Pico-liter injection control to individual nano-liter solution coated by lipid layer

This paper presents the evaluation of ultra-minimal spout amount from micro-nano pipettes into phospholipid-coated micro-droplets. The pipettes can be used to control the local environment around/inside single cells. Conventionally, the microinjection with pipette has been conducted by air pressures. In this method, the spout of high viscosity solutions is difficult because of the frictional forces between the surface of a pipette and a solution. It is also needed to evaluate the spout amount quantitatively. On the other hand, the research about artificial cell model has been actively conducted, injecting various biological samples into liposomes which are vesicle of lipid bilayer membrane. If additional injection of various proteins into liposome is realized with micro/nano pipette, the observation of dynamic reaction of multiple biological samples, which is required for formulation of artificial cell, will become possible. In our research, the spouting method using electro-osmosis is used. The local spouts of the proteins such as GFP and F-actin have been presented experimentally before. In this paper, the amount of spout solution in this method is quantitatively evaluated by injection of fluorescent solution into a phospholipid-coated micro-droplet.