Effect of Oxygen Concentration on Singlet Oxygen Signal and Treatment Outcome Measured By Multispectral Singlet Oxygen Luminescent Dosimetry (MSOLD) In Tumor-Bearing Mice
Abstract
Purpose
Singlet oxygen (SO) is the primary cytotoxic agent in photodynamic therapy (PDT); however, real-time measurement of SO during treatment remains challenging. The purpose of this study is to investigate the dependence of SO signal on tissue oxygenation and treatment conditions in vivo using RIF tumor–bearing C3H mice. Singlet Oxygen Explicit Dosimetry (SOED) is evaluated to assess the potential of MSOLD as a treatment-guidance tool.
Methods
SO signals were measured using MSOLD during PDT with benzoporphyrin derivative (BPD) in water and solid phantoms to characterize system sensitivity and response under controlled conditions. In vivo studies were conducted in RIF tumor–bearing C3H mice, where PDT was delivered following BPD administration. Tissue oxygenation was modulated using medical air breathing for 1 minute and carbogen breathing for 10 minutes and reversal to baseline conditions for comparison. Changes in MSOLD-measured SO signal were recorded during oxygen modulation. Additional PDT mouse studies were performed to monitor treatment outcome and explore the relationship between measured SO signal and therapeutic response.
Results
Clear SO signals were detected by MSOLD in both water and solid phantom studies during PDT with BPD, demonstrating system sensitivity and stability. In vivo measurements showed that the MSOLD-measured SO signal increased during carbogen breathing and decreased during medical air breathing, indicating strong dependence of SO signal on tissue oxygen concentration. Preliminary treatment outcome monitoring suggests a relationship between MSOLD-measured SO signal and PDT efficacy in RIF tumor–bearing C3H mice.
Conclusion
This study demonstrates the feasibility of MSOLD for measuring singlet oxygen during BPD-PDT in phantoms and in vivo. The dependence of SO signal on tissue oxygenation and its association with treatment outcome support MSOLD as a real-time PDT dosimetry tool. Ongoing studies aim to quantify SO–response relationships.