Rihani Rashed T, Stiller Allison M, Usoro Joshua O, Lawson Jennifer, Kim Hyun, Black Bryan J, Danda Vindhya Reddy, Maeng Jimin, Varner Victor D, Ware Taylor H, Pancrazio Joseph J
Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA.
Department of Bioengineering, University of Texas at Dallas, Richardson, TX 75080, USA.
Acta Biomater. 2020 Jul 15;111:54-64. doi: 10.1016/j.actbio.2020.04.032. Epub 2020 May 17.
Intracortical microelectrode arrays (MEAs) are currently limited in their chronic functionality due partially to the foreign body response (FBR) that develops in regions immediately surrounding the implant (typically within 50-100 µm). Mechanically flexible, polymer-based substrates have recently been explored for MEAs as a way of minimizing the FBR caused by the chronic implantation. Nonetheless, the FBR degrades the ability of the device to record neural activity. We are motivated to develop approaches to deploy multiple recording sites away from the initial site of implantation into regions of tissue outside the FBR zone. Liquid Crystal Elastomers (LCEs) are responsive materials capable of programmable and reversible shape change. These hydrophobic materials are also non-cytotoxic and compatible with photolithography. As such, these responsive materials may be well suited to serve as substrates for smart, implantable electronics. This study explores the feasibility of LCE-based deployable intracortical MEAs. LCE intracortical probes are fabricated on a planar substrate and adopt a 3D shape after being released from the substrate. The LCE probes are then fixed in a planar configuration using polyethylene glycol (PEG). The PEG layer dissolves in physiological conditions, allowing the LCE probe to deploy post-implantation. Critically, we show that LCE intracortical probes will deploy within a brain-like agarose tissue phantom. We also show that deployment distance increases with MEA width. A finite element model was then developed to predict the deformed shape of the deployed probe when embedded in an elastic medium. Finally, LCE-based deployable intracortical MEAs were capable of maintaining electrochemical stability, recording extracellular signals from cortical neurons in vivo, and deploying recording sites greater than 100 µm from the insertion site in vivo. Taken together, these results suggest the feasibility of using LCEs to develop deployable intracortical MEAs. STATEMENT OF SIGNIFICANCE: Deployable MEAs are a recently developed class of neural interfaces that aim to shift the recording sites away from the region of insertion to minimize the negative effects of FBR on the recording performance of MEAs. In this study, we explore LCEs as a potential substrate for deployable MEAs. The novelty of this study lies in the systematic and programmable deployment offered by LCE-based intracortical MEAs. These results illustrate the feasibility and potential application of LCEs as a substrate for deployable intracortical MEAs.
皮层内微电极阵列（MEAs）目前在其长期功能方面受到限制，部分原因是在植入物周围紧邻区域（通常在50 - 100微米范围内）产生的异物反应（FBR）。最近，人们探索了基于聚合物的机械柔性基板用于微电极阵列，以此来尽量减少长期植入引起的异物反应。尽管如此，异物反应仍会降低设备记录神经活动的能力。我们致力于开发方法，将多个记录位点从初始植入位点部署到异物反应区之外的组织区域。液晶弹性体（LCEs）是能够进行可编程和可逆形状变化的响应材料。这些疏水材料也是无细胞毒性的，并且与光刻技术兼容。因此，这些响应材料可能非常适合用作智能可植入电子设备的基板。本研究探讨了基于液晶弹性体的可部署皮层内微电极阵列的可行性。液晶弹性体皮层内探针在平面基板上制造，并在从基板释放后采用三维形状。然后使用聚乙二醇（PEG）将液晶弹性体探针固定在平面配置中。聚乙二醇层在生理条件下溶解，使液晶弹性体探针在植入后能够展开。至关重要的是，我们表明液晶弹性体皮层内探针将在类似大脑的琼脂糖组织模型中展开。我们还表明展开距离随微电极阵列宽度增加。然后开发了一个有限元模型来预测嵌入弹性介质中展开探针的变形形状。最后，基于液晶弹性体的可部署皮层内微电极阵列能够保持电化学稳定性，在体内记录皮层神经元的细胞外信号，并在体内将记录位点从插入位点部署到大于100微米的位置。综上所述，这些结果表明使用液晶弹性体开发可部署皮层内微电极阵列的可行性。重要性声明：可部署微电极阵列是最近开发的一类神经接口，旨在将记录位点从插入区域移开，以尽量减少异物反应对微电极阵列记录性能的负面影响。在本研究中，我们探索液晶弹性体作为可部署微电极阵列的潜在基板。本研究的新颖之处在于基于液晶弹性体的皮层内微电极阵列提供的系统且可编程的展开。这些结果说明了液晶弹性体作为可部署皮层内微电极阵列基板的可行性和潜在应用。
