Biocomponent Devices: Developing Actuators from Insect Muscles

所有的人造设备，从最早的史前工具到现在的机器人，都是由非生物材料制成的，其中大多数都是非常僵硬的合成材料。为了使现代设备更适合在接近人类的地方使用，并在自然环境中工作，重要的是我们要找到新的方法来制造生物兼容、可生物降解、环境安全并能够与组织接口的机器。制造这样的生物兼容机器的一个主要挑战是没有合适的马达(执行器)来驱动它们移动。使用来自青蛙和老鼠等动物的肌肉细胞的尝试取得的成功有限，因为脊椎动物组织需要复杂的血液系统，而且它们很容易受到环境条件变化的破坏。在脊椎动物胚胎中发现的使肌肉适当生长的条件也很难复制。这项研究介绍了一种新的生物学方法来制造这种致动器，方法是从变态过程中产生的昆虫细胞中培养它们。成虫组织(如飞行肌肉)直接在现有的幼虫组织上形成，它们的生长可以通过简单的昆虫激素操作来控制。初步研究表明，昆虫肌肉可以在室温下培养，并能存活数月。这项研究将确定产生强大昆虫肌肉所需的条件，并开发培养它们用于活机器的方法。这项工作的成功完成将导致产生一种工程化肌肉，这种肌肉可以持续几个月，并且可以产生比目前在培养中生长的肌肉执行器大十倍的力。这项工作将对揭示导致细胞重新编程的一些过程(遗传、生化和激素)具有更广泛的影响，这些过程必须作为昆虫变态的一部分发生。这有望刺激研究组织规格、生长和修复的新的实验方法。这些研究将检验这样一种假设，即完全形成的组织可以从烟草鹰蛾Manduca sexta的变性细胞体外培养出来。以背纵(飞)肌(DFM)为靶组织，本实验将集中于四个主要目标：1)表征变态和培养过程中伴随DFM形成的生理和分子变化。将使用等长/等张测试和动态工作环来测量体内电特性和收缩特性的变化。发育中的肌肉和生长中的外植体的基因表达谱(转录组)将在不同的阶段进行比较，以帮助识别与Manduca肌肉形成相关的基因网络。2)研究局部(细胞-细胞、机械)和系统(循环)因素在肌肉特化、分化和生长中的作用。这将涉及组织切除和跨阶段移植方法，这些方法已经为昆虫很好地确立了。3)通过改变激素和底物条件，概括了成体背飞肌由幼虫前体在培养过程中的正常形成。体外肌肉的转录本将与本地幼虫和成年DFM进行比较，以寻找关键的发育和生理基因网络的变化。4)在体外培养和维持肌肉结构，以用于实际的致动器应用。我们的目标是设计一种可以持续几个月的肌肉，通过最大化存活、细胞增殖和最终分化，产生比目前的体外肌肉执行器好一个数量级的压力。预计这一过程将产生密集堆积的肌肉纤维，可用于高应力执行器。这些纤维的统一收缩将通过在微电极阵列上生长或通过表达光敏感通道(如ChR2)来控制。这项研究将使研究生参与软机器人的跨学科研究。

All human-made devices, from the very first pre-historic tools to present day robots, have been constructed from non-living materials, most of which are very stiff and synthetic. To make modern devices more suitable for use in close proximity to humans and for work in natural environments it is important that we find new ways to build machines that are biologically compatible, biodegradable, environmentally safe and able to interface with tissues. A major challenge for making such biologically compatible machines is that there are no suitable motors (actuators) to make them move. Attempts to use muscle cells derived from animals such as frogs and mice have had limited success because vertebrate tissues require an intricate blood system and they are easily damaged by changing environmental conditions. It is also hard to replicate the conditions found in a vertebrate embryo that make muscles grow appropriately. This research introduces a new biological approach to making such actuators by growing them from insect cells produced during metamorphosis. Adult insect tissues (such as flight muscles) form directly on existing larval tissues and their growth can be controlled using simple manipulations of insect hormones. Preliminary studies show that insect muscles can be grown in culture at room temperature and that they will survive for many months. This research will identify the conditions needed to generate powerful insect muscles and develop methods to grow them for use in living machines. Successful completion of this work will lead to the production of an engineered muscle that can be sustained for several months and that can generate forces ten times greater than current muscle actuators grown in culture. The work will have wider implications in revealing some of the processes (genetic, biochemical and hormonal) that lead to the re-programming of cells that must occur as part of insect metamorphosis. This is expected to stimulate new experimental approaches to studies of tissue specification, growth and repair. These studies will test the hypothesis that fully formed tissues can be grown ex-vivo from metamorphic cells of the tobacco hawk moth Manduca sexta. Using the dorsal longitudinal (flight) muscles (DFM) as a target tissue the experiments will focus on four main goals: 1) To characterize the physiological and molecular changes that accompany DFM formation during metamorphosis and in culture. Measurements will be made of in vivo changes in electrical characteristics and the contractile properties using isometric/isotonic tests and dynamic work loops. The gene expression profile (transcriptome) of developing muscles and growing explants will be compared at different stages to help identify gene networks associated with Manduca muscle formation. 2) To characterize the roles of local (cell-cell, mechanical) and systemic (circulating) factors in muscle specification, differentiation and growth. This will involve tissue excision and cross stage transplant methods that are well established for insects. 3) To recapitulate the normal formation of adult dorsal flight muscles from larval precursors in culture by engineering the hormonal and substrate conditions. The transcriptomes of the in-vitro muscles will be compared with both native larval and adult DFMs to look for changes in key developmental and physiological gene networks. 4) To grow and maintain muscle constructs in-vitro for practical actuator applications. The goal is to engineer a muscle that can be sustained for several months and that can generate stress an order of magnitude better than current in-vitro muscle actuators by maximizing survival, cell proliferation and eventual differentiation. It is expected that this process will produce densely packed muscle fibers that can be used for high-stress actuators. The unified contraction of these fibers will be controlled by growing them on micro-electrode arrays or though the expression of light-sensitive channels such as ChR2. This research will engage graduate students in cross-disciplinary research in soft robotics.