title: Capillary-channeled polymer (C-CP) fibers for the rapid extraction of proteins from urine matrices prior to detection with MALDI-MS.
abstract: OBJECTIVE
  While MS is a powerful tool for biomarker determinations, the high salt content and the small molecules present in urine poses incredible challenges. Separation/extraction methods must be employed for the isolation of target species at relevant concentrations. Micropipette tips packed with capillary-channeled polymer (C-CP) fibers are employed for the SPE of proteins from a synthetic and a certified urine matrix.
  
  
  METHODS
  Extractions are performed utilizing a very simple centrifugation method to spin-down species through the C-CP fiber tips. Proteins adsorb to the hydrophobic polypropylene fibers and are eluted in a solvent suitable for MALDI-MS analysis. Figures of merit are determined for representative compounds β2-microglobulin, retinol binding protein, and transferrin.
  
  
  RESULTS
  The optimum protein processing included a 100 μL aqueous rinse and an elution solvent composition was 10 μL of 55:45 ACN:water (with triflouroacetic acid). MALDI-MS responses for the target proteins are improved from nondetectable levels to eventually yield LOD ranging from 5 to 180 nM in 1 μL aliquots.
  
  
  CONCLUSIONS
  C-CP fiber tips offer a plethora of advantages including low materials costs, high throughput, microvolume processing, and the determination of sub-nanogram quantities of analyte; allowing determination of biomarkers that are otherwise undetectable in urine matrices.
authors.affiliation: Department of Chemistry, Clemson University, Clemson, SC, USA.
authors.forename: Benjamin T
authors.initials: BT
authors.lastname: Manard
authors.affiliation: Department of Chemistry, Clemson University, Clemson, SC, USA.
authors.forename: Sarah M H
authors.initials: SM
authors.lastname: Jones
authors.affiliation: Department of Chemistry, Clemson University, Clemson, SC, USA.
authors.forename: R Kenneth
authors.initials: RK
authors.lastname: Marcus
mesh_terms: D000327:Adsorption; D002197:Capillary Action; D006801:Humans; D011108:Polymers / Q000737:chemistry; D011507:Proteinuria / Q000652:urine*; D020543:Proteome / Q000302:isolation & purification* / Q000378:metabolism; D052616:Solid Phase Extraction; D012997:Solvents / Q000737:chemistry; D019032:Spectrometry, Mass, Matrix-Assisted Laser Desorption-Ionization; D016482:Urinalysis / Q000379:methods*
chemical_list: D011108:Polymers; D020543:Proteome; D012997:Solvents
keywords: Capillary-channeled polymer fibers; MALDI-MS; Proteins; Solid-phase extraction; Urine