KLK3 and prostate cancer: Several SERS biosensors have been investigated for multiplexed detection of prostate cancer biomarkers, including a silver-nanoparticle-based sensor for the detection of PSA, PSMA, hK2 (Human kallikrein 2) [164], core-shell SERS nanotags [165], and gold nanorod SERS nanotags [166] for the detection of PSA, CEA (carcinoembryonic antigen), and AFP (alpha fetoprotein).