Mixed self-assembled monolayer (mSAM) based impedimetric immunosensors for cardiac troponin I (cTnI) and soluble lectin-like oxidized low-density lipoprotein receptor-1 (sLOX-1)

Immunosensors depend on the specificity of the molecular recognition towards analytes of interest provided by the antibodies. In this study, electrochemical impedance spectroscopy (EIS) was used to monitor the sensor surface assembly and recognition of two different analytes of cardiac pathology, cardiac troponin I (cTnI) and soluble lectin-like oxidized LDL receptor-1 (sLOX-1) on surfaces based on mixed self-assembled monolayers onto gold electrodes. The specificity and longer persistence of cTnI serves as a definitive biomarker in the diagnosis of acute myocardial infarction (AMI). Circulating levels of sLOX-1 serve as a marker for plaque instability or rupture before an AMI becomes apparent and facilitates early diagnosis of acute coronary syndrome (ACS). The immunosensors were highly specific, since a clinically relevant range of analyte concentrations was successfully detected in phosphate buffered saline and in serum with virtually no alteration to the slope of the calibration curve. Detection limits for cTnI and sLOX-1 immunosensors were at least 10−13 M for each analyte. Atomic force microscopy studies were carried out to study each step of fabrication to elucidate the binding characteristics and surface nanotopography of the mSAM based immunosensors.