶囊因其突出的特性而引起了极大的兴趣，包括增强的粘附倾向和释放特性。这些特征可能有益于与食品相关的应用，并通过促进其与上皮的附着来提高封装化合物的生物利用度。然而，用食品级材料制造这种微胶囊的成功有限。在这项研究中，提出了一种使用食品级蛋白质玉米醇溶蛋白生产皱纹微胶囊的简便方法。使用内相分离形成玉米醇溶蛋白微胶囊，并以两种浓度水平（10 mM 和 20 mM）掺入三种酸（植酸、柠檬酸和琥珀酸），以修饰微胶囊中玉米醇溶蛋白的二级结构。结果表明，以纳米压痕为特征的微胶囊的机械性能在很大程度上取决于蛋白质的二级结构，尤其是α-螺旋结构。通过图像分析评估微胶囊的形态。在具有高粘塑性的微胶囊表面上观察到广泛的皱纹。在本研究中使用的三种酸中，植酸显着增加了微胶囊的起皱程度和粘塑性。圆二色性和广角 X 射线散射的进一步表征表明，与使用其他酸或不使用酸制备的样品相比，使用植酸制备的样品中形成的玉米醇溶蛋白二级结构不太有序，