A new radiochemical method to study the stability of metal chelates used in radiopharmaceuticals

Conference · Wed May 01 04:00:00 EDT 1985 · J. Nucl. Med.; (United States)

OSTI ID:6706550

Subramanian, K M; Wolf, W

Bifunctional chelates are more and more actively used to allow radiolabeling of proteins following metal chelation. While there are data in the literature on the stability constants of the free metal chelates in solution, such methods are neither simple nor suitable for the determination of metal-chelate stability constants following coupling of the bifunctional chelate to a protein. The authors present a novel method for determining the stability constants of indium chelates, which is based on the use of ferric ions as displacement cations. Indium-111 or inium-114m labeled 1:1 In-chelates were incubated with molar equivalents of ferric ions at acidic and neutral pH. At equilibrium this mixture was analyzed by paper and cation-exchange chromatography to determine free and complexed indium. The position equilibrium constants 'K' were calculated from the above data. Using the known stability constants of the ferric chelates ..beta.. and the 'K' values, the stability constants of the indium chelates of several amino polycarboxylic acids, such as NTA, EDTA, DTPA and TTHA were determined. The results obtained were: (current work, literature value) - In-NTA: 16.0, 16.9; In-EDTA: 25.3, 25.3; In-DTPA: 28.7, 29.0; In-TTHA: 27.8, -. These results document that the values obtained by this new method agree well with the values reported in the literature determined by potentiometric titrations. The simplicity of the current method and the ease of calculation of the K values renders this procedure easy to use for the study of indium (and probably other metal) chelates. This method may find special use in determining the stability constants of indium labeled chelates conjugated to proteins, such as in monoclonal antibodies.

• Research Organization: Radiopharmacy Program, Univ. of Southern California, Los Angeles, CA
• OSTI ID: 6706550
• Report Number(s): CONF-850611-
• Conference Information: Journal Name: J. Nucl. Med.; (United States) Journal Volume: 26:5
• Country of Publication: United States
• Language: English

Related Subjects

550601* -- Medicine-- Unsealed Radionuclides in Diagnostics
62 RADIOLOGY AND NUCLEAR MEDICINE
ANTIBODIES
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BETA-PLUS DECAY RADIOISOTOPES
CARBOXYLIC ACIDS
CATIONS
CHARGED PARTICLES
CHELATES
CHELATING AGENTS
CHEMICAL PREPARATION
CHROMATOGRAPHY
COMPLEXES
COUPLING
DAYS LIVING RADIOISOTOPES
DIAGNOSTIC USES
DRUGS
ELECTRON CAPTURE RADIOISOTOPES
EQUILIBRIUM
INDIUM 111
INDIUM 114
INDIUM COMPLEXES
INDIUM COMPOUNDS
INDIUM ISOTOPES
INTERMEDIATE MASS NUCLEI
INTERNAL CONVERSION RADIOISOTOPES
ION EXCHANGE CHROMATOGRAPHY
IONS
IRON COMPOUNDS
ISOMERIC TRANSITION ISOTOPES
ISOTOPES
LABELLED COMPOUNDS
LABELLING
MEASURING METHODS
MINUTES LIVING RADIOISOTOPES
MONOCLONAL ANTIBODIES
NUCLEI
ODD-EVEN NUCLEI
ODD-ODD NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
PH VALUE
POTENTIOMETRY
PROTEINS
RADIOACTIVATION
RADIOISOTOPES
RADIOPHARMACEUTICALS
SECONDS LIVING RADIOISOTOPES
SEPARATION PROCESSES
STABILITY
SYNTHESIS
TITRATION
TRANSITION ELEMENT COMPOUNDS
USES