As shown in Fig. 15(a), Lee et al. showed a multiplex biosensor for cancer biomarker detection based on the resonance shift of the LSPR single gold nanoparticles (AuNPs); the selective sensing results with LODs of 91 fM, 94 fM, and 10 fM for the α-fetoprotein (AFP), carcinoembryonic antigen (CEA), and prostate specific antigen (PSA) analytes, respectively, are reported by antibody–antigen binding.43 The gene discussed is KLK3; the disease is cancer.