Reversible and Directional Control of Chemical Wave Propagation in a Hydrogel by Magnetic Migration through Liquid Interfaces
Reversible and Directional Control of Chemical Wave Propagation in a Hydrogel by Magnetic Migration through Liquid Interfaces
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DOI：
10.1021/acs.chemmater.8b03029
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发表时间：
2018-09-11
影响因子：
8.6
通讯作者：
Yoshida, Ryo
中科院分区：
文献类型：
--
作者：
Lee, Eunjong;Kim, Youn Soo;Yoshida, Ryo
为了使大范围的生物事件发生，化学信号必须在空间和时间中传播。分子在空间中扩散的基本机制是简单扩散，即分子由于热能的随机运动。然而，对于更大的信号传输距离，扩散太慢而不能成为在几秒或几分钟内发生的生物事件的管道。此外，扩散倾向于衰减信号，并且生物事件的时空协调通常需要不受阻碍的信号的传播。这些限制可以通过在时空中传播信号的行波化学波来克服。通过利用化学波，生化信号可以长距离传输，或者通过正反馈在相邻区域1 - 4中诱导快速激活。生物系统中化学波的典型例子是神经元中动作电位的传播和心脏收缩期间的钙波。5 - 7此外，化学波在生命系统中的流动性、质量运输和信号传导中起着重要作用，如生物体的蠕动运动、8、9通过肌动蛋白阵列的稳定微铣削的细胞迁移、10耳蜗的听觉通路等所示。在人造材料中引入化学波对于模拟这样的生物系统是必不可少的。作为可以人工诱导的化学波的一个例子，在Belousov-Zhabotinsky（BZ）反应的介质中演化的行波是众所周知的。到目前为止，我们已经开发出一种自振荡水凝胶，显示自主的溶胀/去溶胀，而没有开/关开关的外部刺激，通过采用BZ反应。[12− 16]在BZ反应过程中，与水凝胶网络共聚并作为反应催化剂的三（2，2′-联吡啶）钌（Ru（bpy）3）在氧化态和还原态之间循环。因此，水凝胶分别响应于亲水性的增加和降低而显示自主溶胀和去溶胀。12，17微米大小的自振荡水凝胶像心肌细胞一样产生完全同步的肿胀和去肿胀。然而，当自振荡水凝胶大于化学波的波长超过亚厘米长度尺度时，在水凝胶内出现具有蠕动运动的化学波传播。利用化学波的传播和随之而来的蠕动运动，自主的类蠕虫的质量传输系统已被报道。18 - 20然而，仍然很难预测化学波传播的确切方向，
For a wide range of biological events to occur, chemical signals must spread through space and time. The basic mechanism by which molecules spread through space is simple diffusion; that is, random movement of molecules due to thermal energy. However, for larger signal transmission distances, diffusion is too slow to be the conduit for biological events occurring within a few seconds or minutes. Furthermore, diffusion tends to attenuate signals, and spatiotemporal coordination of biological events often requires propagation of unimpeded signals. These limitations can be overcome by traveling chemical waves that can propagate signals in spacetime. By taking advantage of chemical waves, biochemical signals can be transmitted over long distances or can induce rapid activation in adjacent areas 1− 4 through positive feedback. Typical examples of chemical waves in biological systems are the propagation of action potentials in neurons, and calcium waves during cardiac contraction. 5− 7 Furthermore, chemical waves play important roles in mobility, mass transport, and signaling in living systems, as shown in the peristaltic motion of organisms, 8, 9 cell migration through steady treadmilling of actin arrays, 10 the auditory pathway of the cochlea, 11 etc. Therefore, introduction of chemical waves into man-made materials is essential to mimic such biological systems.As an example of a chemical wave that can be artificially induced, traveling waves evolving in the media of the Belousov− Zhabotinsky (BZ) reaction are well-known. So far, we have developed a self-oscillating hydrogel that shows autonomous swelling/deswelling without the on/off switching of external stimuli by employing the BZ reaction. 12− 16 During the course of the BZ reaction, ruthenium tris (2, 2′-bipyridine)(abbreviated as Ru (bpy) 3), which is copolymerized with the hydrogel networks and acts as a reaction catalyst, cycles between oxidized and reduced states. Consequently, the hydrogel shows autonomous swelling and deswelling in response to increased and decreased hydrophilicity, respectively. 12, 17 The micrometer-sized selfoscillating hydrogel generates entirely synchronized swelling and deswelling like a cardiac muscle cell. However, when the self-oscillating hydrogel is larger than the wavelength of the chemical wave over subcentimeter length scales, chemical wave propagation with peristaltic motion appears within the hydrogel. By using the chemical wave propagation and the consequent peristaltic motion, autonomous intestine-like mass transport systems have been reported. 18− 20 However, it remains difficult to predict the exact direction of chemical wave propagation in