Label-free wavelength and phase detection based SMS fiber immunosensors optimized with cladding etching

Abstract

The performance of E-SMS (Etched Singlemode-Multimode-Singlemode) optical fiber structures as immunosensors has been assessed by the implementation of antibody/antigen immunoassays. Through this procedure it has been proven that E-SMS structures are effective and suitable optical platforms for label-free biosensing. Using the phase shift and tracking the wavelength response it was found that the fabricated E-SMS devices exhibited limits of detection (LOD) down up to concentrations of 0.2 mg/L of antigens in solution. This was achieved by coating the E-SMS with an antibody-based biolayer (goat IgG) that is able to determine the presence of anti-goat IgG antigen. Both a wavelength detection and a fast Fourier transform (FFT) analysis technique were used to perform this analysis. The FFT method showed similar results to those observed with the most traditional wavelength analysis, but with the advantage of a simpler detection system that makes unnecessary the use of sophisticated optical interrogators.

Optical Fiber Immunosensors Optimized with Cladding Etching and ITO Nanodeposition

“…Following the protocol indicated in [4], the IgGanti-IgG interaction was measured by increasing the anti-IgG concentration of the testing solution with rinsing stages of the biosensor using PBS solution in between. The PBS rinse stage was used to establish the baseline associated to each increasing anti-goat IgG concentration and to remove the unbound antibodies from the previous solution.…”

“…The biolayer was composed of a film of IgGs from goat serum (Sigma Aldrich I9140) with a concentration of 11.4 mg/mL. The deposition procedure, solution concentrations, and times involved are detailed in [4]. Fig 1 (b) illustrates the wavelength shift as a function of the external refractive index, which allows calculating the sensitivity.…”

“…In addition, the deposition of a thin film with high refractive index strengthens the interaction with the environment surroundings [3]. The feasibility of Etched SMS (E-SMS) structures as biosensors has been proven recently [4]. The etched structure was able to detect the bound of anti-IgGs to the IgG-based biolayer.…”

Optical Biomedical Diagnostics Using Lab-on-Fiber Technology: A Review

“…The biosensing using these structures can be achieved by immobilizing target-specific sensing medium over the special optical fiber region. Another transmission type FOI has been reported by merging two SMFs and one MMF [72]. Here, the MMF was used as a cavity for interference process.…”

Singlemode-Multimode-Singlemode Fiber Structures for Sensing Applications—A Review

“…If the SNCS fiber structure is functionalized with a specific material, it can be used for detection of other physical and bio-chemical parameters. The variety of application areas is vast, as testified by these exampole: Li et al sealed ferrofluids in a capillary around the SNCS to measure electric current amplitude with a sensitivity of 2.12 dB/A [72] and Zhang used a U-shaped SNCS with magnetic fluid to measure magnetic field strength with a sensitivity of 3185.2 pm/mT [73]; Wen et al used a ZnO-coated SNCS fiber structure for relative humidity and ethanol detection using a fiber ring laser configuration [74]; Singh et al coated gold nanoparticles (AuNPs), silver nanoparticles (PVA-AgNPs) and graphene oxide (GO) on the NCF to excite surface plasmon polaritons to detect L-Cysteine (L-Cys) molecules [75]; Vicente et al coated SnO2-x on the sensor surface to improve sensitivity and applied the structure to IgG detection with limit of detection (LoD) of 0.6 mg/L [76]; As a final example Cardona-Maya et al used functionalized SNCS to detect goat IgG with LoD of 0.2 mg/L [77].…”