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.
Plants synthesis multiple families of sHSPs with monomer sizes ranging from 12 to 42 kDa, are the most diverse and more abundant than in other organisms (Wu et al., 2022). In addition to heat tolerance, the sHSPs suggesting that they may play important roles other cellular processes under normal conditions (Wu et al., 2022). Over the past decades, it has been observed that the expression of certain plant sHSPs is induced by a range of stressors, including heat, salt, drought, osmotic, hormonal, heavy metal, oxidative stresses, as well as developmental signals specific to plants (Wu, et al. 2022). In addition, a multitude of investigation have involved the overexpression of various sHSPs in both homologous and heterologous plant systems, including E. coli and Yeast models (Santhanagopalan, et al. 2015; Waters and Vierling 2020). The outcomes of many of these experiments have revealed that stress protection conferred by these proteins is restricted to specific conditions and narrow range of plant growth stages. On contrast, suppression of CI or CII sHSPs in A. thaliana by RNAi showed that these sHSPs were required for recovery from a severe heat stress (10 h at 45°C) and have independent functions (McLoughlin, et al. 2016; Wu, et al. 2022). However, additional investigations are needed to uncover further applications for these proteins.
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