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AKB: Biologische Physik

AKB 50: Poster Session "Biological Physics"

AKB 50.102: Poster

Freitag, 12. März 2004, 10:30–13:00, B

Contact Resistance of Cell Silicon Junctions Measured with Voltage-Sensitive Dye — •Raimund Gleixner and Peter Fromherz — MPI für Biochemie, Abt. Membran und Neurophysik, Martinsried

The electrical sheet resistance between a cell and a solid substrate is a crucial parameter for bioelectronic coupling. It can be determined by applying transient voltages to a silicon chip, observing the response of the membrane with a voltage-sensitive dye (Braun:PRL86,2905,2002).

We used the novel dye ANNINE-5 (Hübener:JPC,107,7896,2003) to study the contact between HEK293 cells and fibronectin-coated oxidized silicon. We determined the sheet resistance as a function of salt concentration in the bath. A train of voltage transients was applied to the chip and the fluorescence in the attached membrane was averaged in a confocal microscope over several periods. For sinusoidal stimulation, the frequency dependent spatially resolved transfer function was fitted with a core-coat conductor model of the junction.

We found that the sheet resistance was proportional to the bulk specific resistance. This indicated a cleft of 80nm filled with bulk electrolyte. >From fluorescence interference contrast (FLIC)microscopy we obtained a distance of 70nm between membrane and chip, independent of salt concentration. We conclude: (i)The narrow extracellular space of cell adhesion is filled with bulk electrolyte. (ii)The sheet resistance can be enhanced by enhancing the resistance of the bath.