Three-Dimensional MnO2 Nanoflowers Integrated into Flexible Optoelectronic Biointerfaces for Safe and Effective Neuronal Photostimulation

The utilization of optoelectronic biointerfaces for wireless and electrical control of neurons has garnered significant interest, particularly in the field of photovoltaic retinal implants. Three-dimensional pseudocapacitive nanomaterials with porous structures and large surface areas hold high promise for developing efficient optoelectronic biointerfaces that can effectively convert light into stimulating ionic currents because of their high electrode-electrolyte capacitance. In this study, we present the successful integration of flexible optoelectronic biointerfaces with three-dimensional manganese dioxide (MnO2) nanoflowers, enabling the achievement of safe and effective photostimulation of neurons. The synthesis of MnO2 nanoflowers involves a chemical bath deposition process on the return electrode, initially coated with a MnO2 seed layer using cyclic voltammetry. The resulting nanoflowers exhibit remarkable interfacial capacitance (&gt;10 mF.cm-2) and photogenerated charge density (&gt;20 μC.cm-2) even at low light intensity (1 mW.mm-2). Significantly, the MnO2 nanoflowers facilitate the generation of safe capacitive currents through reversible Faradaic reactions and exhibit no toxicity towards hippocampal neurons in vitro, making them a highly promising material for seamless biointerfacing with electrogenic cells. The functionality of the developed optoelectronic biointerfaces is validated through patch-clamp electrophysiology recordings conducted on hippocampal neurons in the whole-cell configuration and we observed repetitive and rapid firing of action potentials in response to light pulse trains. This study demonstrates the vast potential of electrochemically-deposited three-dimensional pseudocapacitive nanomaterials as a robust and versatile nanotool for optoelectronic control of neurons.<br/><br/><b>Reference </b><br/>L. Kaya, O. Karatum, R. Balamur, H. N. Kaleli, A. Onal, S. A. Vanalakar, M. Hasanreisoğlu, S. Nizamoglu, "MnO2 Nanoflower Integrated Optoelectronic Biointerfaces for Photostimulation of Neurons," Advanced Science (2023). (Accepted)<br/><br/><b>Funding</b><br/>SN acknowledges funding by the European Union (ERC, MESHOPTO, 101045289). Views and opinions expressed are however those of the author(s) only and do not necessarily reflect those of the European Union or the European Research Council Executive Agency. Neither the European Union nor the granting authority can be held responsible for them. S.N. also acknowledges the Scientific and Technological Research Council of Turkey (TUBITAK) with Project No.s 121C301, 120E329, and 121E376.