A laser-induced graphene electrochemical immunosensor for label-free CEA monitoring in serum

The cost-effective construction of self-designed conductive graphene patterns is crucial to the fabrication of graphene-based electrochemical devices. Here, a label-free carcinoembryonic antigen (CEA) electrochemical immunosensor is developed based on the surface engineering of a laser-induced graphene (LIG)/Au electrode. The LIG electrode was produced with a smart and inexpensive 450 nm semiconductor laser through three electrode patterns under ambient conditions. Then the LIG/Au electrode was organized by conformal anchoring of Au nanoparticles (NPs) on the LIG work area using chloroauric acid as the precursor. Good electrochemical activity with improved conductivity of the LIG/Au electrode was obtained under optimized conditions of laser intensity, carving depth, and chlorogenic acid dosage, to name a few. The LIG/Au electrode was carbonylated based on Au-S∼COOH using 11-mercaptoundecanoic acid (MUA). The antibody was covalently bound on the work area to form a label-free immunosensor. The constructed immunosensor shows high sensitivity with a good response in the range of low concentrations from 0.01 to 100 ng mL^-1, low detection limit (5.0 pg mL^-1), high selectivity compared with some possible interference, and can be applied in a bovine serum solution without the need of sample labeling and pretreatment. Moreover, the immunosensor is mechanically flexible with minimal change in signal output after bending at different angles. It shows an easy and green electrode preparation method that combines 3D porous structures of graphene, uniform immobilization of Au NPs, binder-free, easy covalent binding of an antibody, and good mechanical properties. Hence, the present method has great potential for applications involving electrochemical biosensors.