Hybrid imaging combining the beneficial properties of radioactivity and optical imaging within one imaging probe has gained increasing interest in radiopharmaceutical research. In this study, we modified the macrocyclic gallium-68 chelator fusarinine C (FSC) by conjugating a fluorescent moiety and tetrazine (Tz) moieties. The resulting hybrid imaging agents were used for pretargeting applications utilizing click reactions with a trans-cyclooctene (TCO) tagged targeting vector for a proof of principle both in vitro and in vivo. Starting from FSC, the fluorophores Sulfocyanine-5, Sulfocyanine-7, or IRDye800CW were conjugated, followed by introduction of one or two Tz motifs, resulting in mono and dimeric Tz conjugates. Evaluation included fluorescence microscopy, binding studies, logD, protein binding, in vivo biodistribution, µPET (micro-positron emission tomography), and optical imaging (OI) studies. 68Ga-labeled conjugates showed suitable hydrophilicity, high stability, and specific targeting properties towards Rituximab-TCO pre-treated CD20 expressing Raji cells. Biodistribution studies showed fast clearance and low accumulation in non-targeted organs for both SulfoCy5- and IRDye800CW-conjugates. In an alendronate-TCO based bone targeting model the dimeric IRDye800CW-conjugate resulted in specific targeting using PET and OI, superior to the monomer. This proof of concept study showed that the preparation of FSC-Tz hybrid imaging agents for pretargeting applications is feasible, making such compounds suitable for hybrid imaging applications.
- Klíčová slova
- PET, click chemistry, fluorescence, fusarinine C, gallium-68, optical imaging,
- MeSH
- fluorescenční protilátková technika MeSH
- kyseliny hydroxamové * chemie MeSH
- multimodální zobrazování * metody MeSH
- optické zobrazování metody MeSH
- ověření koncepční studie MeSH
- pozitronová emisní tomografie MeSH
- radiofarmaka * chemie MeSH
- radioizotopy galia MeSH
- radionuklidy MeSH
- syntetická chemie okamžité shody MeSH
- tkáňová distribuce MeSH
- železité sloučeniny * chemie MeSH
- Publikační typ
- časopisecké články MeSH
- Názvy látek
- fusigen MeSH Prohlížeč
- Gallium-68 MeSH Prohlížeč
- kyseliny hydroxamové * MeSH
- radiofarmaka * MeSH
- radioizotopy galia MeSH
- radionuklidy MeSH
- železité sloučeniny * MeSH
Positron emission tomography (PET) as well as optical imaging (OI) with peptide receptor targeting probes have proven their value for oncological applications but also show restrictions depending on the clinical field of interest. Therefore, the combination of both methods, particularly in a single molecule, could improve versatility in clinical routine. This proof of principle study aims to show that a chelator, Fusarinine C (FSC), can be utilized as scaffold for novel dimeric dual-modality imaging agents. Two targeting vectors (a minigastrin analogue (MG11) targeting cholecystokinin-2 receptor overexpression (CCK2R) or integrin αVβ3 targeting cyclic pentapeptides (RGD)) and a near-infrared fluorophore (Sulfo-Cyanine7) were conjugated to FSC. The probes were efficiently labeled with gallium-68 and in vitro experiments including determination of logD, stability, protein binding, cell binding, internalization, and biodistribution studies as well as in vivo micro-PET/CT and optical imaging in U-87MG αVβ3- and A431-CCK2R expressing tumor xenografted mice were carried out. Novel bioconjugates showed high receptor affinity and highly specific targeting properties at both receptors. Ex vivo biodistribution and micro-PET/CT imaging studies revealed specific tumor uptake accompanied by slow blood clearance and retention in nontargeted tissues (spleen, liver, and kidneys) leading to visualization of tumors at early (30 to 120 min p.i.). Excellent contrast in corresponding optical imaging studies was achieved especially at delayed time points (24 to 72 h p.i.). Our findings show the proof of principle of chelator scaffolding for hybrid imaging agents and demonstrate FSC being a suitable bifunctional chelator for this approach. Improvements to fine-tune pharmacokinetics are needed to translate this into a clinical setting.
- MeSH
- chelátory chemie farmakokinetika MeSH
- heterografty MeSH
- integrin alfaVbeta3 metabolismus MeSH
- kyseliny hydroxamové farmakokinetika MeSH
- lidé MeSH
- molekulární sondy chemie farmakokinetika MeSH
- multimodální zobrazování metody MeSH
- myši MeSH
- nádorové buňky kultivované MeSH
- nádory diagnostické zobrazování metabolismus MeSH
- PET/CT MeSH
- radioizotopy galia farmakokinetika MeSH
- receptor cholecystokininu B metabolismus MeSH
- železité sloučeniny farmakokinetika MeSH
- zvířata MeSH
- Check Tag
- lidé MeSH
- myši MeSH
- zvířata MeSH
- Publikační typ
- časopisecké články MeSH
- práce podpořená grantem MeSH
- Názvy látek
- chelátory MeSH
- fusigen MeSH Prohlížeč
- integrin alfaVbeta3 MeSH
- kyseliny hydroxamové MeSH
- molekulární sondy MeSH
- radioizotopy galia MeSH
- receptor cholecystokininu B MeSH
- železité sloučeniny MeSH
