Protein From Insect Wings Inspires Elastomeric Biomedical Polymer

Danish zoologist Torkel Weis-Fogh, together with Nobel Prize-winning physiologist August Korogh, published what is now known as a landmark study on the desert locust in 1951. In 1960, Weis-Fogh’s research uncovered resilin, a protein he found in the wing-hinge ligament of locusts and elastic tendons of dragonflies. Resilin is now being examined for its potential for medical applications. The protein is extremely elastic, which helps insects to jump and pivot their wings efficiently, and it can withstand high vibration frequencies, which allows insects to beat their wings at rapid rates.

Kristi Kiick, Ph.D., and her colleagues, have authored a new paper that appeared in ACS Macro Letters this July that summarizes their and others’ research on resilin-based materials for biomedical applications. Recombinant versions of resilin were first synthesized in 2005, and exhibit characteristics that best the most advanced synthetic rubbers. It can stretch up to three times its length and spring back without any change in shape or elasticity. Since 2005, scientists have been working on harnessing resilin’s properties for human medical applications. The challenge, which Kiick told Medical Product Outsourcing that her team has partly overcome, is engineering specific biological properties into the protein’s molecules so that it will be compatible to human tissue.

“The resilin gene, as it is expressed in the insect host, carries a mechanical function and has peptide domains—strings of amino acids—that allow it, for instance, to bind to polysaccharides that are common in insects,” explained Kiick. “One of the challenges in trying to develop these materials for medical applications was the inclusion of cell-binding domains that would be relevant for human cells to bind to these materials.”

A key application the Kiick group has investigated, in collaboration with one of Kiick’s colleagues at the University of Delaware, Xinqiao Jia, Ph.D., is resilin’s potential for vocal fold tissue healing. Resilin’s ability to withstand high-frequency vibration makes it ideal for human vocal fold tissue, which can oscillate at a rate of 440 times per second when singers sing A above middle C (for those not familiar with music theory, that’s pretty high). The aim of the research, according to the paper, is to fabricate scaffolds that can be systematically tailored for either implantable or injectable vocal fold tissue therapies.

In 2005, researchers were able to synthesize a resilin-like polypeptide that could be cast into a rubber-like biomaterial that yielded a recombinant material with mechanical properties similar to those of natural resilin. Kiick’s research team is also examining such synthesized materials for applications in other areas, including cardiovascular.

“One could envision making artificial vascular grafts out of these materials, and we’re working with collaborators in Japan around evaluation of these materials for those sorts of applications,” Kiick said. “We’re also looking, with local collaborators, at developing injectable hydrogels that a surgeon could use to augment healing at the site of a surgery. So you could use this material as an injectable implant if you wanted, or an injectable delivery depot for growth factors.”

Recombinant resilin would be useful for cardiovascular applications, the Kiick group speculates, because of its hydrophilicity (its ability to dissolve readily in water). Increased hydrophilicity may have the effect of improving the long-term stability of the proteins encapsulated in a hydrogel material, Kiick explained.

These properties have not been tested yet, but it could certainly be one of the next stages of research in the study of resilin-based materials.