title: Microfluidic chip for continuous monitoring of hormone secretion from live cells using an electrophoresis-based immunoassay.
abstract: A microfluidic device has been developed for the determination of insulin secreted from islets of Langerhans by a capillary electrophoresis competitive immunoassay. Online assays were performed by electrophoretically sampling anti-insulin antibody (Ab), fluorescein isothiocyanate-labeled insulin (FITC-insulin), and insulin from separate reservoirs and allowing them to mix as they traveled through a 4-cm reaction channel heated to 38 degrees C. From the reaction channel, samples were injected onto a 1.5-cm-long electrophoresis channel where the FITC-insulin and FITC-insulin-Ab complex were separated in 5 s using an electric field of 500 V/cm. Detection limits for insulin were 3 nM in this mode of operation. Assays could be collected at 15-s intervals with continuous sampling and online mixing for up to 30 min with no intervention. Relative standard deviation was 2-6% depending on the insulin concentration. Response time to a step change in insulin concentration was 30 s. For live cell monitoring, single islets were placed into a reservoir on the chip and fluid in the immediate vicinity was continuously sampled to detect insulin secretion from the islet. Monitoring of insulin secretion with electropherograms taken at 15-s intervals resolved secretory profiles characteristic of first- and second-phase insulin secretion. The method should be amenable to other cell or tissue types for measurements of release with high temporal resolution.
authors.affiliation: Department of Chemistry and Department of Pharmacology, University of Michigan, Ann Arbor, Michigan 48109-1055, USA.
authors.forename: Michael G
authors.initials: MG
authors.lastname: Roper
authors.forename: Jonathan G
authors.initials: JG
authors.lastname: Shackman
authors.forename: Gabriella M
authors.initials: GM
authors.lastname: Dahlgren
authors.forename: Robert T
authors.initials: RT
authors.lastname: Kennedy
mesh_terms: D000818:Animals; D002478:Cells, Cultured; D004586:Electrophoresis / Q000379:methods*; D006728:Hormones / Q000378:metabolism*; D007118:Immunoassay / Q000379:methods*; D007515:Islets of Langerhans / Q000166:cytology / Q000378:metabolism; D008297:Male; D051379:Mice
chemical_list: D006728:Hormones