Improvement in radiolabelling proteins with the99mTc-tricarbonyl-core [99mTc(CO)3]+, by thiol-derivatization with iminothiolane: application to γ-globulins and annexin V

Abstract

SummaryThe aim of this study was to improve the radiolabelling of proteins with the 99m Tctricarbonyl-[Tc(I)(CO) 3 ] + core by introducing thiol groups to their structure. To achieve this goal, g-globulins and annexin V were derivatized with mercaptobutyrimidyl groups (MBG) after reaction with 2-iminothiolane. The optimal conditions permitted attachment of an average of 3.3 thiol groups on g-globulins and 1.0 to annexin V. The radiolabelling assays were carried out by incubating 3.2 nmol of either g-globulin-SH or unmodified g-globulin with 60 MBq 99m Tc-tricarbonyl produced from an Isolink 1 kit (Mallinckrodt) under different reaction conditions. Results clearly showed that the introduction of three MBG could double the radiolabelling yields to more than 90% in a short time (30 mn, 378C). Such results would never have been reached with unmodified g-globulins alone. Under the same conditions when using 1-2 nmol derivatized annexin V, the average radiolabelling yield was 55% against 19% with the unmodified protein. The 99m Tc-tricarbonyl-conjugates were challenged with cysteine or histidine and showed good stability.

Anti-CD20 Immunoglobulin G Radiolabeling with a 99mTc-Tricarbonyl Core: In Vitro and In Vivo Evaluations

“…99m Tc is an attractive candidate for radiolabeling due to its specific characteristics: emission, radiation protection, radiochemistry, and ready availability in nuclear medicine department. Due to their high kinetic stability, technetium complexes in a low oxidation state (+I) have recently gained considerable attention for the development of novel site-specific radiopharmaceuticals [ 15 ]. The organometallic 99m Tc-tricarbonyl core [ 99m Tc(CO) 3 (H 2 O) 3 ] + is one of these complexes, characterized by its water- and air-stability.…”

“…To functionalize IgG and add SH- groups under milder conditions, Biechlin et al . [ 15 ] tried an alternative way to derivatize IgG with 2-iminothiolane, and high radiolabeling yields (> 95%) of IgG-SH were obtained with low polyclonal IgG amounts (0.5 mg). To develop a mild radiolabeling method applicable to noncommercial monoclonal IgGs and other isotypes, available only in limited quantities, we selected the method described by Biechlin et al .…”

“…To develop a mild radiolabeling method applicable to noncommercial monoclonal IgGs and other isotypes, available only in limited quantities, we selected the method described by Biechlin et al . [ 15 ]. Our results confirmed the derivatization step’s value: a 40% yield increase was obtained with derivatized IgG versus native IgG (0.0375–0.225mg).…”

“…Biechlin et al . demonstrated that the combination of 99m Tc-tricarbonyl with 2-IT derivatization could be applied to various proteins such as IgG with high yields [ 15 ], showing with polyvalent IgG that this radiolabeling was efficient and highly stable. However, the preservation of antibodies structure and affinity, after this two-step radiolabeling method has not been evaluated.…”

Ibogaine labeling with 99mTc-tricarbonyl: Synthesis and transport at the mouse blood–brain barrier

“…It forms kinetically stable complexes due to the low oxidation state 1 of the technetium (þI) and up to three labile water molecules can readily be replaced, especially with aromatic nitrogen compounds like histidine, histamine, 2 or sulfur-containing compound like thioether or thiol. 3,4 Radiolabeling can produce high specific activities and the 99m Tc-tricarbonyl core [ 99m Tc(OH 2 ) 3 (CO) 3 ] þ is readily obtained with the Isolink 1 kit in a routine radiopharmaceutical environment. These recent advances in complex chemistry have opened the door to the development of site-specific radiotracers for single photon emission computed tomography (SPECT).…”