Automated radiosynthesis of N-succinimidyl 3-(di-tert-butyl[18F]fluorosilyl)benzoate ([18F]SiFB) for peptides and proteins radiolabeling for positron emission tomography

Recently, silicon fluoride building blocks (SiFA) have emerged as valuable and promising tools to overcome challenges in the labeling of peptides and proteins for positron emission tomography (PET). Herein, we report a fully automated synthesis of N-succinimidyl 3-(di-tert-butyl[18F]fluorosilyl)benzoate ([18F]SiFB) by a commercially available Scintomics Hot Box 3 synthesis module, to be used as a prosthetic group for peptide and protein labeling. The drying of K2.2.2./K 18F complex was performed according to the Munich method modified by our group (avoiding azeotropic drying) using oxalic acid to neutralize the base from the 18F− containing QMA eluent. This K2.2.2./K 18F complex was then used for SiFA 18F-19F isotopic exchange followed by a fast purification by a solid-phase-extraction (SPE) to afford [18F]SiFB with an average preparative radiochemical yield (RCY) of 24±1% (non-decay corrected (NDC)) within a synthesis time of 30 min. The [18F]SiFB produced by automated synthesis was then used for the 18F-labeling of rat serum albumin (RSA) as a proof of applicability.