Remote Cell Growth Sensing Using Self-Sustained Bio-Oscillations

A smart sensor system for cell culture real-time supervision is proposed, allowing for a significant reduction in human effort applied to this type of assay. The approach converts the cell culture under test into a suitable “biological” oscillator. The system enables the remote acquisition and management of the “biological” oscillation signals through a secure web interface. The indirectly observed biological properties are cell growth and cell number, which are straightforwardly related to the measured bio-oscillation signal parameters, i.e., frequency and amplitude. The sensor extracts the information without complex circuitry for acquisition and measurement, taking advantage of the microcontroller features. A discrete prototype for sensing and remote monitoring is presented along with the experimental results obtained from the performed measurements, achieving the expected performance and outcomes

Practical Characterization of Cell-Electrode Electrical Models in Bio-Impedance Assays

This paper presents the fitting process followed to adjust the parameters of the electrical model associated to a cell-electrode system in Electrical Cell-substrate Impedance Spectroscopy (ECIS) technique, to the experimental results from cell-culture assays. A new parameter matching procedure is proposed, under the basis of both, mismatching between electrodes and time-evolution observed in the system response, as consequence of electrode fabrication processes and electrochemical performance of electrode-solution interface, respectively. The obtained results agree with experimental performance, and enable the evaluation of the cell number in a culture, by using the electrical measurements observed at the oscillation parameters in the test circuits employed.Ministerio de Economía y Competitividad TEC2013-46242-C3-1-

Volume conduction and EEG measurements within the brain: A quantitative approach to the influence of electrical spread on the linear relationship of activity measured at different locations

When recording referentially brain field potentials with several electrodes at relatively small tip separations, a linear relationship between the simultaneously recorded signals may arise solely as a result of volume conduction (electrical spread). A method is described to quantify the linear relationship due to electrical spread in a situation with independent neuronal sources.\ud \ud In rat under urethane anaesthesia, records were made during theta activity in the hippocampus with two electrodes against a reference with electrode tip separations between 0–3 mm. Frequency analysis of EEG epochs and computation of coherence were carried out.\ud \ud As an estimate of linear relationship between the recorded signals due to electrical spread the mean value of coherence (cohm) of a frequency band outside the range containing most power of theta rhythm was calculated.\ud \ud The results show a fairly constant decay of cohm at increasing electrode separation, reaching a value of 0.1 at a distance varying between 0.8-1.4 mm. This means that neurones at a distance of 0.4–0.7 mm from a recording electrode make a contribution of −25 dB to a recorded signal of 0 dB.\ud \ud The results of a simple model of volume conduction producing linear relationship between two recorded signals are in good agreement with the experimental results.\ud \ud The influence of linear relationship of the activity of neurones on volume conduction properties and on coherence is discussed

Non-linear dielectric spectroscopy of microbiological suspensions

<p>Abstract</p> <p>Background</p> <p>Non-linear dielectric spectroscopy (NLDS) of microorganism was characterized by the generation of harmonics in the polarization current when a microorganism suspension was exposed to a sinusoidal electric field. The biological nonlinear response initially described was not well verified by other authors and the results were susceptible to ambiguous interpretation. In this paper NLDS was performed to yeast suspension in tripolar and tetrapolar configuration with a recently developed analyzer.</p> <p>Methods</p> <p>Tripolar analysis was carried out by applying sinusoidal voltages up to 1 V at the electrode interface. Tetrapolar analysis was carried on with sinusoidal field strengths from 0.1 V cm^-1to 70 V cm^-1. Both analyses were performed within a frequency range from 1 Hz through 100 Hz. The harmonic amplitudes were Fourier-analyzed and expressed in dB. The third harmonic, as reported previously, was investigated. Statistical analysis (ANOVA) was used to test the effect of inhibitor an activator of the plasma membrane enzyme in the measured response.</p> <p>Results</p> <p>No significant non-linearities were observed in tetrapolar analysis, and no observable changes occurred when inhibitor and activator were added to the suspension. Statistical analysis confirmed these results.</p> <p>When a pure sinus voltage was applied to an electrode-yeast suspension interface, variations higher than 25 dB for the 3rd harmonic were observed. Variation higher than 20 dB in the 3rd harmonics has also been found when adding an inhibitor or activator of the membrane-bounded enzymes. These variations did not occur when the suspension was boiled.</p> <p>Discussion</p> <p>The lack of result in tetrapolar cells suggest that there is no, if any, harmonic generation in microbiological bulk suspension. The non-linear response observed was originated in the electrode-electrolyte interface. The frequency and voltage windows observed in previous tetrapolar analysis were repeated in the tripolar measurements, but maximum were not observed at the same values.</p> <p>Conclusion</p> <p>Contrary to previous assertions, no repeatable dielectric non-linearity was exhibited in the bulk suspensions tested under the field and frequency condition reported with this recently designed analyzer. Indeed, interface related harmonics were observed and monitored during biochemical stimuli. The changes were coherent with the expected biological response.</p

A comparative study of the physiological properties of the inner ear in Doppler shift compensating bats (Rhinolophus rouxi and Pteronotus parnellit)

Cochlear microphonic (CM) and evoked neural (N-1) potentials were studied in two species of Doppler shift compensating bats with the aid of electrodes chronically implanted in the scala tympani. Potentials were recorded from animals fully recovered from the effects of anesthesia and surgery. InPteronotus p. parnellii andRhinolophus rouxi the CM amplitude showed a narrow band, high amplitude peak at a frequency about 200 Hz above the resting frequency of each species. InPteronotus the peak was 25–35 dB higher in amplitude than the general CM level below or above the frequency of the amplitude peak. InRhinolophus the amplitude peak was only a few dB above the general CM level but it was prominent because of a sharp null in a narrow band of frequencies just below the peak. The amplitude peak and the null were markedly affected by body temperature and anesthesia. InPteronotus high amplitude CM potentials were produced by resonance, and stimulated cochlear emissions were prominent inPteronotus but they were not observed inRhinolophus. InPteronotus the resonance was indicated by a CM afterpotential that occurred after brief tone pulses. The resonance was not affected by the addition of a terminal FM to the stimulus and when the ear was stimulated with broadband noise it resulted in a continual state of resonance. Rapid, 180 degree phase shifts in the CM were observed when the stimulus frequency swept through the frequency of the CM amplitude peak inPteronotus and the frequency of the CM null inRhinolophus. These data indicate marked differences in the physiological properties of the cochlea and in the mechanisms responsible for sharp tuning in these two species of bats