Image courtesy of CLONDIAG
Companies in the microarray sector are trying to take the technology out of core facilities and put it into the hands of individual researchers by developing technologies such as smaller, less-costly scanners and more streamlined software for array analysis. These improvements could make microarray technology more attractive to labs that lack the large budgets required for sophisticated biochip-related equipment. CLONDIAG® Chip Technologies of Jena, Germany, has taken this trend one step further with the launch of its Array Tube® (AT) technology, a new nonfluorescence-based microarray platform that integrates DNA, oligo, or protein arrays with standard reaction tubes.
CLONDIAG's ATs contain a 3 x 3 mm microarray chip embedded in the bottom of a 1.5 ml microcentrifuge tube. Users perform the hybridization, washing, and blocking steps directly in the tube using conventional, microcentrifuge tube- compatible lab instruments, eliminating the need for any specialized microarray equipment. In addition, the reaction mixture is sealed once the tube lid is closed, reducing the possibility of evaporation and contamination. CLONDIAG designed the platform for use with equipment available in almost any lab, says Karin Adelhelm, director of product support and marketing. "[Many] researchers can for the first time work very comfortably with microarrays."
The company manufactures custom arrays and can develop ATs with spotted or in situ-synthesized arrays, depending on the substance class and spot density required by the user. According to CLONDIAG's Web site, the company can apply 144 probes using the former approach and several thousand via the latter. Oligonucleotides, DNA, and proteins are all compatible with the system, says Adelhelm; ATs are currently in use for genotyping and mutation analysis applications. She adds that the system is flexible and can accommodate other experiments such as gene expression profiling and ELISA-like (protein-protein interaction) assays. "The labeling and staining procedure can be used for almost any type of array," notes Adelhelm.
Unlike conventional microarrays, the AT platform uses a nonfluorescent labeling technique based on gold-induced silver precipitation. A biotin-ylated target is stained with a gold-streptavidin conjugate. The gold particles catalyze precipitation of silver particles, which can be detected via a transmission imaging reader rather than a more expensive laser-based confocal scanner. CLONDIAG manufactures a detection system, the ATR01 reader, specifically for the analysis of Array Tubes; the reader costs less than $20,000 (US). The system is supplied with CLONDIAG's IconoClust-AT array analysis software; CLONDIAG also sells the software as a stand-alone package that can be used with any type of array system.
Image courtesy of CLONDIAG
The AT system has been on the market for less than a year, but it is already in place in several European laboratories and biotechnology companies, including Ogham Diagnostics in Muenster, Germany; the Institute for Medical Microbiology and Hygiene in Dresden, Germany; and the University of Bern, Institute for Veterinary Bacteriology in Switzerland. Adelhelm says that CLONDIAG is currently collaborating with Biomedical Photometrics of Waterloo, Ontario to develop a fluorescence reader for the AT system. This would allow use of two-color labeling for specific expression-profiling analyses.
CLONDIAG is also developing a high-end microfluidics-based array platform for point-of-care genotyping called the Assay Processor (AP). The AP consists of a disposable cartridge in which target amplification, labeling, hybridization, and detection can be performed. "Our aim is to insert the sample--for example a drop of blood diluted in the reaction buffer--and do the complete assay inside," says Adelhelm. The system combines a high-density, in situ-synthesized oligo probe array with a miniaturized "reaction cartridge" that contains all required heater and temperature sensor elements. The system is modular, facilitating connection of the cartridge to a fluorescent detector, and will be available in spring 2003, says Adelhelm.