Graphene oxide-functionalized long period grating for biosensing applications

The work presents the design and fabrication of a fiber optic biosensor based on a Long Period Grating (LPG) with multi-layer coating. An LPG working in single-ended configuration was developed, which is very convenient in biological applications. The transducer was optimized in terms of sensitivity by means of a nanometric layer of Polycarbonate, casted by dip coating technique, which was designed to favorite cladding mode transition. Subsequently, a Graphene Oxide thin film was selected as outer layer, which provides an excellent bio-functionalization of the sensor surface due to its carboxylic functional groups. The performance of the sensor was tested towards the detection of the well assessed binding process of biotin to streptavidin. As a result, the detection of biotinylated Bovine Serum Albumin (bBSA) in phosphate buffer solution was achieved at very low concentrations in the atto-molar range.