Ink-jet printing = creates tubes of living tissue - 22 January 2003 - Print

Ink-jet printing creates tubes of living tissue

19:00 22 January 2003=20
Exclusive from New Scientist Print Edition. Sub= scribe=20 and get 4 free issues.=20
Charles Choi

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Creating blood vessels is a huge challenge = (Image: SUSUMU=20 NISHINAGA/SPL)

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Enlarge=20 image

Printing organs

Three-dimensional tubes of living tissue have been printed using = modified=20 desktop printers filled with suspensions of cells instead of ink. The = work is a=20 first step towards printing complex tissues or even entire organs.

"This could have the same kind of impact that Gutenberg's press did," = claims=20 tissue engineer Vladimir Mironov of the Medical University of South=20 Carolina.

Many labs can now print arrays of DNA, proteins or even cells. But = for tissue=20 engineers, the big challenge is creating three-dimensional structures. = Mironov=20 became interested when Thomas Boland of Clemson University, also in = South=20 Carolina, told Mironov how he could print biomaterials using modified = ink-jet=20 printers.

The printers are adapted by washing out the ink cartridges and = refilling them=20 with suspensions of, say, cells. The software that controls the = viscosity,=20 electrical resistances and temperature of the printing fluids is = reprogrammed=20 and the feed systems altered.

Thermo-reversible gel

To create 3D structures, Boland and Mironov used a = "thermo-reversible" gel=20 recently developed by Anna Gutowska at the Pacific Northwest National = Laboratory=20 in Richland, Washington. The non-toxic, biodegradable gel is liquid = below 20 =B0C=20 and solidifies above 32 =B0C.

The team has done several experiments using easily available tissues = such as=20 hamster ovary cells. By printing alternate layers of the gel and clumps = of cells=20 onto glass slides, they have shown 3D structures such as tubes can be = built=20 up.

Biologists have long known that bits of tissue placed next to each = other can=20 fuse. The researchers found that as long as the layers were thin enough = for the=20 clumps to come into contact with each other, the bits of tissue fused. = Once a=20 structure is complete, the gel is easily removed. Details of the team's = initial=20 work will soon be published.

Like printing with different colours, placing different types of = cells in the=20 ink cartridges should make it possible to recreate complex structures = consisting=20 of multiple cell types. "I think this is extremely exciting technology = that has=20 the potential to overcome some of the major obstacles [to tissue = engineering] we=20 have seen in the past," says leading tissue engineer Anthony Atala of = Harvard=20 Medical School in Boston.

Degradable scaffold

Other groups have developed ways of building up tissues layer by = layer=20 (New Scientist print edition, 4 January), but none is as simple = and quick=20 as printing. Most tissue engineers first create a degradable scaffold = and then=20 seed it with cells. This technique can be used to create complex shapes, = such as=20 the infamous "ear on a mouse", but placing different cell types = precisely is=20 very difficult.

Printing should make it easier to position cells, but many other = problems=20 will have to be overcome before entire organs can be created. A huge = challenge=20 in tissue-engineering solid organs, for example, is supplying enough = oxygen and=20 nutrients to sustain cells deep within the structure.

"It's been the holy grail of tissue engineering, to be able to create = adequate circulatory networks for complex organs," Atala says.

Mironov and Boland hope it will be possible to print the entire = network of=20 arteries, capillaries and veins that nourish organs. But to keep cells = alive,=20 the organs would have to be completed within a couple of hours and a = growth=20 medium circulated through the fragile new vessels.

Speed fusion

Large structures might not be strong enough to hold together if the = gel is=20 removed after such a short period. However, the team is already = experimenting=20 with adding substances such as the skin protein collagen to speed fusion = and=20 reinforce structures.

Printing is not the only promising new technique for creating entire = organs.=20 It might one day be possible to grow them in situ. In December, = scientists in=20 Israel reported that they had managed to grow miniature but fully = functional=20 kidneys by implanting fetal pig or human cells into immunodeficient = mice.

But growing organs from scratch will take much longer than printing = them,=20 Mironov says. "Patients don't always have the luxury to wait."

Lab-grown=20 steaks nearing the menu=20
http://www.ne= wscientist.com/article.ns?id=3Ddn3208=20
30 December 2002=20
Working = kidney=20 grown in mouse=20
http://www.ne= wscientist.com/article.ns?id=3Ddn3216=20
23 October 2002=20
Tissue=20 engineers grow penis in the lab=20
http://www.ne= wscientist.com/article.ns?id=3Ddn2781=20
11 September 2002

Weblinks

Medical = University of South=20 Carolina=20
http://www.musc.edu/=20
Clemson=20 University Department of Bioengineering=20
http://www.ces.clemson.edu/bio/=20
Nanotechnology,=20 PNNL=20
http://www.pnl.gov/nano/=20
Transplantation and tissue engineering, Boston = Children's=20 Hospital=20
http://www.childrenshospital.org/research/surgery/trans= lab.html=20
Tissue-engineering.net=20
http://www.tissue-engineering.net/ =

Printed on Tue Jan 30 20:36:46 GMT = 2007