Optical fiber detection system for sensing singlet oxygen luminescence in aqueous solution

摘要

Singlet oxygen (~1O2) is widely recognized as the primary cytotoxic agent during photodynamic therapy (PDT). The quantitation of ~1O2 generation during PDT plays an important role for ~1O_2 based PDT dosimetry. However, it is still a challenging task for direct detection of ~1O_2 using an optical system due to its extremely weak luminescence at 1270 nm. In this paper, a highly sensitive optical fiber detection system was developed to measure the time-resolved ~1O_2 luminescence spectra from two model photosensitizers (Rose Bengal and TMPyP) at various concentrations (1.25, 2.5, 5.0, and 10.0 μM), The ~1O_2 luminescence signal was excited by a diode-pumped, Q-switched, frequency-doubled 523-nm Nd:YLF laser and collected by an optical fiber probe coupled with a highly sensitive NIR photomultiplier tube (PMT). Experimental results indicate that the ~1O_2 luminescence intensity shows a linear enhancement both with the increase of concentrations of Rose Bengal and TMPyP. The ~1O_2 luminescence signal dramatically decreased after the addition of 50 mM sodium azide, a specific ~1O_2 quencher. Furthermore, the signal-to-noise ratio (SNR), calculated under the condition of 10 mM Rose Bengal solution, is higher than those obtained from optical fiber ~1O_2 luminescence detection systems based on InGaAs/InP single photon avalanche diode and superconducting nanowire single-photon detector. Our results suggest that the home-built optical fiber system with a high sensitivity for ~1O_2 luminescence detection will have a great potential for clinical applications in PDT dosimetry.