A picoampere current generator for membrane electroporation

Electroporation is the electric-field induced formation of a voltage-depend ent population of hydrophilic pores within a bilayer lipid membrane (BLM). This phenomenon can be observed as a transient increase in membrane conduct ance after the application of a voltage jump above a certain threshold. A v ery low current source is required to measure voltage fluctuations of a BLM due to voltage induced creation of dynamical pores during the electroporat ion. A current source able to drive a high-resistive load (on the order of 10(12) Ohm) by a constant current of 10 pA has been designed and realized. The current is maintained constant, with an uncertainty of 1.2% even when t he resistive load fluctuates to 10(9) Ohm over a very brief interval (10(-3 ) s). These peculiar features have been obtained by designing a very simple circuit configuration, that gives an excellent match between the planned a nd the experimental behavior. The circuit bandwidth and the current precisi on are not the result of the circuit configuration, but are only limited by active components. (C) 2000 American Institute of Physics. [S0034-6748(00) 04604-9].