An Optical Immunosensor Based on Surface Plasmon Resonance for Human cTnI Determination

Human cardiac troponin I (cTnl) is a specific protein of cardiac muscle. The detection of the content of cTnl in human serum shows high specificity for diagnosing acute myocardial infarction. For preparation of diagnostic reagents of myocardial infarction, cTnl is isolated directly from human cardiac muscle by skeletal TnC-sepharose 4B affinity chromatographic column. The molecular weight and the amino acid composition of isolated cTnl is consistent with reference. A novel optical biosensor based on simultaneous multiwave-length detected surface plasmon resonance (SPR) has been developed for monitoring cTnl. The sensor is designed on the basis of fixing angle of incidence and measuring the reflected intensities in the wavelength range of 400-800 nm. The SPR spectra are shown in terms of reflected light intensity verus wavelength of incident light. The intensity of the reflected light is the minimum at the resonant wavelength. Molecular self-assembling in solution is used to form the sensing membrane on the gold substrate. The processes of sensing monolayer formation were studied in real time through observing the change of resonant wavelength. The modified surface was used as a model immunosensor and successfully detected cTnl. cTnC was detected in the concentration range from 0.143 ~ 50 mug/mL. Under optimum experimental conditions, the sensor has a good repeatability, reversibility and selectivity.