These file attachments have been under embargo and were made available to the public after the embargo was lifted on 12 April 2010.
BACKGROUND: We present a handheld integrated device based on a novel magnetic-optical technology for the sensitive detection of cardiactroponin I, a biomarker for the positive diagnosis of myocardial infarct, in a finger-prick blood sample. The test can be performed with a turn-around time of 5 minutes and can detect concentrations in the picomolar range in a sample volume of less than 25 L. METHOD: The test was completed in a compact, injection molded plasticdisposable with a 0.5 L assay chamber containing integrateddry magnetic nanoparticles and reagents. We have developed a 1-stepassay in which all reaction processes were precisely controlled bythe 3 electromagnetic coils positioned above and below the disposable. In the on-sensor assay, troponin molecules were sandwiched between capture antibodies attached to the detection surface and 500 nm superparamagnetic particles functionalized with tracer anti-troponinantibodies. Nanoparticles bound to the sensor surface were sensitively detected using the optical technique of frustrated total internalreflection (f-TIR). RESULT: A calibration function measured in 100%human plasma using our integrated test demonstrates a limit of detection (mean of blank plus 3 SD) of 0.03 ng/mL (1 pM) cTnI for a turn-around time of approximately 5 minutes. A linear regression analysis of the region 0.03-6.5 ng/mL yields a slope of 37 ± 4, intercept of 0.22±0.01 and linear correlation coefficient of R2=0.98. The measuring range could be extended substantially, to 100 ng/mL, by simultaneously imaging a second spot with lower capture antibody concentration. CONCLUSION: The combination of magnetic particles and their actuation with electromagnets permits the sensitive detection of cTnIto be performed rapidly. Because of the speed, ease-of-use and highanalytical sensitivity of the test, it is well suited for demandingpoint-of-care medical diagnostic applications.