Rapid and Sensitive Detection of Liver Cancer Markers Based on a Microtapered Long-Period Grating Sensor Coated With Gold Nanorods

Hepatocellular carcinoma (HCC) ranks among the top three cancers in terms of both incidence and mortality. Detection of early liver cancer markers is significant in liver cancer treatment. A stable, label-free, and sensitive microtapered long-period fiber grating (mTLPG) sensor coated with functionalized gold nanorods is proposed to detect early liver cancer marker alpha-fetoprotein (AFP). 3-Mercaptopropyltrimethoxysilane (MPTMS) is used to immobilize the gold nanorods (GNRs) on the surface of an optical fiber, and monoclonal antibodies (mAbs) are further immobilized on the GNRs via covalent bonds to construct a biosensor with localized surface plasmon resonance (LSPR) effect. Due to the antigen-antibody interaction, the thickness and density of the biological overlayer increase following the immune response. The change in the resonance wavelength of the mTLPG transmission spectrum is used to detect the AFP. The results show that the proposed sensor is specific and sensitive for the measurement of AFP, showing a linear response over the concentration range of alpha-fetoprotein (human spp.) antigens from 10-400 ng/ml, with a sensitivity of 3 pm/(ng/mL) and a limit of detection of about 17.6 ng/mL. The proposed sensor has a short detection time of about 3 minutes, a simple antibody immobilization method, and prospects for low-cost large-scale production. The biosensor has a promising application in the field of medical diagnosis.