Bioengineers build better beta peptides

For the first time, Australian scientists have shown it is possible to attach self-assembling beta peptides onto different organic molecules. Published in the journal APL Bioengineering, their study shows that molecules that have previously posed challenges to bioengineers can now be used to make new kinds of biomaterials.

Designing bioscaffolds offers bioengineers greater flexibility when it comes to tissue engineering and biomedicine. Systems that use self-assembling peptides can create a variety of materials, with beta peptides having become a key tool in building more robust biomaterials. These synthetic molecules mimic the structure of small proteins but are protected against the processes that degrade natural peptides.

Amino acids are groups of carbon atoms bookended by an amine group on one side and an acidic group on the other, and bound to various residues that give them each unique properties. In nature, most are known as alpha amino acids, meaning only one carbon atom holds all of these parts together. Beta amino acids divide up the work between two carbon atoms.

In beta peptides, the extra carbon makes the molecules hardier against peptide-breaking enzymes in the body. As it turns out, beta peptides can also self-assemble. A bioengineer simply needs to cap the amino end of beta peptides and they will build the sticky molecules themselves.

“We were quite surprised that a very small peptide was able to still assemble, despite the fact that there was something in the middle of it,” said lead researcher Mark Del Borgo, from Monash University.

“One cool thing about these is that they are completely sequence-independent. No matter how they are made up, they assemble entirely on their own.”

Del Borgo and his team investigated flexible and rigid linking molecules for the filler of their beta-foldamers, focusing on arginylglycylaspartic acid (RGD). This alpha peptide sequence found in the extracellular matrix acts as a template for placing cells correctly as they start to spread.

Using beta-foldamers with RGD at the centre, the team constructed a mesh on which they cultured a network of neurons. They found that the neurons properly conduct impulses between one another and shared information.

The researchers believe beta peptide-based structures might provide the bioscaffolding for brain meshes that can help coordinate the growth of neurons after a patient experiences a stroke or traumatic brain injury. For their next project, the group plans to investigate how bioscaffolds can help treat the neurological deficits of mice with these conditions.

Image caption: A topographical view of the mesh capable of growing neurons. Image credit: Mark Del Borgo.