title: Radionuclide imaging of miniaturized chemical analysis systems.
abstract: We propose radionuclide imaging as a valuable tool for the study of molecular interactions in miniaturized systems for chemical analysis. Sensitive and quantitative imaging can be performed with compounds labeled with short-lived positron-emitting radionuclides, such as (11)C and (68)Ga, within selected parts of the system. Radionuclide imaging is not restricted to transparent materials since the relatively energetic positrons can penetrate high optical density materials. Experimentally, a radiotracer is introduced into the object of study, which is subsequently placed on a phosphor storage plate. After exposure, the plate is scanned with a laser and a digital, quantitative image can be reconstituted. To demonstrate the concept, three types of microstructures suited for integration in chemical analysis systems were imaged with (11)C- and (68)Ga-labeled tracers. The influence of factors such as geometry of the object and type of radionuclide on resolution and sensitivity was investigated. The resolution ranged from 0.9 to 2.7 mm (fwhm). Measuring low amounts of radioactivity in the three structures, 2-20 Bq could be detected, which corresponded to 2.3-500 amol or 2.4-110 pM tracer. The imaging approach was applied to study analyte concentration and sample dilution effects on the performance of a capillary extraction column integrated in an automated LC-ESI-MS system. The utility of the technique was further illustrated by imaging of microchannels in a zeonor plastic compact disk and in a poly(dimethylsiloxane) material for the study of nonspecific peptide adsorption.
authors.affiliation: Department of Analytical Chemistry, Institute of Chemistry, Uppsala University, Box 599, SE-751 24 Uppsala, Sweden.
authors.forename: Martin
authors.initials: M
authors.lastname: Lavén
authors.forename: Susanne
authors.initials: S
authors.lastname: Wallenborg
authors.forename: Irina
authors.initials: I
authors.lastname: Velikyan
authors.forename: Sara
authors.initials: S
authors.lastname: Bergström
authors.forename: Majda
authors.initials: M
authors.lastname: Djodjic
authors.forename: Jenny
authors.initials: J
authors.lastname: Ljung
authors.forename: Oskar
authors.initials: O
authors.lastname: Berglund
authors.forename: Niklas
authors.initials: N
authors.lastname: Edenwall
authors.forename: Karin E
authors.initials: KE
authors.lastname: Markides
authors.forename: Bengt
authors.initials: B
authors.lastname: Långström
mesh_terms: D002247:Carbon Isotopes; D002853:Chromatography, Liquid / Q000379:methods; D005710:Gallium Radioisotopes; D056656:Lab-On-A-Chip Devices; D011868:Radioisotopes / Q000737:chemistry; D011877:Radionuclide Imaging / Q000379:methods*; D012680:Sensitivity and Specificity; D021241:Spectrometry, Mass, Electrospray Ionization / Q000379:methods*; D013499:Surface Properties
chemical_list: D002247:Carbon Isotopes; D005710:Gallium Radioisotopes; D011868:Radioisotopes