SERS-based sandwich immunoassay with antibody coated magnetic nanoparticles have been applied in the detection of IgG (LOD 1–10 ng/mL) [46], lung cancer marker carcinoembryonic antigen (CEA, LOD 1–10 pg/mL) [45], Escherichia coli (LOD 8 cfu/mL, cfu represents colony-forming units) [47], etc. we also developed a magnetic immunosensor based on SERS spectroscopy to detect intact but inactivated influenza virus H3N2 (A/Shanghai/4084T/2012). Here, CEACAM5 is linked to lung carcinoma.