American Chemical Society
2018
Femtomolar Detection by Nanocoated Fiber Label-Free Biosensors
GRANCESCO CHIAVAIOLI; PABLO ZUBIATE; IGNACIO DEL VILLAR; CARLOS R. ZAMARREÑO: AMBRA GIANNETTI; SARA TOMBELLI; COSIMO TRONO; FRANCISCO J. ARREGUI; IGNACIO R. MATÍAS; FRANCISCO BALDINI

Abstract

The advent of optical fiber-based biosensors combined with that of nanotechnologies has provided an opportunity for developing in situ, portable, lightweight, versatile, and high-performance optical sensing platforms. We report on the generation of lossy mode resonances by the deposition of nanometer-thick metal oxide films on optical fibers, which makes it possible to measure precisely and accurately the changes in optical properties of the fiber-surrounding medium with very high sensitivity compared to other technology platforms, such as long period gratings or surface plasmon resonances, the gold standard in label-free and real-time
biomolecular interaction analysis. This property, combined with the
application of specialty structures such as D-shaped fibers, permits enhancing the light−matter interaction. SEM and TEM imaging together with X-EDS tool have been utilized to characterize the two films used, i.e., indium tin oxide and tin dioxide. Moreover, the experimental transmission spectra obtained after the deposition of the nanocoatings have been numerically corroborated by means of wave propagation methods. With the use of a conventional wavelength interrogation system and ad hoc developed microfluidics, the shift of the lossy mode resonance can be reliably recorded in response to very low analyte concentrations. Repeated experiments confirm a big leap in performance thanks to the capability to detect femtomolar concentrations in human serum, improving the detection limit by 3 orders of magnitude when compared with other fiber-based configurations. The biosensor has been regenerated several times by injecting sodium dodecyl sulfate, which proves the capability of sensor to be reused.

Fabrication of ITO and SnO2 Thin Film Coated Fibers.

… Regarding the coating procedure of the thin film deposition, both the unclad MMFs and the D-shaped SMFs were placed on the substrate in a DC sputter machine (ND-SCS200 from Nadetech S.L.).

 

Keywords: Optical biosensor; Lossy mode resonance; Optical fiber sensor; Nanometric metal oxide film; Label-free biomolecular interaction; Femtomolar detection limit; Regeneration