Liu Chien-Hao, Lu Yung-Shan, Chen Po-Chun, Lee Chia-Fone
Department of Mechanical Engineering, National Taiwan University, Taipei, Taiwan.
Department of Materials and Mineral Resource Engineering, Institute of Materials Science and Engineering, National Taipei University of Technology, Taipei, Taiwan.
Tzu Chi Med J. 2020 Jul 13;33(1):42-48. doi: 10.4103/tcmj.tcmj_46_20. eCollection 2021 Jan-Mar.
Conventional cochlear implants provide patients who are deaf with hearing via electrical intracochlear stimulations. Stimulation electrodes are inserted into the cochlea through a cochleostomy or round window membrane (RWM) approach. However, these methods might induce cochlear ossificans and loss of residual hearing by damaging inner ear structures. To avoid an invasive electrode insertion, we developed a novel bone-guided extracochlear implant that stimulated the auditory nerves between the cochlear bones and the RWM to prevent cochlea damage. Power consumption plays an important role in wireless implantable electronic devices. Therefore, we aimed to investigate the effects of different electrodes on the stimulating threshold currents of the auditory nerve and the power consumption of bone-guided extracochlear implants using a commercial stimulator.
Inert aurum (Au) electrodes were compared with biocompatible platinum (Pt) and iridium oxide (IrO) electrodes in practical implantable applications. IrO electrodes were used for their high-charge storage capacity, low impedance, and biocompatibility. The electrodes were fabricated via sputtering and were experimentally characterized with cyclic voltammetry and then examined using tests.
Based on electrical auditory brainstem responses, IrO electrodes yielded lower acoustic nerve-stimulating threshold currents (132 μA) compared with Au electrodes (204 μA). IrO electrodes also had a lower acoustic nerve stimulating threshold current (132 μA) compared with Pt electrodes (168 μA).
As expected, IrO electrodes were beneficial in the development of multielectrode bone-guided extracochlear implants, with the lowest acoustic nerve-stimulating threshold and current consumptions compared with Au and Pt electrodes.
传统人工耳蜗通过耳蜗内电刺激为失聪患者提供听力。刺激电极通过耳蜗造口术或圆窗膜（RWM）途径插入耳蜗。然而，这些方法可能会因损伤内耳结构而导致耳蜗骨化和残余听力丧失。为避免侵入性电极插入，我们开发了一种新型骨导式耳蜗外植入物，其刺激耳蜗骨与圆窗膜之间的听神经，以防止耳蜗损伤。功耗在无线可植入电子设备中起着重要作用。因此，我们旨在使用商用刺激器研究不同电极对听神经刺激阈值电流和骨导式耳蜗外植入物功耗的影响。
在实际可植入应用中，将惰性金（Au）电极与生物相容性铂（Pt）和氧化铱（IrO）电极进行比较。使用IrO电极是因其具有高电荷存储容量、低阻抗和生物相容性。电极通过溅射制造，并通过循环伏安法进行实验表征，然后进行测试。
基于电听觉脑干反应，与Au电极（204μA）相比，IrO电极产生的听神经刺激阈值电流更低（132μA）。与Pt电极（168μA）相比，IrO电极的听神经刺激阈值电流也更低（132μA）。
正如预期的那样，IrO电极有利于多电极骨导式耳蜗外植入物的开发，与Au和Pt电极相比，其听神经刺激阈值和电流消耗最低。
