1 January 2011 Multispectral fluorescence imaging to assess pH in biological specimens
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J. of Biomedical Optics, 16(1), 016007 (2011). doi:10.1117/1.3533264
Abstract
Simple, quantitative assays to measure pH in tissue could improve the study of complicated biological processes and diseases such as cancer. We evaluated multispectral fluorescence imaging (MSFI) to quantify extracellular pH (pHe) in dye-perfused, surgically-resected tumor specimens with commercially available instrumentation. Utilizing a water-soluble organic dye with pH-dependent fluorescence emission (SNARF-4F), we used standard fluorimetry to quantitatively assess the emission properties of the dye as a function of pH. By conducting these studies within the spectroscopic constraints imposed by the appropriate imaging filter set supplied with the imaging system, we determined that correction of the fluorescence emission of deprotonated dye was necessary for accurate determination of pH due to suboptimal excitation. Subsequently, employing a fluorimetry-derived correction factor (CF), MSFI data sets of aqueous dye solutions and tissuelike phantoms could be spectrally unmixed to accurately quantify equilibrium concentrations of protonated (HA) and deprotonated (A;) dye and thus determine solution pH. Finally, we explored the feasibility of MSFI for high-resolution pHe mapping of human colorectal cancer cell-line xenografts. Data presented suggest that MSFI is suitable for quantitative determination of pHe in ex vivo dye-perfused tissue, potentially enabling measurement of pH across a variety of preclinical models of disease.
Matthew R. Hight, Donald D. Nolting, Eliot T. McKinley, Adam D. Lander, Shelby K. Wyatt, Mark Gonyea, Ping Zhao, H. Charles Manning, "Multispectral fluorescence imaging to assess pH in biological specimens," Journal of Biomedical Optics 16(1), 016007 (1 January 2011). http://dx.doi.org/10.1117/1.3533264
Submission: Received ; Accepted
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KEYWORDS
Luminescence

Tissues

Tumors

Multispectral imaging

Image filtering

Imaging systems

Bandpass filters

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