An interferometric optical fiber biosensor with high sensitivity for IgG/anti-IgG immunosensing

An immunosensor with low detection limit for detecting human-IgG (IgG, immunoglobulin G) is presented in this work. The sensor was designed using single mode fiber with large core-offset fusion splice based on Mach-Zehnder interferometer (MZI). The refractive index (RI) sensitivity is as high as 13936 nm/RIU in the RI range of 1.3328-1.3398, and the resolution of 1.44×10−6 is obtained. Afterwards, the sensing surface was immobilized with staphylococcal protein A and goat anti-human IgG to detect different concentrations of human-IgG, and a low detection limit of 47 ng/ml was observed. The proposed immunosensor has advantages of far simpler fabrication, high sensitivity, low detection limit, reusability and have promising potential for detecting small refractive index change in biological samples and application in biomedical field.