Ultrasensitive cancer cell sensing based on tapered optical fiber operating near the dispersion turning point

Cancer cell screening is very important for its treatment and prognosis. The screening techniques are required with high sensitivity and specific recognition. Here, an ultrasensitive tapered optical fiber (TOF) biosensor for cancer cell sensing is proposed. The unique property of the dispersion turning point (DTP) in the TOF is utilized to greatly improve the sensing sensitivity. Combined with numerical calculations, the TOF with the extremely high refractive index (RI) sensitivity (close to 18390 nm/RIU) near the DTP is achieved by precisely controlling the diameter of the TOF. In addition, biotin is used to functionalize the TOF for specific recognition of the biotin-overexpressing cancer cells. The sensitivity and selectivity of the TOF were demonstrated by the detection of the biotin receptor protein (streptavidin) and overexpressed cancer cells (lung epithelial adenocarcinoma cells, A549). The experiment results show that the TOF has a low limit of detection (LOD) for streptavidin and cancer cells, which are 28.73 pM and 49 cells/mL respectively. At the same time, the TOF showed the obvious response to another biotin-overexpressed cancer cell (breast cancer cells, 4T1), but is insensitive to normal cells (gastric mucosa cells, GES-1 and mouse epithelioid fibroblasts cells, L929). We believe that the proposed biosensor which exhibited extremely high sensitivity and good selectivity, will have potential application prospects in the field of chemical and biological detection.