In vivo measurement of tissue oxygenation by time-resolved luminescence spectroscopy: advantageous properties of dichlorotris(1, 10-phenanthroline)-ruthenium(Ⅱ) hydrate

摘要

Measuring tissue oxygenation in vivo is of interest in fundamental biological as well as medical applications. One minimally invasive approach to assess the oxygen partial pressure in tissue (pO_2) is to measure the oxygen-dependent luminescence lifetime of molecular probes. The relation between tissue pO_2 and the probes' luminescence lifetime is governed by the Stem-Volmer equation. Unfortunately, virtually all oxygen-sensitive probes based on this principle induce some degree of phototoxicity. For that reason, we studied the oxygen sensitivity and phototoxicity of dichlorotris(1, 10-phenanthroline)-ruthenium(ll) hydrate [Ru(Phen) using a dedicated optical fiber-based, time-resolved spectrometer in the chicken embryo chorioallantoic membrane. We demonstrated that, after intravenous injection, Ru(Phen)'s luminescence lifetime presents an easily detectable pO_2 dependence at a low drug dose (1 mg/kg) and low fluence (120 mJ/cm~2 at 470 nm). The phototoxic threshold was found to be at 10 J/cm~2 with the same wavelength and drug dose, i.e., about two orders of magnitude larger than the fluence necessary to perform a pO_2 measurement. Finally, an illustrative application of this pO_2 measurement approach in a hypoxic tumor environment is presented.