Ultrasensitive deafness gene DNA hybridization detection employing a fiber optic Mach-Zehnder interferometer: Enabled by a black phosphorus nanointerface.

The rapid and efficient detection of deafness gene DNA plays an important role in the clinical diagnosis of deafness diseases. This study demonstrates the ultrasensitive detection of complementary DNA (cDNA) by employing a nanointerface-sensitized fiber optic biosensor. The sensor consists of SMF-TNCF-MMF-SMF (abbreviated as STMS) structure with lateral offset. Besides, it is functionalized with a nanointerface of black phosphorus (BP) to enhance the light-matter interaction and eventually improve the sensing performances. Relying on this nanointerface-sensitized sensor, we successfully realize the in-situ detection of cDNA at concentrations ranging from 1 pM to 1 μM, with a sensitivity of 0.719 nm/lgM. The limit of detection (LOD) is as low as 0.24 pM, which is at least two orders of magnitude lower than those of existing methods. The sensor exhibits the advantages of simple operation, fast response, label-free measurement, excellent repeatability, and high selectivity. Our contribution suggests a convenient approach for deafness gene DNA detection and can be extended for general ultra-low concentration DNA detection applications.