Label-Free Immunosensor Based on Optical Fiber Fabry–Perot Interferometer

A label-free immunosensor based on optical fiber Fabry-Perot interferometer (FPI) is proposed. The FPI is fabricated by splicing both ends of a short section of hollow-core photonic crystal fiber to single mode fibers (SMFs) and cleaving the SMF pigtail to proper length. Then, the end surface of sensor is silanization modified and immobilized with goat anti-rabbit immunoglobulin G (IgG) by covalent binding to detect the specific rabbit IgG. The antibody immobilization and antigen binding will change the thickness of sensing layer, leading to the interference spectrum change of the FPI sensor. The responses of the sensor to immune reaction are analyzed theoretically and demonstrated experimentally. Results show that after antibody immobilization, the wavelength increases by 60 pm and the fringe contrast decreases by about 1 dB. And for antigen binding, the wavelength shows an obvious increase by 190 pm and the fringe contrast decreases by 2.15 dB. The wavelength shift during the antibody-antigen binding process conforms to the immune reaction kinetics. With the advantages of compact structure, good performance, capacity for real-time and label-free detection, easy fabrication, and low cost, the proposed optical fiber FPI sensor shows wide application prospect in label-free immunosensing.