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Paired Agent Fluorescence Imaging of Cancer in a Living Mouse Using Preassembled Squaraine Molecular Probes with Emission Wavelengths of 690 and 830 nm
journal contribution
posted on 2019-12-06, 16:06 authored by Cynthia
L. Schreiber, Canjia Zhai, Janel M. Dempsey, Hannah H. McGarraugh, Braden P. Matthews, Caroline R. Christmann, Bradley D. SmithNew methods are described for the construction of targeted
fluorescence
probes for imaging cancer and the assessment of tumor targeting performance
in a living mouse model. A novel noncovalent assembly process was
used to fabricate a set of structurally related targeted fluorescent
probes with modular differences in three critical assembly components:
the emission wavelength of the squaraine fluorochrome, the number
of cRGDfK peptide units that target the cancer cells, and the length
of the polyethylene glycol chains as pharmacokinetic controllers.
Selective targeting of cancer cells was proven by a series of cell
microscopy experiments followed by in vivo imaging of subcutaneous
tumors in living mice. The mouse imaging studies included a mock surgery
that completely removed a fluorescently labeled tumor. Enhanced tumor
accumulation due to probe targeting was first evaluated by conducting
Single Agent Imaging (SAI) experiments that compared tumor imaging
performance of a targeted probe and untargeted probe in separate mouse
cohorts. Although there was imaging evidence for enhanced tumor accumulation
of the targeted probe, there was moderate scatter in the data due
to tumor-to-tumor variability of the vasculature structure and interstitial
pressure. A subsequent Paired Agent Imaging (PAI) study coinjected
a binary mixture of targeted probe (with emission at 690 nm) and untargeted
probe (with emission at 830 nm) into the same tumor-burdened animal.
The conclusion of the PAI experiment also indicated enhanced tumor
accumulation of the targeted probe, but the statistical significance
was much higher, even though the experiment required a much smaller
cohort of mice. The imaging data from the PAI experiment was analyzed
to determine the targeted probe’s Binding Potential (BP) for
available integrin receptors within the tumor tissue. In addition,
pixelated maps of BP within each tumor indicated a heterogeneous spatial
distribution of BP values. The results of this study show that the
combination of fluorescent probe preassembly and PAI is a promising
new way to rapidly develop targeted fluorescent probes for tumors
with high BP and eventual use in clinical applications such as targeted
therapy, image guided surgery, and personalized medicine.
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Keywords
BP830 nm New methodsSAIPreassembled Squaraine Molecular Probescancer cellscRGDfK peptide unitstumor accumulationcell microscopy experimentsSingle Agent Imagingnovel noncovalent assembly processEnhanced tumor accumulationuntargeted probePaired Agent Fluorescence Imagingmouse imaging studiespolyethylene glycol chainstumor imaging performancePaired Agent ImagingPAI experiment
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