Huang Sizhe, Liu Xinyue, Lin Shaoting, Glynn Christopher, Felix Kayla, Sahasrabudhe Atharva, Maley Collin, Xu Jingyi, Chen Weixuan, Hong Eunji, Crosby Alfred J, Wang Qianbin, Rao Siyuan
Department of Biomedical Engineering, University of Massachusetts, Amherst, MA 01003, United States.
Department of Mechanical Engineering, Massachusetts Institute of Technology, Cambridge, MA, 02139, United States.
Res Sq. 2023 May 9:rs.3.rs-2864872. doi: 10.21203/rs.3.rs-2864872/v1.
Bioelectronic devices made of soft elastic materials exhibit motion-adaptive properties suitable for brain-machine interfaces and for investigating complex neural circuits. While two-dimensional microfabrication strategies enable miniaturizing devices to access delicate nerve structures, creating 3D architecture for expansive implementation requires more accessible and scalable manufacturing approaches. Here we present a fabrication strategy through the control of metamorphic polymers' amorphous-crystalline transition (COMPACT), for hydrogel bioelectronics with miniaturized fiber shape and multifunctional interrogation of neural circuits. By introducing multiple cross-linkers, acidification treatment, and oriented polymeric crystalline growth under deformation, we observed about an 80% diameter decrease in chemically cross-linked polyvinyl alcohol (PVA) hydrogel fibers, stably maintained in a fully hydrated state. We revealed that the addition of cross-linkers and acidification facilitated the oriented polymetric crystalline growth under mechanical stretching, which contributed to the desired hydrogel fiber diameter decrease. Our approach enabled the control of hydrogels' properties, including refractive index (RI 1.37-1.40 at 480 nm), light transmission (> 96%), stretchability (95% - 111%), and elastic modulus (10-63 MPa). To exploit these properties, we fabricated step-index hydrogel optical probes with contrasting RIs and applied them in optogenetics and photometric recordings in the mouse brain region of the ventral tegmental area (VTA) with concurrent social behavioral assessment. To extend COMPACT hydrogel multifunctional scaffolds to assimilate conductive nanomaterials and integrate multiple components of optical waveguide and electrodes, we developed carbon nanotubes (CNTs)-PVA hydrogel microelectrodes for hindlimb muscle electromyographic and brain electrophysiological recordings of light-triggered neural activities in transgenic mice expressing Channelrhodopsin-2 (ChR2).
由柔软弹性材料制成的生物电子设备具有运动自适应特性，适用于脑机接口以及研究复杂的神经回路。虽然二维微加工策略能够将设备小型化以接入精细的神经结构，但创建用于广泛应用的三维架构需要更易实现且可扩展的制造方法。在此，我们提出一种通过控制变质聚合物的非晶-结晶转变（COMPACT）来制造水凝胶生物电子器件的策略，该器件具有小型化的纤维形状并能对神经回路进行多功能检测。通过引入多种交联剂、酸化处理以及在变形下进行定向聚合物晶体生长，我们观察到化学交联的聚乙烯醇（PVA）水凝胶纤维直径减小了约80%，并且能稳定地保持在完全水合状态。我们发现交联剂的添加和酸化促进了机械拉伸下的定向聚合物晶体生长，这有助于实现所需的水凝胶纤维直径减小。我们的方法能够控制水凝胶的性质，包括折射率（480nm处为1.37 - 1.40）、透光率（>96%）、拉伸性（95% - 111%）以及弹性模量（10 - 63MPa）。为了利用这些性质，我们制造了具有对比折射率的阶跃折射率水凝胶光学探针，并将其应用于光遗传学以及在腹侧被盖区（VTA）小鼠脑区的光度记录，并同时进行社会行为评估。为了将COMPACT水凝胶多功能支架扩展以吸收导电纳米材料并集成光波导和电极的多个组件，我们开发了用于后肢肌肉肌电图记录以及对表达通道视紫红质-2（ChR2）的转基因小鼠进行光触发神经活动的脑电生理记录的碳纳米管（CNTs）-PVA水凝胶微电极。
