Ink-jet printers offer novel way to grow cells<br> in 3-D formations

UMASS-DARTMOUTH researchers are using ink-jet technology to create precisely designed cell cultures, such as these human bone-marrow stem cells. /
UMASS-DARTMOUTH researchers are using ink-jet technology to create precisely designed cell cultures, such as these human bone-marrow stem cells. /

Ink-jet printers can create images with great precision. But how about cell cultures, miniature organs, or even – one day – full human organs that can be implanted?
Paul D. Calvert, a materials and textiles professor at the University of Massachusetts-Dartmouth, is using ink-jet technology in his lab to create 3-D cell cultures in precisely defined patterns, and he hopes one day this concept can be developed to creating full-fledged organs.
In the Oct. 12 issue of the journal Science, he explained how this process works and how it might help unravel the mystery of how cells communicate with one another. He explained the technology – and its promise and challenges – in an interview with Providence Business News.

PBN: Why do we need to create human organs in a lab?
CALVERT: We all believe we badly need a way to create organs in the lab because there is no other good source of replacement tissues – not from animals, not from cadavers, not mechanical. We also know that that’s going to be very difficult.
In the short term, we believe that if we could do little bits of tissue that have a lot of the functions of organs, they would be very useful for lab testing of drug action, effects of disease – all those kinds of things.
We think that the ink-jet printer is probably going to be a very good tool to get us there, but a lot of other people are trying other ways of putting cells down.
PBN: How did you arrive at the idea of using an ink-jet printer for this biological application?
CALVERT: All this stuff evolves. I’ve been a biomimetic materials person for a long time. And for a long time the question for us has been, “Why can’t we make composite materials that are more like bone? Why can’t we make ceramics that are as tough as teeth or seashells?”
As we worked on that, we thought, “These things are kind of complicated to make, but maybe we can get there layer by layer because that’s how biology builds things.”
So for a long time, we did free-form fabrication. You built things slice by slice. We used a device that was something like a cake-icing machine.
After doing that for awhile, we realized this cake-icing technique of putting down layers a fraction of a millimeter thick was just too coarse. We couldn’t get the kind of chemistry that we wanted out of it.
So we said, “Let’s use an ink-jet printer, because the drops are much smaller, everything is much finer and the layers are thinner.”
The charm of the ink-jet printer is, you get pretty good resolution in the X, Y direction. You get to put down very thin layers and it’s non-contact, so when you put down a second layer, you don’t mess up everything you just put down in the first layer.

PBN: There was some skepticism about whether the ink-jet technique would work with living cells, wasn’t there?
CALVERT: When we got into this, our assumption was that the cells would all die. To our surprise, the cells survived the process.

PBN: Why did you think the cells would die?
CALVERT: We were using thermal ink-jet printers, which means the cells get shot out by a little hot plate that for a few microseconds goes up to 300 degrees Celsius [572 degrees Fahrenheit]. That creates a little bubble of steam that blasts the cell through a little hole. That works fine with ink, but there was a question of whether that much heat was going to kill the cell.
The answer is, it doesn’t. Yes, 300 degrees will kill anything but not for a few microseconds. That’s far too short a time to do anything.
That’s part one. Part two is that it’s being shot out of little hole, so we assumed the cell would be ripped to pieces by the sheer forces going through the hole.
Then it travels at about 10 meters per second [22 miles per hour] across the gap and whacks into a surface on the other side.
So the whole process, for the cell, is a little like being shot out of a cannon. There are all kinds of reasons why the cells might have died.

PBN: Why didn’t they die?
CALVERT: Because they’re a lot tougher than we thought they were. A researcher in Manchester [England] did some work with a different kind of printer where he measured how many cells were alive and how many were dead, and the living rate was like 95 percent.

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PBN: Are you using off-the-shelf ink-jet technology for this application?
CALVERT: What we’ve had the most success with is actually older technology, here the hole is bigger. We’ve been using Hewlett Packard cartridges, but they’re cartridges, I think, that are mostly used to print things like checks.
If you came and saw the equipment, the only bit you’d recognize is the cartridge.

PBN: How long, if ever, will it be before we can grow organs with this technology?
CALVERT: We can grow individual cell pipes, but when it comes to having multiple pipes work together to make an organ, we just don’t know enough about it. So we don’t know how big a job it is or how small a job it is. •

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