22 March 2013 Label-free biosensor based on long period grating
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Long period gratings have been recently proposed as label-free optical devices for biochemical sensing. A biochemical interaction along the grating region changes the biolayer refractive index and a change in the fiber transmission spectrum occurs. The fiber biofunctionalization was performed with a novel chemistry using Eudragit L100 copolymer as opposed to the commonly-used silanization procedure. An IgG/anti-IgG bioassay was carried out for studying the antigen/antibody interaction. The biosensor was fully characterized, monitoring the kinetics during the antibody immobilization and achieving the calibration curve of the assay. To compare the biosensor performance, two LPG-based biosensors with distinct grating periods were characterized following the same bioassay protocol. Experimental results demonstrated an enhancement of the biosensor performance when the fundamental core mode of a single-mode fiber couples with a higher order cladding mode. Considering an LPG manufactured on a bare optical fiber, in which the coupling occurs with the 7-th cladding mode, a dynamic signal range of 0.33 nm, a working range of 1.7 – 1450 mg L-1 and a LOD of 500 μg L-1 were achieved
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Francesco Baldini, Francesco Chiavaioli, Ambra Giannetti, Massimo Brenci, Cosimo Trono, "Label-free biosensor based on long period grating", Proc. SPIE 8572, Advanced Biomedical and Clinical Diagnostic Systems XI, 857217 (22 March 2013); doi: 10.1117/12.2007399; https://doi.org/10.1117/12.2007399

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