An enhanced SPR optical fiber biosensor using Ti₃C₂T MXene/AuNPs for label-free and sensitive detection of human IgG

Abnormal human immunoglobulin G (IgG) may induce the risk of immune system disorder, infectious diseases, tumors and so on. However, the current detection methods exhibit low sensitivity, which limits their practical application. In this work, an SPR optical fiber sensor (SPR-OFS) with high sensitivity is designed for label-free detection of human IgG. It is fabricated using a heterostructure optical fiber coated with Au film/AuNPs and the Ti₃C₂T MXene biofunctionalized with goat anti-human IgG by polydopamine (PDA). In the experiment, the optimal thickness of the Ti₃C₂T MXene was explored and determined to be about 93 nm by comprehensively considering the refractive index (RI) sensitivity and spectral bandwidth of the SPR sensor. When the largest figure of merit (FOM) is calculated to be 17.8279 RIU^-1, its RI sensitivity was ultimately found to be 2804.5 nm per RIU. The SPR-OFS was employed to detect human IgG within the concentration range of 0-30 μg mL^-1 and its sensitivity is demonstrated to be 1.7046 nm (μg mL^-1)^-1. The SPR-OFS was also proved to have excellent linearity, specificity and stability. The proposed sensor offers outstanding performance with simple fabrication, providing a cutting-edge bioanalytical platform with potential applications in clinical diagnosis.