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

Abstract

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 (pO2) is to measure the oxygen-dependent luminescence lifetime of molecular probes. The relation between tissue pO2 and the probes’ luminescence lifetime is governed by the Stern-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(II) 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 pO2 dependence at a low drug dose (1 mg∕kg) and low fluence (120 mJ∕cm2 at 470 nm). The phototoxic threshold was found to be at 10 J∕cm2 with the same wavelength and drug dose, i.e., about two orders of magnitude larger than the fluence necessary to perform a pO2 measurement. Finally, an illustrative application of this pO2 measurement approach in a hypoxic tumor environment is presented.

The chicken chorioallantoic membrane model in biology, medicine and bioengineering

“…Measuring the local pO2 is also of interest for other types of treatments, such as radiotherapy or photodynamic therapy, as it is well established that tissue oxygenation plays an important role on the outcome of such treatments. The measurements of the pO2 in the CAM was performed, using a micro-O2-electrode [143], the delayed fluorescence [121] or luminescence quenching of a ruthenium derivative [144] monitored with a dedicated optical, fiber-based, time-resolved spectrometer or a fiber-optic oxygen sensor [32]. …”

Measurement of pO2by luminescence lifetime spectroscopy: A comparative study of the phototoxicity and sensitivity of [Ru(Phen)3]2+and PdTCPPin vivo

“…Chick's Chorioallantoic Membrane (CAM) model was selected to study photo‐damage in the CAM vasculature. CAMs were prepared as described previously . The chicken fertilized eggs were incubated blunt end up in the automatic turn incubator during 3 days (37 °C, 65% relative humidity and 155.4 mmHg) and a small part of the shell was removed (3 mm in diameter) and covered by tape (Scotch ® Magic TM , USA).…”

“…Luminescence decays of [Ru(Phen) 3 ] 2+ or PdTCPP were measured in time domain with an optical fiber‐based spectrometer, which was developed in our laboratory and previously described . The laser light (470 nm, <10 ns, 10 Hz) is focused into a single optical fiber (500 µm in diameter) to excite the sample and to collect the luminescence from the sample with the same fiber.…”

“…However, these molecules often are phototoxic and frequently lead to tissue and/or vascular damages during the pO 2 measurements . Recently, we demonstrated that the water soluble oxygen sensitive polypyridyl complex dichlorotris(1,10‐phenanthroline)‐ruthenium(II) hydrate ([Ru(Phen) 3 ] 2+ ) possesses minimal phototoxicity in vivo . In the present study, we compare the phototoxicity of this complex with a commonly used water soluble oxygen sensor Oxyphor “R0” Pd‐meso‐tetra(4‐carboxyphenyl)porphyrin (PdTCPP), a palladium porphyrin.…”

Recent Considerations in the Application of RAPTA‐C for Cancer Treatment and Perspectives for Its Combination with Immunotherapies

“…[38,43,55] In 2011, a phase I dose escalation study for (N)KP1339 was initiated, including 16 patients with solid tumors that received one of six doses following a certain treatment schedule. [60,62,63] Although yet to enter clinical trials, a series of experimental drugs [66][67][68][69] that have been extensively evaluated in pre-clinical models are the so-called RAPTA compounds, with the general formula [Ru(arene)Cl 2 PTA] ( Figure 1). It should be noted that concentrations >400 mg induce a transient green discoloration of the patients' plasma.…”