Sanger R. H.

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R. H.

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  • Preprint
    Electrokinetic measurements of membrane capacitance and conductance for pancreatic β-cells
    ( 2005-10-31) Pethig, Ronald ; Jakubek, L. M. ; Sanger, R. H. ; Heart, E. ; Corson, Erica D. ; Smith, Peter J. S.
    Membrane capacitance and membrane conductance values are reported for insulin secreting cells (primary β-cells and INS-1 insulinoma cells) determined using the methods of dielectrophoresis and electrorotation. The membrane capacitance value of 12.57 (± 1.46) mF/m2 obtained for β-cells, and the values 9.96 (± 1.89) mF/m2 to 10.65 (± 2.1) mF/m2 obtained for INS-1 cells, fall within the range expected for mammalian cells. The electrorotation results for the INS-1 cells lead to a value of 36 (± 22) S/m2 for the membrane conductance associated with ion channels, if values in the range 2nS to 3 nS are assumed for the membrane surface conductance. This membrane conductance value falls within the range reported for INS cells obtained using the whole-cell patch-clamp technique. However, the total ‘effective’ membrane conductance value of 601 (± 182) S/m2 obtained for the INS-1 cells by dielectrophoresis is significantly larger (by a factor of around three-fold) than the values obtained by electrorotation. This could result from an increased membrane surface conductance, or increased passive conduction of ions through membrane pores, induced by the larger electric field stresses experienced by cells in the dielectrophoresis experiments.
  • Preprint
    Dielectrophoretic assembly of insulinoma cells and fluorescent nanosensors into three-dimensional pseudo-islet constructs
    ( 2007-11-14) Pethig, Ronald ; Menachery, Anoop ; Heart, E. ; Sanger, R. H. ; Smith, Peter J. S.
    Dielectrophoretic forces, generated by radio-frequency voltages applied to micromachined, transparent, indium tin oxide electrodes, have been used to condense suspensions of insulinoma cells (BETA-TC-6 and INS-1) into a 10x10 array of threedimensional cell constructs. Some of these constructs, measuring approximately 150 μm in diameter and 120 μm in height, and containing around 1000 cells, were of the same size and cell density as a typical islet of Langerhans. With the dielectrophoretic force maintained, these engineered cell constructs were able to withstand mechanical shock and fluid flow forces. Reproducibility of the process required knowledge of cellular dielectric properties, in terms of membrane capacitance and membrane conductance, which were obtained by electrorotation measurements. The ability to incorporate fluorescent nanosensors, as probes of cellular oxygen and pH levels, into these ‘pseudo-islets’ was also demonstrated. The footprint of the 10x10 array of cell constructs was compatible with that of a 1536 microtitre plate, and thus amenable to optical interrogation using automated plate reading equipment.