Monitoring of changes in oxygen concentration in tissues by the kinetics of delayed fluorescence of exogenous dyes

The dynamics of the consumption of oxygen during photodynamic processes and the subsequent restoration of its concentration in malignant tumors and healthy tissues of mice were studied in vitro by the kinetics of long-term luminescence of xanthene dyes. To assess changes in the oxygen concentration in tissues, delayed fluorescence can be used due to singlet–triplet annihilation of singlet oxygen and a sensitizer in the triplet state. Upon periodic pulse excitation of sensitizers, reversible quenching of delayed fluorescence was detected in tumors, which is associated with a decrease in the amount of oxygen in the tissues during photodynamic processes. A method for visualizing the restoration of the initial oxygen concentration in tissues is proposed.