3D printers can create toys, bicycle parts and models of dinosaur bones. Bio-printers are 3D printers with a difference. They can actually print structures containing living cells, the same kind of cells that make up the human body!
Wouldn’t it be amazing if you could have a new liver or kidney printed for you, if yours was damaged by an accident or disease? It’s a big dream, but scientists are working on the problem now.
One big obstacle to bio-printing a whole organ, like a liver, is that it needs a big network of blood vessels to keep the cells alive. Blood provides cells with life-giving oxygen and nutrients, and also removes waste. Most cells are just a hair’s width from a supply of blood. Blood vessels need to reach everywhere – it’s a big challenge.
Luiz Bertassoni from the University of Sydney is part of the team that has bio-printed blood vessels. The team used two different materials, which were fluid enough to print and then could be made solid. “One material can be solidified with low temperature, it’s a material from seaweed called agarose,” he says. “The other is a jelly-like material (from gelatine), which was solidified by light. Using a combination of both was one of the tricks we had to use to create these vascular networks.”
To create the blood vessels, Luiz used a 3D printer to make a network of agarose. Once the agarose was solid, the structure was covered with a gelatine-like material containing living cells. “Then we removed the agarose structure that we printed, and ended up with little channels left behind,” he says. When endothelial cells – the kind that form blood vessels – were put in the channels, they organised themselves to cover the channel without clogging it. A fluid, such as blood, could pass through this bio-printed blood vessel.
“We’re excited about getting one step closer to creating fully-functional organs, but we’re still a number of years away from that,” says Luiz. “We hope that sometime soon we will be able to create functional organs that could be implanted in patients.”
Bio-printed blood vessels like this bring us a step closer to creating fully-functional organs. Image: Reproduced from Bertassoni, L. E. et al, "Hydrogel bioprinted microchannel networks for vascularization of tissue engineering constructs" Lab Chip, 2014, 14, 2202-2211, with the permission of The Royal Society of Chemistry.
Quiz questions
Which metal gives the planet Mars its red colour? Is it a) copper, b) iron or c) aluminium?
What is the Mariana Trench?
True or false? The vampire squid squirts black ink to confuse and escape predators.
Which hormone starting with i controls how much sugar enters your cells from your blood?
How many cells are in an unfertilised chicken egg (that’s one without a baby chicken growing inside)?
Try this: Thread of life
Place a piece of thick blue wool and thick red wool on paper, and untwist the top ends.
Place six pieces of thin red and blue wool to connect the top ends of the thick wool.
Here's a close-up.
Add pom poms around the thin wool. These represent cells around capillaries.
Take your lentil on a journey around your wool network! It's like a red blood cell moving through blood vessels.
You will need
Thin blue and red wool (the kind that changes colour along the strand)
Thick blue wool
Thick red wool
Scissors
Ruler
A3 paper or larger
Pom poms, about one or two centimetres in diameter
Glue
One lentil
What to do
Cut a piece of thick blue wool about 25 centimetres long, and stretch it out on the paper near the left edge. This will be a venule (a small vein).
Cut the same length of thick red wool, and stretch it out on the paper near the right edge. This will be an arteriole (a small artery).
If your thick wool is made of several strands, untwist the top five centimetres of the two pieces of thick wool.
Cut six pieces of the thin blue and red wool, so that each piece changes colour from red to blue near the middle. The pieces should be 20 centimetres long. These will be capillaries.
Place the blue end of the thin wool so it connects with the untwisted part of the thick blue wool, and the red end of the thin wool connects with the untwisted part of the thick red wool.
Connect all six of the pieces of thin blue and red wool to the thick wool as described in step 5. Spread out the pieces of thin wool, so they don’t touch each other.
Now we have a network of capillaries, we are going to add pom poms around them as the cells.
Put as many pom poms as you like around the pieces of thin red and blue wool.
Take the lentil and notice how much smaller it is than the pom poms. The lentil will be a blood cell. To show how a blood cell will travel around your model, take the lentil on a journey from bottom of the thick red wool, and travel up and through the thin wool, across to the blue wool and down again.
If you’d like to keep your model, use glue to stick the wool in place.
What’s happening?
This colourful model shows you the network of tiny blood vessels called capillaries that are all around your body. Your body is made up of different types of cells, including skin cells, muscle cells and liver cells. Each one needs to be close to a blood supply, because blood carries the oxygen and nutrients the cell needs to survive.
Oxygen is carried by red blood cells, and these cells are smaller than the average human cell. A red blood cell is about eight micrometres across (a micrometre is a millionth of a metre), about the same as the diameter of a capillary. In fact, blood cells can get squished while they move through the capillary! The average human cell is about 20 or 30 micrometres across, though different cells are different sizes.
As they pass through a capillary, red blood cells deliver oxygen to nearby cells, found in the tissue outside the blood vessel. They also collect carbon dioxide, which cells produce as waste. This changes the colour of the blood cell – a blood cell carrying oxygen is bright red, but when it loses the oxygen it becomes blue-red.
Capillaries are just one part of your circulatory system. When you breathe, oxygen from the air moves from your lungs into your blood. The heart pumps the oxygenated blood around the body through large arteries and smaller arterioles to the capillaries. There, the blood delivers oxygen and collects carbon dioxide from nearby cells, before moving on through the capillaries to the venules and into the veins. These veins flow back into the heart, which pumps the blood back to the lungs, where it releases the carbon dioxide and receives more oxygen, and the circle starts again!
Applications
As your body grows, new blood vessels have to be made to make sure every cell gets the oxygen it needs. The process of forming new blood vessels is called angiogenesis. There are medicines that can stop new blood vessels forming, and these can be used as a medicine to fight cancer.
Watch it! If you like 3D printing, check out this video on 4D printing in A Week in Science by the RiAus.
Quiz answers
b) Iron on the surface of Mars makes the planet appear red. Water and carbon dioxide in Mars’s atmosphere makes the iron rust and turn red.
The Mariana Trench is the deepest point in any ocean. It is east of Japan in the Pacific Ocean, and 11 033 metres deep!
False. The vampire squid ejects bioluminescent (glowing) mucus to confuse predators.
Insulin controls how much sugar enters your cells from your blood.
There is just one cell in an unfertilised chicken egg.
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