Sensitive and real-time fiber-optic-based surface plasmon resonance sensors for myoglobin and cardiac troponin I

A sensor to detect markers of cardiac muscle cell death at less than 3 ng ml−1 and in less than 10 min has been achieved. This fiber-optic-based surface plasmon resonance (SPR) sensor is being applied to detect myoglobin (MG) and cardiac troponin I (cTnI) in HEPES buffered saline solution. An in vivo sensor for the early detection of the onset of myocardial infarction (MI) will greatly enhance the patient care. MG and cTnI are two biological markers released from dying cardiac muscle cells during an MI, and their detection at biologically-relevant levels can be diagnostic of MI. Antibodies specific to an antigen of interest are attached to a carboxymethylated dextran layer on a gold SPR surface. With the method developed, the lower limit of detection (LOD) for MG is 2.9 ng ml−1 at 25 °C. The biological level for MG reaches 15–30 ng ml−1 in patient blood after myocardial damage. A Langmuir adsorption isotherm describes the binding well. For cTnI, a lower detection limit of 1.4 ng ml−1 was achieved in preliminary tests. cTnI levels are in the range of 1–3 ng ml−1 in patient blood after myocardial damage. The antibody reaction with the carboxymethylated dextran surface was optimized by modifying the reaction pH, the temperature, and the dextran chain length.