Abstract #3718

Esterase-catalyzed production of hyperpolarized 13C carbon dioxide in tissues for measuring pH

Nesmine R Maptue¹, Weina Jiang¹, Alexander M Funk¹, Wei Chen¹, Craig R Malloy^1,2,3,4, A. Dean Sherry^1,2,5, and Chalermchai Khemtong^1,2

¹Advanced Imaging Research Center, University of Texas Southwestern Medical Center, Dallas, TX, United States, ²Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, United States, ³Department of Internal Medicine, University of Texas Southwestern Medical Center, Dallas, TX, United States, ⁴Veteran Affairs North Texas Health Care System, Dallas, TX, United States, ⁵Department of Chemistry, University of Texas at Dallas, Richardson, TX, United States

¹³C-MRI HP ¹³C-bicarbonate (H¹³CO₃^-) and carbon dioxide (¹³CO₂) is a novel technique for tissue pH mapping. Here, we report ¹³C-enriched ethyl acetyl carbonate (¹³C-EAC) for esterase-catalyzed production of HP-¹³CO₂ and HP-H¹³CO₃^- for pH measurements. Our results showed that ¹³C-EAC was rapidly hydrolyzed by esterase to ¹³C-monoacetyl carbonate, which decomposed to HP-¹³CO₂. Equilibrium between the newly produced ¹³CO₂ and H¹³CO₃^- was established and the ¹³C-NMR signals can be quantified for pH measurements. Finally, in vivo pH measurements using H-₁₃C-EAC was demonstrated in rat livers. These results suggest that HP-¹³C-EAC is a novel imaging probe for in vivo pH measurements of tissues.

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