BUSCADOR RECOLECTA

Background
Electrical stimulation is used for enhanced bone fracture healing. Electrochemical processes occur during the electrical stimulation at the electrodes and influence cellular reactions. Our approach aimed to distinguish between electrochemical and electric field effects on osteoblast-like MG-63 cells. We applied 20 Hz biphasic pulses via platinum electrodes for 2 h. The electrical stimulation of the cell culture medium and subsequent application to cells was compared to directly stimulated cells. The electric field distribution was predicted using a digital twin.

Results
Cyclic voltammetry and electrochemical impedance spectroscopy revealed partial electrolysis at the electrodes, which was confirmed by increased concentrations of hydrogen peroxide in the medium. While both direct stimulation and AC-conditioned medium decreased cell adhesion and spreading, only the direct stimulation enhanced the intracellular calcium ions and reactive oxygen species.

Conclusion
The electrochemical by-product hydrogen peroxide is not the main contributor to the cellular effects of electrical stimulation. However, undesired effects like decreased adhesion are mediated through electrochemical products in stimulated medium. Detailed characterisation and monitoring of the stimulation set up and electrochemical reactions are necessary to find safe electrical stimulation protocols., Open Access funding enabled and organized by Projekt DEAL. This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), grant number SFB ELAINE, 1270/1,2–299150580. We also acknowledge the funding from Atracción de Talento Programme, Modalidad‑1 Ref. 2019‑T1/IND‑1335 and the grant PID2021‑128611OB‑I00 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe., Peer reviewed

This publication contains the original data supporting our results concerning the application of biphasic pulsed electrical stimulation on MG-63 cells. We aim to discriminate between effects of the electric field and electrochemically conditioned medium. The dataset consists of the original output files, excel sheets to consolidate the information for the experiments as well as Readme.txt files with most important information concerning the data. For additional information on the material and methods as well as results see the corresponding research article., This research was funded by the Deutsche Forschungsgemeinschaft (DFG, German Research Foundation), grant number SFB ELAINE, 1270/1,2-299150580. We also acknowledge the funding from Atracción de Talento Programme, Modalidad-1 Ref. 2019-T1/IND-1335 and the grant PID2021-128611OB-I00 funded by MCIN/AEI/10.13039/501100011033 and by ERDF A way of making Europe., Peer reviewed

Resumen del trabajo presentado en el TERMIS European Chapter Meeting 2023, celebrado en Manchester, del 28 al 31 de marzo de 2023, INTRODUCTION
Electrical stimulations (ES), with various intensity, frequency, duration, signal shape, etc. are used to enhance tissue regeneration. However, it is not yet clear which combination of parameters is efficient in each application. A relevant approach to refine these sets of parameters is to reveal the significant electrochemical features linked to the biophysical responses [1,2].
Here, we characterized the electrochemical features of different in vitro ES systems and regimes in biologically relevant conditions.

METHODS
We characterized three different systems: miniaturized devices with electrode plates, coated with either Pt thin film (TF) or Pt nanocolumns (NC)[4]; and an 8-well plate with L-shaped Pt wires (W). Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were measured using a potentiostat. Chronoamperometry was carried out for different ES regimes.

RESULTS
Impedance is significantly reduced when NC is used. The NC effective capacitance is larger than that of TF due to its increased electrochemically active area. The safe limits are between -0.7 V and 1.0 V for both NC and TF. Redox peaks were observed in the same potential ranges for both morphologies. Accumulated charge was considerably larger for both morphologies in the potential regions were oxidation of Pt and adsorption-desorption of H2 occur, showing its dependency on the applied potential ranges. Moreover, charge per pulse was around two orders of magnitude larger for NC than for TF in every region.
DISCUSSION AND CONCLUSIONS
The applied electrical signals are not equal to what cells sense due to the electric double layer at the interface and its characteristics are extractable from EIS. Chronoamperometry provides the accumulated charge in the system. The sum of charges passed to the extracellular fluid highly depends on electrode material, operation voltage range, and signal shape. Finally, even being in the safe operating voltage range, faradaic reactions [3], responsible for production of reactive oxygen species, change with the amount of energy injected to the system. This energy correlates with specific reaction peaks in the CV curve.
Electrochemical characterization will make possible to compare the energy and charge introduced to the system for different ES protocols., Funding from Comunidad de Madrid, Ref. 2019-T1/IND-1335, and MCIN/ AEI/ 10.13039/ 501100011033/ FEDER, UE, Ref. PID2021-128611OB-I00.