Functionalized etched tilted fiber Bragg grating aptasensor for label-free protein detection.

An aptasensor based on etched tilted fiber Bragg grating (eTFBG) is developed on a single-mode optical fiber targeting biomolecule detection. TFBGs were chemically etched using hydrofluoric acid (HF) to partially remove the fiber cladding. The sensor response was coarsely interrogated, resulting on a sensitivity increase from 1.25 nm/RIU (refractive index unit) at the beginning of the process, up to 23.38 nm/RIU at the end of the etching, for a RI range from 1.3418 to 1.4419 RIU. The proposed aptasensor showed improved RI sensitivity as compared to the unetched TFBG, without requiring metal depositions on the fiber surface or polarization control during the measurements. The proposed sensor was tested for the detection of thrombin-aptamer interactions based on silane-coupling surface chemistry, with thrombin concentrations ranging from 2.5 to 40 nM. Functionalized eTFBGs provided a competitive platform for biochemical interaction measurements, showing sensitivity values ranging from 2.3 to 3.3 p.m./nM for the particular case of thrombin detection.