Department of Electrical Engineering and Computer Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Room 36-824, Cambridge, MA 02139, USA.
Lab Chip. 2013 Feb 21;13(4):589-98. doi: 10.1039/c2lc41000a.
Axons in the developing nervous system are directed via guidance cues, whose expression varies both spatially and temporally, to create functional neural circuits. Existing methods to create patterns of neural connectivity in vitro use only static geometries, and are unable to dynamically alter the guidance cues imparted on the cells. We introduce the use of AC electrokinetics to dynamically control axonal growth in cultured rat hippocampal neurons. We find that the application of modest voltages at frequencies on the order of 10(5) Hz can cause developing axons to be stopped adjacent to the electrodes while axons away from the electric fields exhibit uninhibited growth. By switching electrodes on or off, we can reversibly inhibit or permit axon passage across the electrodes. Our models suggest that dielectrophoresis is the causative AC electrokinetic effect. We make use of our dynamic control over axon elongation to create an axon-diode via an axon-lock system that consists of a pair of electrode 'gates' that either permit or prevent axons from passing through. Finally, we developed a neural circuit consisting of three populations of neurons, separated by three axon-locks to demonstrate the assembly of a functional, engineered neural network. Action potential recordings demonstrate that the AC electrokinetic effect does not harm axons, and Ca(2+) imaging demonstrated the unidirectional nature of the synaptic connections. AC electrokinetic confinement of axonal growth has potential for creating configurable, directional neural networks.
在发育中的神经系统中，轴突通过指导线索（guidance cues）进行导向，这些线索在空间和时间上的表达都有所不同，从而形成功能性的神经回路。现有的体外构建神经连接模式的方法仅使用静态几何形状，并且无法动态改变赋予细胞的导向线索。我们引入了交流电动（AC electrokinetics）来动态控制培养的大鼠海马神经元中的轴突生长。我们发现，以 10^5 Hz 量级的频率施加适度电压可以使发育中的轴突在电极附近停止，而远离电场的轴突则不受抑制地生长。通过打开或关闭电极，我们可以可逆地抑制或允许轴突穿过电极。我们的模型表明，介电泳是引起交流电动的原因。我们利用我们对轴突伸长的动态控制，通过一个由一对电极“门”组成的轴突锁定系统来创建一个轴突二极管，该系统允许或阻止轴突通过。最后，我们开发了一个由三个神经元群体组成的神经网络，通过三个轴突锁来分隔，以演示功能性工程神经网络的组装。动作电位记录表明，交流电动效应不会伤害轴突，而 Ca^2+成像表明了突触连接的单向性质。轴突生长的交流电动限制具有创建可配置、定向神经网络的潜力。
