Antibody-labeled liposomes for CT imaging of atherosclerotic plaques: in vitro investigation of an anti-ICAM antibody-labeled liposome containing iohexol for molecular imaging of atherosclerotic plaques via computed tomography

• Published in: Texas Heart Institute journal Vol. 36; no. 5; pp. 393 - 403
• Main Authors: Danila, Delia, Partha, Ranga, Elrod, Don B, Lackey, Melinda, Casscells, S Ward, Conyers, Jodie L
• Format: Journal Article
• Language: English
• Published: United States Texas Heart Institute 2009
• Subjects: Antibodies, Monoclonal - metabolism; Antibody Specificity; Cells, Cultured; Contrast Media - metabolism; Coronary Angiography - methods; Coronary Artery Disease - diagnostic imaging; Coronary Artery Disease - immunology; Coronary Vessels - drug effects; Coronary Vessels - immunology; Cryoelectron Microscopy; Endothelium, Vascular - diagnostic imaging; Endothelium, Vascular - drug effects; Endothelium, Vascular - immunology; Enzyme-Linked Immunosorbent Assay; Ethyldimethylaminopropyl Carbodiimide - pharmacology; Flow Cytometry; Humans; Intercellular Adhesion Molecule-1 - immunology; Iohexol - metabolism; Laboratory Investigation; Light; Liposomes; Microscopy, Fluorescence; Nanoparticles; Scattering, Radiation; Spectrophotometry, Ultraviolet; Succinimides - pharmacology; Tomography, X-Ray Computed - methods; endothelium, vascular; binding sites, antibody; cell adhesion molecules; iohexol/diagnostic use; vulnerable plaque; tomography, X-ray computed; Atherosclerosis; contrast media; ICAM-1; immunoliposome
• ISSN: 0730-2347; 1526-6702

We evaluated the specific binding of anti-intercellular adhesion molecule 1 (ICAM-1) conjugated liposomes (immunoliposomes, or ILs) to activated human coronary artery endothelial cells (HCAEC) with the purpose of designing a computed tomographic imaging agent for early detection of atherosclerotic plaques. Covalent attachment of anti-ICAM-1 monoclonal antibodies to pre-formed liposomes stabilized with polyethylene glycol yielded ILs, with a coupling efficiency of the ICAM-1 to the liposomes of 10% to 24%. The anti-ICAM-1-labeled ILs had an average diameter of 136 nm as determined by dynamic light-scattering and cryogenic electron microscopy. The ILs' encapsulation of 5-[N-acetyl-(2,3-dihydroxypropyl)-amino)-N, N'-bis(2,3-dihydroxypropyl)-2,4,6-triiodo-benzene-1,3-dicarboxamide (iohexol) was determined to be 18% to 19% by a dialysis technique coupled with ultraviolet detection of free iohexol. This encapsulation corresponded to 30 to 38 mg iodine per mL IL solution, and the ILs exhibited 91% to 98.5% iohexol retention at room temperature and under physiologic conditions. The specific binding of the ILs to cultured, activated HCAEC was measured using flow cytometry, enzyme-linked immunosorbent assays, and fluorescence microscopy. The immunosorbent assays demonstrated the specificity of binding of anti-ICAM-1 to ICAM-1 compared with control studies using nonspecific immunoglobulin G-labeled ILs. Flow cytometry and fluorescence microscopy experiments demonstrated the expression of ICAM-1 on the surface of activated HCAEC. Therefore, our iohexol-filled ILs demonstrated potential for implementation in computed tomographic angiography to noninvasively detect atherosclerotic plaques that are prone to rupture.