title: Sensitive, high throughput detection of proteins in individual, surfactant-stabilized picoliter droplets using nanoelectrospray ionization mass spectrometry.
abstract: Droplet-based fluidics is emerging as a powerful platform for single cell analysis, directed evolution of enzymes, and high throughput screening studies. Due to the small amounts of compound compartmentalized in each droplet, detection has been primarily by fluorescence. To extend the range of experiments that can be carried out in droplets, we have developed the use of electrospray ionization mass spectrometry (ESI-MS) to measure femtomole quantities of proteins in individual pico- to nanoliter droplets. Surfactant-stabilized droplets containing analyte were produced in a flow-focusing droplet generation microfluidic device using fluorocarbon oil as the continuous phase. The droplets were collected off-chip for storage and reinjected into microfluidic devices prior to spraying the emulsion into an ESI mass spectrometer. Crucially, high quality mass spectra of individual droplets were obtained from emulsions containing a mixture of droplets at >150 per minute, opening up new routes to high throughput screening studies.
authors.forename: Clive A
authors.initials: CA
authors.lastname: Smith
authors.forename: Xin
authors.initials: X
authors.lastname: Li
authors.forename: Todd H
authors.initials: TH
authors.lastname: Mize
authors.forename: Timothy D
authors.initials: TD
authors.lastname: Sharpe
authors.forename: Edmund I
authors.initials: EI
authors.lastname: Graziani
authors.forename: Chris
authors.initials: C
authors.lastname: Abell
authors.forename: Wilhelm T S
authors.initials: WT
authors.lastname: Huck
mesh_terms: D002256:Carbonic Anhydrases / Q000032:analysis; D002919:Chymotrypsinogen / Q000032:analysis; D045304:Cytochromes c / Q000032:analysis; D004655:Emulsions; D017022:Flow Injection Analysis; D005466:Fluorocarbons / Q000737:chemistry; D057166:High-Throughput Screening Assays / Q000295:instrumentation / Q000379:methods*; D007219:Industrial Oils; D046210:Microfluidic Analytical Techniques / Q000295:instrumentation / Q000379:methods*; D009113:Muramidase / Q000032:analysis; D036103:Nanotechnology; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation / Q000379:methods*; D013501:Surface-Active Agents / Q000737:chemistry
chemical_list: D004655:Emulsions; D005466:Fluorocarbons; D013501:Surface-Active Agents; D045304:Cytochromes c; D002919:Chymotrypsinogen; D009113:Muramidase; D002256:Carbonic Anhydrases