Optical Fiber-Based Localized Surface Plasmon Resonance Biosensor Using Gold Nanorods Encapsulated in Graphene Oxide Nanocomposite Film Applied for Immunoassay

In this study, gold nanorods (GNRs) are immobilized on the surface of fiber probe using a self-assembly method for a localized surface plasmon resonance (LSPR)-based optical fiber biosensor. In order to promote the performances of GNRs films, graphene oxide (GO) is used to encapsulate GNRs, which forms the GNRs@GO structure. Furthermore, the GNRs and GNRs@GO fiber probes are used to detect different refractive indices of surrounding environments from 1.33 to 1.38. The results show that the GNRs fiber probes have the sensitivity of 48 nm/RIU with the linearity of ${R}^{{2}}$ = 0.988. By comparison, for GNRs@GO with 0.2 mg/mL of GO fiber probe, the sensitivity is increased to 218 nm/RIU, and the linearity is improved to ${R}^{{2}}$ = 0.991. After that, anti-mouse IgG is immobilized on the GNRs and GNRs@GO fiber probes for immunoassay. The results show that the limit of detection (LOD) of GNRs fiber probe is 147.9 ng/mL, and the sensitivity is 26.5 nm/ $\mu \text{g}$ mL $^{-{1}}$ with the linearity of ${R}^{{2}}$ = 0.936 in the detecting range of 0.1– $0.5 \mu \text{g}$ /mL. By comparison, for GNRs@GO with 0.2 mg/mL of GO fiber probe, the LOD is improved to 32.7 ng/mL, and the sensitivity as well as the linearity are increased to 61.1 nm/ $\mu \text{g}$ mL $^{-{1}}$ and $R^{{2}}$ = 0.991, respectively. In addition, the optimal concentration of GO encapsulated with GNRs is 0.2 mg/mL, and the optimal response time is 20 min. The results also show that the GNRs@GO fiber probe has a good selectivity. Finally, the GNRs@GO structure shows the potential for applying in an optical fiber biosensor.