Among the several unresolved issues, profound/total loss of low-frequency residual hearing after cochlear implant fixation is the most frequent event. Even after several attempts such as modifications in the design of electrodes, improvement in the surgical procedures and use of protective drugs to minimize the trauma and its after-effects, residual hearing has been retained in less than 50% patients only. Surgical procedure and mechanical trauma at the electrode insertion site are thought to be responsible for excess generation of reactive oxygen species (ROS) following initiation of inflammatory cytokines resulting into loss of residual hearing due to programmed cell death of essential inner ear structures. Though very recent studies have reported the use of conventional antioxidants to preserve the residual hearing, they have their own limitations. With the emerging need of better and effective antioxidants, nanoceria has spurred immense research interest on utilizing its unique catalytic characteristics for ROS-associated diseases. Nanoceria has shown effective protection against several ROS-induced damages compared to conventional antioxidants such as vitamin C and vitamin E. The objective of the present work is to develop an understanding about the underlying mechanism of loss of residual hearing and propose a novel method based on delivery of nanoceria to minimize it. The first part of the article highlights the failure of cochlear implants, nature of failures and revised surgeries due to loss of residual hearing. Subsequently, the article explores the relation among surgical/mechanical trauma, excess generation of ROS at electrode insertion site, progressive death of hair cells and loss of residual hearing. Finally, effectiveness of radical scavenging characteristics of nanoceria along with controlling parameters and involved mechanisms has been reviewed. The present work also focuses on the limitations and challenges of nanoceria in clinical applications. Based on the literature review, it is hypothesized that the residual hearing loss is associated with excess generation of ROS and it is proposed that the delivery of effective antioxidants/radical scavengers having a good longevity and regenerative ability is expected to reduce the excess level of ROS and retain the residual hearing.

中文翻译：

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Nanoceria 的自由基清除最大限度地减少氧化应激引起的残余听力损失：综述

在几个未解决的问题中，人工耳蜗固定后低频残余听力的严重/完全丧失是最常见的事件。即使经过多次尝试，例如修改电极设计、改进手术程序和使用保护性药物以最大程度地减少创伤及其后遗症，仍然只有不到 50% 的患者保留了残余听力。电极插入部位的外科手术和机械创伤被认为是导致炎性细胞因子启动后活性氧 (ROS) 过量产生的原因，导致由于基本内耳结构的程序性细胞死亡而导致残余听力丧失。尽管最近的研究报告了使用传统抗氧化剂来保护残余听力，他们有自己的局限性。随着对更好、更有效的抗氧化剂的新需求，纳米氧化铈激发了对利用其独特的催化特性治疗 ROS 相关疾病的巨大研究兴趣。与维生素 C 和维生素 E 等传统抗氧化剂相比，纳米纤维素已显示出对几种 ROS 诱导的损伤的有效保护。本工作的目的是了解残余听力损失的潜在机制，并提出一种基于纳米纤维素的输送以将其最小化。文章的第一部分重点介绍了人工耳蜗植入的失败、失败的性质以及由于残余听力损失而导致的修正手术。随后，文章探讨了手术/机械创伤与电极插入部位ROS过量产生之间的关系，毛细胞逐渐死亡和残余听力丧失。最后，综述了纳米氧化铈自由基清除特性的有效性以及控制参数和相关机制。目前的工作还侧重于纳米氧化铈在临床应用中的局限性和挑战。根据文献综述，假设残余听力损失与 ROS 的过量生成有关，并提出具有良好寿命和再生能力的有效抗氧化剂/自由基清除剂的递送有望降低 ROS 的过量水平并保留残余听力。目前的工作还侧重于纳米氧化铈在临床应用中的局限性和挑战。根据文献综述，假设残余听力损失与 ROS 的过量生成有关，并提出具有良好寿命和再生能力的有效抗氧化剂/自由基清除剂的递送有望降低 ROS 的过量水平并保留残余听力。目前的工作还侧重于纳米氧化铈在临床应用中的局限性和挑战。根据文献综述，假设残余听力损失与 ROS 的过量生成有关，并提出具有良好寿命和再生能力的有效抗氧化剂/自由基清除剂的递送有望降低 ROS 的过量水平并保留残余听力。