Biosensing with optical fiber gratings

AbstractOptical fiber gratings (OFGs), especially long-period gratings (LPGs) and etched or tilted fiber Bragg gratings (FBGs), are playing an increasing role in the chemical and biochemical sensing based on the measurement of a surface refractive index (RI) change through a label-free configuration. In these devices, the electric field evanescent wave at the fiber/surrounding medium interface changes its optical properties (i.e. intensity and wavelength) as a result of the RI variation due to the interaction between a biological recognition layer deposited over the fiber and the analyte under investigation. The use of OFG-based technology platforms takes the advantages of optical fiber peculiarities, which are hardly offered by the other sensing systems, such as compactness, lightness, high compatibility with optoelectronic devices (both sources and detectors), and multiplexing and remote measurement capability as the signal is spectrally modulated. During the last decade, the growing request in practical applications pushed the technology behind the OFG-based sensors over its limits by means of the deposition of thin film overlays, nanocoatings, and nanostructures, in general. Here, we review efforts toward utilizing these nanomaterials as coatings for high-performance and low-detection limit devices. Moreover, we review the recent development in OFG-based biosensing and identify some of the key challenges for practical applications. While high-performance metrics are starting to be achieved experimentally, there are still open questions pertaining to an effective and reliable detection of small molecules, possibly up to single molecule, sensing in vivo and multi-target detection using OFG-based technology platforms

Sensitivity Analysis of Sidelobes of the Lowest Order Cladding Mode of Long Period Fiber Gratings at Turn Around Point

A new methodology to enhance the sensitivity of a long period fiber grating sensor (LPFG) at the Turn Around Point (TAP) is here presented. The LPFG sensor has been fabricated by etching the fiber up to 20.4 mu m, until the sidelobes of dispersed LP0,2 cladding mode appeared near TAP in aqueous medium. The dual peak sensitivity of the sidelobes was found to be 16,044 nm/SRIU (surrounding refractive index units) in the RI range from 1.333 to 1.3335

Fiber laser strain sensor device

We present a fiber laser strain sensor (FLSS) with noise-equivalent sensitivity equal to or better than 80?p?rms?(Hz)?1/2 at very low frequencies, from 100?mHz to several hundreds of hertz. The strain affects the fiber laser emission wavelength, and an imbalanced Mach?Zender interferometer (MZI) converts wavelength variations into phase-amplitude variations. The sensor has been also tested in the time domain by applying sinusoidal strain bursts: the device also shows a good signal-to-noise ratio at the lowest burst frequencies

Molecular beacon-decorated polymethylmethacrylate core-shell fluorescent nanoparticles for the detection of survivin mRNA in human cancer cells.

One of the main goals of nanomedicine in cancer is the development of effective drug delivery systems, primarily nanoparticles. Survivin, an overexpressed anti-apoptotic protein in cancer, represents a pharmacological target for therapy and a Molecular Beacon (MB) specific for survivin mRNA is available. In this study, the ability of polymethylmethacrylate nanoparticles (PMMA-NPs) to promote survivin MB uptake in human A549 cells was investigated. Fluorescent and positively charged core PMMA-NPs of nearly 60nm, obtained through an emulsion co-polymerization reaction, and the MB alone were evaluated in solution, for their analytical characterization; then, the MB specificity and functionality were verified after adsorption onto the PMMA-NPs. The carrier ability of PMMA-NPs in A549 was examined by confocal microscopy. With the optimized protocol, a hardly detectable fluorescent signal was obtained after incubation of the cells with the MB alone (fluorescent spots per cell of 1.90±0.40 with a mean area of 1.04±0.20µm2), while bright fluorescent spots inside the cells were evident by using the MB loaded onto the PMMA-NPs. (27.50±2.30 fluorescent spots per cell with a mean area of 2.35±0.16µm2). These results demonstrate the ability of the PMMA-NPs to promote the survivin-MB internalization, suggesting that this complex might represent a promising strategy for intracellular sensing and for the reduction of cancer cell proliferation

Pour une poétique de l'interprétation (Lettre et parole en littérature et psychanalyse)

PARIS13-BU Droit-Lettres (930792101) / SudocSudocFranceF

Manufacturing and Spectral Features of Different Types of Long Period Fiber Gratings: Phase-Shifted, Turn-Around Point, Internally Tilted, and Pseudo-Random

The manufacturing and spectral features of different types of long period fiber gratings (LPFGs), ranging from phase-shifted, turn-around point, and internally tilted gratings, to pseudo-random gratings, are described and discussed in detail. LPFGs were manufactured on boron-germanium co-doped photosensitive optical fibers with the point-by-point technique using an excimer KrF laser operating at 248 nm. The developed experimental setup to manufacture high-quality LPFGs was designed to totally customize any type of gratings with the possibility of setting different parameters, such as the grating period (or pitch), the number of grating planes, the number of laser shots for each plane, etc. Some important spectral features of the LPFGs’ spectra were taken into account. This allows realizing homemade devices useful in several fiber-based applications, such as optical filtering, coupling systems, random lasers, physical and chemical sensing, and biosensing

Biosensing with optical fiber gratings

Optical fiber gratings (OFGs), especially long-period gratings (LPGs) and etched or tilted fiber Bragg gratings (FBGs), are playing an increasing role in the chemical and biochemical sensing based on the measurement of a surface refractive index (RI) change through a label-free configuration. In these devices, the electric field evanescent wave at the fiber/surrounding medium interface changes its optical properties (i.e. intensity and wavelength) as a result of the RI variation due to the interaction between a biological recognition layer deposited over the fiber and the analyte under investigation. The use of OFG-based technology platforms takes the advantages of optical fiber peculiarities, which are hardly offered by the other sensing systems, such as compactness, lightness, high compatibility with optoelectronic devices (both sources and detectors), and multiplexing and remote measurement capability as the signal is spectrally modulated. During the last decade, the growing request in practical applications pushed the technology behind the OFG-based sensors over its limits by means of the deposition of thin film overlays, nanocoatings, and nanostructures, in general. Here, we review efforts toward utilizing these nanomaterials as coatings for high-performance and low-detection limit devices. Moreover, we review the recent development in OFG-based biosensing and identify some of the key challenges for practical applications. While high-performance metrics are starting to be achieved experimentally, there are still open questions pertaining to an effective and reliable detection of small molecules, possibly up to single molecule, sensing in vivo and multi-target detection using OFG-based technology platforms

Label-free biosensor based on long period grating

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