Researchers Create Semi-Smart Hydrogels that can Support Bone Growth

Researchers have developed a hydrogel that can support cell growth. The gel changes from liquid to solid at close to body temperature, helping fill the gaps in bone or tissues until the cell regeneration is complete.

The gel was developed by Rice University researchers and colleagues.

Researchers said that the new polymer is semi-smart. It supports cell growth, but starts degenerating once the tissues form.

A major problem with current hermogelling polymers is that once they become solid, they start collapsing and release water in the surrounding area. The process of water expulsion is called syneresis.

 "If the transition gellation temperature is one or two degrees below body temperature, these polymers slowly start to expel water and shrink down until they're one-half or one-third the size. Then the defect-filling goal is no longer accomplished," Brendan Watson, Rice graduate student and the paper's lead author, according to a news release

To overcome the problem, researchers added cross-linkers to the gel's molecules. "It's a secondary mechanism that, after the initial thermogellation, begins to stabilize the gel," he said. "The links begin to form at the same time as the gel, but crosslinking takes up to a half-hour to complete."

According to Watson, the chemical crosslinks are held together by phosphate ester bonds, which can be broken down in the presence of catalyst such as alkaline phosphatase. Growing bone produces alkaline phosphatase in quantities that are enough to break the gel.

"As new bone is formed, the gel should degrade more quickly in that area to allow even more space for bone to form," Watson said.

The study is published in the journal Biomacromolecules and was supported by The National Institutes of Health, the Keck Center Nanobiology Training Program of the Gulf Coast Consortia and the Baylor College of Medicine Medical Scientist Training Program.