Xie Jingwei, Wang Chi-Hwa
Department of Chemical and Biomolecular Engineering, National University of Singapore, 4 Engineering Drive 4, 117576 Singapore.
J Colloid Interface Sci. 2007 Aug 15;312(2):247-55. doi: 10.1016/j.jcis.2007.04.023. Epub 2007 Apr 19.
Entrapment of living cells in microbeads is to protect the encapsulated cells from the host's immune system, which can be used as drug delivery vehicles, immunotherapies and engineered tissues. The main objective of the present study was to investigate the droplet formation and to better develop mono-dispersed microencapsulation of living cells with controllable size. The uniformity of microencapsulation size was realized by performing electrospray in the dripping mode and also stabilized by an additional ring electrode. Reduction of droplet diameter and increase in the dripping frequency were observed with increasing applied voltage to the nozzle using a conventional electrospray setup. The vibration of the needle was found to reduce when high voltage was applied to the nozzle. With increasing voltage applied to the ring electrode, the dripping frequency was found to decrease with the formation of slightly larger sizes of droplets. Hep G2 cell line was taken as the model cell line for encapsulation in calcium alginate microbeads. Relatively uniform microbeads could be achieved when operating under low flow rates with high voltages applied to the nozzle by using a conventional electrospray setup. In contrast, uniform microbeads can not be obtained using a similar setup under high flow rates unless the ring electrode is applied with voltage to stabilize the electrospray in the dripping mode. In this modified electrospray, microbeads with narrow size distribution and slightly larger size can be obtained even for cases under high flow rates. Phase contrast microscope images showed that the diameter of microbeads from around 200 microm to 2 mm could be finely tuned by adjusting various operating parameters.
将活细胞包裹在微珠中是为了保护被包裹的细胞免受宿主免疫系统的影响，这些微珠可用作药物递送载体、免疫疗法和工程组织。本研究的主要目的是研究液滴形成，并更好地开发尺寸可控的活细胞单分散微囊化技术。通过在滴注模式下进行电喷雾实现微囊化尺寸的均匀性，并通过额外的环形电极使其稳定。使用传统的电喷雾装置，随着施加到喷嘴上的电压增加，观察到液滴直径减小且滴注频率增加。当向喷嘴施加高电压时，发现针头的振动会减小。随着施加到环形电极上的电压增加，发现滴注频率降低，同时形成稍大尺寸的液滴。将Hep G2细胞系作为模型细胞系用于包裹在海藻酸钙微珠中。使用传统的电喷雾装置，在低流速且向喷嘴施加高电压的情况下操作时，可以获得相对均匀的微珠。相比之下，在高流速下使用类似装置则无法获得均匀的微珠，除非向环形电极施加电压以在滴注模式下稳定电喷雾。在这种改进的电喷雾中，即使在高流速情况下，也可以获得尺寸分布窄且尺寸稍大的微珠。相差显微镜图像显示，通过调整各种操作参数，可以精细调节直径从约200微米到2毫米的微珠。
