In this study, we present a first-of-a-kind biological-hardware-software tool to evaluate the physiological condition of in vitro myotubes in response to electrical stimulation. We demonstrate that impedance spectroscopy on a microelectrode array can testify for physiological changes of muscle cells under electrical stimulation. The platform is designed for simultaneous bioimpedance spectroscopy, electrical stimulation, and optical microscopy. It includes a microelectrode array, a custom hardware-software interface, and a commercial impedance analyzer. We used a well-established muscle cell model (C2C12) and developed a culture protocol suited for long-term recordings on microelectrode arrays. Electrical stimulation was applied with carbon electrodes and ad hoc electronics for current stimulation. Muscle cell bioimpedance measurement was complemented with optical microscopy video to record contractions. Then, the influence of electrical stimulation on the contractile activity of myotubes and on their bioimpedance was analyzed. Results validated the functionality of the hardware/software platform when used with our contractile muscle model. A bioimpedance-based metric was defined to evaluate changes in myotubes’ physiology. After playing multiple stimulation scenarios, analysis showed that the bioimpedance metric decreases as duration or frequency of stimulation increase.

Repeated fish handling may cause stress, which biases experiments and so affects the results. In order to reduce this, the present study investigates the benefit of using bioimpedance analysis to estimate morphological parameters. Bioimpedance analysis is a non-lethal and integrative electrical measurement that can be used to estimate several kinds of physiological parameters and is used in medicine and ecological studies. In particular, bioimpedance can monitor the individual growth of fish, which is a prerequisite for most biological and ecological studies, as body size is one of the best predictors for numerous life history traits and ecological parameters. After a short review on the use of bioimpedance measurement in medicine and ecology, we illustrate the potential of bioimpedance spectroscopy, as opposed to single frequency measurement, for experimental studies on fish. Using a monolithic four-contact electrode and a cost-effective portable system, we conducted bioimpedance spectroscopy on 159 sardines. The association between the length, weight, and electrical parameters obtained at different frequencies from the bioimpedance spectroscopy was investigated. Our results show that accounting for more than one frequency substantially improves the prediction of length and weight. We conclude that bioimpedance could potentially be a powerful tool for monitoring fish growth in ecological studies.

Bioimpedance spectroscopy consists of measuring the complex impedance of biological tissues over a large frequency domain. This method is particularly convenient for physiological studies or health monitoring systems. For a wide range of applications, devices need to be portable, wearable or even implantable. Next generation of bioimpedance sensing systems thus require to be implemented with power and resource savings in mind. Impedance measurement methods are divided into two main categories. Some are based on “single-tone” signals while the others use “multi-tone” signals. The firsts benefit from a very simple analysis that may consist of synchronous demodulation. However, due to necessary frequency sweep, the total measurement may take a long time. On the other hand, generating a multi-frequency signal allows the seconds to cover the whole frequency range simultaneously. This is at the cost of a more complex analysis algorithm. This makes both approaches hardly suitable for embedded applications. In this paper, we propose an intermediate approach that combines the speed of multi-tone systems with a low-resource analysis algorithm. This results in a minimal implementation using only adders and synchronous adc. For optimal performances, this small footprint digital processing can be synthesized and embedded on a mixed-mode integrated circuit together with the analog front-end. Moreover, the proposed implementation is easily scalable to fit an arbitrary frequency range. We also show that the resulting impact on noise sensitivity can be mitigated.