Label-free Fiber Optical Immunosensor For Detection On Cardiac Biomarkers

Acute myocardial infarction（AMI）is a major disease that endangers human health seriously with characteristic of rapid onset,high fatality rate and complications and no effective prevention and control means so far.Peripheral blood myocardial marker detection is helpful for early screening and prevention of cardiovascular disease.As myocardial injury occurs,for example,due to myocardial cell necrosis type cardiac troponin I（cTn-I）released into the blood,concentration measurement on such biomarker can provide important scientific basis for the diagnosis of myocardial diseases.However,the diagnostic threshold of the biomarker in the blood is extremely low,and the requirement of detection sensitivity is very high.At the same time,the blood environment is complex and contains a variety of biochemical components,so it is necessary to accurately identify the biomarker among numerous biomolecules.In view of the above requirements,we propose a kind of optical biosensor of cTn-I immune detection technology using the phase-shifted Bragg grating inscribed into micro-nano optical fibers.The high sensitivity was obtained by reducing the diameter of the fiber for enhancing the effect of the evanescent field.The limit-of-detection（LOD）on bulk refractive index is as low as 1.1×10^-4 RIU by use of the narrow band notch in reflection which is induced by the phase shift in the grating structure.By means of electrostatic self-assembly,the immobilization of the cTn-I antibody on the fiber surface have been achieved for the device functionalization.Based on the immuno-adsorption of the target antigen,the change of surface refractive index caused by the molecule-binding is transduced into the spectral variation of grating reflection signal.The results show that the sensor can realize the detection within the concentration range of 0.03¹00 ng/mL.In that range,the concentration of cTn-I between 0.1 and 10 ng/mL and the wavelength shift are consistent with the log linear change.The detection limit（LOD）can reach 10.8 pg/mL which meet the need for the detection of myocardial injury markers in early heart failure.We further,through the results in the nonspecific serum and complex environment experiment contrast,validate the biosensor achieve cTn-I specific recognition and complete biomarkers detection in human serum samples.We proposed the phase shift on micro-nano optical fiber grating biosensor with advantages of high sensitivity,low sample size requirements,short cycle time,portable,simple operation and Internet compatibility which provides powerful technical means for the rapid diagnosis and early prevention and control of cardiovascular diseases in this paper.It has great potential in the field of real-time detection,diagnosis of critical diseases（POCT/D）and will be the next generation of smart medical treatment.