Plasmonic Retinal Prosthesis

总结 在包括光遗传学刺激和干细胞疗法在内的各种恢复视力的方法中， 基于电极的视网膜假体已经验证了其临床前景。然而，它受到基本的 局限性：器械植入需要复杂的手术，数量有限且固定 刺激部位的位置，最重要的是，具有低的空间分辨率，因为电流传播在 像视网膜一样的传导介质。十年前，红外光的光热刺激开启了 在没有光遗传学的帮助下“远程”激活神经元，但红外光的强烈吸水性 导致大量组织加热和相关的不利影响。为了实现细胞分辨率，“远程”神经 激活没有大量加热，我们已经证明，结合使用金纳米粒子和近， 红外光（可被水忽略地吸收）可通过表面等离子体共振产生高度局部化的热， 这可以通过产生电容性膜电流和/或打开温度敏感的 离子通道我们还表明，适当的纳米颗粒化学共轭进一步增强了 近红外刺激的功效。然而，这种有前途的神经调节方法还没有 证明了它作为视网膜假体的潜力。在这里，我们建议开发，优化和验证这种新的 技术，称为等离子体视网膜假体，并组成其潜力与几个重要的优势 与基于电极的视网膜假体相比：（1）它不需要任何装置植入， 仅涉及玻璃体内注射金纳米棒（AuNRs）;（2）单细胞分辨率可以在 体内;（3）刺激位置或靶向神经节细胞是自由可调的;（4）可激活的神经节细胞的数量 每单位时间的神经元可以高达每秒100，000个神经元（在我们的试点设置中）;以及（5）性能 随着相关技术的进步， 位于眼睛外面。我们将通过理论研究，体外优化， 体内验证和长期测试。首先，由于在任何新颖的神经接口中， 为了对系统进行精确建模，优化设计，我们将提出我们的数学神经元模型 调查目前正在讨论的两种机制，并确定以下方面的初步参数 动物实验（目标1）。接下来，使用我们定制的实验装置， 和荧光显微镜，我们将开发和优化视网膜神经节神经元的单细胞刺激， 用遗传编码的Ca 2+指示剂的小鼠视网膜外植体，随后证明模式化的 多神经元刺激和AuNR化学的优化（目标2）。最后，我们将整合我们的 实验和理论工作，以验证在体内，图案化的近红外刺激的视网膜诱导 视觉皮层中的神经激活类似于自然视觉刺激，参数被进一步优化， 并将进行纵向实验，以观察和量化其长期疗效和毒性（目标3）。

SUMMARY Among various approaches to restore vision, including optogenetic stimulation and stem cell therapy, only the electrode-based retinal prosthesis has validated its clinical promises. However, it suffers from fundamental limitations: it requires a complicated surgery for device implantation, has both the limited number and fixed location of stimulation sites, and above all, has a low spatial resolution since electric currents spread in conductive media like the retina. A decade ago, photothermal stimulation with infrared light opened the possibility of ‘remotely’ activating neurons without the aid of optogenetics, but the strong water absorption of infrared light leads to bulk tissue heating and associated adverse effects. To enable cellular-resolution, ‘remote’ neural activation without the bulk heating, we have demonstrated that a combined use of gold nanoparticles and near- infrared light (negligibly absorbed by water) can produce highly-localized heat via surface plasmon resonance, and this can activate neurons by generating capacitive membrane currents and/or opening temperature-sensitive ion channels. We also have shown that appropriate chemical conjugation of nanoparticles further enhances the efficacy of near-infrared stimulation. This promising neuromodulation approach, however, has yet not demonstrated its potential as a retinal prosthesis. Here, we propose to develop, optimize, and validate this novel technology, termed plasmonic retinal prosthesis, and compose its potential with several important advantages when compared to the electrode-based retinal prostheses: (1) it does not require any device implantation but only involves intravitreal injection of gold nanorods (AuNRs); (2) the single-cell resolution can be achieved in vivo; (3) stimulation locations or targeted ganglion cells are freely adjustable; (4) the number of activatable neurons per unit time can be as high as 100,000 neurons per second (in our pilot setup); and (5) the performance is further upgradable after ‘installation’ as the relevant technologies advance because every key component locates outside the eye. We will develop this promising technology through theoretical study, ex vivo optimization, in vivo validation, and long-term testing. First, since it is essential in any novel neural interface to have an accurate model of the system in order to optimize the design, we will advance our mathematical neuron model to investigate two mechanisms currently under debate and determine the initial parameters for the following animal experiments (Aim 1). Next, using our custom experimental setup that integrates a scanning laser system and fluorescence microscope, we will develop and optimize single-cell stimulation of retinal ganglion neurons in retina explants of mice with genetically-encoded Ca2+ indicators, followed by both the demonstration of patterned multi-neuron stimulation and the optimization of AuNR chemistry (Aim 2). Finally, we will integrate our experimental and theoretical work to validate in vivo that patterned near-infrared stimulation of the retina induces neural activation in the visual cortex similar to natural visual stimuli, with the parameters being further optimized, and will perform a longitudinal experiment to observe and quantify its long-term efficacy and toxicity (Aim 3).