title: Pipette-surface interaction: current enhancement and intrinsic force.
abstract: There is an intrinsic repulsion between glass and cell surfaces that allows noninvasive scanning ion conductance microscopy (SICM) of cells and which must be overcome in order to form the gigaseals used for patch clamping investigations of ion channels. However, the interactions of surfaces in physiological solutions of electrolytes, including the presence of this repulsion, for example, do not obviously agree with the standard Derjaguin-Landau-Verwey-Overbeek (DLVO) colloid theory accurate at much lower salt concentrations. In this paper we investigate the interactions of glass nanopipettes in this high-salt regime with a variety of surfaces and propose a way to resolve DLVO theory with the results. We demonstrate the utility of this understanding to SICM by topographically mapping a live cell's cytoskeleton. We also report an interesting effect whereby the ion current though a nanopipette can increase under certain conditions upon approaching an insulating surface, rather than decreasing as would be expected. We propose that this is due to electroosmotic flow separation, a high-salt electrokinetic effect. Overall these experiments yield key insights into the fundamental interactions that take place between surfaces in strong solutions of electrolytes.
authors.affiliation: Department of Chemistry, University of Cambridge, Lensfield Road, Cambridge, CB2 1EW, United Kingdom. rwc25@cam.ac.uk
authors.forename: Richard W
authors.initials: RW
authors.lastname: Clarke
authors.forename: Alexander
authors.initials: A
authors.lastname: Zhukov
authors.forename: Owen
authors.initials: O
authors.lastname: Richards
authors.forename: Nicholas
authors.initials: N
authors.lastname: Johnson
authors.forename: Victor
authors.initials: V
authors.lastname: Ostanin
authors.forename: David
authors.initials: D
authors.lastname: Klenerman
mesh_terms: D000818:Animals; D019556:COS Cells; D002522:Chlorocebus aethiops; D004573:Electrolytes / Q000737:chemistry; D020527:Microscopy, Scanning Probe; D058608:Nanopores; D013499:Surface Properties
chemical_list: D004573:Electrolytes