Microfiber biosensor for detection of ultra-low concentration alpha-fetoprotein based on graphene oxide

Alpha-fetoprotein (AFP) is an important hepatocellular carcinoma (HCC) marker, however, its ultra-low concentration in the body of patient with early HCC makes it difficult to diagnose early HCC. In this paper, a microfiber biosensor on the basis of graphene oxide (GO) is proposed for the detection of ultra-low concentration AFP antigen. It is difficult to detect AFP antigen biomolecule solutions with ultra-low concentrations directly, because the variation in the concentration has a negligible impact on the refractive index (RI) of the entire solution. However, GO contains plenty of oxygen-containing groups and binding sites. Therefore, it will adsorb plenty of AFP antigen molecules, which will change the effective surround RI, and consequently, it makes the sensor achieve highly sensitive AFP antigen detection. The biosensor we proposed demonstrates high sensitivity of 1.11582 nm/lg (mol/L) in the linear range from 7 zg/mL to 7 pg/mL (R² = 0.99647). And the detection limit (LOD) of 78 zg/mL is ultra-low. The biosensor achieves detection of ultra-low concentration AFP antigen solution, which indicates exceptional potential prospects in early diagnosis of HCC.