Electrical Impedance Spectroscopy with Bacterial Biofilms: Neuronal-like Behavior.

Negative capacitance at low frequencies for spiking neurons was first demonstrated in 1941 (K. S. Cole) by using extracellular electrodes. The phenomenon subsequently was explained by using the Hodgkin-Huxley model and is due to the activity of voltage-gated potassium ion channels. We show that Escherichia coli (E. coli) biofilms exhibit significant stable negative capacitances at low frequencies when they experience a small DC bias voltage in electrical impedance spectroscopy experiments. Using a frequency domain Hodgkin-Huxley model, we characterize the conditions for the emergence of this feature and demonstrate that the negative capacitance exists only in biofilms containing living cells. Furthermore, we establish the importance of the voltage-gated potassium ion channel, Kch, using knock-down mutants. The experiments provide further evidence for voltage-gated ion channels in E. coli and a new, low-cost method to probe biofilm electrophysiology, e.g., to understand the efficacy of antibiotics. We expect that the majority of bacterial biofilms will demonstrate negative capacitances.

On-Chip Impedance Spectroscopy of Malaria-Infected Red Blood Cells.

Malaria is a disease that affects millions of people worldwide, particularly in developing countries. The development of accurate and efficient methods for the detection of malaria-infected cells is crucial for effective disease management and control. This paper presents the electrical impedance spectroscopy (EIS) of normal and malaria-infected red blood cells. An EIS microfluidic device, comprising a microchannel and a pair of coplanar electrodes, was fabricated for single-cell measurements in a continuous manner. Based on the EIS results, the aim of this work is to discriminate Plasmodium falciparum-infected red blood cells from the normal ones. Different from typical impedance spectroscopy, our measurement was performed for the cells in a low-conductivity medium in a frequency range between 50 kHz and 800 kHz. Numerical simulation was utilized to study the suitability parameters of the microchannel and electrodes for the EIS experiment over the measurement frequencies. The measurement results have shown that by using the low-conductivity medium, we could focus on the change in the conductance caused by the presence of a cell in the sensing electrode gap. The results indicated a distinct frequency spectrum of the conductance between the normal and infected red blood cells, which can be further used for the detection of the disease.

Classification of Sand-Binder Mixtures from the Foundry Industry Using Electrical Impedance Spectroscopy and Support Vector Machines.

Molding sand mixtures used in the foundry industry consist of various sands (quartz sands, chromite sands, etc.) and additives such as bentonite. The optimum control of the processes involved in using the mixtures and in their regeneration after the casting requires an efficient in-line monitoring method that is not available today. We are investigating whether such a method can be based on electrical impedance spectroscopy (EIS). To establish a database, we have characterized various sand mixtures by EIS in the frequency range from 0.5 kHz to 1 MHz under laboratory conditions. Attempts at classifying the different molding sand mixtures by support vector machines (SVM) show encouraging results. Already high assignment accuracies (above 90%) could even be improved with suitable feature selection (sequential feature selection). At the same time, the standard uncertainty of the SVM results is low, i.e., data assigned to a class by the presented SVMs have a high probability of being assigned correctly. The application of EIS with subsequent evaluation by machine learning (machine-learning-enhanced EIS, MLEIS) in the field of bulk material monitoring in the foundry industry appears possible.

Improved bioimpedance spectroscopy tissue classification through data augmentation from generative adversarial networks.

Bioimpedance spectroscopy is a tissue classification technique with many clinical applications. Similarly to other data-driven methods, it requires large amounts of data to accurately distinguish similar classes of tissue. Classifiers trained on small datasets typically suffer from over-fitting and lack the ability to generalise to previously unseen data. However, a large in or ex vivo spectral database is difficult to attain. Data collection is usually limited to studies that occur infrequently, and publicly available data is often not available. A solution to this problem is to artificially increase the training dataset by creating modified, yet accurate, copies of the original dataset. The most common techniques in spectral classification are to add noise to copies of the original data, over-sample it, or randomly interpolate pairs of the original data. However, simply perturbing or interpolating the data does not guarantee that the new dataset captures the key features of the original data needed for accurate classification. This study proposes a novel way to augment bioimpedance spectral data. It uses generative adversarial networks (GAN)-a model in which two neural networks (NN) compete with each other: while one NN artificially manufactures data that could be mistaken for real data, the role of the second NN is to identify which data it receives has been artificially created. The first NN then interactively adapts its output until the second NN can no longer flag artificially created data. The result is a new dataset that truly represents the features of the original data. In this study, three GAN architectures are used, i.e., the vanilla GAN, the deep convolutional GAN, and the Wasserstein GAN. Then, the generated data is used to train five classification methods, and their results are compared to a baseline that only uses the original data. The results from a dataset of 13 different tissue classes show that the deep convolutional GAN is most statistically similar to the original data and improves classification accuracy by 15% when compared to the same model trained only on the original data. The Wasserstein-GAN architecture also provides significant improvements of up to 24% better accuracy.

Low Concentrations of Gold Nanoparticles as Electric Charge Carriers in Piezoelectric Cement-Based Materials.

Piezoelectric cement-based composites could serve to monitor the strain state of structural elements or act as self-powered materials in structural health monitoring (SHM) applications. The incorporation of piezoelectric materials as an active phase within cement matrices has presented a highly attractive avenue until today. However, their application is challenged by the low electrical conductivity of the hydrated cement matrix. Gold nanoparticles (Au NPs) possess substantial potential for elevating the free electrical charge within the matrix, increasing its electrical conductivity between the Au NPs and the cement matrix, thereby enhancing the piezoelectric response of the composite. In this sense, the objective of this study is to investigate the effects of incorporating low concentrations of gold nanoparticles (Au NPs) (442 and 658 ppm) on the electrical and piezoelectric properties of cement-based composites. Additionally, this study considers the effects of such properties when the material is cured under a constant electric field. Electrical impedance spectroscopy was used to evaluate the polarization resistance and piezoresistive properties of the material. Additionally, open-circuit potential measurements were taken alongside the application of mechanical loads to assess the piezoelectric activity of the composites. The findings revealed a notable decrease in the composite's total electrical resistance, reaching a value of 1.5 ± 0.2 kΩ, almost four times lower than the reference specimens. In the realm of piezoelectricity, the piezoelectric voltage parameter g33 exhibited a remarkable advancement, improving by a factor of 57 when compared to reference specimens. This significant enhancement can be attributed to both the concentration of Au NPs and the electrical curing process. In summary, the outcomes of this study underscore the feasibility of creating a highly electrically conductive cement-based matrix, using low concentrations of gold nanoparticles as electric charge carries, and indicate the possible piezoelectric behavior of the studied compposite.

Circuital modelling in muscle tissue impedance measurements.

Electrical impedance spectroscopy (EIS) stands as a widely employed characterization technique for studying muscular tissue in both physio/pathological conditions. This methodology commonly involves modeling tissues through equivalent electrical circuits, facilitating a correlation between electrical parameters and physiological properties. Within existing literature, diverse equivalent electrical circuits have been proposed, varying in complexity and fitting properties. However, to date, none have definitively proven to be the most suiTable for tissue impedance measurements. This study aims to outline a systematic methodology for EIS measurements and to compare the performances of three widely used electrical circuits in characterizing both physiological and pathological muscle tissue conditions. Results highlight that, for optimal fitting with electrical parameters relevant to tissue characterization, the choice of the circuit to be fitted closely hinges on the specific measurement objectives, including measurement parameters and associated physiological features. Naturally, this necessitates a balance between simplicity and fitting accuracy.

Experimental investigation of freeze injury temperatures in trees and their contributing factors based on electrical impedance spectroscopy.

In trees, injuries resulting from subfreezing temperatures can cause damage to the cellular biofilm system, metabolic functions, and fibrous reticulum, and even cell death. Investigating the occurrence of freezing damage and its contributing factors could help understand the mechanisms underlying freezing injury and prevent the subsequent damage in trees. To achieve this, a laboratory experiment was conducted using cut wood samples from Korean pine (Pinus koraiensis Siebold & Zucc) and Simon poplar (Populus simonii Carr.), and the effects of environmental freezing factors, including freezing temperatures, freezing duration, and cooling rate, on the temperature at which freezing injuries occur were examined using the electrical impedance spectroscopy (EIS) method. The semi-lethal temperature (LT50), as an indicator of freezing injury in wood tissue, was theoretically deduced based on the measured extracellular resistance (r e) using EIS. The contributory factors to changes in LT50 were determined and their relationship was established. The results revealed that all freezing factors exhibited significant effects on electrical impedance characteristics (r e, r i, and τ), significantly influencing the LT50 of the wood. Random forest (RF) and support vector machine (SVM) models were used to assess the contribution of the freezing factors and moisture content (MC). Among the factors examined, freezing duration had the greatest impact on LT50, followed by the MC, whereas the contribution of the cooling rate was minimal. The model accuracies were 0.89 and 0.86 for Korean pine and Simon poplar, respectively. The findings of our study illustrate that the occurrence of freezing injury in trees is primarily influenced by the duration of freezing at specific subzero temperatures. Slow cooling combined with prolonged freezing at low subzero temperatures leads to earlier and more severe freezing damage.

Sensing of gene expression in live cells using electrical impedance spectroscopy and DNA-functionalized gold nanoparticles.

A novel electrical impedance spectroscopy-based method for non-destructive sensing of gene expression in living cells is presented. The approach used takes advantage of the robustness and responsiveness of electrical impedance spectroscopy and the highly specific and selective nature of DNA hybridization. The technique uses electrical impedance spectroscopy and gold nanoparticles functionalized with single-stranded DNA complementary to an mRNA of interest to provide reliable, real-time, and quantifiable data on gene expression in live cells. The system was validated by demonstrating specific detection of the uidA mRNA, which codes for the ß-glucuronidase (GUS) enzyme, in Solanum lycopersicum MsK8 cells. Gold nanoparticles were functionalized with single-stranded DNA oligonucleotides consisting of either a sequence complementary to uidA mRNA or an arbitrary sequence. The DNA-functionalized gold nanoparticles were mixed with cell suspensions, allowing the gold nanoparticles to penetrate into the cells. The impedance spectra of suspensions of cells with gold nanoparticles inserted within them were then studied. In suspensions of uidA-expressing cells and gold nanoparticles functionalized with the complementary single-stranded DNA oligonucleotide, the impedance magnitude in the frequency range of interest was significantly higher (146 %) in comparison to all other controls. Due to its highly selective nature, the methodology has the potential to be used as a precision agricultural sensing system for accurate and real-time detection of markers of stress, viral infection, disease, and normal physiological activities.

Electrical lymph node scanning (ELS) system for real-time intra-operative detection of involved axillary lymph nodes in adjuvant breast cancer patients.

Lymph node (LN) status is an essential prognostic factor in breast cancer (BC) patients, with an important role in the surgical and therapeutic plan. Recently, we have been developed a novel system for real-time intra-operative electrical LN scanning in BC patients. The ELS scores were calibrated by pathological evaluation of the LNs. Herein, we evaluated the efficacy of ELS in a prospective study for non-chemo-treated breast cancer patients. This is a prospective study in which ELS scores are blind for pathologists who declare the clearance or involvement of LNs based on permanent pathology as the gold standard. ELS and frozen-section (FS) pathology results were achieved intra-operatively, and samples were sent for the permanent pathology. The score of ELS did not affect the surgeons' decision, and the treatment approach was carried out based on FS pathology and pre-surgical data, such as imaging and probable biopsies. Patients were recruited from October 2021 through November 2022, and 381 lymph nodes of 97 patients were included in the study. In this study we recruited 38 patients (39.2%) with sentinel lymph node biopsy (SLNB) and 59 patients (60.8%) with ALND. Of the 381 LNs scored by ELS, 329 sentinel LNs underwent routine pathology, while others (n = 52) underwent both FS and permanent pathology. ELS showed a sensitivity of 91.4% for node-positive patients, decreasing to 84.8% when considering all LNs. Using ROC analysis, ELS diagnosis showed a significant AUC of 0.878 in relation to the permanent pathology gold standard. Comparison of ELS diagnosis for different tumor types and LN sizes demonstrated no significant differences, while increasing LN size correlated with enhanced ELS sensitivity. This study confirmed ELS's efficacy in real-time lymph node detection among non-chemo-treated breast cancer patients. The use of ELS's pathological scoring for intra-operative LN diagnosis, especially in the absence of FS pathology or for non-sentinel LN involvement, could improve prognosis and reduce complications by minimizing unnecessary dissection.

A Narrative Review on the Clinical Utility of Electrical Impedance Spectroscopy for Diagnosing High-Grade Cervical Intraepithelial Neoplasia.

Colposcopy constitutes a pivotal step in the diagnosis and management of cervical intraepithelial neoplasia; nevertheless, the method has several inherent and external limitations. Electrical impedance spectroscopic (EIS) has been among the adjuncts that have been developed to increase the diagnostic accuracy of colposcopy. EIS is based on the principle that the trajectory of electrical current alters depending on the consistency of the tissues. In the present study, we investigate the diagnostic accuracy and clinical utility of EIS by means of searching the available evidence. Our search yielded 17 articles during the period 2005-2023. Subsequently, we focused on the performance metrics of the included studies. The general concept is that EIS, in combination with colposcopy, is a method with increased sensitivity and specificity in detecting high-grade cervical intraepithelial neoplasia as compared to colposcopy alone. However, we documented a heterogeneous distribution of these and other metrics, including the positive predictive value, the negative predictive value, and the area under the receiver operating characteristic curve (AUC). Additionally, we located potential confounders that might hamper the measurements of EIS and, as such, warrant further investigation in future research. We conclude that future studies should be directed towards randomized multicentric trials, whereas the advent of artificial intelligence might improve the diagnostic accuracy of the method by helping incorporate a large amount of data.

The Diagnostic Accuracy of Electrical Impedance Spectroscopy-Assisted Colposcopy, HPV mRNA Test, and P16/Ki67 Immunostaining as CIN2+ Predictors in Greek Population.

OBJECTIVE: To evaluate the diagnostic accuracy of Electrical Impedance Spectroscopy (EIS)-assisted colposcopy in detecting CIN2+ Greek women towards standalone colposcopy, HPV mRNA testing, and p16/Ki67 immunostaining. METHODS: We conducted a cross-sectional observational study at the Cervical Pathology Clinic of the 2nd Obstetrics-Gynecology University Department of Hippokration Hospital Thessaloniki involving 316 patients from January 2022 to August 2023. All participants provided liquid-based cervical samples for cytology, HPV mRNA testing, and p16/Ki67 immunostaining. MAIN OUTCOME MEASURES: Subsequently, participants underwent both standalone colposcopy and EIS/ZedScan-assisted colposcopy, followed by cervical punch biopsies. RESULTS: The incorporation of EIS significantly enhanced the sensitivity of colposcopy, increasing it from 54.17% to 100%, equivalent to that of HPV mRNA testing and p16/Ki67 immunostaining, while achieving a high specificity (95.45%). The specificities observed with EIS/ZedScan-assisted and standalone colposcopy were notably superior to those of HPV-related biomarkers (HPV mRNA test and p16/Ki67 immunostaining). When compared to standalone colposcopy, HPV mRNA testing, and p16/Ki67 immunostaining, EIS/ZedScan-assisted colposcopy demonstrated the most favorable combination of Positive and Negative Predictive Values, at 90.57% and 100%, respectively. The inclusion of EIS/ZedScan in colposcopy led to the detection of 44 additional cases of true CIN2+ (100% of the total CIN2+ confirmed histologically) that were missed by standalone colposcopy. This discovery suggests a 45.83% increase in the detection of CIN2+ cases. CONCLUSIONS: The integration of EIS with colposcopy has demonstrated effectiveness in detecting cervical lesions, resulting in a significant detection increase of CIN2+ cases while offering optimal levels of sensitivity, specificity, and predictive values for CIN2+ detection.

A new label free spiral sensor using impedance spectroscopy to characterize hepatocellular carcinoma in tissue and serum samples.

Hepatocellular carcinoma (HCC) stands as the most prevalent form of primary liver cancer, predominantly affecting patients with chronic liver diseases such as hepatitis B or C-induced cirrhosis. Diagnosis typically involves blood tests (assessing liver functions and HCC biomarkers), imaging procedures such as Computed Tomography (CT) and Magnetic Resonance Imaging (MRI), and liver biopsies requiring the removal of liver tissue for laboratory analysis. However, these diagnostic methods either entail lengthy lab processes, require expensive imaging equipment, or involve invasive techniques like liver biopsies. Hence, there exists a crucial need for rapid, cost-effective, and noninvasive techniques to characterize HCC, whether in serum or tissue samples. In this study, we developed a spiral sensor implemented on a printed circuit board (PCB) technology that utilizes impedance spectroscopy and applied it to 24 tissues and sera samples as proof of concept. This newly devised circuit has successfully characterized HCC and normal tissue and serum samples. Utilizing the distinct dielectric properties between HCC cells and serum samples versus the normal samples across a specific frequency range, the differentiation between normal and HCC samples is achieved. Moreover, the sensor effectively characterizes two HCC grades and distinguishes cirrhotic/non-cirrhotic samples from tissue specimens. In addition, the sensor distinguishes cirrhotic/non-cirrhotic samples from serum specimens. This pioneering study introduces Electrical Impedance Spectroscopy (EIS) spiral sensor for diagnosing HCC and liver cirrhosis in clinical serum-an innovative, low-cost, rapid (< 2 min), and precise PCB-based technology without elaborate sample preparation, offering a novel non-labeled screening approach for disease staging and liver conditions.

Electrical Impedance Spectroscopy Quantifies Skin Barrier Function in Organotypic In Vitro Epidermis Models.

3 D human epidermal equivalents (HEEs) are a state-of-the-art organotypic culture model in pre-clinical investigative dermatology and regulatory toxicology. Here, we investigated the utility of electrical impedance spectroscopy (EIS) for non-invasive measurement of HEE epidermal barrier function. Our setup comprised a custom-made lid fit with 12 electrode pairs aligned on the standard 24-transwell cell culture system. Serial EIS measurements for seven consecutive days did not impact epidermal morphology and readouts showed comparable trends to HEEs measured only once. We determined two frequency ranges in the resulting impedance spectra: a lower frequency range termed EISdiff correlated with keratinocyte terminal differentiation independent of epidermal thickness and a higher frequency range termed EISSC correlated with stratum corneum thickness. HEEs generated from CRISPR/Cas9 engineered keratinocytes that lack key differentiation genes FLG, TFAP2A, AHR or CLDN1 confirmed that keratinocyte terminal differentiation is the major parameter defining EISdiff. Exposure to pro-inflammatory psoriasis- or atopic dermatitis-associated cytokine cocktails lowered the expression of keratinocyte differentiation markers and reduced EISdiff. This cytokine-associated decrease in EISdiff was normalized after stimulation with therapeutic molecules. In conclusion, EIS provides a non-invasive system to consecutively and quantitatively assess HEE barrier function and to sensitively and objectively measure barrier development, defects and repair.

Espectroscopia de impedancia eléctrica, una herramienta para aplicaciones biotecnológicas con Lactobacillus casei ATCC 393 / Electrical impedance spectroscopy, a tool for biotechnological applications with Lactobacillus casei ATCC 393

RESUMEN La aplicación de espectroscopia de impedancia eléctrica (EIE), es una técnica que se utiliza para monitorear, detectar y cuantificar microorganismos de interés biotecnológico, con la medición de parámetros eléctricos de respuesta rápida de un medio inoculado a temperatura y agitación constante mediante electrodos sumergidos. Realizando una comparación del modelo de crecimiento y el recuento en placa con los parámetros eléctricos de respuesta, se puede dar una correlación para romper la barrera tecnológica entre la microbiología clásica y los métodos rápidos de detección. La comparación de ambas técnicas fue realizada para determinar el máximo crecimiento de Lactobacillus casei (L. casei) ATCC 393. Se encontró que tras la inoculación, después de 24 h en condiciones microaerofílicas (37 °C), el máximo crecimiento microbiano fue registrado por medio de la EIE, mediante los parámetros -Z- (29,1057) y Deg-Deg0 (24,555°). En contraste con la técnica de conteo en placa, el crecimiento máximo se estimó a las 9 h. Los datos experimentales obtenidos mediante la EIE fueron ajustados por un circuito RC en serie, posteriormente, las curvas generadas fueron ajustadas a los modelos de crecimiento de Gompertz y Boltzman. Usando la técnica de EIE, la impedancia del medio resultó el parámetro más eficiente para la estimación del pico máximo exponencial de crecimiento de L. casei. Se demostró que la EIE constituye una alternativa para la detección rápida de la concentración microbiana en procesos de producción de biomasa para la elaboración de productos alimenticios probióticos.

ABSTRACT The application of electrical impedance spectroscopy (EIS) is a technique used to monitor, detect and quantify microorganisms of biotechnological interest, with the measurement of electrical parameters of rapid response of a medium inoculated at temperature and constant agitation by submerged electrodes. By making a comparison of the growth model and the plate count with the electrical response parameters, a correlation can be made to break the technological barrier between classical microbiology and rapid detection methods. The comparison of both techniques was performed to determine the maximum growth of Lactobacillus casei (L. casei) ATCC 393. It was found that after inoculation, after 24 h under microaerophilic conditions (37 °C), the maximum microbial growth was recorded by medium of the EIE, using the parameters -Z- (29,1057) and Deg-Deg0 (24,555°). In contrast to the plate count technique, maximum growth was estimated at 9 h. The experimental data obtained through the EIE were adjusted by a series RC circuit; later, the generated curves were adjusted to the growth models of Gompertz and Boltzman. Using the EIE technique, the impedance of the medium was the most efficient parameter for the estimation of the maximum exponential growth peak of L. casei. It was demonstrated that the EIE constitutes an alternative for the rapid detection of the microbial concentration in biomass production processes for the elaboration of probiotic food products.

Rapid culture-based detection of living mycobacteria using microchannel electrical impedance spectroscopy (m-EIS)

BACKGROUND: Multiple techniques exist for detecting Mycobacteria, each having its own advantages and drawbacks. Among them, automated culture-based systems like the BACTEC-MGIT™ are popular because they are inexpensive, reliable and highly accurate. However, they have a relatively long "time-to-detection" (TTD). Hence, a method that retains the reliability and low-cost of the MGIT system, while reducing TTD would be highly desirable. METHODS: Living bacterial cells possess a membrane potential, on account of which they store charge when subjected to an AC-field. This charge storage (bulk capacitance) can be estimated using impedance measurements at multiple frequencies. An increase in the number of living cells during culture is reflected in an increase in bulk capacitance, and this forms the basis of our detection. M. bovis BCG and M. smegmatis suspensions with differing initial loads are cultured in MGIT media supplemented with OADC and Middlebrook 7H9 media respectively, electrical "scans" taken at regular intervals and the bulk capacitance estimated from the scans. Bulk capacitance estimates at later time-points are statistically compared to the suspension's baseline value. A statistically significant increase is assumed to indicate the presence of proliferating mycobacteria. RESULTS: Our TTDs were 60 and 36 h for M. bovis BCG and 20 and 9 h for M. smegmatis with initial loads of 1000 CFU/ml and 100,000 CFU/ml respectively. The corresponding TTDs for the commercial BACTEC MGIT 960 system were 131 and 84.6 h for M. bovis BCG and 41.7 and 12 h for M smegmatis, respectively. CONCLUSION: Our culture-based detection method using multi-frequency impedance measurements is capable of detecting mycobacteria faster than current commercial systems.

Caracterización del tejido columnar del cérvix mediante espectroscopia de impedancia eléctrica y modelado computacional / Characterization of cervical columnar tissue through electrical impedance spectroscopy and computer modeling

RESUMEN Introducción: En este artículo se presenta la utilización de la espectroscopia de impedancia eléctrica (EIE) en la caracterización del tejido columnar cervical y como herramienta de apoyo a las técnicas diagnósticas del cáncer de cuello uterino. Métodos: Se realizó un estudio de validez diagnóstica a 30 pacientes no menopáusicas que presentaron ectopia cervical durante la colposcopia. Se obtuvieron 129 espectros de impedancia eléctrica de tejido columnar, que fueron diferenciados en cuatro zonas o puntos de toma de medidas, semejantes a las zonas horarias 12, 3, 6, y 9 de un reloj análogo. Los datos experimentales obtenidos fueron ajustados al modelo de Cole-Cole, que describe la fisiología y estructura del tejido mediante parámetros eléctricos de resistividad R y S, frecuencia característica Fc y capacitancia de membrana Cm. Resultados: La comparación entre tejidos columnares sanos y con lesión en cada uno de los puntos de medida se realizó mediante pruebas no paramétricas U de Mann-Whitney, que mostraron diferencias estadísticamente significativas (p <0,05) para las medianas de R y S, con un nivel de confianza del 95%. Los valores promedio de R y S para tejido columnar sano fueron 2,0 Ω-m y 11,36 Ω-m, con desviación estándar 0,41 y 0,51 respectivamente; mientras que para los tejidos con lesiones el valor promedio R y S fueron de 4,21 Ω-m y 7,03 Ω-m, con desviación estándar 0,40 para ambas medidas. Conclusión: Se encontró que la resistividad del líquido extracelular R y la resistividad de la matriz intracelular S son las que mejor discriminan entre epitelios columnares sanos y aquellos afectados por lesiones.

ABSTRACT Introduction: Thi s pape r shows the implementation of Electrical Impedance Spectroscopy (EIS) in the characterization of the cervical columnar tissue and as a supporting tool to the diagnostic techniques of cervical cáncer Methods: A diagnostic validity study was performed on 30 non-menopausal patients who presented cervical ectopy during colposcopy. A total of 129 electric impedance spectra of columnar tissue was obtained, which were differentiated into four measurement zones or points similar to time zones 12, 3, 6, and 9 of an analog clock. The experimental data obtained were adjusted to the Cole-Cole model which describes the physiology and structure of the tissue through electrical resistivity parameters R and S, characteristic frequency Fc and membrane capacitance Mc. Results: The comparison between healthy and damaged columnar tissue at each of the measurement points was performed using non-parametric Mann-Whitney U tests which showed statistically significant differences (p <0.05) for the R and S medians with a 95% confidence level. The average values of R and S for healthy columnar tissue were 2.0 Ω-m and 11.36 Ω-m, with 0.41 and 0.51 standard deviation respectively, whereas for a damaged tissue the average value of R and S were 4.21 Ω-m and 7.03 Ω-m, with 0.40 standard deviation for both measurements. Conclusions: It was found that the resistivity of the extracellular liquid R, and the resistivity of the intracellular matrix S, are the parameters that better discriminate between healthy columnar epithelia and those affected by lesions.

Caracterización de neoplasias mamarias mediante espectroscopia de impedancia eléctrica: modelo canino / Characterization of mammary neoplasia by electrical impedance spectroscopy: canine model

Introducción: La espectroscopia de impedancia eléctrica (EIE) es una técnica fácil de usar y de bajo costo que se puede utilizar para analizar tejidos biológicos en condiciones normales o patológicas. El objetivo de este trabajo fue caracterizar neoplasias de glándula mamaria benignas y malignas aplicando la técnica EIE en muestras extraídas de 45 caninos hembras (Canis lupus familiaris). Métodos: Se utilizó un medidor de impedancia eléctrica, Hioki 3532-50, para determinar los parámetros bioeléctricos: resistencia de la matriz extracelular (R), resistencia de la matriz intracelular (S), frecuencia característica (Fc) y capacitancia de membrana (Cm) en un rango de frecuencias entre 42 Hz y 5 MHz y se analizaron estadísticamente mediante la prueba no paramétrica U de Mann-Whitney (Wilcoxon) de dos colas. La precisión diagnóstica de la EIE se efectuó a través de curvas características de operación del receptor (COR) y tablas de doble entrada, con la histopatología como referencia. Resultados: Se encontraron diferencias estadísticamente significativas entre el tejido mamario sano y las neoplasias benignas para los parámetros R, Fc y Cm, p-value < 0,05. Entre tejido mamario sano y neoplasias mamarias malignas se encontraron diferencias estadísticamente significativas para R y Fc con un p-value < 0,05. La comparación entre lesiones tumorales benignas y malignas no presentó diferencias estadísticamente significativas, p-value > 0,05, para ninguna de las variables incluidas en este estudio. Conclusiones: De los parámetros analizados por EIE, la resistencia de la matriz extracelular es la que mejor permite diferenciar entre tejidos mamarios normales y neoplásicos. La EIE es una herramienta diagnóstica potencial que puede ser utilizada en la detección de cáncer mamario, con una precisión diagnóstica cercana al 80%.

Introduction: Electrical Impedance Spectroscopy (EIS) it is an easy to use and low-cost technique that can be used to analyze biological tissues in normal or pathological condition. The goal of this work was to characterize benign and malign mammary gland neoplasms applying the EIS technique in 45 female dogs (Canis lupus familiaris). Methods: An impedance meter Hioki 3532-50 was used to determine bioelectric parameters, extracellular matrix resistance (R), intracellular matrix resistance (S), characteristic frequency (Cf), and membrane capacitance (Mc), which were obtained in a 42 Hz and 5 MHz frequencies range. Were statistically analyzed with the non-parametric test of two-tailed MannWhitney (Wilcoxon). The diagnostic precision of the test was performed using receiver operating characteristics (ROC) and two-way tables using histopathology results as reference. Results: Significant differences between healthy mammary tissue and benign neoplasms were found for variables R, Cf and Mc (p < 0.05). There were statistically major differences between the healthy mammary tissue and malign mammary tumors groups for R and Cf (p < 0.05). The comparison between malign and benign tumor lesions did not show a statistically significant difference, p-value > 0.05, for any of the variables included in this study. Conclusion: Among all parameters analyzed for EIS, the extracellular matrix resistance R is the one that best allows differentiating between healthy and neoplastic mammary tissues. EIS is a diagnostic tool that can be used for breast cancer detection with a diagnostic precision close to 801%.