title: A generic microfluidic biosensor of G protein-coupled receptor activation-monitoring cytoplasmic [Ca(2+)] changes in human HEK293 cells.
abstract: Cell lines expressing recombinant G-protein coupled receptors (GPCRs) are activated by specific ligands resulting in transient [Ca(2+)] rises that return to basal levels in 30-60s. Yellow Cameleon 3.6 (YC3.6) is a genetically encoded calcium indicator which can be co-expressed to monitor these cytosolic [Ca(2+)] changes in real-time using Förster (Fluorescence) resonance energy transfer (FRET). On this basis, we designed the prototype of a generic microfluidic biosensor of GPCR activation, imaging [Ca(2+)] changes in recombinant human HEK293 cells, which express a combination of a GPCR (Neurokinin 1) and YC3.6. An internal reference for non-specifically induced [Ca(2+)] changes were YC3.6 cells without GPCR but expressing a red fluorescent protein (mCherry) for identification. These cell lines were grown as a mixed population in a flow cell with a volume of ~50µl and a flow cell surface of 170mm(2). Cells were activated by brief exposures to specific and non-specific analytes using an injection valve with a flexible sample volume (tested range 5-100µl) at a flow speed of 100µl/min. A flow cell surface of 0.2mm(2) with 50 cells was imaged every 2-4s to obtain signal kinetics. The lower limit of detection was 30pM Substance P (SP, 2pg/50µl), and reproducible responses to repeated injections every 3min were obtained at 1nM SP. This biosensor was designed for ~50 cells for statistical reasons, but at a lower limit of 1 receptor- and 1 reference-cell, specific ligand detection is still feasible.
authors.affiliation: Plant Research International, Wageningen UR, Droevendaalsesteeg 1, 6708 PB Wageningen, The Netherlands. margriet.roelse@wur.nl
authors.forename: Margriet
authors.initials: M
authors.lastname: Roelse
authors.forename: Norbert C A
authors.initials: NC
authors.lastname: de Ruijter
authors.forename: Elwin X
authors.initials: EX
authors.lastname: Vrouwe
authors.forename: Maarten A
authors.initials: MA
authors.lastname: Jongsma
mesh_terms: D015374:Biosensing Techniques / Q000379:methods*; D002118:Calcium / Q000737:chemistry / Q000378:metabolism*; D002135:Calcium-Binding Proteins / Q000737:chemistry; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D003593:Cytoplasm; D031541:Fluorescence Resonance Energy Transfer; D057809:HEK293 Cells; D006801:Humans; D046210:Microfluidic Analytical Techniques / Q000379:methods*; D011957:Receptors, Opioid / Q000302:isolation & purification* / Q000378:metabolism; D015398:Signal Transduction
chemical_list: D002135:Calcium-Binding Proteins; C091041:G protein-coupled receptor C3; D011957:Receptors, Opioid; C495639:yellow cameleon; D002118:Calcium