Cyclotron production and cyclometallation chemistry of 192Ir
Bibliographic record
Abstract
Introduction To explore new questions and techniques in nuclear medicine, new isotopes with novel chemical and nuclear properties must be developed. We are interested in the small cyclotron production of new radiometals for the development of new radiopharmaceuticals (RX). In an example of RX multifunctionality, Luminescence Cell Imaging (LCI) has been combined with radio-isotopes to allow compounds that can be imaged with both optical microscopy and nuclear techniques [1]. Within this field, iridium cy-clometalates have good potential with excellent photophysical properties [2]. As well, low specific activity iridium-192 has found use in brachy-therapy as a high-intensity beta emitter [3]. Despite this, iridium radioisotopes have yet to be applied to cyclometalation chemistry, or a radiochemical isolation method developed for carrier free production on a medical cyclotron. Our goal is to demonstrate the feasibility of the production and isolation of radio-iridium, and its application to cyclometalate chemistry as a potentially interesting tool for nuclear medicine research. Materials and Methods Following literature precedent [4], natural osmium was electroplated onto a silver disc from basic media containing osmium tetroxide and sulphamic acid. The thin deposits obtained (15–20 mg cm−2) were weighed and characterized with scanning electron microscopy. Targets were irradiated using the TRIUMF TR13 cyclotron, delivering 12.5 MeV protons to the target disc. Initial bombardments were per-formed at 5 μA; gamma spectra of the targets were collected 24 hours after end of bombardment. The irradiated material was oxidized, dissolved from the target backing, and separated via anion exchange. In parallel to the isotope production work, non-radioactive iridium was used to define a chemical procedure suitable for the synthesis of model iridium cyclometalate compounds given low concentrations of radioiridium. These experiments will be performed with radioactive iridium in the next step of the research project. Results and Conclusion Proton bombardment of natural osmium yielded a range of iridium isotopes, with characteristic spectral lines corresponding to 186-190Ir, and 192Ir; no other characteristic radiation was observed. The EOB activity of each isotope was then used in thin target calculations to approximate their (p,n) cross section. Preliminary cross section measurements of the 192Os(p,n)192Ir reaction (53 ± 13 mb @ 12.5 MeV) confirm published data (52.3 ± 5.7 mb @ 12.2 MeV) [6], and provide as-yet unpublished data on the lower mass number isotopes. The progress of radioactive iridium through the radiochemical separation was tracked with a dose calibrator; the osmium complex formed was brightly coloured and could be seen retained on the column. The overall efficiency of the process is estimated at 80 %. Radioactive cyclometallation chemistry is currently under-way. The production and isolation of a range of iridium isotopes in a chemically useful form was demonstrated, and is ready to be applied to a cyclometalate model compound. Future work will investigate the production of 192Ir from enriched 192Os.
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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) | 0.005 | 0.001 |
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".