Trityl radicals in perfluorocarbon emulsions as stable, sensitive, and biocompatible oximetry probes

EPR oximetry with the use of trityl radicals can enable sensitive O-2 measurement in biological cells and tissues. However, in vitro cellular and in vivo biological applications are limited by rapid trityl probe degradation or biological clearance and the need to enhance probe O-2 sensitivity. We synthesized novel perfluorocarbon (PFC) emulsions, similar to 200 nm droplet size, containing esterified perchlorinated triphenyl methyl (PTM) radicals dispersed in physiological aqueous buffers. These formulations exhibit excellent EPR signal stability, over 20-fold greater than free PTM probes, with high oxygen sensitivity similar to 17 mG/mmHg enabling pO(2) measurement in aqueous solutions or cell suspensions with sensitivity > 0.5 mmHg. Thus, PFC-PTM probes hold great promise to enable combined O-2 delivery and sensing as needed to restore or enhance tissue oxygenation in disease. (C) 2016 Elsevier Ltd. All rights reserved.