Feng et al. combined SERS tags, magnetic supports, and target antigens in a sandwich structure to achieve highly selective and highly sensitive recognition and quantification (in the range of 0.1 ng/mL to 1.0 mg/mL) of human carboxylesterase 1 (hCE1), which is a serum marker for early diagnosis of hepatocellular carcinoma, a common and potentially fatal form of liver cancer. Here, CES1 is linked to liver cancer.