Macroscopic singlet oxygen model incorporating photobleaching as an input parameter.

Area of Science:

• Biomedical Engineering
• Photodynamic Therapy Research
• Cancer Treatment Modeling

Background:

• The macroscopic singlet oxygen model is crucial for calculating reacted singlet oxygen concentrations in photodynamic therapy (PDT).
• This model relies on photophysical parameters and threshold singlet oxygen dose, determined via fitting algorithms.
• Key inputs include fluence, photosensitizer concentration, optical properties, and necrosis radius.

Purpose of the Study:

• To optimize the macroscopic singlet oxygen model for photodynamic therapy (PDT) by introducing photobleaching as an additional input variable.
• To fine-tune and verify previously published photophysical parameters using experimental photobleaching data.
• To assess the robustness of the PDT model by comparing experimental and calculated photobleaching ratios.

Main Methods:

• Implemented photobleaching measurement using pre- and post-PDT sensitizer concentrations.
• Utilized a murine fibrosarcoma RIF model for experiments with benzoporphyrin derivative monoacid ring A (BPD) and 2-[1-hexyloxyethyl]-2-devinyl pyropheophorbide-a (HPPH).
• Applied a linear light source with varying fluence rates (12-150 mW/cm²) and total fluences (24-135 J/cm²).

Main Results:

• Photobleaching was successfully integrated as a fitting parameter to optimize PDT model results.
• Previously established photophysical parameters were refined and validated against experimental photobleaching data.
• The study demonstrated that photobleaching serves as an indicator for model robustness in specific experimental conditions.

Conclusions:

• Incorporating photobleaching enhances the accuracy and reliability of the macroscopic singlet oxygen model for PDT.
• The refined model provides a more robust prediction of PDT outcomes, particularly in preclinical cancer models.
• Photobleaching measurements offer valuable insights into the consistency and applicability of the PDT model across different experimental setups.