Mixing solutions in inkjet formed vesicles.

Controlling the contents of liposomes and vesicles is essential for their use in medicine, biotechnology, and basic research. Cargos such as proteins, DNA, and RNA are of growing interest for therapeutic applications as well as for fundamental studies of cellular organization and function, but controlled encapsulation and mixing of biomolecules within vesicles has been a challenge. Recently, microfluidic encapsulation has been shown to efficiently load arbitrary solutions of biomolecules into unilamellar vesicles. This method utilizes a piezoelectrically driven liquid jet to deform a planar bilayer and form a vesicle, with the fluid vortex formed by the jet mixing the solution in the jet with the surrounding solution. Here, we describe the equipment and protocol used for loading mixtures within unilamellar vesicles by microfluidic encapsulation, and we measure the encapsulated fraction to be 79+/-5% using a falling vesicle technique. Additionally, we find that the presence of a continuous flow from the nozzle and changes in actuation voltage polarity do not significantly affect the encapsulated fraction. These results help to guide current applications and future development of this microfluidic encapsulation technique for forming and loading unilamellar vesicles.