<p>Regulation of physiological pH is integral for proper
whole-body and cellular function, and disruptions in pH homeostasis can be both a cause and effect of disease. In light of this, many methods have been
developed to monitor pH in cells and animals. In this study, we report a
chemiluminescence resonance energy transfer (CRET) probe Ratio-pHCL-1,
comprised of an acrylamide 1,2-dioxetane chemiluminescent scaffold with an
appended pH-sensitive carbofluorescein fluorophore. The probe provides an
accurate measurement of pH between 6.8-8.4, making it viable tool for measuring
pH in biological systems. Further, its ratiometric output is independent of
confounding variables. Quantification of pH can be accomplished both using
common fluorimetry and advanced optical imaging methods. Using an IVIS
Spectrum, pH can be quantified through tissue with Ratio-pHCL-1, which has been
shown in vitro and precisely calibrated in sacrificed mouse models. Initial
studies showed that intraperitoneal injections of Ratio-pHCL-1 into sacrificed
mice produce a photon flux of more than 10^10 photons per second, and showed a
significant difference in ratio of emission intensities between pH 6.0, 7.0,
and 8.0.</p>
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