FlyTitle: Bioengineering

A team of researchers makes bots from living cells

一个研究团队用活体细胞制造机器人

经济学人双语版-活体机器人 Robots that come alive

ROBOTS COME in all shapes and sizes. Some are humanoid. Others resemble animals. Many are just a jumble of arms slaving away on a production line. But one thing all robots have in common is that they are mechanical, not biological devices. They are built from materials like metal and plastic, and stuffed with electronics. No more, though—for a group of researchers in America have worked out how to use unmodified biological cells to create new sorts of organisms that might do a variety of jobs, and might even be made to reproduce themselves.

机器人的形态和大小各异。有的类似人形,有的模仿动物,还有许多不过是在生产线上苦干的一堆机器臂。但所有机器人都有一个共同点,那就是它们都是机械,而不是生物性设备。它们由金属和塑料等材料制成,塞满了各种电子器件。不过现在不一样了。美国一个研究团队设法使用未经修改的生物细胞创造出了新型有机体,它们或许能执行多种工作,甚至还可以让它们自我繁殖。

There are several ways to tinker with living organisms. Selective breeding and, more recently, genetic engineering permit the production of novel plants and animals for agriculture and horticulture, and as pets. Souped-up bugs for industrial processes can also be made in these ways. Researchers are working, too, on growing isolated animal organs for testing drugs and eventually, perhaps, for transplant surgery.

现在已经有一些办法来改造有机体。利用选择性育种以及近年的基因工程可以生产出新型的动植物,用于农业、园艺,以及做宠物。用这些方法也可生产出工业用途的增强型昆虫。研究人员还致力于培育离体的动物器官,可用于药物测试,最终甚至还可用于移植手术。

What Joshua Bongard of the University of Vermont and Michael Levin of Tufts University in Massachusetts have come up with is different. As they report in the Proceedings of the National Academy of Sciences, they and their colleagues have designed organic robots from their cellular components, and then set about realising those designs by joining together specific types of stem cells taken from a well-studied species of African frog, Xenopus laevis. The result (pictured) is close to matching the biological definition of an organism, in that it is capable of behaving autonomously and contains cell types that are specialised to perform different roles.

佛蒙特大学的约书亚·邦加德(Joshua Bongard)和马萨诸塞州塔夫茨大学的迈克尔·莱文(Michael Levin)想到的办法与众不同。他们在《美国科学院院报》(Proceedings of the National Academy of Sciences)上发表文章称,他们和同事用细胞组件设计出了有机机器人,并着手将特定类型的干细胞组合起来实现这些设计。这些细胞取自一个经充分研究的物种——非洲爪蟾(Xenopus laevis)。其成果(如图)已经接近符合生物学上有机体的定义,因为它具备自主行为的能力,并包含专门执行不同功能的各类细胞。

Though only a millimetre or so across, the artificial organisms Dr Bongard and Dr Levin have invented, which they call xenobots, can move and perform simple tasks, such as pushing pellets along in a dish. That may not sound much, but the process could, they reckon, be scaled up and made to do useful things. Bots derived from a person’s own cells might, for instance, be injected into the bloodstream to remove plaque from artery walls or to identify cancer. More generally, swarms of them could be built to seek out and digest toxic waste in the environment, including microscopic bits of plastic in the sea.

邦加德和莱文管他们发明的人工有机体叫“xenobot”,虽然直径只有一毫米左右,却能移动并执行简单的任务,例如在培养皿里推动颗粒。这听起来可能没什么,但他们认为可以将这个过程放大,从而完成有用的工作。例如,可以从人的自体细胞培育出机器人,然后再注射到血液中去清除动脉血管壁上的斑块或者识别癌症。在更广泛的应用场景中,它们可以被批量制造出来,在环境中寻找并消化有毒废物,包括海洋中的塑料微粒。

To design their bots Dr Bongard and Dr Levin employed a computer program called an evolutionary algorithm. This worked by creating virtual representations of thousands of arrangements of cells that might achieve a particular task. It then tested those arrangements, using what is known about the biophysics of Xenopus cells, for suitability to perform the task in question, picked the most promising versions to form the basis for thousands more cellular arrangements, and then repeated the process until something properly fit for purpose emerged. That done, it was merely a matter of building the pattern which the algorithm had arrived at out of actual Xenopus cells, using microsurgical techniques to shape groups of cells in the way the pattern dictated.

为了设计这种机器人,两位研究员使用了一种名为进化算法的计算机程序。这个程序创建出成千上万种细胞排列方式的虚拟呈现,它们有潜力完成某种任务。然后利用已知的非洲爪蟾细胞的生物物理知识测试这些排列,确定它们是否适合执行目标任务,再从中挑选出最有希望的方案。接下来,以此方案为基础,继续创建成千上万新的细胞排列方案。不断重复这个过程,直至得到符合目标用途的方案。完成这些之后,就只需要使用显微外科技术,把成批的活体爪蟾细胞按照这个最终方案组装起来。

The demonstration bots Dr Bongard and Dr Levin have made use two types of stem cell. Some are so-called pluripotent cells taken from early-stage embryos. These embryonic cells retain wide powers to turn into other cell types. The others are cardiac progenitor cells, a more specialised type of stem cell already destined to generate heart muscle.

他们的演示机器人使用了两种干细胞。一种是从早期胚胎中提取的,名叫多能干细胞。这些胚胎细胞保留了转化为其他细胞的广泛能力。另一种是心脏祖细胞,这种干细胞比较特殊,专门负责生成心肌。

Placed in a dish, bots made in this way were able to propel themselves along the dish surface via contractions of the heart-muscle cells within them. Besides pushing single pellets, groups of bots put into a dish together were able to work collectively, moving around in circles and gathering the pellets into neat piles.

把用这种方法制造的机器人放在培养皿中,它们能利用自己体内的心肌细胞的收缩推动自己贴着培养皿的表面前行。除了能推动单个颗粒外,如果将一群机器人放入培养皿中,它们还可以集体工作,四处绕圈移动,将颗粒整齐地堆在一起。

Exactly how that happens is not yet clear. “It is possible”, says Dr Bongard, “that the cells are signalling to one another in a way we’re not aware of.” That possibility, and many other questions, will be the subject of further research. The team are also trying to work out how cells can be motivated to build complex, functioning bodies. Such knowledge, says Dr Levin, would be immensely useful in regenerative medicine, which seeks to repair organs and build body parts for transplant.

这种现象的原理还不清楚。“有可能细胞以一种我们不知道的方式互相传递信号。” 邦加德说。这种可能性以及其他许多问题将成为进一步研究的课题。该团队还在试图了解是什么促使细胞构建出复杂的功能体。莱文表示,这种知识对再生医学极有价值,再生医学的目标就是修复器官以及制造出供移植所用的身体“部件”。

Go forth and multiply?

迈步向前,生生不息?

For xenobots to have a practical future, though, someone will have to find a less fiddly way of making them. At present, it takes a microsurgeon hours to handcraft each individual bot, peering down a microscope and using tiny tweezers to do so. One way the process might be automated is by employing three-dimensional printing to build up the necessary layers of cells.

不过,要想让xenobot未来能有切实的用武之地,就必须找到一种不那么繁琐的制造方法。目前这种机器人全靠手工制造,由显微外科医生在显微镜下操作微型镊子进行,每制造一个机器人都需要好几个小时。要实现生产自动化,一种可能的方式是采用3D打印技术来叠加所需的各层细胞。

The new organisms could also do with upgrading in certain ways. At present, for example, they have short lives—a couple of weeks at most. This is because they do not have any apparatus for feeding themselves. In one sense that is a good thing, for it soothes fears about safety. If a bot should escape it would expire at the end of its allotted time and, being made simply of frog cells, would be biodegradable and non-toxic. But because longer-lived bots would be more useful, the researchers are looking at ways to extend their creations’ lives.

这种新的有机体可能也需要某种形式的升级。例如,目前它们的寿命很短,最多只有两三个星期。这是因为它们完全没有摄取食物的器官。某种意义上这也是件好事,因为缓解了人们对安全的担忧。万一有机器人逃逸,它也会在有限的时间内寿终正寝,而且它只是用青蛙细胞制成,完全可以生物降解,也没有毒性。但寿命长的机器人会更有价值,因此研究人员正在寻找延长它们寿命的方法。

A more controversial suggestion is to equip xenobots with reproductive systems—perhaps as simple as allowing them to divide themselves in two, in the way that flatworms can. This would help any application that required a swarm of the critters.

更具争议性的提议是给xenobot配备生殖系统——或许只需让它们像扁形虫那样将自己一分为二。这对于需要用到一大批这种小生物的应用会有帮助。

It might also, though, raise concerns about escapees establishing themselves in the wild. All this, says Dr Bongard, means it will be necessary to work with policymakers to decide how the production of future life forms, as useful as they might be, might be regulated. ■

​不过,这也可能引发对其逃离后在野外繁殖的担忧。邦加德说,尽管应用前景广阔,但这一切都意味着必须与政策制定者合作,共同决定如何监管这些未来生命形式的生产。