99mTc: Labeling Chemistry and Labeled Compounds
Abstract
This chapter reviews the radiopharmaceutical chemistry of technetium related to the synthesis of perfusion agents and to the labeling of receptor-binding biomolecules. To understand the limitations of technetium chemistry imposed by future application of the complexes in nuclear medicine, an introductory section analyzes the compulsory requirements to be considered when facing the incentive of introducing a novel radiopharmaceutical into the market. Requirements from chemistry, routine application, and market are discussed. In a subsequent section, commercially available 99mTc-based radiopharmaceuticals are treated. It covers the complexes in use for imaging the most important target organs such as heart, brain, or kidney. The commercially available radiopharmaceuticals fulfill the requirements outlined earlier and are discussed with this background. In a following section, the properties and perspectives of the different generations of radiopharmaceuticals are described in a general way, covering characteristics for perfusion agents and for receptor-specific molecules. Technetium chemistry for the synthesis of perfusion agents and the different labeling approaches for target-specific biomolecules are summarized. The review comprises a general introduction to the common approaches currently in use, employing the N x S4-x , [3+1] and 2-hydrazino-nicotinicacid (HYNIC) method as well as more recent strategies such as the carbonyl and the TcN approach. Direct labeling without the need of a bifunctional chelator is briefly reviewed as well. More particularly, recent developments in the labeling of concrete targeting molecules, the second generation of radiopharmaceuticals, is then discussed and prominent examples with antibodies/peptides, neuroreceptor targeting small molecules, myocardial imaging agents, vitamins, thymidine, and complexes relevant to multidrug resistance are given. In addition, a new approach toward peptide drug development is described. The section has a focus on coordination and labeling chemistry, but biological results are briefly summarized as well. The last (and shortest) section finally intends to give a (subjective) outlook for the future role of 99mTc-based radiopharmaceuticals. Critical comments are spread over the whole article but are concentrated in this section. Despite the increasing competition of diagnostic radiopharmacy by other commonly applied methods in medicine such as magnetic resonance imaging (MRI) or ultrasound, the authors are convinced that 99mTc will play a key role also in future if novel approaches are added and the requirements from chemistry biology and the market considered in research to a stronger extent.
- Publication:
-
Handbook of Nuclear Chemistry
- Pub Date:
- 2011
- DOI:
- 10.1007/978-1-4419-0720-2_43
- Bibcode:
- 2011honc.book.2073A