Preliminary Trials in Single Living Cells with a Piezoelectric Microinjector

A piezoelectric microinjector which utilizes the expansion of a ceramic cylinder into a surrounding cavity was used for injections of glucose-6-P, Na+ and fluorescein, Na+ into single living EL2 ascites cells. The results were assessed in a microspectrofluorometer by fluorescein emission or NAD(P)H fluorescence associated with glucose-6-P metabolism. With micropipettes exhibiting an orifice of about ~0.5 , ¿, application of an electrical field on the ceramic transducer element may initiate an instantaneous efflux of solution, but the pressure which builds up in the system will result in a prolonged drip. Therefore, the amount injected in a cell will be a function of previous voltage increases and the staying time in the cell, rather than the instantaneous voltage increment. Quantitative injection is possible with larger pipette orifices. Despite the difficulties associated with high tip resistance, the piezoelectcic microinjector opens the way to the intracellular addition of fluorescent and chemiluminescent enzyme mixtures, through smaller micropipette tips (e.g., ~0.5 ¿), better tolerated by the average mammalian cell in culture.