Non-Invasive Drosophila ECG Recording by Using Eutectic Gallium-Indium Alloy Electrode: A Feasible Tool for Future Research on the Molecular Mechanisms Involved in Cardiac Arrhythmia

Abstract

Background Drosophila heart tube is a feasible model for cardiac physiological research. However, obtaining Drosophila electrocardiograms (ECGs) is difficult, due to the weak signals and limited contact area to apply electrodes. This paper presents a non-invasive Gallium-Indium (GaIn) based recording system for Drosophila ECG measurement, providing the heart rate and heartbeat features to be observed. This novel, high-signal-quality system prolongs the recording time of insect ECGs, and provides a feasible platform for research on the molecular mechanisms involved in cardiovascular diseases.MethodsIn this study, two types of electrode, tungsten needle probes and GaIn electrodes, were used respectively to noiselessly conduct invasive and noninvasive ECG recordings of Drosophila. To further analyze electrode properties, circuit models were established and simulated. By using electromagnetic shielded heart signal acquiring system, consisted of analog amplification and digital filtering, the ECG signals of three phenotypes that have different heart functions were recorded without dissection.Results and DiscussionThe ECG waveforms of different phenotypes of Drosophila recorded invasively and repeatedly with n value (n>5) performed obvious difference in heart rate. In long period ECG recordings, non-invasive method implemented by GaIn electrodes acts relatively stable in both amplitude and period. To analyze GaIn electrode, the correctness of GaIn electrode model established by this paper was validated, presenting accuracy, stability, and reliability.ConclusionsNoninvasive ECG recording by GaIn electrodes was presented for recording Drosophila pupae ECG signals within a limited contact area and signal strength. Thus, the observation of ECG changes in normal and SERCA-depleted Drosophila over an extended period is feasible. This method prolongs insect survival time while conserving major ECG features, and provides a platform for electrophysiological signal research on the molecular mechanism involved in cardiac arrhythmia, as well as research related to drug screening and development.

Probing the Fractal Pattern of Heartbeats in Drosophila Pupae by Visible Optical Recording System

“…We note that there was a large phase difference between optically and electronically measured rhythms in the previous study 27 . This phase difference may be resulted from a conductional delay from the origin of pacing to the imaged cardiomyocytes.…”

Strategies for interface issues and challenges of neural electrodes

“…97 After evaluating the electrical impedance and polarization voltage of the electrode, it is believed that the electrodes can meet the demands of practical applications. In addition, the electrode made from EGaIn (eutectic gallium indium) LM can not only be used in vitro to detect ECG physiological signals, 98,99 but also be implanted in vivo for neural activity monitoring. Recently, Dong et al applied the screen printing technology to fabricate a stretchable electrode array (SEA) with EGaIn LM as the conductor and PDMS as the substrate, with a resolution of ∼50 μm.…”

Preparations, Characteristics and Applications of the Functional Liquid Metal Materials

“…With low polarization voltage, the alloy electrode has good signal quality, which is essential for recording weak signals. [102] In addition to the surface bioelectrodes, the liquid metal could also be directly injected into the biological body to make 3D embedded medical electronics, such as the injectable electrodes at the target tissues shown in Figure 10d. As shown in Figure 10c, the EGaIn bioelectrodes were even used for noninvasive ECG measurement on the small insects such as drosophila.…”

“…[109] Similar operation has also been carried out on a mouse with whole body perfusion, and the result is presented in Figure 12c. [102] Copyright 2013, Kuo et al d) Schematics for injectable 3-D fabrication of medical device, and animal tests on electrode injected inside the mouse body. [110] The principle has generalized purpose and can be extended to many engineering applications other than the biomedical field.…”