Editors' ChoiceBiosensors

Escaping Detection, Finally Caught

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Science Translational Medicine  28 Oct 2009:
Vol. 1, Issue 4, pp. 4ec15
DOI: 10.1126/scitranslmed.3000516

Many medical decisions depend on the reliable, accurate detection of disease-related molecules or markers. Low quantitative sensitivity of the method or complex sample composition can interfere, misleading or restricting clinical application. Now, R. Gaster et al. show the utility of magnetic nanosensing technology that bypasses a major roadblock to highly sensitive, accurate assays: interfering components in the biological sample. The magnetic nanosensors take advantage of the fact that most clinical materials lack a detectable magnetic background signal. Exploiting this low magnetic background, the researchers devise a sandwich platform in which one antibody is bound to an underlying magnetic sensor and another is tagged with a superparamagnetic nanoparticle. In an external magnetic field, the nanoparticles magnetize when the target antigen is bound, yielding robust, sensitive quantitation. A considerable advance over technologies such as biobarcode assays, protein microarrays, or ELISAs, these magnetonanosensors maintain accurate, sensitive detection of their targets within a large linear dynamic range—anywhere from femtomolar concentrations to one million times higher. Not only was this study able to show specific multiplexed detection of protein markers in several biological fluids —human serum, urine, and saliva—it was also able to monitor dynamic changes in carcinoembryonic antigen, vascular endothelial growth factor, and epithelial cell adhesion molecule in a human colorectal cancer xenograft mouse model. The method was so specific that it could distinguish clinically relevant tumor markers from irrelevant ones, as well as reveal minute fluctuations over time in a complex biological fluid. The translational application of such a technology includes profiling blood tumor markers in individuals with cancer, as well as aiding in the discovery of new drugs and clinical research.

R.S. Gaster et al., Matrix-insensitive protein assays push the limits of biosensors in medicine. Nat. Med. 11 October 2009 [Abstract (PDF)]

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