Composite spin probes with selectable oxygen sensitivity for electron paramagnetic resonance

Abstract

A novel class of particulate probes for electron paramagnetic resonance (EPR) oximetry with adjustable relaxation rates sensitivity to oxygen partial pressure is described. The probe includes oxygen-sensitive paramagnetic spin probes such as lithium phthalocyanine (LiPc) mixed with non-paramagnetic additives such as bonewax, beeswax, or petroleum jelly. The sensitivity of the probe's relaxation rate constants to oxygen can be controlled through the selection of additives and mixing ratios. The probe exhibits reduced oxygen sensitivity and expanded dynamic range compared to an unmodified probe, enabling pulse EPR measurements across the full physiological oxygen range (0-160 torr) and full oxygen dynamic range (0-760 torr). The probe can be shaped as needed for tissue implantation and serve as multimodal imaging markers for EPR and other imaging modalities.

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