New class of smart, protein-based materials created

Indian-origin scientists have taken proteins from nerve cells and used them to create a 'smart' material that is extremely sensitive to its environment.
This combination of materials science and biology could give birth to a flexible, sensitive coating that is easy and cheap to manufacture in large quantities, researchers said.
The work could lead to new types of biological sensors, flow valves and controlled drug release systems, they said.
"We created a new class of smart, protein-based materials whose structural principles are inspired by networks found in living cells," said principal investigator Dr Sanjay Kumar, University of California Berkeley professor of bioengineering.

Kumar's research team set out to create a biological version of a synthetic coating used in everyday liquid products, such as paint and liquid cosmetics, to keep small particles from clumping together.
The synthetic coatings are often called polymer brushes because of their bristle-like appearance when attached to the particle surface.

To create the biological equivalent of a polymer brush, the researchers turned to neurofilaments, pipe cleaner-shaped proteins found in nerve cells.
By acting as tiny, cylindrical polymer brushes, neurofilaments collectively assemble into a structural network that helps keep one end of the nerve cell propped open so that it can conduct electrical signals.

"We co-opted this protein and turned it into a polymer brush by cloning a portion of a gene that encodes one of the neurofilament bristles, re-engineering it such that we could attach the resulting protein to surfaces in a precise and oriented way, and then expressing the gene in bacteria to produce the protein in large, pure quantities," said Kumar.
"We showed that our 'protein brush' had all the key properties of synthetic brushes, plus a number of advantages," Kumar said.
Kumar noted that neurofilaments are good candidates for protein brushes because they are intrinsically disordered proteins, so named because they don't have a fixed 3-D shape.

The size and chemical sequence of these hair-like proteins are far easier to control when compared with their synthetic counterparts.
The researchers showed that the protein brushes could be grafted onto surfaces, and that they dramatically expand and collapse in reaction to changes in acidity and salinity.
Materials that are environmentally sensitive in this way are often referred to as 'smart' materials because of their ability to adaptively respond to specific stimuli.
Other co-authors on the paper are Nithya Srinivasan, Maniraj Bhagawati, and Badriprasad Ananthanarayanan, all of whom are postdoctoral fellows in Kumar's lab.
The study was published in the journal Nature Communications.