Radiochemistry of cyclen-derived chelators comprising five-membered azaheterocyclic arms with 212Pb2+, 213Bi3+, and 225Ac3+
Bibliographic record
Abstract
In this work, we introduce the cyclen-based metal chelator DOTThia comprising four methylthiazole arms for metal complexation. Together with the recently described congener DOTI-Me bearing four methylimidazole arms, the radiochemistry of these two compounds with 212 Pb, 213 Bi, and 225 Ac was investigated thoroughly. Radiolabeling experiments were performed at various pH values and temperatures to determine the optimal conditions for quantitative radiochemical conversions. Experiments revealed excellent complexation properties of DOTThia for 212 Pb at room temperature, comparable to those of the current gold standard for Pb complexation, TCMC, while it was not well suited for 213 Bi. Contrarily, DOTI-Me exhibited quantitative radiochemical conversions for 213 Bi at pH 5.5 and room temperature, outperforming the metal chelator macropa, but was not able to quantitatively complex 212 Pb under any conditions investigated. Of note, both novel chelators were not able to bind 225 Ac. In preliminary experiments, we could also show that a functionalized DOTI-Me derivative is capable of complexing 213 Bi selectively from 225 Ac solutions. This feature may allow the preparation of 213 Bi-labeled radiotracers directly from 225 Ac solutions without the need for an 225 Ac/ 213 Bi generator. However, more detailed studies are needed to fully explore this potential application. Altogether, our results support the future development of 212 Pb-labeled radiopharmaceuticals using bifunctional derivatives of DOTThia as well as of 213 Bi-labeled radiotracers based on the DOTI-Me scaffold.
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How this classification was reachedexpand
Full frame machine prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. The Gemma side is a direct model label for every work in the frame, read from the title-only record. The Codex side is a classifier learned from the 10,348 direct Codex labels and calibrated to design-weighted sample rates; fields without enough sample support carry no Codex call. Candidate is the union of the two sides; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels.
Distilled classifier scores by category (both heads)
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.000 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.000 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from itClassification
machine, unvalidatedMachine predicted; a candidate call from one source (direct Gemma or distilled Codex), not a consensus.
How this classification was reached, model by model and score by score, is at the end of the page under "How this classification was reached".