Single cell assay with an automated capillary microinjection system.

An automated capillary microinjection system with computer controlled positioning of the cells and of the capillary, and its applications and advantages arc described. About 1500 injections are possible in one hour, with high reproducibility. In cytoplasmic and nuclear injections more than 90% and 85% of the cells are successfully injected. Using FITC-Dextran at a concentration of 0.5% as a fluorescently labelled coinjection marker, 99% of the cells can be retrieved in cultrue medium even 48 hours after unjection. The coordinates of the cells are stored in the computer and accuracy in statistical evaluation of experiments is improved in coparison to the manual techniques. Methods for preparatin and handling of glass capillaries were developed resulting in reproducible form and significantly reduced clogging rate. The improved characteristics offered by this system are demonstrated in studies leading to the confirmation of existence of mRNA(s) inhibiting cell proliferation. Functional screening by cell injections of cDNA libraries and of size fractionated mRNA molecules can be performed efficiently with the automated microinjection system.