Qayyum Anisa S, Jain Era, Kolar Grant, Kim Yonghyun, Sell Scott A, Zustiak Silviya P
Department of Biomedical Engineering, Saint Louis University, Saint Louis, MO, United States of America.
Biofabrication. 2017 May 18;9(2):025019. doi: 10.1088/1758-5090/aa703c.
Electrohydrodynamic spraying (EHS) has recently gained popularity for microencapsulation of cells for applications in cell delivery and tissue engineering. Some of the polymers compatible with EHS are alginate, chitosan, and other similar natural polymers, which are subject to ionotropic or physical gelation. It is desirable to further extend the use of the EHS technique beyond such polymers for wider biofabrication applications. Here, building upon our previous work of making PEG microspheres via EHS, we utilized the principles of EHS to fabricate cell-laden polyethylene glycol (PEG) hydrogel microspheres. The gelation of PEG hydrogel microspheres was achieved by forming covalent crosslinks between multiarm PEG acrylate and dithiol crosslinkers via Michael-type addition. We conducted a detailed investigation of the critical parameters of EHS, such as the applied voltage, inner needle diameter (i.d. needle), and flow rate, to obtain PEG microspheres with high cell viability and tightly-controlled diameters in the range of 70-300 μm. The polydispersity of cell-laden PEG hydrogel microspheres as measured by % coefficient of variation was between 6% and 23% for all conditions tested. We established that our method was compatible with different cell types and that all tested cell types could be encapsulated at high densities of 10-10 and ≥90% encapsulation efficiency. We observed cell aggregation within the hydrogel microspheres at applied voltage >5 kV. Since PEG is a synthetic polymer devoid of cell attachment sites, we could overcome this limitation by tethering Arg-Gly-Asp-Ser (RGDS) peptide to the PEG hydrogel microspheres; upon RGDS tethering, we observed uniform cell dispersion. The microencapsulated cells could be cultured in the PEG hydrogel microspheres of different sizes for up to one week without significant loss in cell viability. In conclusion, the EHS technique developed here could be used to generate cell-laden PEG hydrogel microspheres of controlled sizes for potential applications in cell delivery and organoid cultures.
电流体动力学喷雾（EHS）最近在用于细胞递送和组织工程的细胞微囊化方面受到了广泛关注。一些与EHS兼容的聚合物包括藻酸盐、壳聚糖和其他类似的天然聚合物，它们可通过离子交联或物理凝胶化作用形成凝胶。期望将EHS技术的应用范围进一步扩展到此类聚合物之外，以实现更广泛的生物制造应用。在此，基于我们之前通过EHS制备聚乙二醇（PEG）微球的工作，我们利用EHS原理制备了负载细胞的聚乙二醇（PEG）水凝胶微球。PEG水凝胶微球的凝胶化是通过多臂丙烯酸酯PEG与二硫醇交联剂之间通过迈克尔型加成反应形成共价交联来实现的。我们对EHS的关键参数进行了详细研究，如施加电压、内针直径（内径针）和流速，以获得具有高细胞活力且直径严格控制在70 - 300μm范围内的PEG微球。在所有测试条件下，通过变异系数百分比测量的负载细胞的PEG水凝胶微球的多分散性在6%至23%之间。我们确定我们的方法与不同细胞类型兼容，并且所有测试的细胞类型都可以在10 - 10的高密度下进行封装，封装效率≥90%。我们观察到在施加电压>5 kV时，水凝胶微球内会出现细胞聚集现象。由于PEG是一种缺乏细胞附着位点的合成聚合物，我们可以通过将精氨酸 - 甘氨酸 - 天冬氨酸 - 丝氨酸（RGDS）肽连接到PEG水凝胶微球上来克服这一限制；连接RGDS后，我们观察到细胞均匀分散。微囊化细胞可以在不同大小的PEG水凝胶微球中培养长达一周，而细胞活力不会有显著损失。总之，这里开发的EHS技术可用于生成尺寸可控的负载细胞的PEG水凝胶微球，以用于细胞递送和类器官培养的潜在应用。
