An optical immunosensor employing a composite sensitive membrane and nanobody as a sensing probe for detecting carcinoembryonic antigen

We present an S-tapered fiber (STF) immunosensor featuring a gold nanoparticle/graphene oxide (GNP/GO) composite membrane for specific and label-free detection of carcinoembryonic antigen (CEA). Through spectral monitoring and calculation, we have developed a highly specific and sensitive immunosensor with a sensitivity of 27.9 nm/nM (R2 = 0.996) and a detection limit of 0.01 nM. Moreover, this biosensor demonstrates label-free operation and rapid detection of low concentrations of CEA. The proposed optical biosensor holds significant potential as a biophotonic platform for applications in clinical diagnostics, medical settings, and biomedical research.