For remarkable promotion of the synthetic cell models, direct observation of cell sized liposomes (closed bilayer membrane composed of phospholipid) in microfluidic devices enables us to obtain precise and long-term data on dynamics of liposomes under well-controlled conditions. We have developed a preparation method of cell-sized liposomes from water-in-oil emulsion encapsulating gene expression reagents and a microfluidic device for size sorting and trapping of liposomes. Device-derived artifacts caused by the constant shear stress and the adhesive surface of device should be reduced to the full extent for the combination of these technologies on liposome observation. In this study, we have developed the microfluidic device for size sorting, trapping, and following observation of the liposomes even upon abrupt stop of the flow (Fig. 1).<br/>Liposomes introduced into the device were separated on their size, and only liposomes of targeted size were trapped in juxtaposed large circular spaces (nests) one by one (average diameter: 12.7 µm, CV: 10%). The nest space was large enough to hold the trapped liposomes upon abrupt stop of the flow which was controlled by optimized geometrical design of pipes and valves (Fig. 1A). Surface modification of the device of polydimethylsiloxane using perfluoroalkyl silyl ether after the plasma treatment (Fig. 1B) prevented the adhesion of lipid aggregation and clogging. As a result, liposomes enclosing microbeads (diameter: 1.1 µm) were trapped in the nest (Fig. 1C, D). Further investigation on morphological changes of the trapped liposomes will appear in the presentation.

Microfluidic trapping and observation of size-sorted liposomes prepared by water-in-oil emulsion transfer method

2019 Fall National Meeting

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