Direct laser-induced singlet oxygen in biological systems: application from in vitro to in vivo

In recent years, there has been increasing interest in the singlet form of oxygen as a regulator of the physiological functions of cells. The use of photosensitisers is a classical mechanism for the excitation of the main triplet form of oxygen and the generation of its singlet form. 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. This review article aims to combine recent accumulated experience in the field of direct optical generation of singlet oxygen. We focus on works on the application of a 1267 nm wavelength, which is the most frequently used and well-studied in this area. In this review, we consider the use of laser-induced singlet oxygen in various biomedical applications both at the cellular level and at the level of whole organisms. This review presents the latest results on the use of singlet oxygen for therapeutic effects on cancer cells, as well as for photostimulation of neurons and the vascular and lymphatic systems.