1. Interventional nuclear medicine: “click” chemistry as an in vivotargeting strategy for imaging microspheres and bacteriaElectronic supplementary information (ESI) available. See DOI: 10.1039/d0bm01823f
- Author
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Welling, M. M., Duszenko, N., van Willigen, D. M., Hensbergen, A. W., Buckle, T., Rietbergen, D. D. D., Roestenberg, M., and van Leeuwen, F. W. B.
- Abstract
Aim: Pre-targeting is a proven strategy for in vivodelivery of a diagnostic or therapeutic payload. The pre-targeting concept can be realized through various conjugation strategies, one of which is based on copper-free “click” chemistry. Copper-free click reactions have shown in vivopotential for imaging and radionuclide therapy, but this conjugation strategy has not yet been explored in combination with microspheres or unicellular organisms. This study aims to evaluate the in vivoefficacy of strain-promoted azide–alkyne cycloaddition (SPAAC) reactions to achieve imaging and targeting of azide-functionalized macro-aggregated albumin (MAA) microspheres and Staphylococcus aureusbacteria. Methods: MAA microspheres (diameter 10–90 μm) were functionalized with a biorthogonal Cy5 fluorophore, bearing an azide functionality (N3), to generate MAA-Cy5-N3. S. aureus(diameter ∼1 μm) were functionalized with 99mTc-UBI29–41-Cy5-N3, generating S. aureus-99mTc-UBI29–41-Cy5-N3. In situand in vitroclick conjugation on the –N3moieties was studied for 20 h using a radioactivity-based assay and fluorescence microscopy. For in vivovalidation, both primary entities, radiolabeled with 99mTc, were deposited into the microvasculature of the liver viaintrasplenic injections. Secondary targeting was realized following the intravenous administration of indium-111-radiolabeled diethylenetriaminepentaacetic acid-dibenzocyclooctyne (111In-DTPA-DBCO). To assess click reaction efficiency in vivo, 99mTc and 111In-biodistributions were measured (SPECT and %ID g−1). Use of 111In-DTPA-DBCO in mice without MAA deposits or mice infected with non-functionalized S. aureusserved as controls. Ex vivoconfocal fluorescence imaging was carried out in excised tissues to confirm the presence of functionalized MAA and bacteria. Results: In vitrodata confirmed effective click reactions on both the MAA particles and the bacterial membrane. SPECT imaging and biodistribution studies revealed significantly (p< 0.05) increased accumulation of 111In-DTPA-DBCO at the sites where MAA-Cy5-N3(7.5 ± 1.5%ID g−1vs. 3.5 ± 0.5%ID g−1in control mice) and S. aureus-99mTc-UBI29–41-Cy5-N3(9.3 ± 1.3%ID g−1vs.6.0 ± 0.5%ID g−1in control mice) resided. Ex vivofluorescence imaging confirmed the presence of either functionalized MAA or S. aureusin excised spleens and livers of mice. Conclusion: Copper-free click chemistry between a DBCO moiety and Cy5-N3-functionalized microspheres or bacterial entities in the liver can be used to realize in vivoimaging and targeting.
- Published
- 2021
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