Label Free hCG Concentration Biosensor Based on Suspension Core Fiber Microfluidic Technology

In this paper, a microfluidic sensor based on suspended core fiber (SCF) for detecting the concentration of human chorionic gonadotropin (hCG) has been presented and experimentally demonstrated. The sensor is made by splicing SCF between two sections of drawn-tapered single-mode fiber (SMF). The SCF is a multimode fiber that supports multi-mode optical transmission and generates mode interference in the fiber core. The air holes in the SCF can also be used as microcirculation channels for the sensor, enhancing the interaction between the detection sample and the light field and improving the refractive index (RI) sensitivity. Due to the closed microchannels, the sensor has good anti-interference and stability, can effectively prevent biological pollution. The sensitivity of RI is 1848 nm/RIU in the RI range of 1.3335-1.3419. The sensor can also detect local RI changes on the fiber surface due to biomolecule binding. The hCG antigen can specifically bind to the hCG-β antibody. The hCG-β antibody is immobilized in the air holes of the SCF to specifically detect the concentration of hCG. Experimental results showed that the sensor can specifically detect hCG concentration with a sensitivity of 1.888 nm/(mIU/ml) and a detection limit of 0.049 mIU/ml at a temperature of 25 °C. This sensor has good specificity and potential applications in medical diagnostics, drug testing, and tumor screening.