Mr. Matthias Kress Profile

Matthias Kress

at Univ Ulm

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Author

Publications (3)

Proceedings Article | 19 June 2003 Paper

Fluorescence lifetime imaging (FLIM) using ps-pulsed diode lasers in laser scanning microscopes

Angelika Ruck, Frank Dolp, Claudia Happ, Rudolf Steiner, Michael Beil

Proceedings Volume 4962, (2003) https://doi.org/10.1117/12.477828

KEYWORDS: Luminescence, Fluorescence lifetime imaging, Laser scanners, Semiconductor lasers, Microscopes, Photodynamic therapy, Time resolved spectroscopy, Picosecond phenomena, Microscopy, Spectroscopy

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SPIE Journal Paper | 1 January 2003 Open Access

Time-resolved microspectrofluorometry and fluorescence lifetime imaging of photosensitizers using picosecond pulsed diode lasers in laser scanning microscopes

Matthias Kress, Thomas Meier, Rudolf Steiner, Frank Dolp, Rainer Erdmann, Uwe Ortmann, Angelika Rueck

JBO, Vol. 8, Issue 01, (January 2003) https://doi.org/10.1117/12.10.1117/1.1528595

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This work describes the time-resolved fluorescence characteristics of two different photosensitizers in single cells, in detail mTHPC and 5-ALA induced PPIX, which are currently clinically used in photodynamic therapy. The fluorescence lifetime of the drugs was determined in the cells from time-gated spectra as well as single photon counting, using a picosecond pulsed diode laser for fluorescence excitation. The diode laser, which emits pulses at 398 nm with 70 ps full width at half maximum duration, was coupled to a confocal laser scanning microscope. For time-resolved spectroscopy a setup consisting of a Czerny Turner spectrometer and a MCP-gated and -intensified CCD camera was used. Time-gated spectra within the cells were acquired by placing the laser beam in ‘‘spot scan’’ mode. In addition, a time-correlated single photon counting module was used to determine the fluorescence lifetime from single spots and to record lifetime images. The fluorescence lifetime of mTHPC decreased from 7.5 to 5.5 ns during incubation from 1 to 6 h. This decrease was probably attributed to enhanced formation of aggregates during incubation. Fluorescence lifetime imaging showed that longer lifetimes were correlated with accumulation in the cytoplasm in the neighborhood of the cell nucleus, whereas shorter lifetimes were found in the outer cytoplasm. For cells that were incubated with 5-ALA, a fluorescence lifetime of 7.4 ns was found for PPIX; a shorter lifetime at 3.6 ns was probably attributed to photoproducts and aggregates of PPIX. In contrast from fluorescence intensity images alone, different fluorescence species could not be distinguished. However, in the lifetime image a structured fluorescence distribution in the cytoplasm was correlated with the longer lifetime and probably coincides with mitochondria. In conclusion, picosecond diode lasers coupled to a laser scanning microscope equipped with appropriate detection units allows time-resolved spectroscopy and lifetime imaging with high spatial resolution and provides numerous possibilities in cellular and pharmaceutical research.

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Proceedings Article | 2 November 2001 Paper

Short-pulsed diode lasers as an excitation source for time-resolved fluorescence applications and confocal laser scanning microscopy in PDT

Matthias Kress, Thomas Meier, Tarek El-Tayeb, Ralf Kemkemer, Rudolf Steiner, Angelika Rueck

Proceedings Volume 4431, (2001) https://doi.org/10.1117/12.447408

KEYWORDS: Luminescence, Semiconductor lasers, Time resolved spectroscopy, Laser scanners, Fluorescence spectroscopy, Spectroscopy, Microscopy, Photodynamic therapy, Argon ion lasers, Sensors

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