SLAS

Collection of nanoliter microdiaysate fractions in droplets for off-line in vivo chemical monitoring with up to 2 s temporal resolution

From LabAutopedia

Jump to: navigation, search

Collection of nanoliter microdiaysate fractions in droplets for off-line in vivo chemical monitoring with up to 2 s temporal resolution

                                               Meng Wanga, Thomas Slaneya, Omar Brouka, Robert T. Kennedya,b*

                                        a Department of Chemistry, University of Michigan, 930 North University Avenue, Ann Arbor, MI 48109 

'                                                       b Department of Pharmacology, University of Michigan, Ann Arbor, MI 48109

An off-line in vivo chemical monitoring approach was developed to collect nanoliter microdialysate fractions in the form of “droplets” in a piece of Teflon tubing then to pump the droplet train to a microfluidic chip for electrophoretic separation and laser induced fluorescence detection.  Segmenting microdialysate flow using a perfluorinated oil performed automatic compartmentalization of nanoliter sample droplets.  Since there was no axial dispersion between them, each droplet, with only 2 nL volume that corresponded to 1-20 ms sampling time, acted as a discrete sample collection vial.  Temporal resolution, which was only limited by the microdialysis probe itself,  was up to 2 s.  By slowing down the flow rate  upon pumping the droplet train to a microfluidic chip for analysis, temporal information could be “pseudo-expanded” to more than 100 s, which allowed 50 s electrophoretic separation to be used to simultaneously monitor six neuroactive amino acids, yet still reflecting the true temporal resolution offered by the sampling system.   The system was used to detect rapid dynamics evoked by microinjecting the glutamate uptake inhibitor L-trans-pyrrolidine-2,4-dicarboxylic acid (PDC) or high potassium into the striatum of anesthetized rats.  The resulted showed that affected neurotransmitters reached peak value in 20 s for PDC stimulation and 13 s for high potassium.  The result reflected true temporal response in the in vivo subject, while at the same time revealed detailed information of the microdialysate composition by slower separation time.