Real Time, in vivo Photoacoustic Potassium Imaging and Monitoring

Abstract

metabolism. The luminescence lifetime measurement of oxygen-sensitive molecules is a very promising, non-invasive approach to determine pO2 in vivo. However, this measurement is frequently perturbed by the excited oxygen sensor's phototoxic effect. In this study, we compared two watersoluble oxygen sensors: Pd-meso-tetra(4-carboxyphenyl) porphyrin (PdTCPP) and dichlorotris(1, 10-phenanthroline)-ruthenium(II) hydrate ([Ru(Phen)3]2þ) for their phototoxicity and ability to measure oxygen consumption during hypericin induced photosensitization in vitro (single cells and isolated mitochondria) and in vivo (Chick's chorioallantoic membrane). Hypericin, a molecule with interesting spectral properties, does not perturb PdTCPP and [Ru(Phen)3]2þ lifetime measurements. The excitation of this molecule at 590 nm is spectrally ''far'' from the absorption bands of PdTCPP and [Ru(Phen)3]2þ, which allows induction of photodamages without contributions from these oxygen sensors. Since PdTCPP's stability in biological systems requires that it is bound with serum proteins, the impact of the serum albumins concentration in the system on the reliability of oxygen measurements was evaluated as well. In conclusions, we demonstrated optimal phototoxicity, serum albumin concentration-related lifetime variations, stability and oxygen sensitivity in vitro and in vivo for [Ru(Phen)3]2þ. We could not demonstrate a similar set of properties for PdTCPP.