Immobilization of individual cells by local photo-polymerization on a chip

Abstract

A novel separation method for random screening of target cells from a large heterogeneous population by using a local photo-polymerization is developed. A photo-crosslinkable resin solution is mixed with the sample liquid and we controlled the state from sol to gel by irradiating the near ultraviolet (UV) light with the mercury lamp and He–Cd laser near the target cell. We applied three types of immobilization methods such as direct immobilization method, caging method, and direct immobilization with position control method. The selected cell is immobilized in the cured resin directly or inside the cage of the cured resin. In the position control method, laser tweezers are employed to manipulate the target cell indirectly by using the droplet of the resin as a microtool. The cell is positioned properly by the laser manipulation system and is immobilized in the polymerized resin. After the selected cells are immobilized we can easily remove the other objects by the cleaning flow in the microchannel since the polymerized resin strongly binds with the cover glass and resists more than 466 mm s⁻¹ flow speed in the microchannel (microchannel size: width is 500 micron and depth is 100 micron). We tested the mercury lamp as well as the He–Cd laser for UV-light irradiation at the local area and confirmed improvement of resolution of the cured area by using the He–Cd laser (from 7 micron to 5 micron). Based on this method, we succeeded in single cell immobilization and basic experiments such as culture and fluorescent dyeing of immobilized yeast cells.