In the last decade, among the various cerebral ischemia biomarkers, microRNAs (miRNAs, MW 7-10 kDa) have recently attracted the attention of researchers. These are short endogenous biomolecules of noncoding ribonucleic acids that negatively regulate gene expression. The presence of miRNAs in blood and the ability to measure their level in a non-invasive way, the so-called liquid biopsy approach, has opened new doors in the search for peripheral biomarkers for the diagnosis and prognosis of diseases such as hemorrhagic stroke. In order to perform liquid biopsy, Bloch surface waves supported by one dimensional photonic crystals are exploited to enhance and redirect the fluorescence arising from a sandwiched miRNA recognition assay. Besides, the sensing elements consist of disposable and low-cost plastic biochips coated with a 1DPC. The assay format consists of a first partial hybridization of an oligonucleotidic probe, immobilized onto the 1DPC surface in five regions, with the miRNA target (miR-16-5p, hemorrhagic stroke biomarker) to be revealed in a complex biological medium. The protocol is then completed with a second partial hybridization of the miRNA target with a second synthetic oligonucleotide conjugated with an organic dye. This last step permits to specifically introduce fluorescence where the sandwich assay is accomplished. Thanks to the present technique, we are able to detect miRNA target solutions with a limit of detection of 32 ng/mL in less than 60 minutes. In conclusion, since the recommended therapeutic window is very limited, biomarkers for cerebral ischemia/hemorrhage have the potential to speed-up diagnosis and the assignment of treatments.
The study of the interaction of fibronectin and phosphorylcholine molecules with surfaces is of high relevance to understand the biological performance of bioactive coatings. To accomplish this task, one-dimensional photonic crystals supporting Bloch surface waves were interrogated in label-free and enhanced fluorescence operation modes. In particular, the enhanced fluorescence mode offers the possibility to confirm the presence of proteins with a sharp improvement of the resolution. Bioactive coatings based on fibronectin/ phosphorylcholine have thus the potential to not only enhance the body acceptance of implanted devices, but also extend the lifetime of such devices.
Human epidermal growth factor receptor 2 (HER2) over-expression occurs in 15–20% of breast cancers and it is generally associated with a dismal prognosis. In this work, we report on the use of one-dimensional photonic crystal biochips to detect clinically relevant concentrations of HER2 in human plasma samples. To this aim, we optimized an optical read-out system, combining both label-free and fluorescence detection, which makes use of biochips tailored with specific proteins for specific biological recognition. Our biochips were used to discriminate HER2 positive/negative human plasma samples providing a solid and reliable tool for clinical diagnostics.
The combination of fiber-optic–based platforms for biosensing with nanotechnologies is opening up the chance for the development of in situ, portable, lightweight, versatile, reliable and high-performance optical sensing devices. The route consists of the generation of lossy mode resonances (LMRs) by means of the deposition of nm-thick absorbing metaloxide films on special geometric-modified fibers. This allows measuring precisely and accurately the changes in surface refractive index due to the binding interaction between a biological recognition element and the analyte, with very high sensitivity compared to other optical technology platforms, such as fiber gratings or surface plasmon resonance. The proposed methodology, mixed with the use of specialty fiber structures such as D-shaped fibers, allows improving the light-matter interaction in a strong way. The shift of the LMR has been used to monitor in real-time the biomolecule interactions thanks to a conventional wavelength-interrogation system and an ad-hoc developed microfluidics. A big leap in performance has been attained by detecting femtomolar concentrations in real samples of human serum. The biosensor regeneration has been also studied by using a solution of sodium dodecyl sulphate (SDS), proving the device reusability. Therefore, this technology possibly represents a paradigm shift in the development of a simple, high-specificity and label-free biosensing platform, which can be applied to speed up diagnostic healthcare processes of different diseases toward an early diagnostic and personalized treatment system.
We report on the development of a biosensing platform that combines label-free and fluorescence based detection on disposable Bloch surface wave biochips. This system is applied to the detection of the HER2-neu/ErbB2 clinical biomarker related to breast cancer development. We first describe the design and fabrication of the BSW biochips as well as the principle of operation of the optical reading instrument. Then, the approaches for surface functionalization and immobilization of proteins for specific detection on the biochips are discussed. Finally, experimental results on a sandwich immunoassay for ErbB2 detection in cell lysates are presented.
A biosensor platform based on Bloch Surface Waves and operating in angular interrogation mode is applied to the detection of a clinical biomarker (HER2-neu/ERBB2) related to breast cancer initiation/progression. Preparing regions for specific recognition of different proteins as well as a reference on the biochip enables to correct the signal for nonspecific effects. Additionally, label-free analysis and surface wave enhanced fluorescence detection can be applied and compared directly on the platform. Cell lysates with high and low expression levels of ERBB2 are analyzed. Comparing the signals of such ERBB2 positive and negative samples estimates the limit of detection at 1.7 ng/mL. This is well below the threshold of 15 ng/mL set by the FDA for clinically useful ERBB2 detection in human serum, demonstrating that 1DPC-based biochips are attractive candidates for breast cancer detection/monitoring.
The increasing demand for early detection of diseases drives the efforts to develop more and more sensitive techniques to detect biomarkers in extremely low concentrations. Electromagnetic modes at the surface of one dimensional photonic crystals, usually called Bloch surface waves, were demonstrated to enhance the resolution and constitute an attractive alternative to surface plasmon polariton optical biosensors. We report on the development of Bloch surface wave biochips operating in both label-free and fluorescence modes and demonstrate their use in ovalbumin recognition assays.
For high quality optical coatings the knowledge of the losses of the deposited materials is essential. A precise measurement of low Im(n+iκ)≤ 10-6 at an intended operation wavelength and with low intensity can be achieved in waveguide configurations, whereby leaky waveguide configurations allow one to analyze losses of high- and low-index media of H-L-stacks as well due to resonances in the angle-dependent reflection curve. Numerical investigations reveal that different leaky wave schemes, e.g. Bragg-, Bloch- and Antiresonant-Reflecting waveguides, comply differently with practical requests. Loss figure evaluation requires peculiar attention due to measurement accuracy and ambiguities, thus suitable constraints for layer data and a proper merit-function construction have to be used.
Bloch surface waves (BSW) propagating at the boundary of truncated photonic crystals (1D-PC) have emerged as an attractive approach for label-free sensing in plasmon-like sensor configurations. Due to the very low losses in such dielectric thin film stacks, BSW feature very low angular resonance widths compared to the surface plasmon resonance (SPR) case. Besides label-free operation, the large field enhancement and the absence of quenching allow utilizing BSW coupled fluorescence detection to additionally sense the presence of fluorescent labels. This approach can be adapted to the case of angularly resolved resonance detection, thus giving rise to a combined label-free / labelled biosensor platform. It features a parallel analysis of multiple spots arranged as a one-dimensional array inside a microfluidic channel of a disposable chip. Application of such a combined biosensing approach to the detection of the Angiopoietin-2 cancer biomarker in buffer solutions is reported.
Optical sensors exploiting Bloch surface waves at the truncation edge of one dimensional photonic crystals are used here as a valid alternative to surface plasmon resonance operating in the Kretschmann-Raether configuration, and commonly adopted for label-free optical biosensing. In order to reduce the Bloch surface waves resonance width and increase the resolution it is desirable to work with one dimensional photonic crystals with as small losses as possible. However this makes that the resonances observed in a single polarization reflection scheme are shallow and difficult to track in a sensing experiment. Here we report on the practical implementation of an angularly resolved ellipsometric optical sensing scheme based on Bloch surface waves sustained by tantalia/silica multilayers. The angular resolution is obtained by a focused illumination at fixed wavelength and detecting the angular reflectance spectrum by means of a CMOS array detector. The experimental results, obtained by using one tantalia/silica multilayer with a defined structure, show that the limit of detection can be pushed below 2.1x10-7RIU/Hz1/2.
Bloch surface waves (BSW) propagating at the surface of truncated, one-dimensional crystals are valid candidates to improve sensors based on surface plasmon polaritons, usually referred to as surface plasmon resonance (SPR). The low losses introduced by the dielectric BSW stacks enable to achieve resonance widths much below the ones of SPR, thus proposing improved sensing results. A simplified, bi-linear model of the resonance intensity distribution is applied to estimate the effect of the resonance properties onto the measurement noise. This yields a limit of detection (LoD) that is used to optimize a BSW supporting thin film stack and to quantitatively compare SPR and BSW sensors. The results indicate that an order of magnitude reduction of the LoD is within reach when sufficient sampling of narrow BSW resonances is achieved.
An alternative method to plasmon techniques for the enhancement, control and detection of fluorescence is proposed.
The role of the metallic layer is played by a silicon-based one-dimensional photonic crystal that can sustain Bloch
surface waves (BSWs), which can be regarded as the dielectric analogue of surface plasmon polaritons (SPPs) for
metals. Throughout the paper we explore the route that leads to an enhanced, directionally-controlled and selfreferencing
fluorescence-detection scheme. We first consider a 1DPC that is functionalized with a thin, flat and
homogeneous polymeric layer decorated with a fluorescent dye. The enhancement of the BSW-coupled fluorescence
emission is studied against a similar scheme that uses a common thin glass coveslip. An enhancement as large as 560 is
found. We further investigate the BSW coupling of the illuminating laser light into 30-nm thin polymeric waveguides.
Imaging the BSW-coupled emitted fluorescence through the leakage radiation microscopy is used for the purpose. The
possibility of coupling BSWs into nanometric guiding ridges makes feasible the design of a spatially-resolved and
multiplexing fluorescence-detection scheme, which can be most useful for self-referencing in the biosensing field. We
conclude the paper by investigating the effects on the fluorescence emission of a multistack that consists of a dielectric
multilayer and a thin metallic layer deposited on top. The implications of using a metallo-dielectric structure for the
coupling of the emitted fluorescence with BSW and SPP modes is discussed.
Lithium Fluoride (LiF) presents interesting optical properties and it has been proposed as an active optical material for
colour centre (CC) lasers and amplifiers. The use of a grating to reduce the laser threshold and to narrow the line-width
has also been demonstrated. More recently, LiF gained increased attention due to its unique characteristics as x-ray
imaging detector for high resolution microscopy and for the development of CC lasers using gratings induced by high
energy femtosecond laser pulses. We present a review of our recent work in the production of photonic structures, like
photo-induced Bragg gratings and wave-guides either by laser CW illumination or by femtosecond laser irradiation.
CW laser illuminated gratings were written in both coloured LiF crystals and films. Gratings and wave-guides are
characterized using confocal microscopy, optical absorption and emission spectroscopy, near field scanning, scattering
and insertion loss measurements.
The Rhodamine 6G fluorescence enhanced by the surface electromagnetic waves coupled on surface of 1D
photonic crystals is studied. The fluorescence-mediated surface electromagnetic waves (SEW) distribution
is visualized by means of far-field fluorescence microscopy. The kinetics of Rhodamine 6G bleaching due to
SEW is studied. The way of SEW visualization in reflectivity spectra via fluorescence process is shown. The
prospective for SEW application in the optical sensors field is tested via direct spectroscopy of the photonic
crystal covered by the ethanol and R6G thin film. Spectral flexibility of the SEW excitation depending
on the effective photonic crystal dispersion controlled by its design rather than on material dispersion opens
prospectives for the application of SEW-enhanced fluorescence microscopy in biocensing with increased spatial
and concentration sensitivity and spectral selectivity.
We report on the measurement of the time relaxation of the electro-optic properties of poled side-chin copolymers under illumination with absorbed laser radiation. Films of side- chain Disperse Red 1 substituted poly-Methyl-Methacrylate were sandwiched between ITO and gold electrodes and poled with a standard temperature/electric field cycle. The decay of the electro-optic properties, measured by means of the Teng and Man ellipsometric reflection technique at (lambda) equals 830nm, was measured for several intensities of a circular polarized absorbed laser beam, (lambda) equals 514.5nm, illuminating the sample. The relaxation shows a stretched exponential time dependence, with intensity dependent decay and stretching constants. The relaxation curves are compared with those obtained, for the same sample, in standard temperature stimulated non linear dielectric relaxation measurements.
SiO2 films doped with the organic dye DO3, exhibiting high electron delocalization have been prepared by the sol- gel method and deposited on soda-lime glass substrates. On these films an electric field of 5-7 kV/cm has been successively applied in order to induce orientation of the DO3 molecules and freeze them in the condition by heating and reticulation of the inorganic matrix. The thermal stability of the films and the variation of the molecules' orientation as a function of time have been studied. The films have been characterized by means of differential thermal analysis, thermogravimetry, mass spectrometry, ellipsometry and atomic force microscopy.
We describe, in the present paper, the production and optical characterization of thin noncrystalline waveguiding films of the polar organic polymer poly-phenyl-acetylene. The nonlinear behavior of the grating coupling, due to the third order nonlinear susceptibility of the polymer, has been investigated. We have used laser sources, producing short pulses ((tau) equals 100 ps) at (lambda) equals 1.064 micrometers and ultrashort pulses ((tau) equals 1 ps) at (lambda) equals 610 nm, to study the change in the coupling efficiency with respect to the pulsed beam average input power. In the two cases, the changes are attributed respectively to a thermal and electronic nonlinearity of the refractive index. First theoretical modeling of the obtained data is given in the frame of the coupled mode approach to the nonlinear behavior.
We describe the production and optical characterization of planar dielectric waveguides of the organic polymers Poly-(alpha) -Methyl-Styrene and Poly-Phenyl-Acetylene. Single mode waveguides, at (lambda) equals 1.064 micrometers , were obtained by the use of the spin-coating technique. Propagation losses were measured through detection of the out of plane scattered light are as low as 0.7 dB/cm. The waveguiding films were spun over fused silica substrates that were previously etched in order to obtain two grating couplers with a 0.55 micrometers period. Nonlinear grating coupling was investigated in the case of Poly-Phenyl-Acetylene, with a 70 ps pulsed source at (lambda) equals 1.064 micrometers at high repetition rate (frep equals 76 MHz).
The thermal behavior of a diode laser is studied through the photodeflection method. A new method is proposed to detect the cooling property of laser diode, during its operation. A theoretical model is presented together with some experimental results obtained on AlAs-GaAs lasers.
Dynamics of optical nonlinearity are investigated experimentally in different time scales, from microsecond to nano-, pico-, and femtosecond domains. In addition Z-Scan measurements carried out the competition between permanent photodarkening and electronic nonlinearities in photoinduced absorption and refraction.
Nonlinear properties of chacolgenide glass A52S3 thin films have been measured with a self-diffraction (Z-Scan) technique. Photostructural changes and dynamical effects have been measured.
A pump and probe experiment is described which allows to study input coupling efficiency of a CdS grating on top of a linear glass waveguide as a function of input power for wavelengths shorter than CdS band gap wavelength. A monotonous decrease of coupling efficiency is found by increasing the pump power. Reference is made also to results obtained for wavelengths larger than the band gap wavelength.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.