Potassium-selective atomic force microscopy on ion-releasing substrates and living cells.
A new method for simultaneous mapping of cell topography and ion fluxes was developed. A highly sensitive ion sensor system was generated by coating atomic force microscopy tips with a PVC layer containing valinomycin, an ionophore for potassium. The activity of specific ions was traced on artificial ion-releasing PVC substrates. A boundary potential was generated owing to the selective exchange of a specific ion between coated tip and ion-releasing substrate. The boundary potential was detectable as a force induced by ion-selective electrostatic interactions. The selectivity coefficient of valinomycin for potassium against sodium (K(K,Na)f) was -2.5 +/- 0.5. Potassium efflux was measured on living MDCK-F1 cells expressing BK(Ca) channels. We could demonstrate localized areas of high potassium concentrations at the cell surface. The potassium efflux could be reversibly inhibited by thapsigargin, which is known to inhibit the efflux of potassium from BK(Ca) channels by suppression of calcium ATPase.
Center for Chemical Sensors/Biosensors and Bioanalytical Chemistry, Institute of Pharmaceutical Sciences, Swiss Federal Institute of Technology, Zürich. prisca.zammaretti@rdls.nestle.com
Prisca
P
Schär-Zammaretti
Urs
U
Ziegler
Ian
I
Forster
Peter
P
Groscurth
Ursula E
UE
Spichiger-Keller
D015374:Biosensing Techniques / Q000379:methods*; D002461:Cell Line, Transformed; D002477:Cells / Q000737:chemistry* / Q000378:metabolism; D006801:Humans; D007473:Ion Channels / Q000187:drug effects / Q000378:metabolism; D007477:Ions / Q000378:metabolism; D018625:Microscopy, Atomic Force; D011188:Potassium / Q000378:metabolism*; D014634:Valinomycin / Q000494:pharmacology
D007473:Ion Channels; D007477:Ions; D014634:Valinomycin; D011188:Potassium