In this article, we report the effect of the pH of bovine serum albumin and egg serum albumin solutions on the microstructured optical fiber transmission spectra fluctuations near proteins isoelectric point. The demonstrated effect may be important in the development of perspective optical microstructured optical fiber-based biosensors in a labeled and label-free formats for a wide range of analytes.
Photonic crystal fibers with hollow core (HC PCFs) are a specific class of optical fibers characterized by microstructure with periodic holes oriented along fiber. The combination of HC PCF with Raman spectroscopy for biosensors creation is attractive in the terms of the low sample volume, the possibility to increase the integration time without sample degradation and maintaining constant focus during experiments. Here we propose layer-by-layer polyelectrolyte coating of HC PCF inner surface in order to obtain charge-selective absorption of analyte, stabilization of Surface-Enhanced Raman scattering (SERS)-active gold nanoparticles. Distance between SERS hotspots and glass reduces nonlinear signals from glass, and increases signal-to-noise ratio of SERS spectra.
Microstructural optical waveguides with the hollow core are actively studied as a promising support for heterogeneous immunoassay in development of new optical biosensor elements for medicine and biology. Overcoming of the limitations associated with the low sorption capacity of glass used for the waveguides production is a crucial step for this assay format. In this work the possibility of silanization of microstructural optical waveguides with the hollow core using (3-glycidyloxypropyl) trimethoxysilane and their further application to enzymatic immunoassay was studied.
The use of photonic crystal fibers as a basis elements for biosensor construction is a perspective trend. The advantages of this approach are the use of micro and nano volumes of samples and a significant strengthening of the analytical signal while increasing the optical path length. Quantum dots are the most promising fluorescent markers for use in the photonic crystal fibers based analysis.
The advantages of quantum dots, in this case, are associated with stability, wide range of excitation and extremely narrow range of high luminescence intensity. In this work we have investigated the behavior and optical properties of CdSe core-shell nanocrystals (quantum dots) after they including into hollow central defect of hollow core chirped photonic crystal fibers with internal surface modified by polyaniline films.
We introduce a sensitive method that allows one to distinguish positive and negative agglutination reactions used for blood typing and determination of Rh affinity with a high precision. The method is based on the unique properties of photonic crystal waveguides, i.e., microstructured waveguides (MSWs). The transmission spectrum of an MSW smart cuvette filled by a specific or nonspecific agglutinating serum depends on the scattering, refractive, and absorptive properties of the blood probe. This concept was proven in the course of a laboratory clinical study. The obtained ratio of the spectral-based discrimination parameter for positive and negative reactions (I+/I−) was found to be 16 for standard analysis and around 2 for used sera with a weak activity.
The advantages of microstructured fibers application to photometrical determination of positive and negative agglutination reaction is discussed. One can use this method for blood typing and determination of Rh affinity. The method is based on discrimination of the scattering properties of blood probes with a specific and a non-specific agglutinating serum.
The aspects of application of the hollow core photonic crystal waveguides for spectroscopic analysis of liquid medium
were considered. The possibility of using these structures for analysis of a fruit juice was evaluated. The principles of
processing of photonic crystal waveguide transmission spectra, which is sensitive to quality of juice, its composition, and
main component concentration, were revealed.
Possibility of photonic crystal fiber-based glucose sensor developing is discussed. We considered the concept of the use
of chirped photonic crystal fiber with big grating period as a fiber refractometer and "smart" photometric cuvette, and
possibility to combine refractometric and oxidase methods for glucose determination. Influence of refractive index
change of the liquid medium, determined by significant increase of containing glucose, to spectral characteristics of
photonic crystal fiber was studied and the optical response to insignificant change (tenths of millimoles per liter) of
glucose concentration was obtained.
A new type of photonic crystal fibers (PCFs) that can be used as sensitive elements of chemical and biological
sensors is presented. Hollow core photonic crystal fibers refer to a type of optical waveguides, showing
unique optical properties such as photonic band gap formation and high sensitivity for refraction index,
absorption and scattering coefficient of a medium within a hollow core. A significant influence of internal
medium scattering coefficient on a PCF's guiding properties becomes basis for design of blood typing
automatization technique specifically. Recently obtained experimental results, regarding PCF's sensitivity for
internal medium optical properties changing, are presented as well.
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