DTU Fotonik, Technical University of Denmark, Lyngby, Denmark.
Department of Neuroscience, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
J Neural Eng. 2022 Feb 24;19(1). doi: 10.1088/1741-2552/ac5267.
. Optical fiber devices constitute significant tools for the modulation and interrogation of neuronal circuitry in the mid and deep brain regions. The illuminated brain area during neuromodulation has a direct impact on the spatio-temporal properties of the brain activity and depends solely on the material and geometrical characteristics of the optical fibers. In the present work, we developed two different flexible polymer optical fibers (POFs) with integrated microfluidic channels (MFCs) and an ultra-high numerical aperture (UHNA) for enlarging the illumination angle to achieve efficient neuromodulation.. Three distinct thermoplastic polymers: polysulfone, polycarbonate, and fluorinated ethylene propylene were used to fabricate two step-index UHNA POF neural devices using a scalable thermal drawing process. The POFs were characterized in terms of their illumination map as well as their fluid delivery capability in phantom and adult rat brain slicesA 100-fold reduced bending stiffness of the proposed fiber devices compared to their commercially available counterparts has been found. The integrated MFCs can controllably deliver dye (trypan blue) on-demand over a wide range of injection rates spanning from 10 nl minto 1000 nl min. Compared with commercial silica fibers, the proposed UHNA POFs exhibited an increased illumination area by 17% and 21% under 470 and 650 nm wavelength, respectively. In addition, a fluorescent light recording experiment has been conducted to demonstrate the ability of our UHNA POFs to be used as optical waveguides in fiber photometry.. Our results overcome the current technological limitations of fiber implants that have limited illumination area and we suggest that soft neural fiber devices can be developed using different custom designs for illumination, collection, and photometry applications. We anticipate our work to pave the way towards the development of next-generation functional optical fibers for neuroscience.
光纤器件是调制和检测中深层脑区神经元回路的重要工具。神经调节过程中被照亮的大脑区域直接影响大脑活动的时空特性，而这仅取决于光纤的材料和几何特性。在本工作中，我们开发了两种具有集成微流控通道（MFC）和超高数值孔径（UHNA）的新型柔性聚合物光纤（POF），以扩大照明角度，实现高效的神经调节。我们使用三种不同的热塑性聚合物：聚砜、聚碳酸酯和氟化乙烯丙烯来制作两种阶跃折射率 UHNA POF 神经器件，采用可扩展的热拉伸工艺。我们从照明图谱以及在幻影和成年大鼠脑片中的流体输送能力两方面对 POF 进行了表征。与市售的同类光纤相比，所提出的光纤器件的弯曲刚度降低了 100 倍。集成的 MFC 可按需以 10 nl min 至 1000 nl min 的广泛注射速率来控制地输送染料（台盼蓝）。与商业的石英光纤相比，所提出的 UHNA POF 在 470nm 和 650nm 波长下分别将照明区域增加了 17%和 21%。此外，我们还进行了荧光光记录实验，以证明我们的 UHNA POF 可作为光纤光度测定中的光学波导使用。我们的结果克服了纤维植入物当前的技术限制，即有限的照明区域，并且我们建议可以使用不同的定制设计来开发用于照明、收集和光度测定应用的软神经纤维器件。我们期望我们的工作为下一代神经科学功能光纤的发展铺平道路。
