Petrovic Jelena, Lange Fred, Hohlfeld Dennis
Institute for Electronic Appliances and Circuits, Faculty of Computer Science and Electrical Engineering, University of Rostock, Albert-Einstein-Str. 2, 18059 Rostock, Germany.
Institute for Biomedical Engineering, ETH Zürich, 8092 Zürich, Switzerland.
J Neural Eng. 2023 May 9;20(3). doi: 10.1088/1741-2552/accecf.
Optogenetic modulation of neuronal activity requires precise and flexible light delivery to deep brain regions. Flat cleaved optical fibers combined with electrodes are widely used in implantable optogenetic devices for light delivery and electrical monitoring of neural activity. However, the flat fiber tip geometry induces serious tissue damage upon insertion, and makes it difficult to adjust and control the spatial extent of illumination within the brain. With their strongly increased tissue-compatibility and the possibility of spatial illumination control, tapered fibers outperform cleaved fibers in targeted neural photo-stimulation.In this work, we describe our device concept, and present a novel approach for reproducible fabrication of tapered fiber tips via grinding. Furthermore, we characterize recording electrodes by commenting data obtained from electrochemical impedance spectroscopy (EIS). We also investigate the impact of different cone angles (14°, 30°, 60°, and 90°) on the illumination profile and optical throughput.. We fabricated a fiber-based optrode with cone tip and two deposited electrodes. Custom grinding setup for fabrication of tapered fiber tips with various cone angles is developed as a part of our research. Microscope images showed very good optical quality of cone tips. The results of transmitted optical power measurements performed with integrating sphere suggest that, compared to the flat cleaved optical fiber, transmitted power decreases exponentially with cone angle reduction. Obtained emission profiles (as induced fluorescence in Rhodamine 6G water solution) indicate very strong effect of cone angle on shape and size of illumination volume. Results obtained from EIS show the effect of electrode size on its recording capability.. Compared to optrodes with flat cleaved optical fiber, the demonstrated fiber-based optrode with cone tip allows controlled light delivery with reduced invasiveness. The possibility to fabricate reproducible fiber tips with various cone angles enables control of light delivery in optogenetic experiment. The results presented here give neuroscientists the possibility to choose the appropriate tissue-compatible cone geometry depending on their stimulation requirements.
神经元活动的光遗传学调制需要将精确且灵活的光传递至脑深部区域。扁平切割光纤与电极相结合,被广泛应用于可植入光遗传学设备中,用于光传递以及对神经活动的电监测。然而,扁平光纤尖端的几何形状在插入时会导致严重的组织损伤,并且难以调整和控制脑内照明的空间范围。锥形光纤具有更强的组织相容性以及空间照明控制的可能性,在靶向神经光刺激方面优于切割光纤。在这项工作中,我们描述了我们的设备概念,并提出了一种通过研磨可重复制造锥形光纤尖端的新方法。此外,我们通过对从电化学阻抗谱(EIS)获得的数据进行评论来表征记录电极。我们还研究了不同锥角(14°、30°、60°和90°)对照明轮廓和光通量的影响。我们制造了一个带有锥形尖端和两个沉积电极的基于光纤的光电极。作为我们研究的一部分,开发了用于制造具有各种锥角的锥形光纤尖端的定制研磨装置。显微镜图像显示锥形尖端具有非常好的光学质量。用积分球进行的透射光功率测量结果表明,与扁平切割光纤相比,透射功率随着锥角减小呈指数下降。获得的发射轮廓(如罗丹明6G水溶液中的诱导荧光)表明锥角对照明体积的形状和大小有非常强烈的影响。从EIS获得的结果显示了电极尺寸对其记录能力的影响。与带有扁平切割光纤的光电极相比,所展示的带有锥形尖端的基于光纤的光电极能够以更低的侵入性实现可控的光传递。制造具有各种锥角的可重复光纤尖端的可能性使得在光遗传学实验中能够控制光传递。这里展示的结果使神经科学家能够根据他们的刺激需求选择合适的与组织相容的锥形几何形状。