Dr. Mantas Grigalavicius Profile

Dr. Mantas Grigalavicius

at Oslo Univ Hospital

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Proceedings Article | 24 June 2021 Presentation

Detection of chemiluminescence-induced photosensitizer activation through fluorescence and concomitant singlet oxygen generation

Mantas Grigalavicius, Kristian Berg, Theodossis Theodossiou

Proceedings Volume 11786, 117860B (2021) https://doi.org/10.1117/12.2600610

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In the course of experiments for our FET open project Lumiblast, we set off to measure the excitation of various photoactive drugs (photosensitizers, PS) by the luminescence emission of luminol. Luminol (5-Amino-2,3-dihydrophthalazine-1,4-dione) is a chemical that interacts with reactive oxygen species (ROS) in basic conditions, and in the presence of metal catalysts like Fe or Cu, gives out a characteristic blue luminescence. When dissolved in organic solvents like DMSO, however, luminol only requires the addition of bases like KOH, NaOH or potassium terbutoxide, to fulfil the conditions for luminescence emission. In the present work we employed a detection system based on a spectrograph coupled to a ccd camera to register fluorescence (Fig 1B) or luminescence (Fig 1 A, C). In the case of characteristic fluorescence registration (Fig. 1B), the PSs investigated were excited by a 532 nm laser with a variable power output. We have documented the energy transfer from chemically induced luminol luminescence to a number of PSs including rose bengal, erythrosin B, hypericin amongst others. In all cases both the luminol emission and the luminol luminescence-induced PS fluorescence were registered as shown in the example of luminol and erythrosine b in Fig. 1C. We further attempted to register the generation of singlet oxygen from luminol-excited PSs. To achieve this, we employed the near-infrared (NIR) photomultiplier tube (PMT) shown in Fig.1 E, with a cut-off filter at 900nm and a bandpass filter at 1270±30 nm. This allowed only radiation within this spectral region to reach the PMT, corresponding to the characteristic phosphorescence of singlet oxygen, spin forbidden de-excitation to ground state triplet oxygen. A characteristic steady state singlet oxygen registration can be seen in Fig. 1D, for erythrosine b which has a high singlet oxygen quantum yield. The luminol luminescence was initiated by addition of terbutoxide to the DMSO luminol solution, at which point we can see a rise of the signal at 1270 nm. Upon addition of the singlet oxygen quencher, L-histidine, the signal dropped steeply to background levels. NOTE: Figures are not available.

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