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Colella L.,Ecole Polytechnique Federale de Lausanne | Beyer C.,ETH Zurich | Frohlich J.,ETH Zurich | Talary M.,Biovotion | Renaud P.,Ecole Polytechnique Federale de Lausanne
Bioelectrochemistry | Year: 2012

The dielectric response of biconcave erythrocytes exposed to d-glucose and l-glucose has been investigated using a double array of planar interdigitated microelectrodes on a glass microchip. Erythrocytes are analyzed under physiological conditions suspended in hypo-osmolar balanced solutions containing different glucose concentrations (0-20. mM). The glucose effect on the cellular dielectric properties is evaluated by analyzing the spectra using two different approaches, the equivalent circuit model and a modified model for ellipsoidal particles. The results show that at elevated glucose concentration (15. mM) the membrane capacitance increases by 36%, whereas the cytosol conductivity slightly decreases with a variation of about 15%. On the contrary, no variation has been registered with l-glucose, a biologically inactive enantiomer of d-glucose. The paper discusses the possible mechanism controlling the membrane dielectric response. As the external d-glucose increases, the number of activated glucose transporter in the erythrocyte membrane raises and the transition from sugar-free state to sugar-bounded state induces a change in the dipole moments and in the membrane capacitance. © 2011 Elsevier B.V.

PubMed | University of Basel, Hebrew University of Jerusalem, Biovotion and ETH Zurich
Type: Comparative Study | Journal: Journal of diabetes science and technology | Year: 2015

We study here the influence of different patients and the influence of different devices with the same patients on the signals and modeling of data from measurements from a noninvasive Multisensor glucose monitoring system in patients with type 1 diabetes. The Multisensor includes several sensors for biophysical monitoring of skin and underlying tissue integrated on a single substrate.Two Multisensors were worn simultaneously, 1 on the upper left and 1 on the upper right arm by 4 patients during 16 study visits. Glucose was administered orally to induce 2 consecutive hyperglycemic excursions. For the analysis, global (valid for a population of patients), personal (tailored to a specific patient), and device-specific multiple linear regression models were derived.We find that adjustments of the model to the patients improves the performance of the glucose estimation with an MARD of 17.8% for personalized model versus a MARD of 21.1% for the global model. At the same time the effect of the measurement side is negligible. The device can equally well measure on the left or right arm. We also see that devices are equal in the linear modeling. Thus hardware calibration of the sensors is seen to be sufficient to eliminate interdevice differences in the measured signals.We demonstrate that the hardware of the 2 devices worn on the left and right arms are consistent yielding similar measured signals and thus glucose estimation results with a global model. The 2 devices also return similar values of glucose errors. These errors are mainly due to nonstationarities in the measured signals that are not solved by the linear model, thus suggesting for more sophisticated modeling approaches.

Safrai E.,Hebrew University of Jerusalem | Ishai P.B.,Hebrew University of Jerusalem | Caduff A.,Hebrew University of Jerusalem | Caduff A.,Biovotion | And 4 more authors.
Bioelectromagnetics | Year: 2012

Recent work has demonstrated that the reflection coefficient of human skin in the frequency range from 95 to 110GHz (W band) mirrors the temporal relaxation of stress induced by physical exercise. In this work, we extend these findings to show that in the event of a subtle trigger to stress, such as mental activity, a similar picture of response emerges. Furthermore, the findings are extended to cover not only the W band (75-110GHz), but also the frequency band from 110 to 170GHz (D band). We demonstrate that mental stress, induced by the Stroop effect and recorded by the galvanic skin response (GSR), can be correlated to the reflection coefficient in the aforementioned frequency bands. Intriguingly, a light physical stress caused by repeated hand gripping clearly showed an elevated stress level in the GSR signal, but was largely unnoted in the reflection coefficient in the D band. The implication of this observation requires further validation. © 2011 Wiley Periodicals, Inc.

Zanon M.,University of Padua | Sparacino G.,University of Padua | Facchinetti A.,University of Padua | Talary M.S.,Biovotion | And 3 more authors.
Sensors (Switzerland) | Year: 2013

In diabetes research, non-invasive continuous glucose monitoring (NI-CGM) devices represent a new and appealing frontier. In the last years, some multi-sensor devices for NI-CGM have been proposed, which exploit several sensors measuring phenomena of different nature, not only for measuring glucose related signals, but also signals reflecting some possible perturbing processes (temperature, blood perfusion). Estimation of glucose levels is then obtained combining these signals through a mathematical model which requires an initial calibration step exploiting one reference blood glucose (RBG) sample. Even if promising results have been obtained, especially in hospitalized volunteers, at present the temporal accuracy of NI-CGM sensors may suffer because of environmental and physiological interferences. The aim of this work is to develop a general methodology, based on Monte Carlo (MC) simulation, to assess the robustness of the calibration step used by NI-CGM devices against these disturbances. The proposed methodology is illustrated considering two examples: the first concerns the possible detrimental influence of sweat events, while the second deals with calibration scheduling. For implementing both examples, 45 datasets cbance. The second case study shows how to identify the best time interval to update the model's calibration for improving the accuracy of the estimated glucose. The methodology proposed in this work is of general applicability and can be helpful in making those incremental steps in NI-CGM devices development needed to further improve their performance. © 2013 by the authors; licensee MDPI, Basel, Switzerland.

Ishai P.B.,Hebrew University of Jerusalem | Talary M.S.,Biovotion | Caduff A.,Biovotion | Levy E.,Hebrew University of Jerusalem | Feldman Y.,Hebrew University of Jerusalem
Measurement Science and Technology | Year: 2013

In this review, we present an overview of the state of the art concerning the fundamental properties of electrode polarization (EP) of interest in the measurement of high conductivity samples and its implications for both dielectric (DS) and impedance spectroscopy (IS). Initially a detailed description of what constitutes EP is provided and the problems that it induces. Then, we review some of the more popular models that have been used to describe the physical phenomena behind the formation of the ionic double layer. Following this we shall enumerate the common strategies used historically to correct its influence on the measured signals in DS or in IS. Finally we also review recent attempts to employ fractal electrodes to bypass the effects of EP and to offer some physical explanation as to the limitations of their use. © 2013 IOP Publishing Ltd.

Puzenko A.,Hebrew University of Jerusalem | Levy E.,Hebrew University of Jerusalem | Shendrik A.,Hebrew University of Jerusalem | Talary M.S.,Biovotion | And 2 more authors.
Journal of Chemical Physics | Year: 2012

In this, the third part of our series on the dielectric spectrum symmetrical broadening of water, we consider the nucleotide aqueous solutions. Where in Parts I [E. Levy, J. Chem. Phys. 136, 114502 (2012)10.1063/1.3687914] and II [E. Levy, J. Chem. Phys. 136, 114503 (2012)10.1063/1.3691183], the dipole-dipole or ion-dipole interaction had a dominant feature, now the interplay between these two types of dipole-matrix interactions will be considered. We present the results of high frequency dielectric measurements of different concentrations of adenosine monophosphateadenosine-5′- triphosphate aqueous solutions. We observed the Cole-Cole broadening of the main relaxation peak of the solvent in the solutions. Moreover, depending on the nucleotide concentration, we observed both types of dipole-matrix interaction. The 3D trajectory approach (described in detail in Part I) is applied in order to highlight the differences between the two types of interaction. © 2012 American Institute of Physics.

Zanon M.,University of Padua | Sparacino G.,University of Padua | Facchinetti A.,University of Padua | Riz M.,University of Padua | And 3 more authors.
Medical and Biological Engineering and Computing | Year: 2012

Non-invasive continuous glucose monitoring (NI-CGM) sensors are still at an early stage of development, but, in the near future, they could become particularly appealing in diabetes management. Solianis Monitoring AG (Zurich, Switzerland) has proposed an approach for NI-CGM based on a multi-sensor concept, embedding primarily dielectric spectroscopy and optical sensors. This concept requires a mathematical model able to estimate glucose levels from the 150 channels directly measured through the Multisensor. A static multivariate linear regression model (with order and parameters common to the entire population of subjects) was proposed for such a scope (Caduff et al., Biosens Bioelectron 26:3794-3800, 2011). The aim of this work is to evaluate the accuracy in the estimation of glucose levels and trends that the NI-CGM Multisensor platform can achieve by exploiting different techniques for model identification, namely, ordinary least squares, subset variable selection, partial least squares and least absolute shrinkage and selection operator (LASSO). Data collected in human beings monitored for a total of 45 study days were used for model identification and model test. Several metrics of standard use in the diabetes scientific community to measure point and clinical accuracy of glucose sensors were used to assess the models. Results indicate that the LASSO technique is superior to the others shrinking many channel weights to zero thus leading to smoother glucose profiles and resulting in a more robust model to possible artifacts in the Multisensor data. Although, as expected, the performance of the NI-CGM system with the LASSO model is not yet comparable with that of enzyme-based needle glucose sensors, glucose trends are satisfactorily estimated. Considering the non-invasive nature of the multi-sensor platform, this result can have an immediate impact in the current clinical practice, e.g., to integrate sparse selfmonitoring of blood glucose data with an indication of the glucose trend to aid the diabetic patient in dealing with, or even preventing in the short time scale, the threats of critical events such as hypoglycaemia. © International Federation for Medical and Biological Engineering 2012.

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Embodiments of the present invention comprise systems and methods for noninvasion measurements of physiological properties of tissues. The system comprises a light emitter, an optical detector, a mechanical sensor and a processor. The light emitter is capable of emitting light of at least two different wavelengths and comprises at least one light source. The processor is capable of evaluating physiological properties of the tissues from measurements of the optical and the mechanical sensor. More precisely, the processor is capable of evaluating physiological properties of venous blood by using data measured by the mechanical sensor and the optical detector. For example, the oxygenation of venous blood can be measured. Furthermore, the systems can optionally comprise a light emitter which emits three wavelengths and/or the light emitter and the optical detector are arranged in reflection geometry and are located at a distance of at most 10 mm from each other.

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