title: Toward LocalizedIn VivoBiomarker Concentration Measurements.
abstract: We know a great deal about the biochemistry of cells because they can be isolated and studied. The biochemistry of the much more complexin vivoenvironment is more difficult to study because the only ways to quantitate concentrations is to sacrifice the animal or biopsy the tissue. Either method disrupts the environment profoundly and neither method allows longitudinal studies on the same individual. Methods of measuring chemical concentrationsin vivoare very valuable alternatives to sacrificing groups of animals. We are developing microscopic magnetic nanoparticle (mNP) probes to measure the concentration of a selected moleculein vivo. The mNPs are targeted to bind the selected molecule and the resulting reduction in rotational freedom can be quantified remotely using magnetic spectroscopy. The mNPs must be contained in micrometer sized porous shells to keep them from migrating and to protect them from clearance by the immune system. There are two key issues in the development of the probes. First, we demonstrate the ability to measure concentrations in the porous walled alginate probes both in phosphate buffered saline and in blood, which is an excellent surrogate for the complex and challengingin vivoenvironment. Second, sensitivity is critical because it allows microscopic probes to measure very small concentrations very far away. We report sensitivity measurements on recently introduced technology that has allowed us to improve the sensitivity by two orders of magnitude, a factor of 200 so far.
authors.affiliation: Department of Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA ; Department of Physics, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: Xiaojuan
authors.initials: X
authors.lastname: Zhang
authors.affiliation: Geisel School of Medicine, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: Daniel
authors.initials: D
authors.lastname: Reeves
authors.affiliation: Geisel School of Medicine, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: Yipeng
authors.initials: Y
authors.lastname: Shi
authors.affiliation: Department of Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA.
authors.forename: Barjor
authors.initials: B
authors.lastname: Gimi
authors.affiliation: Department of Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA ; Department of Physics, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: Krishnamurthy V
authors.initials: KV
authors.lastname: Nemani
authors.affiliation: Department of Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA ; Department of Physics, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: Irina M
authors.initials: IM
authors.lastname: Perreard
authors.affiliation: Department of Physics, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: Seiko
authors.initials: S
authors.lastname: Toraya-Brown
authors.affiliation: Department of Physics, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: Steven
authors.initials: S
authors.lastname: Fiering
authors.affiliation: Department of Radiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756 USA ; Geisel School of Medicine, Dartmouth College, Hanover, NH 03755 USA ; Department of Physics, Dartmouth College, Hanover, NH 03755 USA.
authors.forename: John B
authors.initials: JB
authors.lastname: Weaver
keywords: Magnetic particle imaging; perpendicular magnetic particle imaging; sMSB