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Multiplexed non-invasive tumor imaging of glucose metabolism and receptor-ligand engagement using dark quencher FRET acceptor.

ABSTRACT: Rationale: Following an ever-increased focus on personalized medicine, there is a continuing need to develop preclinical molecular imaging modalities to guide the development and optimization of targeted therapies. Near-Infrared (NIR) Macroscopic Fluorescence Lifetime Förster Resonance Energy Transfer (MFLI-FRET) imaging offers a unique method to robustly quantify receptor-ligand engagement in live intact animals, which is critical to assess the delivery efficacy of therapeutics. However, to date, non-invasive imaging approaches that can simultaneously measure cellular drug delivery efficacy and metabolic response are lacking. A major challenge for the implementation of concurrent optical and MFLI-FRET in vivo whole-body preclinical imaging is the spectral crowding and cross-contamination between fluorescent probes. Methods: We report on a strategy that relies on a dark quencher enabling simultaneous assessment of receptor-ligand engagement and tumor metabolism in intact live mice. Several optical imaging approaches, such as in vitro NIR FLI microscopy (FLIM) and in vivo wide-field MFLI, were used to validate a novel donor-dark quencher FRET pair. IRDye 800CW 2-deoxyglucose (2-DG) imaging was multiplexed with MFLI-FRET of NIR-labeled transferrin FRET pair (Tf-AF700/Tf-QC-1) to monitor tumor metabolism and probe uptake in breast tumor xenografts in intact live nude mice. Immunohistochemistry was used to validate in vivo imaging results. Results: First, we establish that IRDye QC-1 (QC-1) is an effective NIR dark acceptor for the FRET-induced quenching of donor Alexa Fluor 700 (AF700). Second, we report on simultaneous in vivo imaging of the metabolic probe 2-DG and MFLI-FRET imaging of Tf-AF700/Tf-QC-1 uptake in tumors. Such multiplexed imaging revealed an inverse relationship between 2-DG uptake and Tf intracellular delivery, suggesting that 2-DG signal may predict the efficacy of intracellular targeted delivery. Conclusions: Overall, our methodology enables for the first time simultaneous non-invasive monitoring of intracellular drug delivery and metabolic response in preclinical studies.

SUBMITTER: Rudkouskaya A

PROVIDER: S-EPMC7481426 | biostudies-literature | 2020

REPOSITORIES: biostudies-literature

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Multiplexed non-invasive tumor imaging of glucose metabolism and receptor-ligand engagement using dark quencher FRET acceptor.

Rudkouskaya Alena A Sinsuebphon Nattawut N Ochoa Marien M Chen Sez-Jade SJ Mazurkiewicz Joseph E JE Intes Xavier X Barroso Margarida M

Theranostics 20200815 22

<b>Rationale:</b> Following an ever-increased focus on personalized medicine, there is a continuing need to develop preclinical molecular imaging modalities to guide the development and optimization of targeted therapies. Near-Infrared (NIR) Macroscopic Fluorescence Lifetime Förster Resonance Energy Transfer (MFLI-FRET) imaging offers a unique method to robustly quantify receptor-ligand engagement in live intact animals, which is critical to assess the delivery efficacy of therapeutics. However, ...[more]

PMID: 32929350

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Project description:Dark quenchers are chromophores that primarily relax from the excited state to the ground state nonradiatively (i.e., are dark). As a result, they can serve as acceptors for Förster resonance energy transfer experiments without contributing significantly to background in the donor-emission channel, even at high concentrations. Although the advantages of dark quenchers have been exploited for ensemble bioassays, no systematic single-molecule study of dark quenchers has been performed, and little is known about their photophysical properties. Here, we present the first systematic single-molecule study of dark quenchers in conjunction with fluorophores and demonstrate the use of dark quenchers for monitoring multiple interactions and distances in multichromophore systems. Specifically, using double-stranded DNA standards labeled with two fluorophores and a dark quencher (either QSY7 or QSY21), we show that the proximity of a fluorophore and dark quencher can be monitored using the stoichiometry ratio available from alternating laser excitation spectroscopy experiments, either for single molecules diffusing in solution (using a confocal fluorescence) or immobilized on surfaces (using total-internal-reflection fluorescence). The latter experiments allowed characterization of the dark-quencher photophysical properties at the single-molecule level. We also use dark-quenchers to study the affinity and kinetics of binding of DNA Polymerase I (Klenow fragment) to DNA. The measured properties are in excellent agreement with the results of ensemble assays, validating the use of dark quenchers. Because dark-quencher-labeled biomolecules can be used in total-internal-reflection fluorescence experiments at concentrations of 1 ?M or more without introducing a significant background, the use of dark quenchers should permit single-molecule Förster resonance energy transfer measurements for the large number of biomolecules that participate in interactions of moderate-to-low affinity.

Dataset Information

Multiplexed non-invasive tumor imaging of glucose metabolism and receptor-ligand engagement using dark quencher FRET acceptor.

Publications

Multiplexed non-invasive tumor imaging of glucose metabolism and receptor-ligand engagement using dark quencher FRET acceptor.

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