title: Silicon micropillar array electrospray chip for drug and biomolecule analysis.
abstract: We have developed a lidless micropillar array electrospray ionization chip (microPESI) combined with mass spectrometry (MS) for analysis of drugs and biomolecules. The microPESI chip, made of silicon, contains a sample introduction spot for a liquid sample, an array of micropillars (diameter, height, and distance between pillars in the range of 15-200, 20-40, and 2-80 microm, respectively), and a sharpened tip for direct electrospray formation. The microchips were fabricated using deep reactive ion etching (DRIE) which results in accurate dimensional control. The chip, providing a reliable open-channel filling structure based on capillary forces and a electrospray emitter tip for ionization, allows an easy operation and reliable, non-clogging liquid transfer. The microPESI chip can be used for a fast analysis using single sampling or for continuous infusion measurements using a syringe pump for sample introduction. The microPESI-MS shows high sensitivity, with limit of detection 30 pmol/L (60 amol or 28 fg) for verapamil measured with tandem mass spectrometry (MS/MS) and using a sample volume of 2.5 microL. The system shows also good quantitative linearity (r2 > 0.99) with linear dynamic range of at least six orders of magnitude and good ion current stability (standard deviation <5%) in 1-h continuous flow measurement. The microPESI-MS is shown to be a very potential method for direct analysis of drugs and biomolecules.
authors.affiliation: Division of Pharmaceutical Chemistry, P.O. Box 56, FI-00014 University of Helsinki, Finland.
authors.forename: Teemu
authors.initials: T
authors.lastname: Nissilä
authors.forename: Lauri
authors.initials: L
authors.lastname: Sainiemi
authors.forename: Tiina
authors.initials: T
authors.lastname: Sikanen
authors.forename: Tapio
authors.initials: T
authors.lastname: Kotiaho
authors.forename: Sami
authors.initials: S
authors.lastname: Franssila
authors.forename: Risto
authors.initials: R
authors.lastname: Kostiainen
authors.forename: Raimo A
authors.initials: RA
authors.lastname: Ketola
mesh_terms: D000818:Animals; D000889:Anti-Arrhythmia Agents / Q000032:analysis*; D008832:Microchemistry / Q000295:instrumentation* / Q000379:methods; D010455:Peptides / Q000032:analysis; D004364:Pharmaceutical Preparations / Q000032:analysis; D021241:Spectrometry, Mass, Electrospray Ionization / Q000295:instrumentation* / Q000379:methods; D053719:Tandem Mass Spectrometry / Q000295:instrumentation / Q000379:methods; D014700:Verapamil / Q000032:analysis*
chemical_list: D000889:Anti-Arrhythmia Agents; D010455:Peptides; D004364:Pharmaceutical Preparations; D014700:Verapamil