Optical fiber immunosensor based on nanobody for the detection of carcinoembryonic antigen

We engineered two highly specific, label-free optical fiber immunosensors incorporating innovative nanobodies as biological probes. These sensors, named the graphene oxide (GO) immunosensor and gold nanoparticles (GNP) immunosensor, leverage GO and GNP as bio-sensitive materials for the unlabeled detection of carcinoembryonic antigen (CEA). By employing a layer-by-layer self-assembly technique, we precisely coated the sensitive material onto the optical fiber microstructure, subsequently adsorbing nanobodies onto the coated surface. The detection mechanism hinges on monitoring refractive index changes induced by CEA adsorption onto nanobodies, distinguishing them from changes induced by other analytes. Experimental results showcase the sensitivities of the GO immunosensor and GNP immunosensor at 15.1 nm/nM and 20.2 nm/nM, respectively, with corresponding lower detection limits of 0.05 nM and 0.02 nM. Notably, both biosensors exhibit outstanding specificity, operate label-free, and enable rapid detection of low concentrations of CEA. This proposed optical immunosensor holds significant promise as a biophotonic platform for clinical diagnostics, offering advancements in medical applications.