Light-oxygen effect in cells and its potential applications in tumour therapy (review)

The light-oxygen effect (POE) represents damage (and at low optical doses, activation) of cells by photogeneration of molecular singlet oxygen from O₂ dissolved in cells, in accordance with the reaction: ³O₂+hν→¹O₂→ biological effect. The phases of evolution of the LOE are similar to the phases, observed in cell experiments, of the photodynamic effect (PDE) the mechanism of which is the basis of the familiar method of photodynamic cancer therapy. The reported proofs of the occurrence of the LOE are in the form of detailed spectra of the biological action of optical radiation on cells recorded in four spectral intervals with the aid of tunable lasers. Allowances are made for the relationships governing a new type of cell excitation, associated with reversible structural transitions in the biomembrane. A demonstration is reported of the same efficiency of cw and pulsed irradiation. An analysis is made of the reasons why the optical doses initiating the PDE and the LOE are comparable. The results are given of the first experimental applications of the LOE in tumour therapy. Identification of the primary photoacceptor (O₂) in cell biostimulation and photodestruction provides a scientific basis for the development of low-intensity laser light-oxygen cancer therapy methods.