Temperature-Compensated Fabry–Perot Fiber-Optic Microcavity Biosensor for the Detection of Label-Free Deafness Gene DNA

A fiber-optic DNA biosensor with temperature compensation for the specific detection of label-free deafness gene is proposed and demonstrated. The biosensor is fabricated by splicing a section of exposed-core microstructure fiber (ECF) between two single-mode fibers (SMFs) to form an optical fiber microcavity Fabry-Perot interferometer (FPI). The ECF eliminates the temperature cross-sensitivity and improves the sensitivity of the sensor. In this study, a sensitive film layer is prepared by coating poly-L-lysine (PLL) on the surface of the sensor. The probe DNA (pDNA) is immobilized on the surface by layer-by-layer assembly. The sensor can detect local refractive index (RI) changes that occur on the surface of the fiber due to the specific binding of complementary DNA (cDNA) to pDNA. Therefore, the sensor can achieve high sensitivity and high selectivity detection of cDNA. Experimental results show that the sensor can detect cDNA concentrations as low as $1~\mu $ M by demodulating the phase change of the interference spectrum. The proposed fiber-optic DNA biosensor has the ability to label free, selective, and real-time detection, and has broad application prospects in the fields of medical diagnosis, cancer screening, and environmental science.