High-intensity electrostatic-field exposure system for cultured biological cells.

We describe a new system for exposing cultured biological cells that have been plated on coverslips to strong electrostatic fields at magnitudes greater than 10(3) V/cm. Techniques are described that make use of mineral oil to render insignificant electrical conduction currents (total leakage current is less than 1.0 nA or less than 0.1 nA/coverslip), joule heating (less than 10(-6) W), or current-induced magnetic fields (less than 10(-13) T) in regions inhabited by cells. The mineral oil also eliminates a reduction in the strength of the applied field, which otherwise can occur from increased electrode-to-medium impedance at the site of application. Thus the applied field is reliably specified in the vicinity of a cell membrane. Control and electrostatic field chambers are housed in a grounded metal incubator. Cylindrical mu-metal shields can be used to reduce background magnetic fields in each chamber from 40 microT static and approximately 1 microT ac to, respectively, less than 3 microT static and approximately 100 nT ac. Contamination of cells by impurity atoms that may leach from electrodes was measured by atomic-absorption spectrophotometry and found to be negligible. Stray magnetic- and electric-field components within the incubator were measured, as were background fields around the laboratory.