Modeled after adhesive proteins produced by mussels and other creatures, ELY16 contains a highly elastic protein found in connective tissue and tyrosine, an amino acid
A non-toxic glue modeled after adhesive proteins produced by mussels and other creatures has been found to outperform commercially available products, pointing toward potential surgical glues to replace sutures and staples.
“Sutures and staples have several disadvantages relative to adhesives, including patient discomfort, higher risk of infection and the inherent damage to surrounding healthy tissue,” said Julie Liu, an associate professor of chemical engineering and biomedical engineering at Purdue University.
The Purdue researchers created a new adhesive material called ELY16, an elastin-like polypeptide, or ELP. It contains elastin, a highly elastic protein found in connective tissue, and tyrosine, an amino acid. The ELY16 was modified by adding the enzyme tyrosinase, converting tyrosine into the adhesive DOPA molecule and forming mELY16.
Both ELY16 and mELY16 are not toxic to cells and work well under dry conditions. Modification with dihydroxyphenylalanine, or DOPA increases adhesion strength in highly humid conditions. Moreover, the modified version is tunable to varying environmental conditions and might be engineered to match the properties of different tissue types.
Research findings were detailed in a research paper published in April in Biomaterials. The paper was authored by graduate student M Jane Brennan; undergraduate Bridget F Kilbride; Jonathan Wilker, a professor of chemistry and materials engineering; and Liu.
The research was supported by Purdue’s Davidson School of Chemical Engineering and the College of Engineering, the National Science Foundation (Awards DMR-1309787 to JCL and JJW, CHE- 0952928 to JJW, and a Graduate Fellowship to MJB), a 3M Nontenured Faculty Award, a Purdue Research Foundation Summer Faculty Grant, a Steven C Beering Fellowship and the Office of Naval Research.
“To our knowledge, mELY16 provides the strongest bonds of any engineered protein when used completely underwater, and its high yields make it more viable for commercial application compared to natural adhesive proteins,” Liu said. “So it shows great potential to be a new smart underwater adhesive.”
“Our goal was to mimic the type of adhesion that mussel adhesive proteins have, and much other work has focused on the DOPA molecule as being critical to that adhesion,” said Liu. “We found that when the adhesive materials were exposed to large amounts of moisture, proteins containing DOPA had a much higher adhesion strength compared to unconverted proteins containing only tyrosine. So, DOPA conferred much stronger adhesion in wet environments.”
The researchers tested the polymer with mouse cells called NIH/ 3T3 fibroblasts. These cells are often used in research to assess toxicity by examining how well cells survive and grow when exposed to new materials. To test for biocompatibility, the researchers measured the viability of NIH/3T3 fibroblasts cultured for 48 hours directly on a layer of ELY16, mELY16, and a control. In all groups, viability was greater than 95 per cent.
Future research will include work to optimise the formulation of the adhesive and perform tests with natural materials.
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