Common menu bar links
Related Information
Institutes & Programs
- NRC Biotechnology Research Institute
- NRC Canadian Neutron Beam Centre
- NRC Canadian Photonics Fabrication Centre
- NRC Genomics and Health Initiative
- NRC Imaging Network Portal
- NRC Institute for Biodiagnostics
- NRC Institute for Biological Sciences
- NRC Institute for Marine Biosciences
- NRC Institute for Microstructural Sciences
- NRC Institute for Nutrisciences and Health
- NRC Plant Biotechnology Institute
- National Institute for Nanotechnology
- National Research Council Canada
Key Sectors
Areas of Research
Communities
Careers
News
Events
Contact
Phone: 204-983-7692
Fax: 204-983-3154
Email: ibd.research@nrc-cnrc.gc.ca
Fluorescence Imaging
Fluorescence imaging is a sensitive technique widely used for the in vivo detection of particular components of biomolecular moieties such as live cells. For this purpose a fluorophore (fluorescent dye) can be chemically linked, or labelled, to proteins, cells, nucleic acids or antibodies, among other biological molecules. These fluorophores are designed to localize a biological specimen, monitor the distribution and quantification of treatments, or to respond to specific stimulus in vivo.
To obtain a fluorescent image, the fluorophore is stimulated by light at a particular wavelength from an external source, such as a laser diode, to promote an excited electronic state in the fluorophore. Once excited, the fluorophore will emit light at a longer wavelength than the excitation wavelength. A filter in front of the detector can pass the emitted light but block the excitation light, allowing only the fluorescence emitted to be detected by a high sensitivity CCD imaging array and monitored.
Two types of fluorescence are found in tissues: endogenous (i.e. arising from naturally occurring materials in tissues) and exogenous (i.e. arising from a material added to allow tracking or labelling).
Endogenous fluorophores, such as nicotinamide adenine dinucleotide (NADH), provide information on cellular energetics. Collagen, on the other hand, provides information on the amount and integrity of connective tissue.
In the case of exogenous fluorophores, an antibody for a particular type of cancer can be labelled with a fluorophore. By tracking the fluorescence of the labelled antibody, the interaction between the antibody and a particular cancer cell can be monitored. The detection of this labelled-antibody can then be used as an indication of the presence of a tumour.
Figure 1
Tumour xenograft model in nude mice, near infrared image of the distribution of the labelled antibody with fluorescent dye (Cy 5). This antibody preferentially localized in the kidneys, showed some accumulation at the tumour site.
Moreover, if an anticancer (therapeutic) drug can be attached to the antibody, the antibody can be used to deliver the drug only to the tumour cells, as the antibody will not recognize and bind to other types of cells. This means that drugs can be specifically targeted to tumours, reducing unwanted side effects and increasing the chances that the drug will kill all of the tumour cells. By monitoring this labelled therapeutic antibody it is possible to determine the biodistribution and pharmacokinetics of new therapeutic drugs in live animal models as a function of time. As this technique is non-invasive, the same animal may be imaged at multiple time points, decreasing the number of animals required to study the effectiveness of the therapeutic.
A number of excellent fluorescent dyes are commercially available in forms that are readily conjugated to proteins. NRC-IBD researchers have extensive experience labelling proteins with Cy5, Fluorescein and GFP (Green Fluorescent Protein); these dyes have excellent optical properties (absorption and emission wavelengths, quantum yield).
Related Information
Read more about Fluorescence Imaging:
- Bioluminescence Imaging
- Diagnostic Technologies
- Diffuse Reflectance Spectroscopy
- Frequency Modulated Spectroscopy
- High Throughput Diagnostics
- MRI Studies
- Molecular Imaging - Spectroscopy
- Non-linear Optical Microscopic Imaging
- Optical Coherence Tomography
- Raman Spectroscopy
- Speckle Imaging
- Thermal Imaging
