Broadband Dielectric Spectroscopy for Quantitative Analysis of Glucose and Albumin in Multicomponent Aqueous Solution

Abstract

We show the measurement of the physiological range of glucose in a multicomponent aqueous solution through multivariate analysis of broadband dielectric spectra from 500 MHz to 50 GHz. To obtain higher glucose selectivity, we apply spectral preprocessing to the dielectric loss spectra to extract feature values of glucose. Using regression models derived from different concentrations of glucose in a solution with bovine serum albumin (BSA), we analyze solutions considering the physiological range of both components. Prediction errors for the glucose and BSA concentrations are estimated to be 54 and 83 mg/dL, respectively, even for varied concentrations of each component. We also investigate the dependence of the glucose prediction error on the solution temperature. The prediction error for the glucose concentrations is estimated to be 99 mg/dL at a difference of ±1 K. This technique will be ease to implement with a broadband microwave sensor or with biomedical sensors that require the capability to analyze multiple components in solutions.

On the Selectivity of Planar Microwave Glucose Sensors with Multicomponent Solutions

“…However, the relative variations of the dielectric losses for water-albumin solutions seem lower than those for water-glucose solutions, which allows us to expect reduced errors for the glucose concentration detection due to the presence of unknown concentrations of albumin, especially for comparatively low concentrations of albumin when frequencies up to ~4-5 GHz are involved. This phenomenon is expected to be more accentuated for higher frequencies (~5-15 GHz) [68].…”

“…Sets of solutions involved in this study (concentrations in g/dL). Considering the dielectric properties of these solutions, the dielectric loss (i.e., the imaginary part of the effective permittivity, ε") of water-glucose and water-albumin solutions shows, in general, a similar behavior for both solutes separately [68]. It would be, therefore, logical to expect a sensitivity reduction for the combined variation of both solutes in the solution, although this could also depend on other effects derived from possible interactions between these solutes.…”

“…Finally, restricted by the permittivitybased measurement principle, the selectivity only to glucose concentration changes has been singled out as one of the main current challenges for these sensors [28,66,67]. Very recent works have started to face the selectivity challenge by means of broadband [68] or multifrequency [69] measurements followed by a modeling and postprocessing extraction of multiple features from the sample.…”

Noninvasive Glucose Sensing in Dielectrically Equivalent Multilayer Skin Phantoms

“…Minimally invasive measurements can be made with microneedle patches − or implantable sensors , consisting of glucose-responsive materials such as glucose oxidase ,, or phenylboronic acid gel. − Although securing enough glucose selectivity is a challenging issue, noninvasive measurements using electromagnetic waves, − ultrasonic waves, and magnetic resonance have great potential to liberate patients of the above-mentioned burden. In particular, gigahertz-band electromagnetic waves (microwaves) that penetrate the skin can be used to measure glucose in aqueous solutions, − saline solutions, − and hydrogels, − as well as in animals and humans. , In addition, there are various means of radiating radio waves, for example, open-ended coaxial probes, split-ring resonators, , microstripe antennas, patch antennas, cavity sensors, coplanar sensors, and multimodality analysis . Biomimetic homogeneous hydrogel phantoms − made of, for instance, gelatin, agarose, poly­(methyl methacrylate), and flour can be used in combination with computer simulations , for validation before the experiments are conducted on actual organisms.…”

“…In particular, gigahertz-band electromagnetic waves (microwaves) that penetrate the skin can be used to measure glucose in aqueous solutions, 23−26 saline solutions, 27−29 and hydrogels, 30−32 as well as in animals 11 and humans. 33,34 In addition, there are various means of radiating radio waves, for example, openended coaxial probes, 35 split-ring resonators, 36,37 microstripe antennas, 38 patch antennas, 39 cavity sensors, 40 coplanar sensors, 41 and multimodality analysis. 42 Biomimetic homogeneous hydrogel phantoms 43−46 made of, for instance, gelatin, 43 agarose, 44 poly(methyl methacrylate), 45 and flour 46 can be used in combination with computer simulations 47,48 for validation before the experiments are conducted on actual organisms.…”