Analysis of single-cell differences by use of an on-chip microculture system and optical trapping

A method is described for continuous observation of isolated single cells t hat enables genetically identical cells to be compared; it uses an on-chip microculture system and optical tweezers. Photolithography is used to const ruct microchambers with 5-mum-high walls made of thick photoresist (SU-8) o n the surface of a glass slide. These microchambers are connected by a chan nel through which cells are transported, by means of optical tweezers, from a cultivation microchamber to an analysis microchamber, or from the analys is microchamber to a waste microchamber. The microchambers are covered with a semi-permeable membrane to separate them from nutrient medium circulatin g through a "cover chamber" above. Differential analysis of isolated direct descendants of single cells showed that this system could be used to compa re genetically identical cells under contamination-free conditions. It shou ld thus help in the clarification of heterogeneous phenomena, for example u nequal cell division and cell differentiation.