Synthesis of a new HYNIC-DAPI derivative for labelling with 99mTechnetium and its in vitro evaluation in an FRTL5 cell line

Abstract

4′,6-Diamidine-2-phenylindole (DAPI) is a common fluorochrome that is able to bind to deoxyribonucleic acid (DNA) with distinct, sequence-dependent enhancement of fluorescence. This work presents the synthesis of a new multifunctional compound that includes the fluorescent dye as a ^99mTechnetium (^99mTc) carrier. A new technique for the bioconjugation of DAPI with 6-hydrazinonicotinic acid (HYNIC) through an amide linkage was developed. The radiolabelling was performed with HYNIC as a chelator and N-(2-hydroxy-1,1-bis(hydroxymethyl)ethyl)glycine (tricine) as a coligand. Furthermore, experimental evidence showed that ^99mTc complexes with DAPI as DNA-binding moieties are detectable in living Fischer rat thyroid follicular cell line 5 (FRTL5) and their nuclei. The investigations indicated further that the new HYNIC-DAPI derivative is able to interact with double-stranded DNA. This establishes the possibility of locating ^99mTc in close proximity to biological structures of living cells, of which especially the genetic information-carrying cell compartments are at the centre of interest. In this context, further investigations are related to the radiotoxic effects of DNA-bound ^99mTc-HYNIC-DAPI derivatives and dosimetric calculations.