Dual isotope labeling: Conjugation of 32P-oligonucleotides with 18F-aryltrifluoroborate via copper(I) catalyzed cycloaddition

A one-pot-two-step labeling of an oligonucleotide with an ¹⁸F-ArBF₃^?(aryltrifluoroborate) radioprosthetic is reported herein. In order to characterize labeling in terms of radiochemistry, phosphorus-32 was also introduced to the 5′-terminus of the oligonucleotide via enzymatic phosphorylation. A pendant azide group was subsequently conjugated to the 5′-phosphate of the oligonucleotide. Copper(I) catalyzed [2+3] cycloaddition was undertaken to conjugate an alkyne-bearing¹⁸F-ArBF₃^? to the oligonucleotide. Following polyacrylamide gel electrophoresis, this doubly-labeled bioconjugate exhibited decay properties of both the phosphorus-32 and fluorine-18, that were confirmed by autoradiography at selected lengths of time, which in turn provided concrete evidence of successful conjugation. These results are corroborated by HPLC analysis of the labeled material. Taken together this work demonstrates viable use of ¹⁸F-ArBF₃^? prosthetics for labeling oligonucleotides for use in PET imaging.