Rapid assembly of living micro-tissues with holographic optical tweezers; Cell 'LEGO' for regenerative medicine

这个项目的标题是“激光引导的活细胞定位和活微组织的构建——一种用于药物测试和再生医学的新的细胞规模制造工艺”。该项目展示了来自组织工程和光学物理学看似无关的背景的科学家如何合作开发新的医疗保健技术。该项目的驱动力是越来越需要在培养皿中生产出结构和功能尽可能接近体内组织的活体人体组织，并利用这些体外组织更有效地测试、开发和改进新的和现有的药物和疗法。这种方法可以最大限度地减少在研究中使用动物，还可以减少新药在健康和经济方面可能代价高昂的失败。我们有能力实现这个雄心勃勃的目标，用激光制造活的微型组织，这是由一种叫做光学镊子的仪器支持的。20世纪80年代发明的光镊利用了一种现象，即紧密聚焦的激光束在其焦点处产生局部力，并具有吸引小粒子向其靠近的效果——即所谓的光阱或光阱。将颗粒悬浮在流体中会产生一种阻尼力，产生一个在三维（3D）中稳定的单束（激光）光阱——通过移动激光束，被捕获的颗粒也可以在多个方向上移动和控制，随后以“激光精度”定位在定义的点/位置。一系列不同类型和大小的颗粒可以被捕获和移动，包括2微米（1毫米的1 / 500）的玻璃珠到活的人类细胞，这些细胞通常是10微米（1毫米的1 / 100）的大小。重要的是，激光的特性，就其功率和波长而言，它对细胞的损害很小或没有损害，而且在捕获和移动细胞所花费的时间（秒/分钟）内是肯定的。该仪器的一个改进是全息光学镊子，其中单个激光束被分裂成多个陷阱，每个陷阱都能够容纳和移动粒子。这是使用空间光调制器（SLM）完成的，这是一个通常在架空和/或数据投影仪中发现的组件。SLM充当衍射光学元件或全息图，并且可以通过计算机程序不断更新。因此，可以在3D中创建多个陷阱，并且每个陷阱独立控制和定位以创建预定的配置和图案。使用传统的光学显微镜和操纵杆或iPad触摸屏，这些陷阱可以实时可视化，并通过“虚拟手”的灵巧性进行控制。在这里，我们将使用这项技术对活细胞的运动和定位施加迄今为止无法达到的控制水平，具有类似于组织发育和形成的自然过程的预定义精度。随着单个细胞规模的动态，精确控制，我们将展示全息光学镊子如何用于制造可定义和可调谐的3D微组织；微组织成分，如细胞或含有药物的小（~5微米）聚合物颗粒，可以在几分钟内以类似于“细胞乐高”的方式组装在一起。凭借对制造复杂性的固有控制，我们可以提供“简单”的3D细胞聚集体，应用于药物发现和药物测试，每个聚集体与下一个聚集体一致，由精确数量的细胞和载药微粒组装而成。这将是这个项目阶段的重点。进一步开发该项目，我们还将寻求突破制造更复杂的定制结构的界限，这些结构可以模拟肝脏、皮肤、心脏等特定组织，并可用于更好地了解疾病过程并开发新的治疗方法。

The headline or sound bite for this project is 'laser-guided positioning of live cells and building of living micro-tissues - a new, cell scale manufacturing process for pharmaceutical testing and regenerative medicine'. The project showcases how scientists from seemingly unrelated backgrounds in tissue engineering and optical physics are collaborating to develop new healthcare technologies. The driver for the project is the increasing need to produce living human tissues, in the culture dish, with structures and functions that are as close as possible to those in the body and to use these in vitro tissues to more effectively test, develop and improve new and existing medicines and therapies. This approach can minimize use of animals in research and also reduce potentially costly, both health and economic, failures with new medicines.Our ability to achieve this ambitious goal of manufacturing living micro-tissues with lasers is underpinned by an instrument called an optical tweezers. Optical tweezers, invented in the 1980s exploit a phenomenon, whereby a tightly focused beam of laser light creates a localized force at its point of focus and has the effect of attracting small particles towards it - a so called optical trap or optical trapping. Suspending the particles within fluid gives a damping force producing a single (laser) beam optical trap that is stable in three dimensions (3D) - by moving the beam of laser light, the trapped particle can be also moved and controlled in multiple directions and subsequently positioned at defined points/locations with 'laser precision'. A range of different types and sizes of particles can be trapped and moved including, 2 micron (one 500th of a millimetre) glass beads to live human cells, which are typically 10 microns (one 100th of a millimetre) in size. Importantly, the properties of the laser, in terms of its power and wavelength are such that it causes little or no damage to cells and certainly in the time taken (seconds/minutes) to trap and move them.An evolution of this instrument is the holographic optical tweezers, where the single laser beam is split to create multiple traps, each capable of holding and moving particles. This is done using a spatial light modulator (SLM), a component typically found in an overhead and/or data projector. The SLM acts as a diffractive optical element, or hologram, and can be continuously updated via a computer program. Thus, multiple traps can be created in 3D and each trap independently controlled and positioned to create predetermined configurations and patterns. Using conventional microscope optics and a joy stick or iPad touch screen, the traps can be visualized in real time and controlled with the dexterity of a 'virtual hand'. Here, we will use this technology to exert hitherto unattainable levels of control over the movements and positioning of live cells, with the predefined precision akin to natural processes of tissue development and formation. With dynamic, precision control at the scale of the individual cell, we will show how holographic optical tweezers can be used to manufacture definable and tuneable, 3D micro-tissues; micro-tissue components, such as cells or small (~5 micron) polymer particles containing drugs, can be assembled together within minutes in a manner similar to building with 'cell LEGO'. With inherent control over manufacturing complexity we can deliver 'simple' 3D cell aggregates with applications in drug discovery and pharmaceutical testing, each aggregate consistent with the next, assembled with an exact number of cells and drug-loaded microparticles. This will be the focus of this phase of the project. Developing the project further we will also seek to push the boundaries for manufacture of more complex, bespoke structures that mimic specific tissues like liver, skin, heart etc and can be used to better understand disease processes and develop new therapies.