Radiolabeled biomolecules

Keywords. Radiolabeled biomolecules. Receptor ligands. Radiopharmaceuticals... 

As part of the coordinated research project (CRP) on comparative evaluation of therapeutic radiopharmaceuticals, the ior-CEAl-(scFv)2 fragment and the somatostatin peptide analogues ior-P1394 and [DOTA,Tyr ]octreotate (DOTATATE) were evaluated as targeted agents. The results obtained from in vitro and in vivo studies deomonstrate the clinical usefulness of these radiolabelled biomolecules as radiotherapeutic agents. 

Studies to evaluate the in vitro and in vivo stability of radiolabeled mAbs and peptides are an integral part of their development. Kits used to prepare radiolabeled biomolecules (Section 6.7.7.7) must meet specifications established for labeling efficiency, immunoreactivity/receptor binding, homogeneity, sterility and apyrogenicity, and other quality control tests over the expected storage period [145]. Similarly, the radiolabeled biomolecule must maintain the specified level of RCP over the interval from the time of labeling until it is administered. The results... 

Radiolabeled mAbs and peptides intended for RIT or PDRT of malignancies need to be first evaluated preclinically in mouse tumor xenograft models. These studies involve administration of increasing doses of the radiolabeled biomolecules to mice... 

Liu S (2005) 6-Hydrazinonicotinamide Derivatives as Bifunctional Coupling Agents for "mTc-Labeling of Small Biomolecules. 252 117-153 Liu S, Robinson SP, Edwards DS (2005) Radiolabeled Integrin avp Antagonists as Radio-pharmaceuticals for Tumor Radiotherapy. 252 193-216 Liu XY (2005) Gelation with Small Molecules from Formation Mechanism to Nanostructure Architecture. 256 1-37... 

These factors make 125I the iodine label of choice for radiolabeling biological molecules. Its commercial availability from a number of suppliers at relatively low cost further adds to its popularity. Even though it has lower specific activity than 131I, iodine-125 still provides much greater sensitivity than 14C, 32P, 35S, or 3H in labeling biomolecules. In fact, the use of a radioactive iodine label can create probes that have 150-fold more sensitivity than tritiated molecules and as much as 35,000 times the detectability of 14C-labeled molecules (Bolton and Hunter, 1986). 

In order to facilitate analysis of FeBABE produced fragments, the prey protein or biomolecule is labeled at one end with a tag that can be detected after electrophoresis, usually in a transfer blot. The tag can be a fusion tag, such as 6X His, or any other group that can be targeted with an antibody and detected. Alternatively, radiolabels and fluorescent labels have been used with prey molecules, including the use of end-labeled DNA to study where DNA binding proteins dock onto the oligonucleotide sequence. 

In the last decade, a large number of radiolabeled small biomolecules have been studied for their potential as radiopharmaceuticals for diagnosis and radiotherapy of various diseases. This review wiU focus on some fundamental aspects of receptor-based diagnostic radiopharmaceuticals, including radiopharmaceutical design, receptors and receptor imaging, choice of biomolecule, and modification of pharmacokinetics. 

Because of concerns about the safety of radioisotope use, researchers are developing fluorescent and chemiluminescent methods for detection of small amounts of biomolecules on gels. One attractive approach is to label biomolecules before analysis with the coenzyme biotin. Biotin forms a strong complex with enzyme-linked streptavidin. Some dynamic property of the enzyme is then measured to locate the biotin-labeled biomolecule on the gel. These new methods approach the sensitivity of methods involving radiolabeled molecules, and rapid advances are being made. 

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