Oxygen-Enriched Photosensitizer Medium with Red Blood Cells to Study Tissue Interaction of Photosensitization Reaction.

Background: It has been reported that the oxygen pressure of a photosensitizer medium decreases during an irradiation leading to decrease in the efficacy of the photosensitization reaction against the target cell in vitro.

Objective: The aim of this study was to obtain solutions with high dissolved oxygen levels in cultivated wells with perceiving oxygen environment and photosensitizer bleaching for photosensitization reaction studies.

Materials and methods: We used a 10-mm-wide optical cell cuvette with a 1-mm optical path length as the well. A red blood cell (RBC) suspension with a hematocrit level of 0.625% was employed as the optical sample. The photosensitizer talaporfin sodium was added to a concentration of 30 μg/mL. The optical sample was irradiated by a 663-nm diode laser at 120 mW/cm², for a total radiant exposure of 0-20 J/cm², to induce a photosensitization reaction. Absorption spectra of the samples in the range of 475-700 nm were measured before and after each irradiation condition. Visible spectroscopy was selected to distinguish between the major three hemoglobin (Hb) types: oxygenated Hb, deoxygenated Hb, and met Hb. Also, this wavelength range was selected to investigate photobleaching using the Q band absorption peak. Each Hb concentration was estimated using a multiple regression analysis applied to the obtained absorption spectra.

Results: The relationship between oxygen saturation and the absorption peak in the Q band from the talaporfin sodium dynamics with increasing radiant exposure was revealed by our method with approximately twofold oxygen-dissolved solution.

Conclusions: We could perceive the oxygen environment and the photosensitization reaction progression simultaneously with increasing dissolved oxygen by adding RBCs to the cell medium and measuring the absorption spectrum of it.