Artificial silk of green lacewings for medical technology

Interview with Martin Schmidt, Fraunhofer Institute for Applied Polymer Research IAP, Functional Protein Systems/Biotechnology

03/01/2017

Researchers have often "looked over nature’s shoulder", sometimes with amazing results. Now the lacewing was given this honor. The way they put their eggs on bend-resistant stems, researchers want to use for new films, globules or capsules. COMPAMED has asked how far the process has progressed.

Bild: Egg stalks produced by green lacewings ; Copyright: Wikimedia Commons, Karthik R. Bhat

Egg stalks produced by green lacewings only measure 15 microns in thickness and are extremely rigid. They always point upwards, even if the leaf they are attached to moves or rotates; © Wikimedia Commons, Karthik R. Bhat

Mr. Schmidt, what is the difference between the silk proteins of the common green lacewing and the silk proteins that are already being used in the industry?

Martin Schmidt
: You are most likely referring to spider silk proteins with your question. The fibers of this particular type of silk exhibit high tensile strength. The fibers of a spider web built to catch an insect need to have a specific stability and elasticity to be able to absorb the enormous tensile force. That’s why its design features crystalline structures that are aligned parallel to the fiber. However, in the case of silk of green lacewings, the crystalline regions in the form of antiparallel beta sheets run vertically to the fiber axis. This gives them a high level of flexural rigidity and creates entirely new fields of potential applications for us.
Image: Smiling man in lab coat with glasses - Martin Schmidt; Copyright: Fraunhofer IAP, Foto: Till Budde

Martin Schmidt; © Fraunhofer IAP, Foto: Till Budde

You want to make artificial silk of green lacewings. What is your process?

Schmidt: The preliminary work has been carried out at the University of Bayreuth under the leadership of Professor Thomas Scheibel, who examined the natural genetic sequence and then transferred it to an E.coli bacterium. The bacterium is now able to produce the desired silk protein. In collaboration with our partner AMSilk GmbH, our task is to produce this silk material not just on an academic scale of several hundred milligrams but to convert it into a ”gram per liter scale“. This is why a large portion of the project is dedicated to fermentation and ensures that the bacterium exhibits the best conditions to produce the protein. We also want to find ways to extract the material from the bacterium in the most cost-effective and purest form possible.

The material is pulled upwards with the common green lacewing. Are you pursuing a similar process?

Schmidt: Unfortunately, it is not quite so easy to copy nature. There are many different types of processes the common green lacewing uses to produce this type of fiber. We will have to examine what technical processes lend themselves to us for this.
Picture: A green plastic frame, in which a picture of the lacewing eggs can be seen. Before this, a film is stretched, which consists of artificial silk of green lacewings; Copyright: Fraunhofer IAP

The photo shows a frame in which a film of artificial silk is stretched. Behind the foil is a picture of the lacewing eggs; & Copy; Fraunhofer IAP

What do you have in mind?

Schmidt
: The common green lacewing produces the outlined silk proteins in a gland. They are excreted onto the leaf surface. Then the green lacewing lays an egg into the protein secretion and pulls it upwards, thereby producing the fiber. In our case, we initially produce the protein using bacteria. Then we need to obtain the protein in pure form so that we can have it in powder form for instance. We subsequently produce the materials using this powder. These can be fibers but also films, globules or capsules – all of these are possible options.

You want to use the material in medical technology. What are some potential applications?

Schmidt: Due to the flexural rigidity of the material, scaffolds made of green lacewing silk are conceivable for example. Coatings on implants are also possible. There are several examples where spider silk is used to coat breast implants to prevent the body’s rejection response. This would also be possible using green lacewing silk.

Is there any early research on the biocompatibility of green lacewing silk?

Schmidt: The University of Bayreuth has also completed some preliminary work in this regard to examine the cell growth. However, further tests are still absolutely essential.

How long is the "green lacewing" project going to run?

Schmidt: The project that is funded by the "Agency for Renewable Resources (FNR)" started in September 2014 and will end in August of this year. At that point, the main portion of the project, the allocation of “artificial“ green lacewing silk as well as the material considerations, will have been completed. This is subsequently followed by future projects pertaining to material development.

Foto: Simone Ernst; Copyright: B. Frommann

© B. Frommann

The interview was conducted by Simone Ernst and translated by Elena O'Meara.
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