title: 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.
  
  
  METHODS
  In 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.
  
  
  CONCLUSIONS
  The 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.
  
  
  CONCLUSIONS
  Noninvasive 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.
authors.affiliation: Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan.
authors.forename: Po-Hung
authors.initials: PH
authors.lastname: Kuo
authors.affiliation: Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan.
authors.forename: Te-Hsuen
authors.initials: TH
authors.lastname: Tzeng
authors.affiliation: Graduate Institute of Biomedical Electronics and Informatics, National Taiwan University, Taipei, Taiwan.
authors.forename: Yi-Chun
authors.initials: YC
authors.lastname: Huang
authors.affiliation: Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan.
authors.forename: Yu-Hao
authors.initials: YH
authors.lastname: Chen
authors.affiliation: Center for Dynamical Biomarkers and Translation Medicine, National Central University, Taoyuan, Taiwan; and Research Center for Adaptive Data Analysis, National Central University, Taoyuan, Taiwan.
authors.forename: Yi-Chung
authors.initials: YC
authors.lastname: Chang
authors.affiliation: Section of Cardiology, Department of Internal Medicine, National Taiwan University Hospital and National Taiwan University College of Medicine, Taipei, Taiwan.
authors.forename: Yi-Lwun
authors.initials: YL
authors.lastname: Ho
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: June-Tai
authors.initials: JT
authors.lastname: Wu
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Hsiu-Hsian
authors.initials: HH
authors.lastname: Lee
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Po-Jung
authors.initials: PJ
authors.lastname: Lai
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Kwei-Yan
authors.initials: KY
authors.lastname: Liu
authors.affiliation: Institute of Molecular Medicine, College of Medicine, National Taiwan University, Taipei, Taiwan.
authors.forename: Ya-Chen
authors.initials: YC
authors.lastname: Cheng
authors.affiliation: Graduate Institute of Electronics Engineering, National Taiwan University, Taipei, Taiwan.
authors.forename: Shey-Shi
authors.initials: SS
authors.lastname: Lu
mesh_terms: D000818:Animals; D001145:Arrhythmias, Cardiac / Q000175:diagnosis / Q000503:physiopathology; D004330:Drosophila; D004562:Electrocardiography; D004566:Electrodes; D012106:Research