University of Utah hydrogel plays critical part in organ 'printing' study

11/11/05

Hydrogel 'paper' helps grow new tissue

SALT LAKE CITY--A hydrogel developed by University of Utah medicinal chemist Glenn D. Prestwich, Ph.D., will play an integral role in a $5 million National Science Foundation-funded (NSF) study that includes a component for organ "printing."

Organ printing is a developing branch of medicine in which cells are taken from a damaged organ and used to literally print living, three-dimensional tissue for repairing diseased and damaged organs. The technology potentially can help millions of people who need transplants.

"Our gel is an essential part of the whole process for organ printing," said Prestwich, presidential professor of medicinal chemistry at the U College of Pharmacy. "I believe in five years we're going to be able to print simple organs, such as a cardiovascular network or a urethra."

The five-year study, led by organ-printing pioneer Gabor Forgacs, Ph.D., professor of biological physics at the University of Missouri-Columbia, aims first to understand basic mechanisms that control biological self-assembly. Self-assembly is a fundamental process in which disordered parts of a living system come together to form patterns and structures, such as blood vessels and organs. Forgacs particularly is interested in the self-assembly mechanisms that regulate changes in shape as a human being develops from a spherical egg to a fully grown person.

Once he understands the mechanisms of self-assembly, Forgacs' goal is to mimic the process and apply that knowledge to organ printing. That's where Prestwich's gelatin-like hydrogel comes in.

Like any printing process, organ printing requires ink, paper, and printer.

The "bio-ink" consists of cells taken from an organ, such as a blood vessel or heart valve. The "bio-paper" is Prestwich's hydrogel. The printer can be a standard ink-jet model, modified to use a solution of cells and liquid hydrogel instead of ink, or one designed for using bio-ink.

The cells and liquid hydrogel are placed in the printer cartridge and then dropped in three-dimensional, 1-microliter dots that form layers as the hydrogel solidifies. After many layers have been made, the cells fuse into tissue that forms 3-D structures. The hydrogel is removed, and new healthy tissue is left to implant into a damaged or diseased organ.

"We already have printed 3-D structures that mimic blood vessels," Forgacs said.

Prestwich's hydrogel consists of two sugar chains that, when mixed with a reactive substance, crosslink--the chemical equivalent of weaving cloth--and change within minutes from liquid into gel. The hydrogel breaks down and the cells use these fragments to build a scaffolding that induces tissue regeneration and, in the cases of wounds, promotes faster healing.

"The beauty of our gel is that cells can digest it and turn it into a new matrix that allows them to create what they need to make tissue," Prestwich said. "The key feature is that the gels crosslink, turning from liquid to solid in the presence of living cells."

Forgacs said he'd used other hyrdrogels, but likes Prestwich's because of its bio-compatibility with cells.

The grant was one of three issued, among about 90 applicants, through the NSF's Frontiers in Integrative Biological Research program. The awards support interdisciplinary research leading to new technologies that address important biological questions, such as the ones Prestwich and Forgacs want to answer.

As part of the grant, the studies must include an educational component that includes exhibiting and explaining the researchers' work in a museum. In Salt Lake City, the organ printing will be exhibited at the Leonardo at Library Square at the Salt Lake City Library.

Source: Eurekalert & others

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