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Princeton Instruments cameras enable monitoring of singlet oxygen

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Princeton Instruments, a leading manufacturer of sensitive low-light imaging and spectroscopic instruments, is pleased to recognize the innovative work of the Optical Spectroscopy Group headed by Jan Hála within the Department of Chemical Physics and Optics at Charles University (Prague, Czech Republic). A recently published paper in Photochemical & Photobiological Sciences details the group’s development of a new experimental setup that enables direct microspectroscopic monitoring of singlet oxygen using NIRvana: 640, a 2D-array InGaAs camera specially designed for scientific research with excellent linearity and near-infrared sensitivity (Marek Scholz, Roman Didic, Jan Valenta, Thomas Breitenbach and Jan Hála: Real-time luminescence microspectroscopy monitoring of singlet oxygen in individual cells, Photochem. Photobiol. Sci., 2014,13, 1203-1212, DOI: 10.1039/C4PP00121D). 

Singlet oxygen, the first excited state of molecular oxygen, is a highly reactive species that plays an important role in a wide range of biological processes, including cell signaling, immune response, macromolecule degradation, and elimination of neoplastic tissue during photodynamic therapy. Often, a photosensitizing process is employed to produce singlet oxygen from ground state oxygen.

The researchers at Charles University in Prague utilized two detection channels (VIS and NIR) to perform real-time imaging of the very weak near-infrared phosphorescence of singlet oxygen and photosensitizer simultaneously with visible fluorescence of the photosensitizer. Their new experimental setup enables acquisition of spectral images based on singlet oxygen and photosensitizer luminescence from individual cells, where one dimension of the image is spatial and the other is spectral, covering a spectral range from 500 to 1700 nm.

To achieve these results, a Princeton Instruments NIRvana® 640, 2D InGaAs camera was coupled to an imaging spectrograph (Acton SpectraPro® 2500i, Princeton Instruments). According to Dr. Marek Scholz, the main advantage of the near-infrared–sensitive NIRvana camera over previously utilized 1D InGaAs detectors is the NIRvana detection array’s two-dimensionality, which leads to a dramatic reduction of acquisition times and avoids some of the problems caused by photobleaching of the sample. A back-illuminated, silicon CCD camera (Spec-10:400B, Princeton Instruments) was used to detect visible light in the setup.

Scholz et al. indicate that the introduction of spectral images for such studies addresses the issue of a potential spectral overlap of singlet oxygen phosphorescence with NIR-extended luminescence of the photosensitizer and provides a powerful tool for distinguishing and separating them, which can be applied to any photosensitizer manifesting NIR luminescence.