title: A microfluidic device for reversible environmental changes around single cells using optical tweezers for cell selection and positioning.
abstract: Cells naturally exist in a dynamic chemical environment, and therefore it is necessary to study cell behaviour under dynamic stimulation conditions in order to understand the signalling transduction pathways regulating the cellular response. However, until recently, experiments looking at the cellular response to chemical stimuli have mainly been performed by adding a stress substance to a population of cells and thus only varying the magnitude of the stress. In this paper we demonstrate an experimental method enabling acquisition of data on the behaviour of single cells upon reversible environmental perturbations, where microfluidics is combined with optical tweezers and fluorescence microscopy. The cells are individually selected and positioned in the measurement region on the bottom surface of the microfluidic device using optical tweezers. The optical tweezers thus enable precise control of the cell density as well as the total number of cells within the measurement region. Consequently, the number of cells in each experiment can be optimized while clusters of cells, that render subsequent image analysis more difficult, can be avoided. The microfluidic device is modelled and demonstrated to enable reliable changes between two different media in less than 2 s. The experimental method is tested by following the cycling of GFP-tagged proteins (Mig1 and Msn2, respectively) between the cytosol and the nucleus in Saccharomyces cerevisiae upon changes in glucose availability.
authors.affiliation: Department of Physics, University of Gothenburg, SE-41296, Gothenburg, Sweden.
authors.forename: Emma
authors.initials: E
authors.lastname: Eriksson
authors.forename: Kristin
authors.initials: K
authors.lastname: Sott
authors.forename: Fredrik
authors.initials: F
authors.lastname: Lundqvist
authors.forename: Martin
authors.initials: M
authors.lastname: Sveningsson
authors.forename: Jan
authors.initials: J
authors.lastname: Scrimgeour
authors.forename: Dag
authors.initials: D
authors.lastname: Hanstorp
authors.forename: Mattias
authors.initials: M
authors.lastname: Goksör
authors.forename: Annette
authors.initials: A
authors.lastname: Granéli
mesh_terms: D018929:Cell Culture Techniques / Q000295:instrumentation*; D002469:Cell Separation / Q000295:instrumentation*; D017753:Ecosystem; D004867:Equipment Design; D019544:Equipment Failure Analysis; D017022:Flow Injection Analysis / Q000295:instrumentation*; D052898:Optical Tweezers; D012441:Saccharomyces cerevisiae / Q000502:physiology*