title: Molecular imaging with optical coherence tomography using ligand-conjugated microparticles that detect activated endothelial cells: rational design through target quantification.
abstract: OBJECTIVE
  Optical coherence tomography (OCT) is a high resolution imaging technique used to assess superficial atherosclerotic plaque morphology. Utility of OCT may be enhanced by contrast agents targeting molecular mediators of inflammation.
  
  
  RESULTS
  Microparticles of iron oxide (MPIO; 1 and 4.5 μm diameter) in suspension were visualized and accurately quantified using a clinical optical coherence tomography system. Bound to PECAM-1 on a plane of cultured endothelial cells under static conditions, 1 μm MPIO were also readily detected by OCT. To design a molecular contrast probe that would bind activated endothelium under conditions of shear stress, we quantified the expression (basal vs. TNF-activated; molecules μm(-2)) of VCAM-1 (not detected vs. 16 ± 1); PECAM-1 (132 ± 6 vs. 198 ± 10) and E-selectin (not detected vs. 46 ± 0.6) using quantitative flow cytometry. We then compared the retention of antibody-conjugated MPIO targeting each of these molecules plus a combined VCAM-1 and E-selectin (E+V) probe across a range of physiologically relevant shear stresses. E+V MPIO were consistently retained with highest efficiency (P < 0.001) and at a density that provided conspicuous contrast effects on OCT pullback.
  
  
  CONCLUSIONS
  Microparticles of iron oxide were detectable using a clinical OCT system. Assessment of binding under flow conditions recommended an approach that targeted both E-selectin and VCAM-1. Bound to HUVEC under conditions of flow, targeted 1 μm E+V MPIO were readily identified on OCT pullback. Molecular imaging with OCT may be feasible in vivo using antibody targeted MPIO.
authors.affiliation: Department of Cardiovascular Medicine and Oxford Acute Vascular Imaging Centre, University of Oxford, John Radcliffe Hospital, Oxford OX3 9DU, United Kingdom.
authors.forename: Andrew
authors.initials: A
authors.lastname: Jefferson
authors.forename: Rohan S
authors.initials: RS
authors.lastname: Wijesurendra
authors.forename: Martina A
authors.initials: MA
authors.lastname: McAteer
authors.forename: Janet E
authors.initials: JE
authors.lastname: Digby
authors.forename: Gillian
authors.initials: G
authors.lastname: Douglas
authors.forename: Thomas
authors.initials: T
authors.lastname: Bannister
authors.forename: Francisco
authors.initials: F
authors.lastname: Perez-Balderas
authors.forename: Zsolt
authors.initials: Z
authors.lastname: Bagi
authors.forename: Alistair C
authors.initials: AC
authors.lastname: Lindsay
authors.forename: Robin P
authors.initials: RP
authors.lastname: Choudhury
mesh_terms: D000818:Animals; D000911:Antibodies, Monoclonal / Q000378:metabolism; D001160:Arterioles / Q000276:immunology / Q000378:metabolism; D015415:Biomarkers / Q000378:metabolism; D002478:Cells, Cultured; D003331:Coronary Vessels / Q000276:immunology / Q000378:metabolism*; D019040:E-Selectin / Q000276:immunology / Q000378:metabolism; D005290:Ferric Compounds / Q000378:metabolism*; D005434:Flow Cytometry; D061307:Human Umbilical Vein Endothelial Cells / Q000276:immunology / Q000378:metabolism*; D006801:Humans; D007150:Immunohistochemistry; D018836:Inflammation Mediators / Q000276:immunology / Q000378:metabolism; D008024:Ligands; D008297:Male; D008856:Microscopy, Fluorescence; D018715:Microscopy, Video; D057054:Molecular Imaging / Q000379:methods*; D015335:Molecular Probes; D010316:Particle Size; D019408:Platelet Endothelial Cell Adhesion Molecule-1 / Q000276:immunology / Q000378:metabolism; D011485:Protein Binding; D051381:Rats; D017208:Rats, Wistar; D012107:Research Design; D013314:Stress, Mechanical; D041623:Tomography, Optical Coherence; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism; D019010:Vascular Cell Adhesion Molecule-1 / Q000276:immunology / Q000378:metabolism
chemical_list: D000911:Antibodies, Monoclonal; D015415:Biomarkers; D019040:E-Selectin; D005290:Ferric Compounds; D018836:Inflammation Mediators; D008024:Ligands; D015335:Molecular Probes; D019408:Platelet Endothelial Cell Adhesion Molecule-1; C546936:SELE protein, human; D014409:Tumor Necrosis Factor-alpha; D019010:Vascular Cell Adhesion Molecule-1; C000499:ferric oxide