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Biomedicine

Growing Organs and Helping Wounds Heal

A strong, stretchy material could provide a scaffold for growing organs or making wounds heal faster.

A stretchy new fabric made by linking together the proteins found in muscle tissue could provide a scaffold for growing new organs. It could also be used as a coating for bandages to help wounds heal quickly and with less scarring. The fabric was made in the laboratory of Kevin Kit Parker, a professor at Harvard’s School of Engineering and Applied Science.

Protein pattern: This computer rendering shows ripples on fabric made from protein. Such fabrics could be used as scaffolds for growing organs.

When the body grows new tissue, cells secrete fibronectin–a strong, stretchy type of protein that acts as a supportive scaffold. The shape and structure that fibronectin adopts directs the subsequent growth of new cells, giving the resulting tissue the correct form.

Parker’s team creates the fabric by depositing fibronectin molecules on top of a water-repelling polymer surface. This causes the proteins, which are normally bundled up, to unravel. Next, the protein layer is stamped onto a dissolvable, water-attracting polymer sheet on top of a piece of glass. Adding water and warming the mixture to room temperature makes the proteins link together to form the fabric. It also dissolves the polymer so that the fabric can be peeled away and collected.

The team made swatches of material 10 nanometers thick and about 2.5 centimeters wide. The researchers can control the architecture and mechanical characteristics of the fabric by using different proteins, or changing the way they are aligned.

Different research groups are developing ways to grow replacement tissue in the lab, but a big challenge is providing the right direction for the growth of new cells. Researchers have previously made cellular scaffolds by flushing the living cells from harvested livers and hearts, and by creating cellular skeletons made from polymers.

By building the new scaffold from the protein up, Parker’s team can program direction cues into the architecture of the scaffold, and thus direct the growth of cells in the desired direction. Using natural proteins rather than synthetic polymers or decellularized organs reduces the likelihood that the new tissue will be rejected once it’s implanted.

In one experiment, the research team grew heart muscle cells on top of a piece of finished fabric. The fabric caused the muscle cells to link together to form a tissue that “beat,” when stimulated electrically, for one week.

“It’s a very clever approach,” says Juan Hinestroza, assistant professor and director of the Textiles Nanotechnology Laboratory at Cornell University. “The control of the architecture of the scaffold is really, really novel. And the scalability– you can use it to make bigger patterns.”

Other than building three-dimensional scaffolds for organ reconstruction, the new fabric could be embedded in bandages, accelerating wound healing and minimizing scar formation.

The material could also find other novel uses. An appealing feature is its unusual elasticity. The fibronectin protein, which forms the base thread of the fabric, is part of the molecular machinery that allows muscles to contract and relax.

“[Fibronectin] is compressed like a spring when you’re contracting your muscle, and when you relax, it pushes it back,” says Parker. This structure gives the fabric its elasticity, and allows it to be stretched up to 18 times its original length. “When you pull on the fabric, you unfold the proteins,” providing additional strength, says Parker.

Parker’s team is exploring the mechanical properties of the new fabric, examining its strength and stretchiness. The new stamping method could let them make larger, more complex fabrics. “The base technology is down,” says Parker. “Now we need to facilitate the spinout applications.”

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