Fluorescence Detection for Forensics Applications Using a Xenon Lamp Excited Image Analyzer: An Affordable Alternative to Laser Based Image Analyzers
Gary Osaka, Dean Burgi, Hank Schwartz, Sandie Yu, and Don Kessler
Genomyx Corp., a wholly owned subsidiary of Beckman Instruments, Inc.
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The research community has recognized the significant advantages of the use of fluorophores and the advancements in the chemistries available for fluorescent labeling and detection. In response to this, several companies developed imagers for fluorescence-based DNA fragment analysis. Most of the original systems relied upon lasers to excite the fluorophore. These imagers allowed for the greatest sensitivity of detection, which was necessary in years past because of the limited availability and low efficiency of fluorophore labeling chemistries. Laser technology has persisted, and is currently being utilized in several commercial fluorescence imagers.
However, the new fluorophore reagents available today have allowed for both, greater efficiency and increased emission signals, thus obviating the requirement for highly energetic lasers in forensic applications which are not mass limited. Such applications would include those which are PCR based and those which allow direct incorporation of the fluorophore.
We wish to report the development and demonstrate the imaging capabilities of a new and much more affordable, non-laser based fluorescence image analyzer for multiple applications in nucleic acid based forensic assays. The GenomyxSC
Ô Fluorescent Scanner utilizes a 300W Xenon lamp, fiber optics and wavelength specific filters for both, maximal excitation of the specific fluorophore label and detection of the emission wavelength. The advantage of the Xenon lamp source is that it allows one to customize any combination of excitation and emission wavelength filters for many types of fluorophores. This feature is very significant because it allows a wide choice of alternative fluorophores without the need to add additional expensive lasers. By choosing fluorophores with very different excitation and emission wavelengths spectral "pull-up" can be eliminated. The GenomyxSCÔ is currently configured for single or dual wavelength capabilities (Fluoroscein/FAM, 520nm and F-red/Cy5, 670nm or TMR/rhodamine, 585nm) which will allow two different fluorophores to be analyzed simultaneously. A cooled CCD (charged-coupled device) camera captures and digitizes the emission data converting it to image data. The imaged data is available as an on-screen image, in digitized format or as a full image printed on paper or transparency film.The GenomyxSC
Ô also allows direct gel imaging following electrophoresis while many of the laser based systems rely on electrophoresing the fluorescent compounds past a fixed detector. The advantages of direct gel imaging are a decrease in the total data acquisition time, and recovery of desirable products for further analysis. Furthermore, the actual gel image is always available so that the researcher can visualize and correct any errors made by even the best analysis software. The GenomyxSCÔ also allows the use of different gel sizes accommodating several standard electrophoresis systems. Fluorescent imaging can be performed on, but is not limited to, the following list of nucleic acid based forensic assays.Go to proceedings home page