Use of L-lysine fluorescence derivatives as tracers to enhance the performance of polarization fluoroimmunoassays. A study using two herbicides as model antigens

Fluorescence polarization immunoassay (FPIA) is a convenient homogeneous assay, the use of which is restricted in environmental analysis by low sensitivity and matrix effects. We selected the herbicides 2,4D and 2,4,5T to synthesize new L-lysine-based fluorescent tracers using solid-phase chemistry. In addition, three different immunogens of 2,4,5T were prepared for immunization and antibody production. The new tracers and antibodies were adapted to FPIA. Tracers with the hapten attached to the alpha-aminogroup of L-lysine and fluorescein to the e-amino group exhibited at least a 5-fold increased sensitivity when compared to the previously reported ethylenediamine-based tracer (2,4D-EDA-F). The isomeric structure (hapten attached to the e-amino and fluorescein to the alpha-amino group) appeared 7.6 times less sensitive, and all other alternative structures exhibited even lower sensitivities. This observation was confirmed against the monoclonal anti-2,4D antibody E2/G2 and polyclonal anti-2,4,5T antibodies. The affinity constant of 2,4D-EDA-F with E2/G2 was 8.1 times higher when compared with the new tracer, suggesting the more specific nature of the L-lysine-based tracer, the use of which leads to a more sensitive assay. This type of tracer could improve performance and lower substantially the detection limits of FPIAs.     

Prepatation of [18F]Fluorobenzyl Bromides for Their Use in Asymmetric Synthesis of Fluorinated α-Amino Acids,Radiotracers for Positron Emission Tomography

Procedures were developed for synthesis of 3,4-methylenedioxy-6-[^{1 8}F]fluorobenzyl bromide I and 2-[^{1 8}F]fluoro-4-methoxybenzyl bromide Ia, which are intermediates in asymmetric synthesis of fluorinated -amino acids used in positron emission tomography (PET). The bromination procedures involving two brominating agents, an ethereal solution of HBr or triphenyldibromophosphorane in various solvents, as well as purification procedures, were compared. An optimized procedure was suggested for synthesis of I and Ia using an Anatech robotic system; the total synthesis time is 45-48 min. The radiochemical yield of I and Ia, corrected for the ^{1 8}F decay, was 35-40 and 60-65%, respectively. The suggested scheme can be adapted to modern automated modules for production of radiopharmaceuticals.