Oscillation-Based Spectroscopy for Cell-Culture Monitorization

Biological Impedance is a physical property related to the state and inherent evolution of biological samples. Among the existing impedance measurement methods, Oscillation-Based (OB) tests are a simple and smart solution to indirectly measure impedance correlated with the amplitude and frequency of the generated oscillation which are proportional to the sample under test. An OB test requires tuning of the system blocks to specifications derived from every measurement problem. The OB setup must be done to obtain the optimum measurement sensitivity for the specific constraints imposed by the system under test, electronic interfaces, and electrodes employed for test. This work proposes the extension of OB measurement systems to spectroscopy test, enabling a completely new range of applications for this technology without the restrictions imposed by setting a fixed frequency on the electrical oscillator. Some examples will be presented to the measurement of cell cultures samples, considering the corresponding circuit interfaces and electric models for the electrode-cell system. The proposed analysis method allows the selection of the best oscillator elements for optimum sensitivity range in amplitude and frequency oscillation values, when a specific cell culture is monitored for the OB system

DC electrical stimulation enhances proliferation and differentiation on N2a and MC3T3 cell lines

Background: Electrical stimulation is a novel tool to promote the differentiation and proliferation of precursor cells. In this work we have studied the effects of direct current (DC) electrical stimulation on neuroblastoma (N2a) and osteoblast (MC3T3) cell lines as a model for nervous and bone tissue regeneration, respectively. We have developed the electronics and encapsulation of a proposed stimulation system and designed a setup and protocol to stimulate cell cultures. Methods: Cell cultures were subjected to several assays to assess the effects of electrical stimulation on them. N2a cells were analyzed using microscope images and an inmunofluorescence assay, differentiated cells were counted and neurites were measured. MC3T3 cells were subjected to an AlamarBlue assay for viability, ALP activity was measured, and a real time PCR was carried out. Results: Our results show that electrically stimulated cells had more tendency to differentiate in both cell lines when compared to non-stimulated cultures, paired with a promotion of neurite growth and polarization in N2a cells and an increase in proliferation in MC3T3 cell line. Conclusions: These results prove the effectiveness of electrical stimulation as a tool for tissue engineering and regenerative medicine, both for neural and bone injuries. Bone progenitor cells submitted to electrical stimulation have a higher tendency to differentiate and proliferate, filling the gaps present in injuries. On the other hand, neuronal progenitor cells differentiate, and their neurites can be polarized to follow the electric field applied.Universidad de Sevilla US-1380661Junta de Andalucía P18-FR-2038. 2020–202

A Plethysmography Capacitive Sensor for Real-Time Monitoring of Volume Changes in Acute Heart Failure

A small, wearable, low-weight, and low-power-consumption device for plethysmography capacitive sensing is proposed herein. The device allows carrying out real-time monitoring of leg volume changes in patients suffering from heart failure (HF) conditions. The dynamic of fluid overload in patients with acute HF serves as a prognosis marker for this type of severe disease and, consequently, these patients can benefit from a wearable monitoring system to measure their body volume evolution during and after hospitalization. Our approach is based on contactless capacitive wearable structures implemented by two different sensor realizations located in the ankle: 180°-parallel capacitor plates (two modes of operations are compared, with the patient’s body connected to ground and to the average voltage between plates) and planar-parallel capacitor plates whose overlapped surface varies with the volume of the patient’s leg. Both realizations exhibit good sensitivity to leg volume changes. The acquisition of capacitance values is performed via a simple circuit that achieves notable performance in simulated volume analysis. A preliminary pilot clinical prototype is described as well

Body posture determination for Heart Failure patients from ankle orientation measurements

Heart-Failure (HF) is among the leading hospitalization causes in modern healthcare systems. In this paper, a method for performing continuous patient monitoring is presented with a focus on low power consumption. A prototype wearable device is being developed at the University of Sevilla to collect measurements. Among the sensing components there are two major blocks formed by a commercial biological impedance analog frontend from Analog Devices (AD5940) and an Inertial Motion Unit (IMU) capable of estimating attitude of the device. This information could provide a tremendous amount of information for the physician and help diagnose and remote monitor patients with HF. A major factor that can be analyzed to provide information on patient status is activity level and body states; time spent walking or standing, laying down or seated. In this work, a body tracking / activity estimation method is proposed for low power continuous monitoring. This study reports good results characterizing the laying down position and discriminating between laying down and standing/walking and seated. The presented results are relevant for clinical practice since body motion and position can serve as a health marker for patients. Additionally, the acquired motion information can be further processed to better understand artifacts and variations in the analog impedance measurements

From Bioimpedance to Volume Estimation: A Model for Edema Calculus in Human Legs

Heart failure (HF) is a severe disease and one of the most important causes of death in our society nowadays. A significant percentage of patients hospitalized for decompensation of heart failure are readmitted after some weeks or months due to an expected bad and uncontrolled HF evolution due to the lack of the patient supervision in real time. Herein is presented a straightforward electric model useful for volume leg section calculus based on the bioimpedance test as a way to assist with the acute HF patient’s supervision. The method has been developed for time-evolution edema evaluation in patients’ corresponding legs. The data are picked up with a wearable device specifically developed for acute heart failure patients. As an initial step, a calibration method is proposed to extract the extracellular volume component from bioimpedance measurements done in healthy subjects, and then applied to unhealthy ones. The intra- and extracellular resistance components are calculated from fitted Cole–Cole model parameters derived from BI spectroscopy measurements. Results obtained in a pilot assay, with healthy subjects and heart failure subjects, show sensitivities in leg volume [mL/Ω], with much lower values for healthy than in unhealthy people, being an excellent biomarker to discriminate between both. Finally, circadian cycle evolution for leg volume has been measured from the bioimpedance test as an extension of the work, enabling an alternative parameter for the characterization of one day of human activity for any person.Ministerio de Ciencia, Innovación y Universidades DTS19/00134, DTS19/00137Plan Andaluz de Investigación, Desarrollo e Innovación AT21-00010-US