Sensitive DNA biosensor based on a long-period grating formed on the side-polished fiber surface.

We demonstrate a sensitive DNA biosensor based on a long period grating (LPG) formed by a photolithograph process on the surface of a side-polished fiber. The biomolecules of the biosensor were immobilized on the silica surface between LPG patterns. The resonance wavelength was red-shifted after the binding of the poly-L-lysine, probe ssDNA and target ssDNA to the sensor surface. The overall wavelength shift after the successful DNA hybridization was 1.82 nm. The proposed LPG-based DNA biosensor is approximately 2.5 times more sensitive than the previously reported fiber grating-based DNA biosensors.