Dr. Theodossis A. Theodossiou Profile

Dr. Theodossis A. Theodossiou

Project Group Leader at Oslo Univ Hospital

SPIE Involvement:

Author

Publications (6)

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

Read Abstract +

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.

Proceedings Article | 26 October 2001 Paper

Novel diagnostic method for the detection of far-red fluorescence emission from several tumor-seeking photosensitizers

Theodossis Theodossiou, Vladimir Hovhannisyan, P. Kastaniotis, Konstantine Politopoulos, Dido Yova

Proceedings Volume 4433, (2001) https://doi.org/10.1117/12.446511

KEYWORDS: Luminescence, Glasses, Tissues, Tissue optics, Natural surfaces, Fluorescence spectroscopy, Absorption, Diagnostics, Photodynamic therapy, Magnesium

Read Abstract +

Proceedings Article | 26 October 2001 Paper

CN violet-band emission as a time-resolved optical probe of transient temperature induced by laser ablation of type I collagen from bovine Achilles tendon

Michael Kompitsas, Theodossis Theodossiou

Proceedings Volume 4433, (2001) https://doi.org/10.1117/12.446525

KEYWORDS: Plasma, Laser ablation, Collagen, Temperature metrology, Pulsed laser operation, Molecules, Thermodynamics, Atmospheric plasma, Molybdenum, Laser tissue interaction

Read Abstract +

SPIE Journal Paper | 1 January 2001 Open Access

Photochemical effects and hypericin photosensitized processes in collagen

Dido Yova, Vladimir Hovhannisyan, Theodossis Theodossiou

JBO, Vol. 6, Issue 01, (January 2001) https://doi.org/10.1117/12.10.1117/1.1331559

KEYWORDS: Collagen, Luminescence, Chromophores, Laser irradiation, Visible radiation, Ultraviolet radiation, Absorption, Photodynamic therapy, Skin, Tumors

DOWNLOAD PAPER

Proceedings Article | 16 November 2000 Paper

Broadly tunable optical harmonic generation in type I collagen using IR nanosecond laser pulses

Theodossis Theodossiou, Efstratios Georgiou, Vladimir Hovhannisyan, Konstantine Politopoulos, Georgia Rapti, Dido Yova

Proceedings Volume 4161, (2000) https://doi.org/10.1117/12.409310

KEYWORDS: Collagen, Second-harmonic generation, Harmonic generation, Tissue optics, Upconversion, Nd:YAG lasers, Signal detection, Nonlinear optics, Scattering, Biomedical optics

Read Abstract +

Proceedings Article | 4 January 1999 Paper

Photoinduced effect of hypericin on collagen and tissues with high collagen content

Dido Yova, Theodossis Theodossiou, Vladimir Hovhannisyan

Proceedings Volume 3565, (1999) https://doi.org/10.1117/12.335800

KEYWORDS: Collagen, Luminescence, Tissues, Second-harmonic generation, Arteries, Nd:YAG lasers, Harmonic generation, Skin, Hydrogen, Laser irradiation

Read Abstract +

Showing 5 of 6 publications

View contact details

UPDATE YOUR PROFILE

Is this your profile? Update it now.

Sign into your SPIE.org account

Don’t have a profile and want one?

Create an account on SPIE.org

Keywords/Phrases

Search In:

Publication Years