There are currently hundreds of thousands 
of people on transplant lists,

waiting for critical organs like kidneys, 
hearts, and livers

that could save their lives.

Unfortunately,

there aren’t nearly enough donor organs 
available to fill that demand.

What if instead of waiting,

we could create brand-new, customized 
organs from scratch?

That’s the idea behind bioprinting,

a branch of regenerative medicine 
currently under development.

We’re not able to print complex 
organs just yet,

but simpler tissues including blood
vessels and tubes

responsible for nutrient 
and waste exchange

are already in our grasp.

Bioprinting is a biological 
cousin of 3-D printing,

a technique that deposits layers of 
material on top of each other

to construct a three-dimensional object 
one slice at a time.

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.

The bulk of many bioinks are water-rich 
molecules called hydrogels.

Mixed into those are 
millions of living cells

as well as various chemicals that 
encourage cells to communicate and grow.

Some bioinks include a 
single type of cell,

while others combine several different 
kinds to produce more complex structures.

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.

It’s made up of cells called chondrocytes,

and you’ll need a healthy supply of 
them for your bioink.

These cells can come from donors whose
cell lines are replicated in a lab.

Or they might originate from a 
patient’s own tissue

to create a personalized meniscus less
likely to be rejected by their body.

There are several printing techniques,

and the most popular is extrusion-based 
bioprinting.

In this, bioink gets loaded into a 
printing chamber

and pushed through a round nozzle 
attached to a printhead.

It emerges from a nozzle that’s rarely 
wider than 400 microns in diameter,

and can produce a continuous filament

roughly the thickness 
of a human fingernail.

A computerized image or file guides the 
placement of the strands,

either onto a flat surface or into a 
liquid bath

that’ll help hold the structure in place 
until it stabilizes.

These printers are fast, producing the 
meniscus in about half an hour,

one thin strand at a time.

After printing, some bioinks 
will stiffen immediately;

others need UV light or an additional 
chemical or physical process

to stabilize the structure.

If the printing process is successful,

the cells in the synthetic tissue

will begin to behave the same way
cells do in real tissue:

signaling to each other, exchanging 
nutrients, and multiplying.

We can already print relatively simple 
structures like this meniscus.

Bioprinted bladders have also been 
successfully implanted,

and printed tissue has promoted facial 
nerve regeneration in rats.

Researchers have created lung tissue,
skin, and cartilage,

as well as miniature, semi-functional 
versions of kidneys, livers, and hearts.

However, replicating the complex 
biochemical environment

of a major organ 
is a steep challenge.

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.

One of the most formidable challenges

is how to supply oxygen and nutrients 
to all the cells in a full-size organ.

That’s why the greatest successes so far

have been with structures 
that are flat or hollow—

and why researchers are busy 
developing ways

to incorporate blood vessels 
into bioprinted tissue.

There’s tremendous potential to use 
bioprinting

to save lives and advance our 
understanding

of how our organs function 
in the first place.

And the technology opens up a dizzying 
array of possibilities,

such as printing tissues with 
embedded electronics.

Could we one day engineer organs that 
exceed current human capability,

or give ourselves features like 
unburnable skin?

How long might we extend human life 
by printing and replacing our organs?

And exactly who—and what—

will have access to this technology 
and its incredible output?