Indium radiolabelled

Molecular imaging may potentially address not only the pathophysiology of ischemia but also vascular inflammation causing rupture of atherosclerotic plaques before major ischemic events. Initial approaches have used imaging of "indium radiolabeled monocytes [150], upregulated metallo-proteinases [151], and imaging of apoptosis in atherosclerotic lesions [152]. However, none have evolved into clinically useful tests. 

Figure 20.18 The bifunctional chelating reagent DTPA may be used to modify amine groups on antibody molecules, forming amide bond linkages. Indium-111 then may be complexed to the chelator group to create a radiolabeled-targeting reagent.

Hnatowich, D. J. (1990) Recent developments in the radiolabeling of antibodies with iodine, indium, and technetium. Sem. Nuclear. Med. 20, 80-91. 

Virgolini I, Muller C, Eitscha P, Chiba P, Sinzinger H. Radiolabeling autologous monocytes with 111-indium-oxine for reinjection in patients with atherosclerosis. Prog Clin Biol Res 1990 355 271-280... 

DOTA is of particular interest as a BFC for radiolabeling of small BMs with yttrium and lanthanide isotopes. The macrocyclic framework is well organized so that it forms yttrium and indium complexes with high thermodynamic stability and kinetic inertness. The pXa values of the carboxylic groups are in the range 2-5. Lower pKa values result in less competition from protons, high stability of the metal complex, and minimum acid-assisted demetallation, even... 

Each vial contains 0.5 mg of capromab pendetide in 1 mL of sodium phosphate-buffered saline solution adjusted to pH 6 the sodium acetate solution must be added to the sterile, nonpyrogenic high-purity Indium In 111 chloride solution to buffer it prior to radiolabeling. 

Radiolabeled Compounds of Biomedical Interest Containing Radioisotopes of Gallium and Indium... 

Comparisons to the known structure of indium DTPA and to other divalent metal DTPA bis-amide complexes indicate that the indium cation binds to the three amine nitrogen atoms, the four carboxylate oxygen atoms, and the one carboxairdde oxygen atom of the DTPA monoamide ligand. Addition of an acidic In chloride solution to a ly-ophilized DTPA-octreotide pellet at room temperature readily fomis In DTPA-octreotide, known clinically as OctreoScan. In a rat model of pancreatic carcinoma In DTPA-octreotide showed clear visualization of the tumors and rapid, primarily renal, clearance of the radiophamiaceutical/ Moreover, pretreatment with 1 mg of octreotide prevents uptake of " in DTPA-octreotide in the tumors and adrenal glands, an observation that verifies that this radiolabeled peptide binds to receptor sites. 

Initial work on radiolabeling of autologous polymorphonuclear leukocytes was performed by McAfee and Thakur [30]. One of the compounds they examined was the nonpolar, lipid-soluble complex 8-hydroxyquinoline (oxine) (Fig. 2). Indium forms a neutral, lipid-soluble complex with oxine which will penetrate cellular membranes. Subsequently, studies showed that this technique could be used to label leukocytes and platelets with retention of biological activity [31]. After diffusing intracellularly, the ln-oxine complex dissociates and the " In is bound to nuclear and cytoplasmic proteins (Fig. 3) [32-34]. Due to the high stability of indium with the blood protein transferrin, it is necessary to label platelets or WBCs in the absence of plasma. In addition, a final wash of the labeled cells using plasma will remove any loosely bound indium by complexation with transferrin [35,36]. 

Pascu et al. developed intrinsically fluorescent gallium and indium bis(thiosemicarbazonato) for rapid radiolabelling. Uptake in cells indicated localisation in mitochondria, lysosomes and additionally for indium complexes in the nucleus, therefore opening up the possibility Auger electron emission therapy via In, using a complex such as 17 (Fig. 24). 

---