Ultra-low limit of detection of a carcinoembryonic antigen fiber sensor based on microfiber

Fiber optic sensors have been widely applied to address issues such as cardiovascular diseases, pathogen detection, and cancer biomarker detection. In this work, an ultra-low limit of detection, high-specificity, and label-free optical fiber biosensor for the detection of carcinoembryonic antigen (CEA) was proposed and experimentally demonstrated. A microfiber interferometer with refractive index sensitivity of up to 1915.955 nm/RIU was employed as the sensor head. The sensitivity of the sensor was further enhanced by the incorporation of molybdenum disulfide (MoS₂), which facilitated the immobilization of CEA antibodies as specific detection markers on the microfiber surface. Experimental results showed that the proposed sensor achieved a detection limit of 15.86 fg/mL. The sensitivity of the biosensor was 4.727 nm/log(mg/mL). Notably, this biosensor demonstrated excellent specificity and label-free operation and enabled the detection of low-concentration CEA in approximately 15 minutes. The proposed micro fiber CEA sensor provided a highly sensitive and low-cost method for the early diagnosis of cancer.