title: Shape-changing magnetic assemblies as high-sensitivity NMR-readable nanoprobes.
abstract: Fluorescent and plasmonic labels and sensors have revolutionized molecular biology, helping visualize cellular and biomolecular processes. Increasingly, such probes are now being designed to respond to wavelengths in the near-infrared region, where reduced tissue autofluorescence and photon attenuation enable subsurface in vivo sensing. But even in the near-infrared region, optical resolution and sensitivity decrease rapidly with increasing depth. Here we present a sensor design that obviates the need for optical addressability by operating in the nuclear magnetic resonance (NMR) radio-frequency spectrum, where signal attenuation and distortion by tissue and biological media are negligible, where background interferences vanish, and where sensors can be spatially located using standard magnetic resonance imaging (MRI) equipment. The radio-frequency-addressable sensor assemblies presented here comprise pairs of magnetic disks spaced by swellable hydrogel material; they reversibly reconfigure in rapid response to chosen stimuli, to give geometry-dependent, dynamic NMR spectral signatures. The sensors can be made from biocompatible materials, are themselves detectable down to low concentrations, and offer potential responsive NMR spectral shifts that are close to a million times greater than those of traditional magnetic resonance spectroscopies. Inherent adaptability should allow such shape-changing systems to measure numerous different environmental and physiological indicators, thus providing broadly generalizable, MRI-compatible, radio-frequency analogues to optically based probes for use in basic chemical, biological, medical and engineering research.
authors.affiliation: 1] Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA [2] Electromagnetics Division, Physical Measurements Laboratory, National Institute of Standards and Technology, Boulder, Colorado 80305, USA.
authors.forename: G
authors.initials: G
authors.lastname: Zabow
authors.affiliation: Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: S J
authors.initials: SJ
authors.lastname: Dodd
authors.affiliation: Laboratory of Functional and Molecular Imaging, National Institute of Neurological Disorders and Stroke, National Institutes of Health, Bethesda, Maryland 20892, USA.
authors.forename: A P
authors.initials: AP
authors.lastname: Koretsky
mesh_terms: D000818:Animals; D001672:Biocompatible Materials / Q000737:chemistry; D057219:Biofouling / Q000517:prevention & control; D002477:Cells / Q000378:metabolism; D003124:Colorimetry; D004285:Dogs; D020100:Hydrogels / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D007477:Ions / Q000032:analysis; D061985:Madin Darby Canine Kidney Cells; D008279:Magnetic Resonance Imaging; D009682:Magnetic Resonance Spectroscopy; D008280:Magnetics; D059346:Magnets / Q000737:chemistry*; D015335:Molecular Probes / Q000737:chemistry*; D049329:Nanostructures / Q000737:chemistry*; D011846:Radio Waves; D062211:Spatio-Temporal Analysis
chemical_list: D001672:Biocompatible Materials; D020100:Hydrogels; D007477:Ions; D015335:Molecular Probes