Detection of Cardiac Biomarkers Using Micellar Electrokinetic Chromatography and a Cleavable Tag Immunoassay

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Abstract
Biomarkers provide clinicians with an important tool for disease assessment. Many different biomarkers have been discovered, but few of them suffice as stand-alone indicators for disease presence or prognosis. Because no single biomarker can be relied upon for accurate disease detection there has been a substantial push for new multianalyte screening methods. Furthermore, there is a need to push assays toward a point-of-care technology to reduce the time between clinical analysis and medical intervention and minimize artifacts created during sample storage. There currently are, however, few inexpensive multianalyte methods for disease detection that can function in a point-of-care setting. A new approach which bridges the gap between traditional immunoassays and high-density microarrays by utilizing microfluidics, immunoassays, and micellar electrokinetic chromatography (MEKC) is discussed here. This chemistry, the cleavable tag immunoassay (CTI), is a low- to medium-density heterogeneous immunoassay designed to detect 1-20 analytes simultaneously. Although similar to traditional sandwich immunoassays, this approach is unique because the signal is not imaged on the surface; instead, a fluorescent tag is chemically cleaved from the antibody and analyzed by microchip MEKC. In this report, the CTI chemistry is used for the detection of four cardiac biomarkers elevated in acute myocardial infarction. Limit of detection (LOD) and dynamic range are reported for all biomarkers with LODs on the order of low nanograms per milliliter to low picograms per milliliter. Most importantly, the dynamic range for each of the biomarkers spans the boundary between normal and elevated levels. Finally, elevated marker levels were measured in spiked human serum samples.