Femtosecond-Pulsed Laser Written and Etched Fiber Bragg Gratings for Fiber-Optical Biosensing

Abstract

We present the development of a label-free, highly sensitive fiber-optical biosensor for online detection and quantification of biomolecules. Here, the advantages of etched fiber Bragg gratings (eFBG) were used, since they induce a narrowband Bragg wavelength peak in the reflection operation mode. The gratings were fabricated point-by-point via a nonlinear absorption process of a highly focused femtosecond-pulsed laser, without the need of prior coating removal or specific fiber doping. The sensitivity of the Bragg wavelength peak to the surrounding refractive index (SRI), as needed for biochemical sensing, was realized by fiber cladding removal using hydrofluoric acid etching. For evaluation of biosensing capabilities, eFBG fibers were biofunctionalized with a single-stranded DNA aptamer specific for binding the C-reactive protein (CRP). Thus, the CRP-sensitive eFBG fiber-optical biosensor showed a very low limit of detection of 0.82 pg/L, with a dynamic range of CRP detection from approximately 0.8 pg/L to 1.2 µg/L. The biosensor showed a high specificity to CRP even in the presence of interfering substances. These results suggest that the proposed biosensor is capable for quantification of CRP from trace amounts of clinical samples. In addition, the adaption of this eFBG fiber-optical biosensor for detection of other relevant analytes can be easily realized.

Long period grating in double cladding fiber coated with graphene oxide as high-performance optical platform for biosensing

“…Despite a slightly larger standard deviation ( 0.042 nm for LPG-B and 0.037 nm for LPG-C) as expected from the spectral features of the resonance, a LOD of about 0.32 ng/mL and 0.15 ng/mL is attained with LPG-B and LPG-C, respectively, a value roughly 60-fold lower (LPG-C) than that reported in the literature using the same assay protocol based on the anti-CRP/CRP interaction, but making use of an optical transducer based on the SPR phenomenon ( Aray et al, 2016 ). While the LOD attained is not the lowest reported in the literature ( Schulze et al, 2018 ), it should be pointed out that the results here described have been achieved with a complex matrix of human serum and in repeated independent experiments, and the robustness and practical usage of the optical transducer could be a critical issue to consider in the case of extremely etched or very complicated in-fiber devices. Moreover, from Fig.…”

“…In 2015, an etched fiber Bragg grating (eFBG) coated with anti-CRP antibody - graphene oxide (GO) complex, was reported with a LOD of 0.01 μg/mL in serum ( Sridevi et al, 2015 ). More recently, with the same eFBG technology, a very low LOD of 0.82 fg/mL was obtained in modified buffer solution ( Schulze et al, 2018 ). Furthermore, the physical phenomenon of lossy mode resonance (LMR) has been applied for the detection of CRP, where an Indium Tin Oxide (ITO)-coated D-shaped fiber device attained a LOD of 0.0625 μg/mL in tri-buffer solution ( Zubiate et al, 2017 ).…”

Hybrid LPG-FBG Based High-Resolution Micro Bending Strain Sensor

“…The fiber core located at the outer 70% of the volume from the center of the fiber. A 1.54 cm pitch helical core was geometrically applied to the external strain as a basis for highly efficient dynamic modeling of the spiral spring element [64,65]. The Bragg grating formed an optical wave path designed as an extended period chirp grating, and the sub-short-period Bragg grating between the long-period grating and the grating was processed with a femtosecond laser.…”

Fiber optic biosensor for inflammatory markers based on long period grating

“…For example, a surface plasmon resonance device based on plastic optical fiber demonstrated a LOD of 9 ng/mL in serum [9], whereas the lossy mode resonance sensor based on indium tin oxide-coated D-shaped fiber from [10] attained a LOD of 62.5 ng/mL in tri-buffer solution. More recently, a 0.82 fg/mL limit of detection was obtained in buffer solution using an etched fiber Bragg grating [11].…”