Technetium-99m exchange labeling of sensitive molecules
Considerable interest hnas been shown by researchers in radiolabelling biologically interesting and often complex molecules with technetium-99m (Tc-99m) to detect and study various disease states in vivo. Examples of such molecules include enzymes, metabolic substrates such as glucose, ligands that bind to inter- and extracellular receptors, and monoclonal antibodies. Unfortunately many of these potentially useful compounds contain functional groups essential for maintaining biological activity which do not tolerate conventional Tc-99m labeling techniques that employ reducing conditions. The authors report on a new labeling technique which avoids having to expose sensitive target molecules to reducing agents. Moreover, the technique has the potential for being applied to a wide variety of biologically useful molecules. The method employs the concept of exchange labeling. A strong chelator which is covalently bound to the target molecule extracts the metal from a suitable labile Tc-99m complex in which the metal exists in a reduced oxidation state. The authors have found, for example, that the technetium(V) moiety in the no carrier added N-methyl N,N'-bis(2-hydroxyethyl)ethylenediamine complex is transferred quantitatively to functionalized, N,N '-bis(2-mercaptoethyl)ethylenediamine ligands within an hour at concentrations below l0/sup -6/M. The optimum choice of chelate, labile Tc-99m complex, and exchange conditions depends upon a variety of factors which are currently being studied and evaluated.
- Research Organization:
- The Johns Hopkins Medical Institutions, Baltimore, MD
- OSTI ID:
- 6854148
- Report Number(s):
- CONF-840619-; TRN: 87-010821
- Journal Information:
- J. Nucl. Med.; (United States), Vol. 25:5; Conference: 31. annual meeting of the Society of Nuclear Medicine, Los Angeles, CA, USA, 5 Jun 1984
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
37 INORGANIC
ORGANIC
PHYSICAL AND ANALYTICAL CHEMISTRY
AMINES
LABELLING
TECHNETIUM 99
CHEMICAL PREPARATION
RADIOCHEMISTRY
CHELATES
ENZYMES
IN VIVO
LIGANDS
MOLECULES
MONOCLONAL ANTIBODIES
OXIDATION
QUANTITY RATIO
RECEPTORS
REDUCING AGENTS
TRACER TECHNIQUES
ANTIBODIES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
CHEMICAL REACTIONS
CHEMISTRY
COMPLEXES
HOURS LIVING RADIOISOTOPES
INTERMEDIATE MASS NUCLEI
ISOMERIC TRANSITION ISOTOPES
ISOTOPE APPLICATIONS
ISOTOPES
MEMBRANE PROTEINS
NUCLEI
ODD-EVEN NUCLEI
ORGANIC COMPOUNDS
PROTEINS
RADIOISOTOPES
SYNTHESIS
TECHNETIUM ISOTOPES
YEARS LIVING RADIOISOTOPES
550601* - Medicine- Unsealed Radionuclides in Diagnostics
400202 - Isotope Effects
Isotope Exchange
& Isotope Separation