In Vivo Fluorescence Lifetime Imaging Monitors Binding of Specific Probes to Cancer Biomarkers

One of the most important factors in choosing a treatment strategy for cancer is characterization of biomarkers in cancer cells. Particularly, recent advances in Monoclonal Antibodies (MAB) as primary-specific drugs targeting tumor receptors show that their efficacy depends strongly on characterization of tumor biomarkers. Assessment of their status in individual patients would facilitate selection of an optimal treatment strategy, and the continuous monitoring of those biomarkers and their binding process to the therapy would provide a means for early evaluation of the efficacy of therapeutic intervention. In this study we have demonstrated for the first time in live animals that the fluorescence lifetime can be used to detect the binding of targeted optical probes to the extracellular receptors on tumor cells in vivo. The rationale was that fluorescence lifetime of a specific probe is sensitive to local environment and/or affinity to other molecules. We attached Near-InfraRed (NIR) fluorescent probes to Human Epidermal Growth Factor 2 (HER2/neu)-specific Affibody molecules and used our time-resolved optical system to compare the fluorescence lifetime of the optical probes that were bound and unbound to tumor cells in live mice. Our results show that the fluorescence lifetime changes in our model system delineate HER2 receptor bound from the unbound probe in vivo. Thus, this method is useful as a specific marker of the receptor binding process, which can open a new paradigm in the “image and treat” concept, especially for early evaluation of the efficacy of the therapy

METAL-DIRECTED SYNTHESIS OF MACROCYCLIC TETRAAMINES WITH PENDANT NITRO OR AMINE GROUPS, BASED ON TRANS-CYCLOHEXANE-1,2-DIAMINE

Reaction of R,R:S,S-, R,R:R,R(or S,S:S,S)-bis(trans-cyclohexane-1,2-diamine)copper(II) with formaldehyde and nitroethane in aqueous base yields the macrocyclic molecular cation (4,15-dimethyl-4,15-dimethyl-4,15-dinitro-2,6,13,17-tetraazatricyclo[16.4.0.0(7,12)]docosane)copper(II) with two -NH-CH2-C(Me)(NO2)-CH2-NH- links completing the macrocycle, as well as the molecular cation [N,N'-bis(2-aminocyclohexyl)-2-methyl-2-nitropropane-1,3-diamine]copper(II) with a single such link inserted. The rigid polycylic macrocycle, based on a 14-membered tetraazacycloalkane (cyclam) frame, may exist as a number of isomers. Spectroscopic and chiroptical properties of the isolated complexes are reported. Reduction of the nitro groups with zinc in aqueous acid produces the corresponding molecules with primary amine (or ammonium) pendants in good yield, as metal-free hydrochloride salts