Singlet Oxygen Imaging

Molecular oxygen is one of the most important molecules in maintaining life as well as in mechanisms by which life is extinguished and materials destroyed. For several decades, researchers have been intrigued by the physical and chemical properties of molecular oxygen’s lowest excited state, singlet oxygen (1O2). In particular, singlet oxygen has a unique reactivity that can result in polymer degradation or the death of biological cells. Its role as an intermediate in cell death is exploited by photodynamic therapy (PDT) for cancer, a technique in which light is utilized as a medical tool1,2.

In PDT, a photosensitizer is incorporated into abnormal tissues and then irradiated with visible light so that it transfers energy to ground-state oxygen via the type II photochemical pathway, producing singlet oxygen (which can be directly detected by its weak 1270 nm emission)3. Owing to the special interest in elucidating the biochemical action of singlet oxygen on the subcellular level, several high-spatial-resolution methods have been proposed to detect 1O2 luminescence using either a single photomultiplier tube (PMT), a linear InGaAs detector array, or a two-dimensional InGaAs detector3.

Additional details can be found in “Real-Time Imaging of Singlet Oxygen via Innovative Microspectroscopy Instrument.

1. Schweitzer C. and Schmidt R. Physical mechanisms of generation and deactivation of singlet oxygen. Chem. Rev. 103, 1685–1757 (2003). 2. Skovsen, E. Progress report: Non-linear two-photon singlet oxygen emission microscopy. Department of Chemistry, University of Aarhus, Denmark (2004). 3. Hu B., He Y., and Liu Z. NIR area array CCD-based singlet oxygen luminescence imaging for photodynamic therapy. Journal of Physics: Conference Series 277 (2011).

 

PI’s Picks:

PI recommends the NIRvana:640 camera for singlet oxygen imaging. We designed this 16-bit camera specifically for scientific research applications requiring superb linearity and excellent near-infrared sensitivity. Its 640 x 512 InGaAs detection array, which delivers response from 0.9 μm to 1.7 μm, can be thermoelectrically cooled as low as -85°C in order to minimize thermally generated noise and improve signal-to-noise ratio.

Singlet Oxygen experimental outputDOI: 10.1039/c4pp00121d - Reproduced by permission of The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC. http://pubs.rsc. org/en/content/articlelanding/2014/pp/ c4pp00121d#!divAbstract
The diagram below shows a novel microspectroscopy setup that uses a NIRvana:640 camera from Princeton Instruments. Marek Scholz of Charles University (Prague) reports that the camera’s two-dimensional InGaAs array has allowed himself and fellow members of the Optical Spectroscopy Group headed by Jan Hála to address the issue of potential spectral overlap of 1O2 phosphorescence with the NIR-extended luminescence of the photosensitizer, thus providing an effective means of distinguishing and separating them for the first time4.
 
The experimental setup utilizes 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 the visible fluorescence of the photosensitizer. This innovative setup enables acquisition of spectral images based on singlet oxygen and photosensitizer luminescence from individual cells. One dimension of the image is spatial and the other is spectral, covering a spectral range from 500 to 1700 nm.
 
4. Scholz M., Dedic R., Valenta J., Breitenbach T., and Hála J. Real-time luminescence microspectroscopy monitoring of singlet oxygen in individual cells. Photochem. Photobiol. Sci. 13, 1203–1212 (2014). DOI: 10.1039/c4pp00121d

 

singlet oxygen experimental setup

NIR luminescence microspectroscopy setup: lower portion of diagram depicts spectral regions detected by VIS and NIR paths. For more details, refer to “Real-Time Imaging of Singlet Oxygen via Innovative Microspectroscopy Instrument”.

DOI: 10.1039/c4pp00121d - Adapted by permission of The Royal Society of Chemistry (RSC) on behalf of the European Society for Photobiology, the European Photochemistry Association, and RSC. http://pubs.rsc.org/en/content/articlelanding/2014/pp/c4pp00121d#!divAbstract

Application Notes

Real-Time Imaging of Singlet Oxygen via Innovative Microspectroscopy Instrument
New Two-Dimensional InGaAs Detector Thermoelectrically Cooled to –85°C Facilitates Scientific Research

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