Solute transport on the sub 100 ms scale across the lipid bilayer membrane of individual proteoliposomes
Journal article, 2012

Screening assays designed to probe ligand and drug-candidate regulation of membrane proteins responsible for ion-translocation across the cell membrane are wide spread, while efficient means to screen membrane-protein facilitated transport of uncharged solutes are sparse. We report on a microfluidic-based system to monitor transport of uncharged solutes across the membrane of multiple (>100) individually resolved surface-immobilized liposomes. This was accomplished by rapidly switching (<10 ms) the solution above dye-containing liposomes immobilized on the floor of a microfluidic channel. With liposomes encapsulating the pH-sensitive dye carboxyfluorescein (CF), internal changes in pH induced by transport of a weak acid (acetic acid) could be measured at time scales down to 25 ms. The applicability of the set up to study biological transport reactions was demonstrated by examining the osmotic water permeability of human aquaporin (AQP5) reconstituted in proteoliposomes. In this case, the rate of osmotic-induced volume changes of individual proteoliposomes was time resolved by imaging the self quenching of encapsulated calcein in response to an osmotic gradient. Single-liposome analysis of both pure and AQP5-containing liposomes revealed a relatively large heterogeneity in osmotic permeability. Still, in the case of AQP5-containing liposomes, the single liposome data suggest that the membrane-protein incorporation efficiency depends on liposome size, with higher incorporation efficiency for larger liposomes. The benefit of low sample consumption and automated liquid handling is discussed in terms of pharmaceutical screening applications.

Author

Gabriel Ohlsson

Chalmers, Applied Physics, Biological Physics

Seyed Tabaei

Chalmers, Applied Physics, Biological Physics

J. P. Beech

Lund University

Jan Kvassman

Lund University

Urban Johanson

Lund University

Per Kjellbom

Lund University

J. O. Tegenfeldt

University of Gothenburg

Fredrik Höök

Chalmers, Applied Physics, Biological Physics

Lab on a Chip - Miniaturisation for Chemistry and Biology

1473-0197 (ISSN) 1473-0189 (eISSN)

Vol. 12 22 4635-4643

Areas of Advance

Nanoscience and Nanotechnology (2010-2017)

Life Science Engineering (2010-2018)

Subject Categories

Biological Sciences

Nano Technology

DOI

10.1039/c2lc40518k

More information

Latest update

3/2/2018 9