Rapid and sensitive detection of cardiac troponin I using a force enhanced immunoassay with nanoporous membrane

There is a need for point of care diagnostic technologies that are rapid, sensitive, easy to use, and relatively inexpensive. In this article we describe an assay that uses an antibody functionalized nanoporous membrane and superparamagnetic beads to capture and detect human cardiac troponin I (cTnI), which is an important biomarker for acute myocardial infarction (AMI). The membrane assisted force differentiation assay (mFDA) is capable of detecting cTnI at a sensitivity of 0.1 pg ml −1 in 15% serum in less than 16 minutes, which is a significant improvement in performance over conventional lateral flow immuosorbant assays. The speed of this assay results from the rapid concentration of cTnI on the surface of the nanoporous membrane and the use of the magnetic beads to react with the analyte, which rapidly react with the immobilized cTnI. The increased sensitivity of assay results from the use of magnetically controlled forces that reduce the nonspecific background and modify both the on-rate and off-rate. We believe that the improved performance and ease of application of the mFDA will make it useful in the early identification of AMI as well as other diseases based on the detection of 1 pg ml −1 variations in the concentrations cTnI in blood. Schematic of the loading of superparamagnetic beads (red spheres) into a nanoporous membrane (orange membrane) in a lab on a chip device with window (on top) for the rapid and ultrasensitive detection of cardiac troponin I.