Determination and analysis of singlet oxygen quantum yields of talaporfin sodium, protoporphyrin IX, and lipidated protoporphyrin IX using near-infrared luminescence spectroscopy.

In photodynamic therapy (PDT), singlet oxygen ([Formula: see text]) is the main species responsible for promoting tumor cell death. The determination of the quantum yield (Φ) of a photosensitizer (PS) is important for dosimetry. The purpose of this paper is to quantify the [Formula: see text] generated by the PS by near-infrared spectroscopy (NIRS). The Φ of different PS species were measured by the detection of near-infrared [Formula: see text] luminescence. From the measurement results, the Φ of talaporfin sodium, protoporphyrin IX (PpIX), and lipidated PpIX (PpIX lipid) were measured as 0.53, 0.77, and 0.87, respectively. In addition, the Φ values of PpIX in a hypoxic and oxic solution were evaluated, since tumors are associated with regions of hypoxia. The measured Φ indicated a same value at high (DO: 20%) and low (DO: 1%) oxygen concentrations. Using the measured Φ, the amount of [Formula: see text] generated by the PSs was estimated using [[Formula: see text]] = DΦ, where D is the total excited PS concentration. The generated [Formula: see text] amounts were little different at the high and the low oxygen concentrations, and the generated [Formula: see text] amount for each PS was different depending on each Φ. The NIRS measurement determined the Φ of talaporfin sodium, PpIX, and PpIX lipid. The quantitative evaluation based on the measured Φ will support the development of PDT treatment monitoring and design.