Gadolinium‐based contrast agents for magnetic resonance cancer imaging

Whole body MR images of mice injected with 0.03 mmol‐Gd kg⁻¹ of PAMAM G9 (a), G7 (b), and G3 (c) Gd‐DTPA conjugates, and 0.1 mmol‐Gd kg⁻¹ of Gd‐DTPA (d) at 3 min post‐injection. (Reprinted with permission from Ref 52. Copyright 2005 Elsevier Ltd)

Coronal T₁‐weighted gradient echo images of VX2 tumor‐bearing rabbits at 1.5 T showing tumor rim (white, short, and thick arrow) and peritumoral vessels (yellow, thin, and long arrows) before and at 1, 10, and 60 min and 24 and 72 h after i.v. injection of Gd(DTPA‐BMA) (Omniscan^®) and Dextran‐(Gd‐DTPA) at 0.1 mmol‐Gd kg⁻¹. (^∗︁, water phantom; T, tumor). (Reprinted with permission from Ref 44. Copyright 2004 Association of University Radiologists)

Examples of macromolecule‐based Gd(III) contrast agents.

Structures of the Gd(III)‐based MRI contrast agents currently used in the clinical practice.

The r₁ relaxivities of MAGNEVIST (▪), GADOMER (•) (polylysine dendrimer and Gd‐DOTA complexes) and MS‐325 (▴) in water or plasma at different magnetic field intensity.12

The illustration of folate‐targeted bimodal liposomes containing Gd(III) chelates for MR imaging of ovarian cancer. (Reprinted with permission from Ref 92. Copyright 2009 American Chemical Society)

The expression α_νβ₃ integrin and ACPL localization in tumor tissue sections. (a) An immunohistochemical staining section for α_νβ₃ integrin from the tumor margin (Figure 13(a)); (b) an adjacent tissue section stained for ACPLs; (c) a staining section showed a high density of stained α_νβ₃ positive vessels from the tumor with strong MR enhancement with the ACPLs; (d) a staining section showing a relative paucity of α_νβ₃ positive vessels from the tumor with relatively weak MR enhancement with ACPLs. (Reprinted with permission from Ref 95. Copyright 1998 Nature Publishing Group)

T1 MR images of rabbit tumors before and 24 after injection of anti‐α_νβ₃ (LM609) ACPLs. Arrows indicate tumors. (a) Coronal images of tumor in the right thigh muscle; (b) axial images of a intramuscle tumor; (c) coronal images of a subcutaneously implanted V2 carcinoma; (d) LM609 ACPLs improved visualization of a subcutaneous tumor; (e) axial images of hyperintense intramuscle tumor with central necrosis and the post‐contrast image with LM609 ACPLs; (f) coronal image of tumor growing in left thigh muscle and minimal tumor enhancement at 24 h after injection of isotype‐matched control ACPLs; (g) axial images of a rabbit subcutaneous tumor and almost no enhancement 24 h after administration of avidin‐conjugated control paramagnetic liposomes. Inset illustrates the structure of ACPLs. (Reprinted with permission from Ref 95. Copyright 1998 Nature Publishing Group)

MR 3D maximum intensity projection images (a, b) and 2D axial T₁‐weighted spin‐echo images of tumor tissue (c, d) of nu/nu female nude mice bearing MDA MB‐231 tumor xenografts before and at various time points after intravenous injection of G2 (a, c) and CLT1 peptide‐targeted G2 (b, d) nanoglobular MRI contrast agents at 0.03 mmol‐Gd kg⁻¹. Arrows indicate tumor. (Reprinted with permission from Ref 85. Copyright 2010 American Chemical Society)

Synthesis of peptide CLT1‐targeted nanoglobular contrast agents. (Reprinted with permission from Ref 85. Copyright 2010 American Chemical Society)

(a) The illustration of two‐component Gd‐based avidin–biotin system binding to HER‐2/neu receptor. (b) T₁‐weighted MR images of mice bearing EMT‐6 and NT5 tumors before contrast and at 1, 8, 24, and 48 h postinjection of avidin‐(Gd‐DTPA)_12.5. Arrow points to the tumor tissue and water phantom is used as reference. (c) Signal enhancement in the tumor relative to the muscle tissue at 24 h after contrast. ‘NT5 treated’ and ‘EMT6’ groups were pretreated with anti‐HER‐2/neu biotinylated antibody. ‘NT5 control’ group was treated with BSA instead of antibody. Error bars represent SE. The signal enhancement was significant (P < 0.05) for prelabeled NT‐5 tumors. (Reprinted with permission from Ref 77. Copyright 2003 American Association for Cancer Research)

The structure of CLT1‐(Gd‐DTPA) and T₁‐weighted 2D spin‐echo MR images of mice bearing HT‐29 xenografts before contrast and at 10, 30, and 60 min postinjection of CLT1‐(Gd‐DTPA), Omniscan and competitive mixture of CLT1‐(Gd‐DTPA) and free CLT1. Arrow points to the tumor tissue. (Reprinted with permission from Ref 75. Copyright 2008 American Chemical Society)

The chemical structure of RGD‐(Gd‐DOTA) (a), normalized signal intensities of the tumor as a function of time measured by MRI with RGD‐(Gd‐DOTA) (▪) and Omniscan (□) (b), and MR T₁‐weighted images of mice with hepatocellular carcinoma before (c, e) and after (d, f) injection of RGD‐(Gd‐DOTA) (f, injected with c‐(RGDyK) 30 min before). (Reprinted with permission from Ref 73. Copyright 2008 John Wiley & Sons, Inc)

Coronal T₂‐weighted images of the rat brain with glioma obtained before and 5 min, 1 day, and 3 days after administration of the Gd(III)‐liposome at a dose of 0.25 mmol‐Gd kg⁻¹ on a 9.4 T MRI. (Reprinted with permission from Ref 71. Copyright 2008 IOP Publishing Ltd)

(a) Schemes of core‐encapsulated gadolinium chelate (CE‐Gd) liposomes, surface‐conjugated gadolinium chelate (SC‐Gd) liposomes, and liposomes containing both encapsulated and conjugated gadolinium chelates (Dual‐Gd). (b) T₁ relaxation rates (R₁) of liposomal‐Gd formulations for different lipid concentrations (*P < 0.05).68

Polydisulfide macromolecular Gd(III)‐chelates with different chemical structures around the biodegradable disulfide bonds.