Open AccessFluorescence lifetime imaging of activatable target specific molecular probes
Author(s) -
Alford Raphael,
Ogawa Mikako,
Hassan Moinuddin,
Gandjbakhche Amir H.,
Choyke Peter L.,
Kobayashi Hisataka
Publication year - 2010
Publication title -
contrast media & molecular imaging
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.714
H-Index - 50
eISSN - 1555-4317
pISSN - 1555-4309
DOI - 10.1002/cmmi.360
Subject(s) - internalization , fluorophore , in vivo , conjugate , fluorescence , alexa fluor , chemistry , fluorescence lifetime imaging microscopy , molecular imaging , in vitro , preclinical imaging , biophysics , fluorescence microscope , monoclonal antibody , live cell imaging , antibody , cell , biology , biochemistry , immunology , mathematical analysis , physics , microbiology and biotechnology , mathematics , quantum mechanics
In vivo optical imaging using fluorescently labeled self‐quenched monoclonal antibodies, activated through binding and internalization within target cells, results in excellent target‐to‐background ratios. We hypothesized that these molecular probes could be utilized to accurately report on cellular internalization with fluorescence lifetime imaging (FLI). Two imaging probes were synthesized, consisting of the antibody trastuzumab (targeting HER2/neu) conjugated to Alexa Fluor750 in ratios of either 1:8 or 1:1. Fluorescence intensity and lifetime of each conjugate were initially determined at endosomal pHs. Since the 1:8 conjugate is self‐quenched, the fluorescence lifetime of each probe was also determined after exposure to the known dequencher SDS. In vitro imaging experiments were performed using 3T3/HER2 + and BALB/3T3 (HER2 − ) cell lines. Changes in fluorescence lifetime correlated with temperature‐ and time‐dependent cellular internalization. In vivo imaging studies in mice with dual flank tumors [3T3/HER2 + and BALB/3T3 (HER2 − )] detected a minimal difference in FLI. In conclusion, fluorescence lifetime imaging monitors the internalization of target‐specific activatable antibody–fluorophore conjugates in vitro . Challenges remain in adapting this methodology to in vivo imaging. Copyright © 2010 John Wiley & Sons, Ltd.