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This article proposes a method for measuring glucose concentration as a possible promising way to create a non-invasive glucometer. The dependence of the complex resistance of a solution of sodium chloride with different concentrations of glucose is investigated. In fist the glucose concentrations were calculated in saline to carry out these measurements. Further we prepared solutions (test samples) with a content of 3, 5, and 10 mmol per liter. We also created a board layout for measurements, that allowed us to vary solutions with different glucose concentrations. Using an immittance meter, we measured the complex resistance as a function of frequency in the range from 25 Hz to 1 MHz. At a medium frequency, we observed a resonance. We also found that at a frequency of 2 kHz there is a clear dependence of the complex resistance on the increase in glucose in solution. The obtained measurement data is of great interest for non-contact monitoring of glucose concentration in biological fluids.

Although blood remains a gold standard diagnostic fluid for most health exams, it involves an unpleasant and relatively invasive sampling procedure (finger pricking or venous draw). Saliva contains many relevant and useful biomarkers for diagnostic purposes, and its collection, in contrast, is noninvasive and can be obtained with minimal effort. Current saliva analyses are, however, achieved using chromatography or lateral flow assays, which, despite their high accuracy and sensitivity, can demand expensive laboratory-based instruments operated by trained personnel or offer only semiquantitative results. In response, we investigated electrochemical aptamer-based (E-AB) biosensors, a reagentless sensing platform, to allow for continuous and real-time measurements directly in undiluted, unstimulated human whole saliva. As a proof-of-concept study, we developed E-AB biosensors capable of detecting low-molecular-weight analytes (glucose and adenosine monophosphate (AMP)). To our knowledge, we report the first E-AB sensor for glucose, an approach that is inherently independent of its chemical reactivity in contrast to home glucometers. For these three sensors, we evaluated their figures of merits, stability, and reusability over short- and long-term exposure directly in saliva. In doing so, we found that E-AB sensors allow rapid and convenient molecular measurements in whole saliva with unprecedented sensitivities in the pico- to nanomolar regime and could be regenerated and reused up to 7 days when washed and stored in phosphate-buffered saline at room temperature. We envision that salivary molecular measurements using E-AB sensors are a promising alternative to invasive techniques and can be used for improved point-of-care clinical diagnosis and at-home measurements.

Interest in sensors and their applications is rapidly evolving, mainly driven by the huge demand of technologies whose ultimate purpose is to improve and enhance health and safety. Different electromagnetic technologies have been recently used and achieved good performances. Despite the plethora of literature, limitations are still present: limited response control, narrow bandwidth, and large dimensions. MetaSurfaces, artificial 2D materials with peculiar electromagnetic properties, can help to overcome such issues. In this paper, a generic tool to model, design, and manufacture MetaSurface sensors is developed. First, their properties are evaluated in terms of impedance and constitutive parameters. Then, they are linked to the structure physical dimensions. Finally, the proposed method is applied to realize devices for advanced sensing and medical diagnostic applications: glucose measurements, cancer stage detection, water content recognition, and blood oxygen level analysis. The proposed method paves a new way to realize sensors and control their properties at will. Most importantly, it has great potential to be used for many other practical applications, beyond sensing and diagnostics.

Abstract: In this study we synthesized Pt nanoparticles supported on carbon Vulcan (Pt/C), a cheap and high surface area carbon. Compared to the commercialized Pt/C, which showed a moderate activity towards the oxidation of H2O2 and a high catalytic activity to the interferences specially AP; the synthesized Pt/C illustrated a high activity towards the oxidation of H2O2 and negligible response towards the oxidation of the interferences at high applied potentials (>0.6V). This difference in the catalytic behavior was attributed to the homogenous distribution of the synthesized Pt nanoparticles in the supporting carbon Vulcan as well as, to their relatively bigger size (8–9nm) compared to (1–2nm) estimated for the commercialized Pt/C. This particular and interesting behavior of the synthesized Pt/C was used to encapsulate glucose oxidase along with a small amount of Nafion for the manufacturing of a glucose sensor. The resulting glucose sensor has a high sensitivity of 1.25μA/mMmm2, which compares very well with other glucose sensors based on precious metal nanoparticles and carbon nanotubes, an extended linear range up to 45mM without using any outer polymer layer, low interference from endogenous species, short response time (<5s), was stable for at least 1 month and, found to be dependable for glucose determination in human serum. [Copyright &y& Elsevier]

Abstract: A new glucose microbiosensor based on glucose oxidase immobilized on the transducer surface by alternating current electrophoretic deposition (AC-EPD) is described. Deposition is carried out by applying an asymmetrical alternating current (AC) polarization between two electrodes to an enzyme dissolved in a low conductivity solution. This process, based on enzyme electrophoresis, allows the rapid manufacturing of biosensors with a very good sensitivity. Current responses to glucose up to 430nA/mMmm2 were obtained using a low-activity enzyme (5.6U/mg), which is due to the preservation of the enzyme activity. The latter was confirmed by FT-IR. The thick enzymatic layer deposited on the transducer prevents a number of the interferences influencing the biosensor response, thus the need in an inner permselective membrane at formation of the biosensor recognition element is avoided. In order to optimize the linearity of the sensor response and provide a biocompatible interface in contact with biological samples, an outer layer of polyurethane (PU) was applied after the deposition of the enzyme. The resulting glucose sensor with PU outer layer had a sensitivity of at least 13nA/mMmm2, a linear range up to 60mM, low interference from endogenous species, short response time (<6s) and was stable for at least 45 days. Contrary to the GOx electrode where errors in the measurements were observed due to the moderate linearity, the sensor with the PU outer layer is shown to be effective for the determination of glucose concentrations in critically sick rabbits where the concentration of glucose might be more than 30mM. [Copyright &y& Elsevier]

Objectives: To investigate factors contributing to analytical bias in POCT glucose values generated by the NICU versus the core laboratory.Methods: The LifeScan Flexx hospital system glucose meters (SureStep) were used in precision and comparison studies between the NICU and laboratory (ABL715 and Vitros 950).Results: Analysis of 40 neonatal blood samples revealed a positive bias between the NICU glucose meters versus either the laboratory glucose meter or instrument (mean difference of 0.28 and 0.21 mmol/L, respectively). Linear regression analysis (R2 = 0.0584) of the difference in glucose results versus time elapsed between measurements indicated that the bias observed between the NICU and laboratory glucose meters was not due to in vitro glycolysis for samples transported on ice. Further analysis indicated that the bias appeared to be mostly operator driven, with different NICU operators exhibiting different mean biases. Increasing the amount of blood applied to the SureStep Pro test strip (e.g., 60 vs. 20 μL), led to higher values for glucose concentration for the same blood. Nearly 50% of all glucose values reported for the NICU were obtained by the SureStep Flexx glucose meters in a 3-month period following the introduction of POCT, yet the number of laboratory-reported glucose results for the same period increased by 21% as compared to the previous year.Conclusions: Operator error appears to be a source of bias present between the NICU and laboratory, and despite glucose meter utilization in the NICU, the number of glucose measurements by the central laboratory increased after POCT introduction. [Copyright &y& Elsevier]

Interest in sensors and their applications is rapidly evolving, mainly driven by the huge demand of technologies whose ultimate purpose is to improve and enhance health and safety. Different electromagnetic technologies have been recently used and achieved good performances. Despite the plethora of literature, limitations are still present: limited response control, narrow bandwidth, and large dimensions. MetaSurfaces, artificial 2D materials with peculiar electromagnetic properties, can help to overcome such issues. In this paper, a generic tool to model, design, and manufacture MetaSurface sensors is developed. First, their properties are evaluated in terms of impedance and constitutive parameters. Then, they are linked to the structure physical dimensions. Finally, the proposed method is applied to realize devices for advanced sensing and medical diagnostic applications: glucose measurements, cancer stage detection, water content recognition, and blood oxygen level analysis. The proposed method paves a new way to realize sensors and control their properties at will. Most importantly, it has great potential to be used for many other practical applications, beyond sensing and diagnostics. [ABSTRACT FROM AUTHOR]

A modeling and design approach is proposed for nanoparticle-based electromagnetic devices. First, the structure properties were analytically studied using Maxwell’s equations. The method provides us a robust link between nanoparticles electromagnetic response (amplitude and phase) and their geometrical characteristics (shape, geometry, and dimensions). Secondly, new designs based on “metamaterial” concept are proposed, demonstrating great performances in terms of wide-angle range functionality and multi/wide behavior, compared to conventional devices working at the same frequencies. The approach offers potential applications to build-up new advanced platforms for sensing and medical diagnostics. Therefore, in the final part of the article, some practical examples are reported such as cancer detection, water content measurements, chemical analysis, glucose concentration measurements and blood diseases monitoring. [ABSTRACT FROM AUTHOR]