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New Hydrogel Material May Replace Damaged Cartilage in Human Joints

Harvard scientists create biocompatible “super gel” (Sept. 6)

A team of experts in mechanics, materials science, and tissue engineering at Harvard University has created an extremely stretchy and tough gel that may suggest a new method for replacing damaged cartilage in human joints.

The new material, a hydrogel, is a strong hybrid of two weak gels. Not only can it stretch to 21 times its original length, but it is also tough, self-healing, and biocompatible — attributes that open up new opportunities in medicine and tissue engineering.

The new material is described in the September 6 issue of Nature.

To create the new hydrogel, the researchers combined two common polymers. The primary component is polyacrylamide, known for its use in soft contact lenses; the second component is alginate, a seaweed extract that is commonly used to thicken food.

Separately, these gels are both very weak — alginate, for instance, can stretch to only 1.2 times its length before it breaks. Combined in an 8-to-1 ratio, however, the two polymers form a complex network of cross-linked chains that reinforce one another. The chemical structure of this network allows the molecules to pull apart very slightly over a large area instead of permitting the gel to crack.

Importantly, the new hydrogel is capable of maintaining its elasticity and toughness over multiple stretches.

Beyond artificial cartilage, the researchers see potential for the new hydrogel in soft robotics, in optics, in artificial muscle, and as a protective covering for wounds.

For more information, visit the Harvard University Web site.

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