AFP and cancer: SERS‐active substrate and probe were generally prepared by Au and Ag NPs that showed outstanding SERS properties due to their exceptional LSPR effect.[178] Important cancer biomarkers like prostate‐specific antigen, carcinoembryonic antigen (CEA), mucoprotein1 (mucin‐1), and alpha‐fetoprotein (AFP) were detected successfully by using SERS‐based immunoassays.[179] α‐Fetoprotein or AFP was not only a key biomarker for the diagnosis of hepatocellular carcinoma but was also found to be vital in hepatectomy, chemotherapy, and liver transplantation prognosis.