Enhanced fluorescence detection of miRNA-16 on a photonic crystal

Abstract

We report a novel sensing method for fluorescence-labelled microRNAs (miRNAs) spotted on an all-dielectric photonic structure. Such a photonic structure provides an enhanced excitation and a directional beaming of the emitted fluorescence, resulting in a significant improvement of the overall signal collected. As a result, the Limit of Detection (LoD) is demonstrated to decrease by a factor of about 50. A compact read-out system allows a wide-field imaging-based detection, with little or no optical alignment issues, which makes this approach particularly interesting for further development for example in microarray-type bioassays.

Gold nanoparticle triggered dual optoplasmonic-impedimetric sensing of prostate-specific antigen on interdigitated porous silicon platforms

“…This experiment involves two biorecognition steps to enhance the selectivity and to amplify the sensor response. This first step includes a silanization at room temperature with (3-Glycidyloxypropyl)trimethoxysilane (GPTMS) (Sigma-Aldrich), a molecule containing an epoxy group, which reacts with the SiOH groups on the surface of PSi (formed by the chemical oxidation) leading to a large surface density of epoxy groups[27,28].Then, the capture antibody (monoclonal mouse anti-prostate specific antigen 1H12 antibody) is immobilized on the PSi surface for 2 h at 37ºC at a concentration of 50 μg/mL in 10 mM MES (pH 3.8), and the free surface is blocked with (aminoethyl)polyethylene glycol (PEG) (Sigma-Aldrich) at 1 mg/mL in 10 mM MES with 0.05% Tween ® (pH 5.5) overnight and 4ºC in order to avoid non-specific interactions. Then, an immunoreaction between PSA and the capture antibodies takes place by immersion of PSi-based devices in PSA:fetal bovine serum (FBS) 1x in a range of concentrations from 0.1 to 500 ng/mL at 37ºC.…”

Leaky Bloch-like surface waves in the radiation-continuum for sensitivity enhanced biosensors via azimuthal interrogation

“…For TiO 2 the presence of voids can reduce the index from that predicted; however, with careful fabrication 45 , the values used here are valid. There is ample evidence in the experimental literature that such multilayers, including those with surface grating structures 2, 4, 12, 13, 20, 23 , can be readily fabricated.

Figure 1Schematic of a grating coupling technique to excite leaky Bloch surface waves on the surface of a dielectric multilayer.

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“…Following the prediction 1 and experimental observation 2 of BSWs in photonic crystals, these modes have been studied, both theoretically and experimentally, in various configurations 3–6 . The resulting strong field/energy localization at the surface layer and the evanescently extending field in the homogeneous medium are of interest in applications such as label-free biosensing based on enhanced diffraction 7–9 , surface-enhanced Raman spectroscopy 10, 11 , spectral and angular resonance shift 12–16 , fluorescence-based detection 17–20 , slow-light enhanced nonlinear effects 21, 22 , integrated optical circuits 23 , and optical slow-light devices and sensors 24, 25 . BSWs are evanescent in nature; they are perfectly bound non-radiative states that lie below the light line of the homogeneous layer material.…”

Bloch surface wave enhanced biosensor for the direct detection of Angiopoietin-2 tumor biomarker in human plasma

“…In general, the advent of biosensors based on photonic crystals and their improvements allowed the realization of simple and low-cost bioassays [13]. Indeed, during the last decade Bloch surface waves (BSW) sustained by 1DPC have been considered as a viable alternative to surface plasmon polaritons in both label-free [14][15][16][17][18][19][20] and fluorescence [21][22][23] optical biosensors. The most interesting feature of BSW relies on the enhanced and confined electromagnetic field in close proximity of the interface, leading to an increase of the labelfree resolution and of the fluorescence excitation rate of fluorophores located at the 1DPC surface.…”