The sensitivitywas obtained by tracking the most sensitive mode of the spectrum.The surface of the TFBG–ball resonator served as a platformfor immobilizing the sHER2-specific antibody Trastuzumab and evaluatingits performance for the detection of the breast cancer biomarker HER2.The immobilization of the antibody was achieved by silane couplingsurface chemistry. Here, ERBB2 is linked to breast cancer.