KLK3 and prostate cancer: For example, anSPR-based hybrid colorimetric and plasmonic sensor was employed todetect prostate-specific antigen (PSA), a biomarker for prostate cancer,achieving a LOD of 9 pg/mL. In this approach,triangular AuNPs conjugated with PSA-binding antibodies were reactedwith PSA molecules in the presence of magnetite nanoparticles coatedwith secondary antibodies.