AFP and cancer: Similarly, a U-shaped microfiber coated with Au@WS2 nanosheets achieved one of the lowest recorded detection limits, 3.07 × 10−27 M, for alpha-fetoprotein (AFP), enabled by synergistic plasmonic enhancement and an increased binding surface area [77], as shown in Figure 5D. These studies, spanning diverse targets from cancer biomarkers to environmental nanoparticles, establish optical microfiber systems as highly tunable and scalable platforms for single-molecule applications.