PdTCPP is potentially phototoxic under certain experimental conditions and can induce damage in peripapillary retina and optic nerve head after light exposure. The severity of tissue damage correlates with the phosphorescence measurements.
Articles you may be interested inTime-resolved scanning system for double reflectance and transmittance fluorescence imaging of diffusive media Rev. Sci. Instrum. 79, 013103 (2008); 10.1063/1.2828054Fluorescence lifetime imaging using a compact, low-cost, diode-based all-solid-state regenerative amplifier Rev.
Tissue characterization by endoscopic fluorescence imaging of endogenous or exogenous fluorochromes is a promising method for early cancer detection. However, the steady-state fluorescence contrast between healthy tissue and lesions such as early-stage carcinomas is generally poor. The authors propose to improve this contrast by using the additional information contained in the fluorescence lifetime (FLT). The FLT of several fluorochromes is sensitive to their physico-chemical environment.The FLT can be measured by frequency-domain methods. The excitation light from a continuous wave (CW) laser is modulated in amplitude at radio-frequencies by an electro-optic modulator, and delivered to the tissue via an optical fibre. The endoscopie site is imaged by an endoscope on to an optical device. The gain of the fluorescence image detector is also modulated at the same frequency for homodyning. The tissue fluorescence image is recorded at several phases between the excitation and the detection modulations during an acquisition cycle. With these images, an image processor calculates the apparent FLT for each pixel and constructs a lifetime image of the endoscopie site. This process is performed at quasi-video frequencies.The influence of various physical parameters (modulation frequency, number of images by cycle, shot noise, tissue optical properties etc.) has been investigated by analytical analysis, simulation methods and experimentation.Preliminary results obtained on human tissues are also presented to illustrate the potentiality of the method.
Quantitative measurement of diffusive and directional processes of intracellular structures is not only critical in understanding cell mechanics and functions, but also has many applications, such as investigation of cellular responses to therapeutic agents. We introduce a label-free optical technique that allows non-perturbative characterization of localized intracellular dynamics. The method combines a field-based dynamic light scattering analysis with a confocal interferometric microscope to provide a statistical measure of the diffusive and directional motion of scattering structures inside a microscopic probe volume. To demonstrate the potential of this technique, we examined the localized intracellular dynamics in human epithelial ovarian cancer cells. We observed the distinctive temporal regimes of intracellular dynamics, which transitions from random to directional processes on a timescale of ~0.01 sec. In addition, we observed disrupted directional processes on the timescale of 1~5 sec by the application of a microtubule polymerization inhibitor, Colchicine, and ATP depletion.
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