Bio-imaging is an easy-to-use, fast but powerful in vivo technology for researchers to non-invasively study molecular and biological processes of disease, track disease progression, or evaluate therapeutic effectiveness. Fluorescence and bioluminescence imaging each offer unique benefits for pre-clinical imaging of small laboratory animals. Fluorescence imaging is particularly useful for quantifying and monitoring the cell behavior of biological targets, and optimal for studying dynamic processes. With time-lapse imaging of live cells, researchers can acquire key information through observation over hours or days. The unique features of bioluminescence imaging provide precise quantification and specificity, allowing researchers to detect and monitor gene expression related to tumor growth, as well as to use for therapeutic monitoring. Bioluminescence imaging also is used to track bacteria, viruses, and other pathogens.
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Figure 1. Luminescece images of T41-luc cell. Breast luminescent tumor cell injected S.C. in right dorsal-lateral side.
How fluorescence and bioluminescence imaging work
Fluorescence imaging involves the emission of light by a substance that has absorbed light or other electromagnetic radiation. For in vivo imaging experiments, a fluorescent dye called a fluorophore is injected into a laboratory animal and then excited with an external light source. Fluorescent dyes are non-protein molecules that absorb light and re-emit it at a specific wavelength under the excitation light and are thus useful in the fluorescent labelling of biomolecules.
The tissue or cells labeled with fluorescence are inside the body, so the camera imaging needs suitable light for the fluorophore and the appropriate filter to transmit only the emitted light. The colors will vary depending upon the fluorophore. The intensity is relatively strong and can be changed according to the concentration of the fluorophore and the strength of the excitation light. The excitation filter controls the selection of the excitation wavelength, which in turn determines the tissue penetration depth that will be imaged.
Figure 2: Correlation of the excitation wavelength and the penetration depth to be imaged.
Bioluminescence imaging involves spontaneous emission of light by a substance not resulting from heat. It can be caused by chemical reactions, electrical energy, subatomic motions, or stress on a crystal. In most bioluminescent imaging, a natural light-emitting protein such as luciferase is used to trace the movement of certain cells or to identify the location of specific chemical reactions within the body. Bioluminescent imaging is an optimal research method for both studying gene expression and therapeutic monitoring, including in vivo studies of infection (with bioluminescent pathogens), cancer progression (using a bioluminescent cancer cell line), and reconstitution kinetics (using bioluminescent stem cells).
In bioluminescence imaging, the light-emitting protein (such as luciferase) is injected into the body. The luciferase-expressed cells or organs are studied inside the body for in vivo experiments, and thus have some unique requirements for imaging with the camera. While there is no need for an excitation light or filter such as is required for fluorescence imaging, the weak intensity of emitted light requires a dark room and long exposure time. The camera requires high sensitivity in order to detect weak signals, as well as cooling ability to reduce the noise of the sensor.
Figure 3: Bioluminescence imaging.
The CleVue™ software, designed exclusively for the Visque InVivo Series of bio-imaging systems, provides tools that help researchers analyze both fluorescent and bioluminescent images. In addition, Visque’s patented algorithms are useful in real-time imaging and kinetics studies. These advanced and powerful capabilities have been achieved from long term studies in cooperation with researchers, and make it easy to generate images and statistics for research papers and documentation.
Biodistribution in an experimental animal involves tracking the movement of compounds of interest as they travel through the organism or are retained within an organ or tissues. Biodistribution is the primary use for an in vivo imaging system, often for research in pharmacology, toxicology, and oncology. The pharmacokinetics and tissue distribution of the compounds or nanoparticles help researchers understand their therapeutic effect and toxicity. Chemical and physical properties, including size, surface charge, and surface chemistry, are important factors that determine biodistribution.
Biodistribution Research Fields
Analyzing blood flow helps researchers to understand basic physiological processes and many pathological conditions, since many diseases alter blood flow. In addition, monitoring blood flow helps researchers to better understand pharmacokinetics, such as the dissolution of a medicine into the body. Research in these areas involved fast response kinetics and the analysis of time-lapse images with Visque’s unique and powerful analysis algorithms.
Kinetic Analysis Research Fields
Kinetic Analysis Possible Studies
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