Home > Features >

Features

Spider cellulose

Date: 2017-05-26 13:57:25.0
Author: Jon Evans

 

Artificial biofilm

A close-up of the surface of a fiber made
from the nanocellulose-spider silk hybrid.

 

Spider silk is one of the strongest structural materials produced by animals and cellulose is one of the strongest structural materials produced by plants, so why not combine them to produce a novel super-strong material? This is what a team of Swedish scientists led by Daniel Söderberg at the KTH Royal Institute of Technology has now done, with the resulting material demonstrating great potential for medical applications.

Combining spider silk with cellulose also offers a neat solution to the difficulty of generating spider silk in large quantities, which is still the case even though spider silk proteins can now be produced by transferring the genes into microbes grown in a bioreactor. This inability to produce large quantities of spider silk is hampering its development as a useful material. In contrast, cellulose is the most abundant organic polymer on Earth. So combining a small amount of spider silk with a lot of cellulose, in the form of cellulose nanofibrils, should hopefully produce an abundant material that possesses the impressive properties of both its components.

To do this, Söderberg and his team simply mixed a solution of cellulose nanofibrils, which are around 5–10nm wide and have already been used to produce several strong and tough materials (see Cellulose adapts to new roles), with two different recombinant spider silk proteins. The resultant mixture comprises 90% cellulose nanofibrils and 10% spider silk proteins.

The researchers were able to produce two different materials from this solution. If they simply coated a surface with the solution and let it dry, the end result was a thin film in which the cellulose nanofibrils were orientated randomly. If, instead, they flowed the solution through a sheath to align the nanofibrils in the same direction and then transformed it into a gel, the end result was a thin fiber.

Studies on the resultant films and fibers with a scanning electron microscope and an atomic force microscope showed that the cellulose nanofibrils formed a compact network. The spider silk proteins were then distributed over this network, forming firm bonds with both the nanofibrils and each other. This arrangement conferred great strength and toughness, especially when the nanofibrils were aligned in the fibers.

As Söderberg and his team report in a paper in ACS Nano, the best fibers had a stiffness of 55GPa, a strength at break of 1015MPa and a toughness of 55MJ/m3, making them the strongest fibers ever produced from bio-based materials. “The strength of the fiber is significantly better than any man-made, silk-based material to our knowledge, and on the same level as what can be found in nature from spiders,” said Söderberg.

In addition to their great strength and toughness, these natural films and fibers should also be perfectly biocompatible, allowing them to be used within the human body as a scaffold for growing new biological tissue such as ligaments. To test the feasibility of this idea, Söderberg and his team tried growing various different human cells, including human dermal fibroblasts and microvascular endothelial cells, on both the films and fibers.

They found that the cells would grow readily on both, whereas they didn’t grow as well on fibers made purely from cellulose nanofibrils and wouldn’t grow at all on films made from cellulose nanofibrils. Other groups have also struggled to get human cells to grow on cellulose-based materials, and Söderberg and his team think that the spider silk proteins help the cells to bind with the films and fibers.

Up to now, though, the scientists haven’t tested whether the fibers could also allow a costumed superhero to swing through city streets.


The views represented here are solely those of the author and do not necessarily represent those of John Wiley and Sons, Ltd. or of the SCI.


Displaying 12 keywords used to tag this article:
  • Moncler Casacos Mulheres: 2.014 Mon  
  • Perfect Rolex Daytona Watch - DRW31  
  • Copy Omega Watches - De Ville 413.1  
  • pandora bracciale  
  • Replica Patek Philippe Aquanaut Ser  
  • Mont Blanc Meisterstuck Pen [6576]   
  • Copy Alarm watch Blancpain Series 2  
  • Replica Gorgeous Breitling Navitime  
  • Replica Longines - Australia best m  
  • Rolex GMT-Master II : Professional   
  • Replica Cool Ferrari Working Chrono  
  • Moncler Scarf & Caps Generous Dark