Glucose Water Solution Research Articles

Measurements of glucose concentration in aqueous solutions using reflected THz radiation for applications to a novel sub-THz radiation non-invasive blood sugar measurement method.

The terahertz (THz) frequency range corresponds to molecular vibrations or relaxation modes such as those for the hydrogen bond. Most biomolecules are activated only in aqueous solutions, thus, to understand the function and structure of biomolecules, it is necessary to investigate the characteristics of electromagnetic waves in hydrated samples. THz radiation causes little damage to the human body, thus it is expected that it can be applied for noninvasive examinations. However, spectrometry of the transmitted light is difficult, since the absorption of THz radiation in water is extremely high. In this study, we used sub-THz radiation (frequencies near to 0.1 THz), where the absorption is lower than for THz radiation, to measure the reflectance of a glucose water solution. We found that the reflectance decreases in proportion with the glucose concentration. These results suggest that sub-THz radiation can be used in the noninvasive measurement of blood glucose levels.

Dielectric characterization of water glucose solutions using a transmission/reflection line method

Abstract Diabetes mellitus (DM) is a disease that affects millions of people worldwide. In order to be managed, it requires the individuals to measure their blood glucose level in an uncomfortable way several times every day. Thereby, a reliable non-invasive, non-painful blood glucose monitoring system is desirable. Microwave technology has been regarded previously to develop such a sensor by dielectric means, but no clear dielectric characterization of blood glucose dielectric behavior has been hitherto shown. In this paper, a novel study of the effect on the dielectric behavior of water when glucose is added is presented, as a simplified case of blood glucose dielectric behavior. Different water glucose solutions have been dielectrically characterized using a transmission/reflection line method and the effect of the changes of the glucose level in the dielectric behavior has been discussed. Conclusions concerning the development of a non-invasive blood glucose sensor are offered and their validity is discussed.

Refractive Index Sensing in Rectangular Glass Micro-Capillaries by Spectral Reflectivity Measurements

We report the application of rectangular glass micro-capillaries with cross-section of 20 μm × 200 μm and 50 μm × 500 μm as capillary-driven liquid-core optical cavities for fluid refractive index sensing. Reflected power spectra in two wavelength bands (around 1.3 μm and 1.55 μm) are detected with readout broadband radiation crossing the capillary in orthogonal direction with respect to the flat sides. Using a fiberoptic scheme for remote, non-contact measurements and inserting glucose or bovine serum albumin solutions in water at different concentrations as test fluids, we have revealed the shift of the wavelength position of the reflectivity minima due to refractive index variations. The combination of these low-cost devices with a spectral readout method allows achieving sensitivities higher than 250 nm/RIU and limits of detection better than 1.3 × 10−3 RIU.

Development and validation of a theoretical model for osmotic evaporation

In this work, a mathematical model developed to describe the heat and mass transfer over time during the osmotic evaporation process is reported. The model predicted the vapor permeation flux and sugar concentration kinetics with error values of ≤36% and ≤16% respectively, during the evaporation of glucose–water solutions up to 50°Brix. Predictions of the model were experimentally validated in the range of vapor permeate flux values between 0.4 and 2kgm−2h−1. According to the model the variables having the most important effect on flux were temperature and the brine concentration. It also indicates anisotropy in the polarization of both temperature and concentration between the feed and brine sides of the membrane and points out that the heat and mass transfer phenomena occurring in the feed side of the membrane are the mechanisms controlling the process. The model was also used to describe the experimental flux and concentration kinetics of cassava starch hydrolysates. Deviations between predictions and data obtained with cassava starch hydrolysates are attributed to the high viscosity of this feed and to the increased mass transfer resistance among fibers inside the module.

A liquids refractive index spectrometer

In this paper, we report about the use of an optical fiber sensor for measurements of the refractive index (η) of liquids as a function of wave-length (λ). The method uses only one optical fiber. Different laser diodes are used to carry out measurements at several wavelengths. The principle of measurement is based on the detection of the intensity of reflected light. Periodical intensity modulated light of a given λ is transmitted using an optical liquid fiber through the sample contained in a quartz glass cuvette, being reflected by a mirror located at the rear side of the cuvette back to the same fiber, through which it arrives to a photodetector after passing through a beam splitter that blocks the original beam. The signal amplitude is measured using a Lock-in amplifier synchronized at the modulation frequency as a function of the distance between the fiber tip and the cuvette for different samples of well-known η. A linear calibration curve is obtained by plotting the refractive index versus the amplitude maximum value, which can be used to measure the value of η for an unknown sample, as demonstrated by measurement of the refractive index of sodium chlorine and glucose in water solutions (in the range between 0 and 25 weight%) for different wave-lengths. Good agreement has been obtained with values reported and/or measured with an Abbe refractometer values. A dispersion relation, η (λ), is obtained for these samples. The described refractometer has a sensitivity of 0.56V/RIU, its linearity is of more than 99% in the investigated range between 1 and 1.5 RIU. The limit of detection was estimated as 1.4×10−3RIU (RIU=Refractive Index Unit) at the used wave-lengths.

Non-contact reflectometric readout of disposable microfluidic devices by near infra-red low-coherence interferometry

We are here demonstrating the functionality of infra-red low-coherence reflectometry for the spot optical readout of solution concentrations in commercially available microfluidic devices. Disposable polymeric microfluidic devices composed by 100-µm-deep channels were connected to an external fluidic path that allowed flow-through of water-glucose solutions at different concentrations. Measurements were performed with near-infrared low-power sources, namely a tungsten lamp and a Superluminescent Light Emitting Diode (SLED), allowing the read-out in a wavelength region of minimum invasiveness for biological fluids. The selected optical scheme based on an all-fiber Michelson configuration is well suited for non-contact, remote investigations of the fluids flowing in plastic microfluidic devices, with arbitrary layout and thickness. For the first time, using the SLED, we exploited the double round trip of light in the fluid channel for doubling the sensitivity with respect to the standard single pass set-up, previously demonstrated.

Transmission optical coherence tomography based measurement of optical material properties.

We present transmission optical coherence tomography (transmission OCT) as a versatile tool to measure optical material properties of turbid media. The transmission OCT signal is described in detail and it is demonstrated how the group refractive index (n(g)), group velocity dispersion (GVD) and optical attenuation can be determined from this signal. We experimentally validate the refractive index properties of glasses, liquids and glucose water solutions in terms of n(g) and GVD. Measurements of scattering coefficients are determined using transmission OCT for suspensions of silica particles. Quantitative agreement is obtained with a dependent scattering model, both for the average as well as the wavenumber resolved optical attenuation coefficient. Good agreement is observed between our measurements and literature values.

Simple system for measuring optical rotation of glucose solution using liquid-crystal grating

We demonstrate an optical system for measuring the concentrations of optically active media using liquid-crystal polarization gratings (LCPGs). The optical rotation angle is determined by measuring the intensities of two diffracted light beams from an LCPG combined with a quarter-wave plate (QWP). The intensity ratio is used to evaluate the optical rotation angle, minimizing the dependence on changes in light source intensity and wavelength and reducing the influence of temperature-drift-induced LC birefringence shifts. We demonstrate the system by measuring the concentration of a glucose–water solution. The measurement error caused by the slight wavelength dependence of the QWP’s retardation is assessed numerically.

Sensitivity and Limit of Detection of biosensors based on ring resonators

In this work, we present a study of the Sensitivity (S) and Limit of Detection (LOD) of microring based photonic biosensors as a function of the waveguide composition and dimensions. The target is Aflatoxin, which is a toxin of major concern for south Europe dairy industry. The sensing device is based on an array of multiple SiON microring resonators, fiber-coupled to both an 850nm VCSEL and a silicon photodetectors, packaged with a microfluidic circuit. Volumetric sensing with glucose–water solutions of various concentrations yields a best sensitivity of 112nm/RIU. To link these results to the Limit of Detection of the sensors, we also measured the noise of our experimental readout system and then calculated the LOD of our sensors. We found a best value of LOD of 1.6×10−6RIU (referred to volumetric sensing). Finally, we detected Aflatoxin in solutions of various concentrations (down to 1.58nM) by functionalized sensors. The functionalization is based on a wet silanization and specific DNA-aptamer binding on the chip. Reproducibility and re-usability of the sensor are investigated by several chemical treatments. Optimum procedure allows multiple sequential measurements with a good endurance. This work was supported by the FP7 EU project “Symphony” (Grant agreement no.: 610580).

Design and Optimization of SiON Ring Resonator-Based Biosensors for Aflatoxin M1 Detection.

In this article, we designed and studied silicon oxynitride (SiON) microring-based photonic structures for biosensing applications. We designed waveguides, directional couplers, and racetrack resonators in order to measure refractive index changes smaller than 10−6 refractive index units (RIU). We tested various samples with different SiON refractive indexes as well as the waveguide dimensions for selecting the sensor with the best performance. Propagation losses and bending losses have been measured on test structures, along with a complete characterization of the resonator’s performances. Sensitivities and limit of detection (LOD) were also measured using glucose-water solutions and compared with expected results from simulations. Finally, we functionalized the resonator and performed sensing experiments with Aflatoxin M1 (AFM1). We were able to detect the binding of aflatoxin for concentrations as low as 12.5 nm. The results open up the path for designing cost-effective biosensors for a fast and reliable sensitive analysis of AFM1 in milk.

Rapid, sensitive, and reusable detection of glucose by a robust radiofrequency integrated passive device biosensor chip.

Tremendous demands for sensitive and reliable label-free biosensors have stimulated intensive research into developing miniaturized radiofrequency resonators for a wide range of biomedical applications. Here, we report the development of a robust, reusable radiofrequency resonator based integrated passive device biosensor chip fabricated on a gallium arsenide substrate for the detection of glucose in water-glucose solutions and sera. As a result of the highly concentrated electromagnetic energy between the two divisions of an intertwined spiral inductor coupled with an interdigital capacitor, the proposed glucose biosensor chip exhibits linear detection ranges with high sensitivity at center frequency. This biosensor, which has a sensitivity of up to 199 MHz/mgmL−1 and a short response time of less than 2 sec, exhibited an ultralow detection limit of 0.033 μM and a reproducibility of 0.61% relative standard deviation. In addition, the quantities derived from the measured S-parameters, such as the propagation constant (γ), impedance (Z), resistance (R), inductance (L), conductance (G) and capacitance (C), enabled the effective multi-dimensional detection of glucose.

Fuel Gas Production from Biomass Sources by Radio Frequency In-Liquid Plasma Method

Cellulose is a kind of saccharide that is the main component in cell walls of plants and therefore is the organic compound that exists in the largest amount in nature. The purpose of this experiment is to convert cellulose to a fuel. Radio frequency (RF) in-liquid plasma is generated in a cellulose distributed solution and a glucose solution, and the generation gas rate is measured. While hydrogen is the main gas generated by the plasma breakdown, carbon monoxide, carbon dioxide, and low-grade flammable gases are also produced. In the glucose water solution or the glucose distributed solution, the solution itself evaporates and decomposes inside the plasma but since the saccharides are non-volatile, they cannot penetrate into the plasma and are not decomposition. However, when the cellulose is at concentrations of 30 wt% or more, it becomes granular and can directly enter the plasma as a solid, where the plasma decomposes the cellulose itself, significantly increasing the amount of gas generated. In addition, the spectrometry of the plasma emission shows the solution after the creation of plasma has the ability to absorb ultraviolet light.

The Design and Operation of Ultra-Sensitive and Tunable Radio-Frequency Interferometers.

Dielectric spectroscopy (DS) is an important technique for scientific and technological investigations in various areas. DS sensitivity and operating frequency ranges are critical for many applications, including lab-on-chip development where sample volumes are small with a wide range of dynamic processes to probe. In this work, we present the design and operation considerations of radio-frequency (RF) interferometers that are based on power-dividers (PDs) and quadrature-hybrids (QHs). Such interferometers are proposed to address the sensitivity and frequency tuning challenges of current DS techniques. Verified algorithms together with mathematical models are presented to quantify material properties from scattering parameters for three common transmission line sensing structures, i.e., coplanar waveguides (CPWs), conductor-backed CPWs, and microstrip lines. A high-sensitivity and stable QH-based interferometer is demonstrated by measuring glucose-water solution at a concentration level that is ten times lower than some recent RF sensors while our sample volume is ~1 nL. Composition analysis of ternary mixture solutions are also demonstrated with a PD-based interferometer. Further work is needed to address issues like system automation, model improvement at high frequencies, and interferometer scaling.

Polymeric slot waveguide interferometer for sensor applications

A refractive index sensor based on slot waveguide Young interferometer was developed in this work. The interferometer was fabricated on a polymer platform and operates at a visible wavelength of 633 nm. The phase shift of the interference pattern was measured with various concentrations of glucose-water solutions, utilizing both TE and TM polarization states. The sensor was experimentally observed to detect a refractive index difference of 6.4 × 10(-6) RIU. Furthermore, the slot Young interferometer was found to compensate for temperature variations. The results of this work demonstrate that high performance sensing capability can be obtained with a polymeric slot Young interferometer, which can be fabricated by a simple molding process.

Peculiarities of the light scattering in dilute water-glucose solutions

This work is devoted to the behavior of the light scattering coefficient study in dilute waterglucose solutions near the characteristic temperature T=315 K (42ºC). Two methods of the integral light scattering are applied. Evolution and temperature dependence of the angular anisotropy index for different solutions’ concentrations are studied. We detected peaks of the light scattering intensity in a 5 wt % aqueous solution of glucose near the characteristic temperatures of a human body. In our opinion, this could be related to the peculation cluster formation and solution’s structuring.

Optical clearing at cellular level

Strong light scattering in tissues and blood reduces the usability of many optical techniques. By reducing scattering, optical clearing enables deeper light penetration and improves resolution in several optical imaging applications. We demonstrate the usage of optical tweezers and elastic light scattering to study optical clearing [one of the major mechanisms-matching of refractive indices (RIs)] at the single particle and cell level. We used polystyrene spheres and human red blood cells (RBCs) as samples and glycerol or glucose water solutions as clearing agents. Optical tweezers kept single microspheres and RBCs in place during the measurement of light scattering patterns. The results show that optical clearing reduces the scattering cross section and increases g. Glucose also decreased light scattering from a RBC. Optical clearing affected the anisotropy factor g of 23.25-μm polystyrene spheres, increasing it by 0.5% for an RI change of 2.2% (20% glycerol) and 0.3% for an RI change of 1.1% (13% glucose).

Fermentable Sugar Production and Separation from Water Hyacinth Using Enzymatic Hydrolysis

Water hyacinth containing a remarkable amount of cellulose which is found throughout the world as unusable material that can be used as one of the promising source for the production of glucose, initial step to produce bio ethanol. In this current study different types of treatments highest glucose concentration was obtained by hot water treated method. In addition, glucose was produced from water hyacinth using cellulytic enzyme pseudomonas sp., isolated from cow dung. Glucose concentration and production rate increases with the increasing of substrate concentration and enzyme loading, particle size 45µm and a pH 6.00 and temperature 40°C are the optimum for glucose production. A kinetic model rate expression has been developed for enzymatic hydrolysis of water hyacinth based on the Michaelis – Mentens model and parameters are determined. 0.15gm Reducing sugar are separated from the mixture of glucose water solution using 2 gm of water hyacinth. 0.531mg/l Cellulytic composition in water hyacinth are determined.

Association of vertically coupled polymer micro-resonator and phase-sensitive optical low coherence interferometer for label-free biosensing applications

We report on a new accurate investigation tool whose principle is that of a Michelson interferometer with a broadband source, namely a phase-sensitive optical low-coherence interferometer, used to interrogate an optical micro-resonator based sensor for label-free biosensing applications. This set-up, which is able to provide the amplitude and also the phase of the guided mode in a single measurement, is also used to evaluate the performances of the micro-resonators. The best vertically coupled polymer racetrack micro-resonator fabricated displays a Q-factor higher than 38 000 and a finesse of 21 at 1527.7 nm when immersed in deionized water. The association of the phase-sensitive optical low coherence interferometer and the vertically coupled polymer micro-resonator in an opto-fluidic cell for biosensing applications was tested and allowed the detection of a concentration of glucose in water solution around 0.23 mg ml−1.

Fast, broadband, rugged spectrometer for near-infrared measurements of organic solutions and multicomponent mixtures

The mode of operation and theoretical concept behind a type of near-infrared spectrometer is discussed, which is used to measure concentrations of glucose, ethanol, CaCl2, and KCl solutions in water, respectively. The main features of the instrument are its potential for short time-to-measurement resolution on the order of tens of milliseconds, its broad spectral bandwidth from 1.0 to 2.4 μm, and its ruggedness. These features allow the device to operate remotely in field applications and to utilize a wide variety of optical interfaces based on state-of-the-art fiber optic technology. Also, they provide a straightforward path to miniaturization with the concomitant enhancement in time resolution and applicability of the instrument and the technique.

Properties of Molecular Nanojets in Different Solutions

Molecular nanojets generated by sub-nanosecond pulsed laser irradiation have been observed under different conditions such as in glucose–water solutions with different viscosities and in salt-water solutions with different concentrations. Time-resolved shadowgraphy imaging of the molecular nanojets under the different conditions was performed. The molecular nanojets were ejected through the center of a cavitation bubble, which was generated by pulsed laser irradiation of the liquid. The speed and shape of the molecular nanojets and the size of the cavitation bubble changed markedly with the conditions. The speed of a molecular nanojet can be controlled by changing of the viscosity of the glucose–water solution and the concentration of the salt-water solution.