Dataset Information

Microwave-assisted synthesis of [⁵²Mn]Mn-porphyrins: Applications in cell and liposome radiolabelling.

ABSTRACT:

Background

Manganese porphyrins have several therapeutic/imaging applications, including their use as radioprotectants (in clinical trials) and as paramagnetic MRI contrast agents. The affinity of porphyrins for lipid bilayers also makes them candidates for cell/liposome labelling. We hypothesised that metalation with the positron emission tomography (PET) radionuclide ⁵²Mn (t_1/2 = 5.6 d) would allow long-term in vivo biodistribution studies of Mn-porphyrins, as well as a method to label and track cells/liposomes, but methods for fast and efficient radiolabelling are lacking.

Results

Several porphyrins were produced and radiolabelled by addition to neutralised [⁵²Mn]MnCl₂ and heating using a microwave (MW) synthesiser, and compared with non-MW heating. MW radiosynthesis allowed >95 % radiochemical yields (RCY) in just 1 h. Conversely, non-MW heating at 70 °C for 1 h resulted in low RCY (0-25 % RCY) and most porphyrins did not reach radiolabelling completion after 24 h. Formation of the ⁵²Mn-complexes were confirmed with radio-HPLC by comparison with their non-radioactive ⁵⁵Mn counterparts. Following this, several [⁵²Mn]Mn-porphyrins were used to radiolabel liposomes resulting in 75-86 % labelling efficiency (LE). Two lead [⁵²Mn]Mn-porphyrins were taken forward to label MDA-MB-231 cancer cells in vitro, achieving ca. 11 % LE. After 24 h, 32-45 % of the [⁵²Mn]Mn-porphyrins was retained in cells.

Conclusions

In contrast to standard methods, MW heating allows the fast synthesis of [⁵²Mn]Mn-porphyrins with >95 % radiochemical yields that avoid purification. [⁵²Mn]Mn-porphyrins also show promising cell/liposome labelling properties. Our reported technique can potentially be exploited for the in vivo imaging of Mn-porphyrin therapeutics, as well as for the accurate in vivo quantification of Mn-porphyrin MRI agents.

SUBMITTER: Gawne PJ

PROVIDER: S-EPMC10236072 | biostudies-literature | 2022 Nov-Dec

REPOSITORIES: biostudies-literature

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Publications

Microwave-assisted synthesis of [<sup>52</sup>Mn]Mn-porphyrins: Applications in cell and liposome radiolabelling.

Gawne Peter J PJ Pinto Sara M A SMA Nielsen Karin M KM Keeling George P GP Pereira Mariette M MM T M de Rosales Rafael R

Nuclear medicine and biology 20220902

<h4>Background</h4>Manganese porphyrins have several therapeutic/imaging applications, including their use as radioprotectants (in clinical trials) and as paramagnetic MRI contrast agents. The affinity of porphyrins for lipid bilayers also makes them candidates for cell/liposome labelling. We hypothesised that metalation with the positron emission tomography (PET) radionuclide <sup>52</sup>Mn (t<sub>1/2</sub> = 5.6 d) would allow long-term in vivo biodistribution studies of Mn-porphyrins, as wel ...[more]

PMID: 36088876

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Project description:PurposeDue to their long circulation time in the blood, monoclonal antibodies (mAbs) such as trastuzumab, are usually radiolabeled with long-lived positron emitters for the development of agents for Positron Emission Tomography (PET) imaging. Manganese-52 (52Mn, t1/2 = 5.6 d, β+ = 29.6%, E(βave) = 242 keV) is suitable for imaging at longer time points providing a complementary technique to Zirconium-89 (89Zr, t1/2 = 3.3 d, β+ = 22.7%, E(βave) = 396 keV)) because of its long half-life and low positron energy. To exploit these properties, we aimed to investigate suitable bifunctional chelators that could be readily conjugated to antibodies and labeled with 52Mn under mild conditions using trastuzumab as a proof-of-concept.ProceduresTrastuzumab was incubated with S-2-(4-isothiocyanatobenzyl)-1,4,7,10-tetraazacyclododecane tetraacetic acid (p-SCN-Bn-DOTA), 1-Oxa-4,7,10-tetraazacyclododecane-5-S-(4-isothiocyantobenzyl)-4,7,10-triacetic acid (p-SCN-Bn-Oxo-DO3A), and 3,6,9,15-tetraazabicyclo[9.3.1] pentadeca-1(15),11,13-triene-4-S-(4-isothiocyanatobenzyl)-3,6,9-triacetic acid (p-SCN-Bn-PCTA) at a tenfold molar excess. The immunoconjugates were purified, combined with [52Mn]MnCl2 at different ratios, and the labeling efficiency was assessed by iTLC. The immunoreactive fraction of the radiocomplex was determined through a Lindmo assay. Cell studies were conducted in HER2 + (BT474) and HER2- (MDA-MB-468) cell lines followed by in vivo studies.ResultsTrastuzumab-Oxo-DO3A was labeled within 30 min at 37 °C with a radiochemical yield (RCY) of 90 ± 1.5% and with the highest specific activity of the chelators investigated of 16.64 MBq/nmol. The labeled compound was purified with a resulting radiochemical purity of > 98% and retained a 67 ± 1.2% immunoreactivity. DOTA and PCTA immunoconjugates resulted in < 50 ± 2.5% (RCY) with similar specific activity. Mouse serum stability studies of [52Mn]Mn-Oxo-DO3A-trastuzumab showed 95% intact complex for over 5 days. Cell uptake studies showed higher uptake in HER2 + (12.51 ± 0.83% /mg) cells compared to HER2- (0.85 ± 0.10%/mg) cells. PET images of mice bearing BT474 tumors showed high tumor uptake that was consistent with the biodistribution (42.02 ± 2.16%ID/g, 14 d) compared to MDA-MB-468 tumors (2.20 ± 0.80%ID/g, 14 d). Additionally, both models exhibited low bone uptake of < 1% ID/g.ConclusionThe bifunctional chelator p-SCN-Bn-Oxo-DO3A is promising for the development of 52Mn radiopharmaceuticals as it was easily conjugated, radiolabeled at mild conditions, and illustrated stability for a prolonged duration both in vitro and in vivo. High-quality PET/CT images of [52Mn]Mn-Oxo-DO3A-trastuzumab were obtained 14 d post-injection. This study illustrates the potential of [52Mn]Mn-Oxo-DO3A for the evaluation of antibodies using PET imaging.

Dataset Information

Microwave-assisted synthesis of [⁵²Mn]Mn-porphyrins: Applications in cell and liposome radiolabelling.

Background

Results

Conclusions

Publications

Microwave-assisted synthesis of [<sup>52</sup>Mn]Mn-porphyrins: Applications in cell and liposome radiolabelling.

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OmicsDI is part of the ELIXIR infrastructure

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Dataset Information

Microwave-assisted synthesis of [52Mn]Mn-porphyrins: Applications in cell and liposome radiolabelling.

Background

Results

Conclusions

Publications

Microwave-assisted synthesis of [<sup>52</sup>Mn]Mn-porphyrins: Applications in cell and liposome radiolabelling.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets

Microwave-assisted synthesis of [⁵²Mn]Mn-porphyrins: Applications in cell and liposome radiolabelling.