Comparative analysis of multichannel singlet oxygen luminescence dosimetry (MSOLD) and singlet oxygen explicit dosimetry (SOED) in benzoporphyrin derivative (BPD)-mediated photodynamic therapy: a mouse model study

Direct detection of singlet-state oxygen ([¹O₂]) is a crucial objective in type II photodynamic therapy (PDT), achievable through the implementation of multispectral singlet oxygen dosimetry (MSOLD). To accurately assess the amount of reactive singlet oxygen, the Singlet Oxygen Explicit Dosimetry (SOED) model was developed, incorporating parameters such as light fluence rate, photosensitizer concentration, and ground-state oxygen concentration. This study focuses on comparing the results obtained from MSOLD and SOED in mouse model by measuring the singlet oxygen signal via a Avantes InGaAs spectrometer and subsequently calculating reactive singlet oxygen based on the SOED theory. A continuous-wave laser operating at 690nm was employed to excite benzoporphyrin derivative (BPD) in mice at a concentration of approximately 4mg/kg. 1.5mm optic fiber coupled with Avantes spectrometer is used to detect the singlet oxygen signal. To simulate clinical PDT scenarios, real-time singlet oxygen spectra are collected over 900 seconds. Ground-state oxygen concentration is measured using a commercial oxygen probe while the laser is inactive, and photosensitizer concentration is assessed via a custom-made contact probe. Additionally, the fluence rate of the laser is measured using an isotropic detector. The Reactive Singlet Oxygen is then calculated using the SOED model, incorporating the photosensitizer concentration, oxygen concentration, and photon fluence rate. Detailed comparisons between MSOLD and SOED results are presented, offering valuable insights into the accuracy and reliability of both methods in quantifying singlet-state oxygen during PDT.