State-of-the-Art Detection of Laser-induced Singlet Oxygen
Elena Zharkikh, Irina Novikova, Andrey Vinokurov, Elena Potapova, Viktor Dremin
Research and Development Center of Biomedical Photonics, Orel State University, Orel, Russia
Abstract
Singlet oxygen (SO) is an electronically excited state of triplet oxygen which is less stable than molecular oxygen in the electronic ground state and produced by photochemical, thermal, chemical, or enzymatic activation. Recent studies show that the singlet form of oxygen can participate in physiological cellular processes and modulate the cellular redox potential.
The classical mechanism for the excitation of the main triplet oxygen form and the generation of its singlet form is the use of photosensitizers, which, under the influence of light, transfer the electronic excitation energy to the triplet oxygen. At the same time, it has been shown that there is a possibility of direct optical excitation of the main oxygen form into the singlet state by light at certain wavelengths. Along with the development of a methodology for the use of SO for therapeutic purposes, an important task is the development of methods for detecting SO concentrations. The existing approaches can be divided into three main groups: using chemical traps, fluorescent probes and spectroscopy. In this study, we review these approaches and conduct experimental studies to identify their advantages and weaknesses.
First, directly induced SO production was measured in the prepared water-based solution by histidine-mediated chemical trapping. The Clark oxygen electrode (Oxytherm+R, Hansatech Instruments Ltd, UK) was used to measure the SO concentration by chemical trapping. SO generation was carried out using a 1267 nm CW laser.
SO production was also measured using Singlet Oxygen Sensor Green (SOSG, Invitrogen, Oregon, USA) (excitation 488 nm laser with emission 525 nm).
Spectroscopic detection is a challenging task because of the low level of SO produced and the high probability of its quenching by the medium. SO shows a weak emission band at 1270 nm. To measure this luminescence signal, we implemented synchronous detection based on a high sensitivity InGaAs avalanche photodiode.
The study was supported by the Russian Science Foundation under the project №22-75-10088.
Speaker
Elena Zharkikh
Research & Development Center of Biomedical Photonics, Orel State University
Russia
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