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Sep 15, 2010 (Vol. 30, No. 16)

Multiple Drivers Shape Fate of MDx

Solution Providers Address Need for Increased Speed, Reduced Cost, and Easier Patient Access

  • GC-Rich Sequences

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    TriLink BioTechnologies’ CleanAmp™ dNTPs are part of the firm’s line of PCR-enhancing products. CleanAmp supports applications in the diagnostics field that require high specificity of target amplification.

    TriLink BioTechnologies has long supplied reagents to the molecular diagnostics field and “is now uniquely poised to play a more direct role,” says Natasha Paul, scientific investigator.

    “Our CleanAmp™ hot-start PCR technology can support applications in the diagnostics field that require high specificity of target amplification.” TriLink’s CleanAmp dNTP technology is based on the use of a 3´-thermolabile dNTP protecting group that prevents primer extension at low temperatures. The protecting group is removed during the hot-start activation step of PCR, increasing the specificity of amplification of the intended target.

    As molecular diagnostics trend toward advanced amplification strategies, new targets are often located in highly GC-rich regions, including promoter and enhancer sequences known to play a pivotal role in gene regulation.

    Assays targeting these regions are often plagued by low-amplification specificity. Substitution of dGTP with 7-deaza-dGTP has improved specificity by disrupting complex secondary structure formation within these sequences.

    TriLink BioTechnologies has made this valuable tool into a hot-start solution called CleanAmp 7-deaza-dGTP. Reactions with CleanAmp 7-deaza-dGTP significantly improved amplification specificity for targets containing as much as 84% GC content, Paul reports. “We are encouraged by these results and are exploring development of reagents for clinically relevant targets.” 

    Over the past few years, point-of-care (POC) applications have became a significant driving force in the diagnostics field. In part, this is being driven by aging patients and a growing need to perform routine diagnostic analysis at home or at specialized-care facilities.

  • Point-of-Care Device

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    Argento Diagnostics, a spinout from National Physical Laboratory, has launched an analysis technology that reportedly enables multiple quantitative measurements to be made from a single sample (e.g., blood, urine, or saliva) in a fully portable handheld device.

    “A host of other human health, animal health, and environmental needs could be addressed by point-of-care testing,” notes Keith Page, CEO of Argento Diagnostics. “However, achieving true portability while maintaining quality on par with a large clinical laboratory remains a challenge. A diagnostic system in field situations must accept a variety of common sample sources, often with poor quality.”

    Argento’s platform technology can be compacted to the size of a typical smart phone. The touch-screen interface requires minimal technical savvy, and the data can be transmitted via Internet. Miniaturization of Argento’s technology is made possible by a novel detection method that amplifies the signal 106 times.

    According to the company, its electrochemical immunoassay system is capable of detecting 30 viral particles in 1 mL of nasal lavage. Argento utilizes a familiar immunoassay with the analyte captured on antibody-coated magnetic beads.

    The complexes are detected by silver nanoparticles composed of 106 silver ions coated with a specific binding molecule. The unique attribute of this technology comes from the detection of silver ions by anodic stripping voltammetry. This method involves coating the silver particles with ammonium isothiocyanite that attributes a negative charge to the particles.

    The coated particles are drawn to the positively charged electrodes on the assay chips, where the particles are dispersed into silver ions. The number of silver ions is directly proportional to the number of complexes.

    Argento’s technology eliminates the need for harsh oxidative chemicals used to generate silver ions. The system can utilize copper, gold, and silver detection systems in a multiplex reaction with a common sample entry point. The time for analysis depends on the viscosity of the sample. An assay based on saliva takes about three to five minutes, Page says.

    “The use of proteins for diagnostic tests is typically limited by the detection methods, which are only sensitive enough when the protein concentrations have already reached critical thresholds and disease has progressed. Our current detection capabilities are on par with clinical labs, and the detection could be improved further depending on a clinical need.”

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