Sticky mussels inspire medical ‘super glue’

tube of super glue

A synthetic version of a high-strength adhesive produced by mussels is nontoxic to living cells, suggesting it may be useful for surgical or other biomedical applications.

“One long-term goal is to potentially replace sutures and screws owing to the trauma caused from punching holes into healthy tissue. These classic methods to join tissue also concentrate mechanical stresses on the tissues as well as creating sites for infection,” says Jonathan Wilker, professor of chemistry and materials engineering at Purdue University. “A possibly improved approach would be to use adhesives for connecting tissues.”

The findings, published in the Journal of Biomedical Materials Research Part A show that the polymer, poly[(3,4-dihydroxystyrene)-co-styrene], is nontoxic to cells, says Julie Liu, associate professor of chemical engineering and biomedical engineering.

The polymer, which the researchers have named catechol-polystyrene, is designed after a natural protein that mussels produce for sticking to surfaces. The animals extend hair-like fibers that connect to surfaces with a natural adhesive. A synthetic polymer is needed because the natural proteins are not practical for industrial applications.

[Molecule gets its glue from mussel feet]

“We designed this polymer to be a mimic of the natural proteins,” Wilker says. “It can be stronger than Super Glue under some conditions. You can also get the polymer to set completely underwater, which is not too common for most adhesives.”

The researchers tested the polymer with mouse cells called NIH/3T3 fibroblasts, cells that are often used to assess toxicity by examining how well they survive and grow when exposed to new materials.

The findings were detailed in a research paper that appeared online in January in the Journal of Biomedical Materials Research Part A. The paper also was authored by graduate students M. Jane Brennan, Heather J. Meredith and Courtney L. Jenkins.

“We are trying to assess whether the glue is toxic or tolerated well by the cells,” Liu says.

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The tests using two types of assays revealed that the cells continue to function properly when exposed to the polymer. In one of the assays, the cells with intact membranes produce a key enzyme, which indicates that they are alive.

“We are not yet at the point where we can claim bio-compatibility,” Liu says. “At this stage, we are providing the first step to show that this polymer system does not seem to affect cell response. We are asking the questions—do the cells live, do they divide, do they change shape? All indications are very good so far.”

The polymer contains “pendant groups” that dangle from the central backbone and are similar to such groups in the natural proteins. “The polymer is a simplified version of the proteins made by mussels for adhesion,” Wilker says.

The National Science Foundation, a 3M Nontenured Faculty Award, a Steven C. Beering Fellowship, and the Office of Naval Research funded the work.

Source: Purdue University

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