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【技术产业】新型创伤愈合材料（医师报约稿）
Description：Researchers are developing scaffold-like materials designed to be injected into the body where they will quickly solidify to fit any space, repairing damaged bones, spinal cords, arteries and other tissues.
Researchers are developing scaffoldlike materials designed to be injected into the body where they will quickly solidify to fit any space, repairing damaged bones, spinal cords, arteries and other tissues.
Because the material starts out as a liquid, it fills in the gaps between damaged or missing tissue before hardening into a gel, or "three-dimensional matrix" that eventually disintegrates as it is replaced by healthy tissue, said Alyssa Panitch, an associate professor in Purdue University's Weldon School of Biomedical Engineering.
This gel could be loaded with time-released therapeutic drugs, such as "growth factors" needed to enhance healing. The approach also could be used to improve "drug-eluting stents," which are metal scaffolds inserted into arteries to keep them open after surgeries to treat clogs. Once in place, the stents release therapeutic agents, but scientists have recently learned that the stents can cause new clogs, leading to heart attacks.
New findings about the matrix materials were detailed in a research paper presented Monday (March 26) during the American Chemical Society's 233rd National Meeting & Exposition, which is taking place through Thursday (March 29) in Chicago. The paper was written by Panitch; Brandon Seal, a former doctoral student working with her at Arizona State University where Panitch began this work before coming to Purdue; Arizona State graduate student Karen Chao Butterfield; and John Chaput, an assistant professor of chemistry and biochemistry at Arizona State.
The method harnesses natural interactions in the body between molecules called polysaccharides and protein building blocks called peptides to control the assembly of the three-dimensional matrices. The polysaccharides interact with proteins and help the proteins come together and assemble scaffolds. Researchers have used the interaction between a polysaccharide called heparin and a peptide fragment of a protein called antithrombin III, which is contained in the bloodstream to control clotting.
"But we could have chosen peptides from many other proteins instead of antithrombin III and also different polysaccharides to tailor our matrix for specific applications," Panitch said.
The proteins exist in the "extracellular matrix" located between cells in tissues, where cells secrete the protein molecules. The researchers attached heparin-binding peptides from antithrombin III to a synthetic material called polyethylene glycol.
Mixing solutions of this peptide-polyethylene glycol combination with heparin instantly produces a three-dimensional matrix.
"It's very rapid assembly," said Panitch, who specializes in regenerative medicine. "The matrix can have any shape you want it to. If you had a defect in the bone, you could inject it into the defect. It would solidify immediately to fill the defect and release bone morphogenic proteins to enhance healing."
The technology could have several future applications, including controlled release of drugs and growth factors, which are used in wound healing, bone regeneration and other medical applications. Growth factors control cell behavior and are used to help bone grafts integrate with surrounding bone tissue. Controlling how strongly they bind to polysaccharides could enable researchers to develop gels that, when injected, would release therapeutic peptides over months, weeks, days or hours, depending on the application.
"We control how strongly it binds to the heparin, and changing the binding strength changes how long it takes to release therapeutic proteins encapsulated in the gel," she said. "The stronger it binds, the more slowly the therapeutic drugs are released."
The gels are "thermally reversible," which means heating them turns them back into a liquid.
"You can cool them down and they become solid, a characteristic that could be important for controlled release for drug therapy," Panitch said. "If you wanted to locally heat up the tissue to make the release faster, you could do that."
Future research may include work to increase the gels' strength. The researchers have shown how the gels are strengthened by using polymers that have more "functional groups." These functional groups are segments that attach to other molecules to fortify the matrix by forming "crosslinks" from one molecule to the next.
The research has shown that this crosslinking can be used to strengthen the matrix about 10 times, and the engineers have increased the original strength of the material, which could be likened to the consistency of mayonnaise or Jell-O, to something closer to the strength of cartilage or the material used to make contact lenses.
"The key is strengthening it as much as you want but still having that instantaneous assembly that was based on the polysaccharide-protein interaction," Panitch said. "That's what we've been able to do. We've been able to get essentially an instantaneous assembly and increase the strength of the material and still be able to control the release of therapeutic agents."
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作者:admin@医学,生命科学 2011-04-18 17:11
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