Background: We present a prototype handheld device based on a newly developed optomagnetic technology for the sensitive detection of cardiac troponin I (cTnI) in a finger-prick blood sample with a turnaround time of 5 min.
Methods: The test was completed in a compact plastic disposable with on-board dry reagents and superparamagnetic nanoparticles. In our one-step assay, all reaction processes were precisely controlled using electromagnets positioned above and below the disposable. Nanoparticle labels (500 nm) bound to the sensor surface via a sandwich immunoassay were detected using the optical technique of frustrated total internal reflection.
Results: A calibration function measured in plasma demonstrates a limit of detection (mean of blank plus 3-fold the standard deviation) of 0.03 ng/mL cTnI. A linear regression analysis of the region 0.03-6.5 ng/mL yields a slope of 37+/-4, and a 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 a lower antibody concentration.
Conclusions: The combination of magnetic particles and their fine actuation with electromagnets permits the rapid and sensitive detection of cTnI. Because of the potential high analytical performance and ease-of-use of the test, it is well suited for demanding point-of-care diagnostic applications.
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