Continuous immunosensing of myoglobin in human serum as potential companion diagnostics technique

To attain early diagnosis of acute myocardial infarction (AMI) with enhanced accuracy, continuous immunosensing has been investigated to measure myoglobin concentration in real-time. To this end, a capture antibody showing rapid reaction kinetics was immobilized on the surface of a surface plasmon resonance sensor. Three problems associated with the continuous sensing of myoglobin in human serum needed to be overcome: non-specific binding of the analyte, aggregation of serum components, and drift of the sensor baseline. Non-specific binding was controlled by pretreating the sample with a detergent mixture consisting of sodium dodecyl sulfate and P20, and adjusting the micelle size and net charge. Aggregation was managed by inactivating certain serum constituents through chelation of heavy metals. Baseline drift perceived in the sensorgram was able to be corrected by compensating for the slope calculated by a linear regression. Under the optimal conditions, the continuous sensor reproducibly traced the varying doses of myoglobin over about 8h with periodic one-point calibration every 3h. The dose-response curve of the sensor was linear with acceptable variations (CVs<4.91% in average) between the detection limit (31.0 ng/mL) and about 2000 ng/mL in the arithmetic scale (R(2)>0.98), covering the clinical concentration range. The immunosensor performance correlated with the Pathfast reference system (R(2)>0.98) and analytical consistency could be maintained for longer than a month if appropriately calibrated. Such immunosensing could be used as a companion diagnostic means along with real-time electrocardiographic measurement, significantly enhancing the sensitivity of AMI diagnosis and thereby enabling treatment at an early stage.