Silk proteins paired with renewable wood
nanocellulose produces possibly the strongest artificial spider silk yet
Date: May 17, 2017
Source: KTH The Royal Institute of Technology
Summary: Possibly the strongest hybrid silk fibers
yet have been created by scientists using all renewable resources. Combining
spider silk proteins with nanocellulose from wood, the process offers a
low-cost and scalable way to make bioactive materials for a wide range of
medical uses.
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FULL STORY
“The strength of the
fiber is significantly better than any human-made, silk-based material to our
knowledge, and on the same level as what can be found in nature from spiders,”
says Daniel Söderberg, a researcher with the Wallenberg Wood Science Center at
KTH.
Credit: Image courtesy
of KTH The Royal Institute of Technology
Possibly the strongest
hybrid silk fibers yet have been created by scientists in Sweden using all
renewable resources. Combining spider silk proteins with nanocellulose from
wood, the process offers a low-cost and scalable way to make bioactive
materials for a wide range of medical uses.
Published in ACS
Nano by researchers from KTH Royal Institute of Technology in
Stockholm, the technique brings together the structural and mechanical
performance of inexpensive cellulose nanofibrils with the medicinal properties
of spider silk, which is difficult and expensive to fabricate on a larger
scale.
The bioactive
properties of spider silk have been known for centuries. In ancient Rome,
spider webs were used to dress soldiers' battle wounds. But producing large
scale amounts of spider silk material today has proven an expensive process,
which often relies on fossil-based sources.
KTH Researcher My
Hedhammar says that by comparison, wood-based nanocellulose is cheap and
sustainable. Furthermore, the technique of combining it with only small amounts
of spider silk protein yields a biofunctional material that can be used for
such medical purposes as promoting cell growth.
"The strength of
the fiber is significantly better than any human-made, silk-based material to
our knowledge, and on the same level as what can be found in nature from
spiders," says Daniel Söderberg, a researcher with the Wallenberg Wood
Science Center at KTH.
Today, cellulose
nanofibrils obtained from trees receive scientific and commercial attention not
only because they are renewable, biodegradeable, virtually non-toxic and
available in large volumes, but they also offer outstanding mechanical properties.
Söderberg says that
the fabricated filament material could potentially be used, for example, as a
building-block for ligaments.
To make the material,
the researchers use what are known as recombinant silk proteins. Rather than
using a spider as host, the researchers take the gene encoding the silk protein
and combine it with a gene encoding some desired function, such as
cell-binding, Hedhammar says. "We transfer this fusion gene to a simple,
easily-cultured lab bacteria, which then produces the functionalized silk
proteins that can be purified in the lab," she says.
"Spider silk
fusion proteins are then added to the dispersed cellulose nanofibrils, and
thanks to the favorable interactions between the two components, a composite
material can be produced."
Söderberg says
technique uses hydrodynamics to align the fibers' internal structure on the
micro- and nano-scale. "When the nanocellulose is aligned in the
macroscopic material we can achieve super performance," he says.
Story Source:
Materials provided by KTH The Royal Institute of Technology. Note:
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Journal Reference:
1. Nitesh Mittal, Ronnie Jansson, Mona Widhe,
Tobias Benselfelt, Karl M. O. Håkansson, Fredrik Lundell, My Hedhammar, L.
Daniel Söderberg. Ultrastrong and Bioactive Nanostructured Bio-Based
Composites. ACS Nano, 2017; DOI: 10.1021/acsnano.7b02305
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