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There are currently hundreds of thousands of people on transplant lists,
目前有数十万人在器官移植名单上，
waiting for critical organs like kidneys, hearts, and livers that could save their lives.
等待重要器官捐赠，像是肾、心脏和肝，来拯救他们的生命。
Unfortunately, there aren't nearly enough donor organs available to fill that demand.
很遗憾，器官捐赠供不应求。
What if instead of waiting, we could create brand-new, customized organs from scratch?
如果除了等待，我们还有办法从无到有，创造出全新的、定制的器官呢？
That's the idea behind bioprinting, a branch of regenerative medicine currently under development.
这就是生物打印的理念。生物打印是再生医学的分支，目前处于发展阶段。
We're not able to print complex organs just yet,
我们尚未能打印出复杂的器官，
but simpler tissues including blood vessels and tubes responsible for nutrient and waste exchange are already in our grasp.
但例如血管和负责交换营养和废物的管道这些较简单的组织已经在我们掌握之中。
Bioprinting is a biological cousin of 3-D printing,
生物打印和3D打印原理相似，
a technique that deposits layers of material on top of each other to construct a three-dimensional object one slice at a time.
将层层的材料堆叠在一起，一次一层，建构出一个三维物体。
Instead of starting with metal, plastic, or ceramic, a 3-D printer for organs and tissues uses bioink: a printable material that contains living cells.
普通的3D打印机使用金属、塑料或陶瓷，而制作器官和组织的3D打印机使用“生物墨水”：一种含有活细胞的可打印材料。
The bulk of many bioinks are water-rich molecules called hydrogels.
许多生物墨水的主体是一种富含水的分子，称作水凝胶。
Mixed into those are millions of living cells as well as various chemicals that encourage cells to communicate and grow.
水凝胶里混合了上百万个活细胞和各种用来促进细胞交流和生长的化学物质。
Some bioinks include a single type of cell, while others combine several different kinds to produce more complex structures.
有些生物墨水只含单一一种细胞，有些则结合许多不同种的细胞，来制造出更复杂的结构。
Let's say you want to print a meniscus, which is a piece of cartilage in the knee that keeps the shinbone and thighbone from grinding against each other.
假设你想要打印一个半月板，半月板是膝盖里的一块软骨，用来避免胫骨和股骨互相摩擦。
It's made up of cells called chondrocytes, and you'll need a healthy supply of them for your bioink.
它由软骨细胞组成，你需要有健康的软骨组织供应，来制作你的生物墨水。
These cells can come from donors whose cell lines are replicated in a lab.
这些细胞可能来自捐赠者，他们的细胞系在实验室里被复制。
Or they might originate from a patient's own tissue to create a personalized meniscus less likely to be rejected by their body.
这些细胞也可能来自病患自身的组织，这种定制的半月板可以有效避免发生排斥反应。
There are several printing techniques, and the most popular is extrusion-based bioprinting.
现在有几种打印技术，其中最常用的是挤压式生物打印。
In this, bioink gets loaded into a printing chamber and pushed through a round nozzle attached to a printhead.
这项技术将生物墨水载入打印机，然后将它挤入打印头上的柱状喷嘴。
It emerges from a nozzle that's rarely wider than 400 microns in diameter,
墨水会从喷嘴挤出，喷嘴的直径一般不会超过400微米，
and can produce a continuous filament roughly the thickness of a human fingernail.
可以挤出连续不断的线丝，厚度和人的指甲差不多。
A computerized image or file guides the placement of the strands, either onto a flat surface
计算机图像或档案会引导线丝布局在平面，
or into a liquid bath that'll help hold the structure in place until it stabilizes.
或是辅助固定结构的液槽里，直到其稳定。
These printers are fast, producing the meniscus in about half an hour, one thin strand at a time.
打印机的速度很快，一次一线的制造出一个半月板，只要半小时。
After printing, some bioinks will stiffen immediately; others need UV light or an additional chemical or physical process to stabilize the structure.
打印完成后，有些生物墨水会立即变硬；有些则需要紫外线，或额外的化学或物理加工来稳定结构。
If the printing process is successful, the cells in the synthetic tissue will begin to behave the same way cells do in real tissue:
如果打印过程顺利的话，人造组织里的细胞会开始表现得和真实组织里的细胞一样：
signaling to each other, exchanging nutrients, and multiplying.
互相发出信号、交换养分以及分裂繁殖。
We can already print relatively simple structures like this meniscus.
我们已经能够打印出像半月板这样相对简单的结构，
Bioprinted bladders have also been successfully implanted, and printed tissue has promoted facial nerve regeneration in rats.
也已经成功植入过生物打印的膀胱，打印出来的组织还成功促进了老鼠脸部神经再造。
Researchers have created lung tissue, skin, and cartilage, as well as miniature, semi-functional versions of kidneys, livers, and hearts.
研究人员已经创造出人造肺组织、皮肤及软骨，还有微缩版、半功能性的肾、肝和心脏。
However, replicating the complex biochemical environment of a major organ is a steep challenge.
然而，复制主要器官复杂的生化环境是一项严峻的挑战。
Extrusion-based bioprinting may destroy a significant percentage of cells in the ink if the nozzle is too small, or if the printing pressure is too high.
挤压式生物打印可能会破坏墨水里很大一部分的细胞，如果喷头太小或打印压力太高。
One of the most formidable challenges is how to supply oxygen and nutrients to all the cells in a full-size organ.
其中一项最艰巨的挑战，是如何为一个原尺寸的器官里所有的细胞供给氧气和营养。
That's why the greatest successes so far have been with structures that are flat or hollow
这就是为什么到目前为止，最成功的案例都是平坦或空心的结构，
and why researchers are busy developing ways to incorporate blood vessels into bioprinted tissue.
这也是为什么研究人员正积极研发将血管纳入生物打印中的方法。
There's tremendous potential to use bioprinting to save lives and advance our understanding of how our organs function in the first place.
生物打印具有极大的潜能，它可以用来拯救生命，以及提高我们对器官运作的了解。
And the technology opens up a dizzying array of possibilities, such as printing tissues with embedded electronics.
这项科技开启了一系列的可能性，像是用嵌入式电子产品打印组织。
Could we one day engineer organs that exceed current human capability, or give ourselves features like unburnable skin?
在未来，我们是否能够设计出超越现在人类能力的器官，或是赋予人们特殊功能，例如不可燃的皮肤？
How long might we extend human life by printing and replacing our organs?
打印及更换器官能延长人类寿命多久？
And exactly who -- and what -- will have access to this technology and its incredible output?
什么人，什么领域有权使用这项科技和其惊人的成果？
