Abstract
This study investigates a fiber-optic biosensor based on a tilted fiber Bragg grating (TFBG) partially-coated with a thin gold film on its axis and around its cross-section. The effects induced in the TFBG transmitted amplitude spectrum were analyzed for different input light directions for surrounding refractive index (SRI) changes in the range 1.3356 – 1.3370. Partially-coated gratings present the potential ability to sense both volume and surface refractive index changes, which is interesting in biosensing to enhance the signal-to-noise ratio. The gold film was bio-functionalized by human epidermal growth factor receptor (HER2) aptamers using thiol chemistry. The detection of HER2 proteins (a relevant cancer biomarker) at 10-9 g/mL, 10-8 g/mL and 10-6 g/mL demonstrated the advantage to identify environmental perturbations through the bare area of the TFBG. The non-specific drifts that could exist in samples are eliminated and a wavelength shift only related to the surface modification is obtained.
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