title: Solid MRI contrast agents for long-term, quantitative in vivo oxygen sensing.
abstract: Targeted MRI contrast agents have proven useful in research and clinical studies for highlighting specific metabolites and biomarkers [Davies GL, et al. (2013) Chem Commun (Camb) 49(84):9704-9721] but their applicability in serial imaging is limited owing to a changing concentration postinjection. Solid enclosures have previously been used to keep the local concentration of contrast agent constant, but the need to surgically implant these devices limits their use [Daniel K, et al. (2009) Biosens Bioelectron 24(11):3252-3257]. This paper describes a novel class of contrast agent that comprises a responsive material for contrast generation and an injectable polymeric matrix for structural support. Using this principle, we have designed a contrast agent sensitive to oxygen, which is composed of dodecamethylpentasiloxane as the responsive material and polydimethylsiloxane as the matrix material. A rodent inspired-gas model demonstrated that these materials are functionally stable in vivo for at least 1 mo, which represents an order of magnitude improvement over an injection of liquid siloxane [Kodibagkar VD, et al. (2006) Magn Reson Med 55(4):743-748]. We also observed minimal adverse tissue reactions or migration of contrast agents from the initial injection site. This class of contrast agents, thus, represented a new and complementary method to monitor chronic diseases by MRI.
authors.affiliation: Departments of Electrical Engineering and Computer Science and Materials Science and Engineering and The David H. Koch Institute for Integrative Cancer Research, Massachusetts Institute of Technology, Cambridge, MA 02139.
authors.forename: Vincent H
authors.initials: VH
authors.lastname: Liu
authors.forename: Christophoros C
authors.initials: CC
authors.lastname: Vassiliou
authors.forename: Syed M
authors.initials: SM
authors.lastname: Imaad
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Cima
mesh_terms: D000818:Animals; D015374:Biosensing Techniques / Q000379:methods; D003287:Contrast Media / Q000008:administration & dosage / Q000737:chemistry*; D004129:Dimethylpolysiloxanes / Q000737:chemistry; D006801:Humans; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008863:Microspheres; D010100:Oxygen / Q000032:analysis*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012833:Siloxanes / Q000008:administration & dosage / Q000737:chemistry*
chemical_list: D003287:Contrast Media; D004129:Dimethylpolysiloxanes; D012833:Siloxanes; C013830:baysilon; D010100:Oxygen
keywords: implantable sensors; molecular imaging
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