Fluorine-18 labeling of proteins

Area of Science:

• Radiochemistry
• Bioconjugation
• Biochemistry

Background:

• Fluorine-18 (18F) radiolabeling is crucial for Positron Emission Tomography (PET) imaging.
• Developing efficient and versatile 18F labeling methods for proteins remains a challenge.

Purpose of the Study:

• To synthesize and evaluate two novel 18F-labeled reagents for covalent protein modification.
• To assess the efficiency and conditions for attaching 18F to various proteins.

Main Methods:

• Synthesis of methyl 3-[18F]fluoro-5-nitrobenzimidate and 4-[18F]fluorophenacyl bromide.
• Covalent labeling of human serum albumin, fibrinogen, and immunoglobulin A with the synthesized reagents.
• Optimization of reaction conditions including pH, protein concentration, time, and temperature.
• Purification of 18F-labeled proteins using size exclusion chromatography.

Main Results:

• Both reagents were prepared in moderate yields (30-50% EOB) within 50-70 minutes.
• Protein labeling was efficient (up to 95% corrected yield), pH-independent, and protein concentration-dependent.
• Labeling reactions proceeded within 5-60 minutes under mild conditions (pH 8.0, 25-37°C).
• Purification of radiolabeled proteins was successfully achieved via size exclusion chromatography.

Conclusions:

• Methyl 3-[18F]fluoro-5-nitrobenzimidate and 4-[18F]fluorophenacyl bromide are effective reagents for 18F protein labeling.
• The developed method offers a robust and efficient approach for preparing 18F-labeled proteins for potential diagnostic applications.