In-situ DNA hybridization detection with a reflective microfiber grating biosensor

A label-free fiber-optic biosensor with a reflective microfiber Bragg grating (mFBG) configuration for in-situ DNA hybridization detection has been proposed and experimentally demonstrated. A single straight Bragg grating inscribed in the silica microfiber provides two well-defined resonances in reflection, which show different response to external medium refractive index (RI) and present the same temperature sensitivity. By monitoring the wavelength separation between these two resonances, temperature-compensated RI measurement has been achieved. The label-free bio-recognition scheme used demonstrates that the sensor relies on the surface functionalization of a monolayer of poly-l-lysine (PLL), synthetic DNA sequences that bind with high specificity to a given target. In addition to monitoring the surface functionalization of the fiber in real-time, the results also show how the fiber biosensor can detect the presence of the DNA hybridization with high specificity, in various concentration of target DNA solutions, with lowest detectable concentration of 0.5 µM.