Cardiac Biomarker Immunosensor Using Harmonic Optical Micro-fiber Bragg Grating

Sudden onset,high fatality,multiple complications make acute myocardial infarction(AMI)a critical and risky disease worldwide.When AMI attacks a patient,specific cardiac biomarkers,for example,the cardiac troponin I(cTn-I),would be dissociated in the patient’s blood.There will be specific cardiac biomarkers free in the patient’s blood,for example,the cardiac troponin I(cTn-I).Precise and short-term test of the cardiac biomarkers is essential for the definite diagnosis and the patient rescue.Fiber-optic biosensors are a promising candidate due to their fast response,high sensitivity,biocompatibility,small and flexible structure,enabling the potential of point of care testing(POCT)for cardiac marker detection.However,the temperature crosssensitivity in the optical fiber sensor significantly handicaps the precise test results.It is thereby urgently tempting to find suitable solutions to eliminate the temperature cross-talk in the test.To address the issue,we proposed a new type of fiber sensing device named harmonic optical microfiber Bragg grating(H-m FBG).By investigating the impact of the UV Talbot pattern on the core of the fiber,the third harmonic resonance in 1030nm-wave-band was achieved in the microfiber for the first time.An ultra-short time(<10 seconds)UV irradiation can result in a third harmonic resonance which is stronger than 12 d B.The third harmonic resonance presents a distinct RI sensitivity but a considerably similar temperature sensitivity,in contrast with the Bragg resonance attributed to the second harmonic standing wave.Thus,simultaneous measurement of RI and temperature can be achieved by simply interrogating the wavelength shifts of the two resonances and solving the analytical matrix.The proposed method represents a new way to overcome temperature cross-sensitivity in microfiber Bragg grating refractive index sensors.Furthermore,we have proposed and demonstrated a harmonic microfiber grating mediated immunosensor for the determination of cTn-I.The covalent bonding method was adopted to enable a stable surface functional configuration.Based on the immunoadsorption of the target antigen,the change of surface refractive index caused by the molecule-binding is transduced into the spectral drift of the grating reflection signal.The H-m FBG orchestrates the harmonic reflections to eliminate the temperature crosstalk,and obtain the absolute immuno-adsorption response of the target antigen.The limit of detection(LOD)of this H-m FBG immunosensor could reach 13.5 ng/m L.More importantly,we can simulate the in-vivo detection by adjusting the temperature to the human body temperature(37 ℃),in which the maximum activities of the proteins was be spurred.The response rate was significantly elevated due to the strengthening of the enzymatic activity,facilitating the acceleration of the cardiac biomarker test.The demonstration and scientific findings in this work provide guidance for future attempts to achieve fast and in-vivo tests for acute cardiac disease.