Intracellular Protein Binding of Zr-89 Oxine Cell Labeling for PET Cell Tracking Studies

Area of Science:

• Radiochemistry
• Cellular Biology
• Nuclear Medicine

Background:

• Ex vivo cell labeling with Zirconium-89 oxine (89Zr-oxine) allows for in vivo cell tracking using positron emission tomography (PET) for up to two weeks.
• Understanding the intracellular binding and distribution of 89Zr is crucial for optimizing cell labeling protocols.

Purpose of the Study:

• To investigate the factors influencing 89Zr-oxine labeling and the intracellular distribution of 89Zr within various cell types.
• To compare the protein binding stability and intracellular localization of 89Zr-oxine with 111In-oxine.

Main Methods:

• Multiple cell types (primary immune cells and cell lines) were labeled with 89Zr-oxine or 111In-oxine.
• Protein binding, labeling thresholds, and radioactivity retention were determined.
• Autoradiography and biodistribution studies were performed to assess binding stability and in vivo retention.

Main Results:

• 89Zr-oxine incorporation correlated with cell size and protein mass, with >97% protein binding primarily in the cytoplasm, membrane, and nuclear fractions.
• In contrast, 111In-oxine exhibited lower protein binding (59-65%) and cytoplasmic localization.
• 89Zr-oxine demonstrated stable protein binding across all subcellular fractions, whereas 111In-oxine showed unstable binding. In vivo studies showed greater retention of 89Zr-labeled cells.

Conclusions:

• 89Zr-oxine exhibits significantly higher and more stable intracellular protein binding compared to 111In-oxine.
• The stable, widespread intracellular protein binding of 89Zr-oxine underpins its efficacy for long-term in vivo cell tracking using PET.