Killer silk: Making silk fibers that kill anthrax and other microbes in minutes

March 14, 2012
Killer silk: Making silk fibers that kill anthrax and other microbes in minutes

A simple, inexpensive dip-and-dry treatment can convert ordinary silk into a fabric that kills disease-causing bacteria — even the armor-coated spores of microbes like anthrax — in minutes, scientists are reporting in the journal ACS Applied Materials & Interfaces. They describe a range of potential uses for this new killer silk, including make-shift curtains and other protective coatings that protect homes and other buildings in the event of a terrorist attack with anthrax.

Rajesh R. Naik and colleagues explain that in adverse conditions, bacteria of the Bacillus species, which includes anthrax, become dormant , enclosing themselves in a tough coating. These spores can survive heat, radiation, antibiotics and harsh environmental conditions, and some have sprung back to life after 250 million years. Certain chemicals — most popular among which are oxidizing agents, including some chlorine compounds — can destroy bacterial spores, and they have been applied to fabrics like cotton, polyester, nylon and Kevlar. These treated fabrics are effective against many bacteria, but less so against spores. The researchers tried a similar coating on to see if it could perform better against these hardy microbes.

They developed a chlorinated form of silk, which involves soaking silk in a solution that includes a substance similar to household bleach and letting it dry. Silk treated for just an hour killed essentially all of the E. coli bacteria tested on it within 10 minutes and did similarly well against spores of a close relative used as a stand-in. "Given the potent bactericidal and sporicidal activity of the chlorinated silk fabrics prepared in this study, silk-Cl materials may find use in a variety of applications," the authors say. Other applications, they add, include purifying water in humanitarian relief efforts and in filters or to mitigate the effects of toxic substances.

Explore further: Clemson researchers develop nanotechnology

More information: Sporicidal/Bactericidal Textiles via the Chlorination of Silk, ACS Appl. Mater. Interfaces, Article ASAP, DOI: 10.1021/am2018496

Bacterial spores, such as those of the Bacillus genus, are extremely resilient, being able to germinate into metabolically active cells after withstanding harsh environmental conditions or aggressive chemical treatments. The toughness of the bacterial spore in combination with the use of spores, such as those of Bacillus anthracis, as a biological warfare agent necessitates the development of new antimicrobial textiles. In this work, a route to the production of fabrics that kill bacterial spores and cells within minutes of exposure is described. Utilizing this facile process, unmodified silk cloth is reacted with a diluted bleach solution, rinsed with water, and dried. The chlorination of silk was explored under basic (pH 11) and slightly acidic (pH 5) conditions. Chloramine-silk textiles prepared in acidified bleach solutions were found to have superior breaking strength and higher oxidative Cl contents than those prepared under caustic conditions. Silk cloth chlorinated for ≥1 h at pH 5 was determined to induce >99.99996% reduction in the colony forming units of Escherichia coli, as well as Bacillus thuringiensis Al Hakam (B. anthracis simulant) spores and cells within 10 min of contact. The processing conditions presented for silk fabric in this study are highly expeditionary, allowing for the on-site production of protein-based antimicrobial materials from a variety of agriculturally produced feed-stocks.

Related Stories

Clemson researchers develop nanotechnology

October 3, 2006

Picture a spider web coated with sugar. But instead of luring in unsuspecting creatures, this spider web pulls in deadly anthrax spores, rendering them harmless.

Killer Kevlar -- clothing that shields from germs

July 21, 2008

Protective clothing worn by firemen and other emergency workers may soon get a germ-fighting upgrade. Researchers in South Dakota report progress toward the first Kevlar fabrics that can kill a wide range of infectious agents, ...

New partnership looks to industrialize spider silk production

September 15, 2011

( -- For thousands of years, human beings have looked with envy upon the silk webs spun by spiders; not only are they stronger than steel but they are tougher too (a vest made of spider web material can stop bullets ...

Most stretchable spider silk reported

February 8, 2012

The egg sac silk of the cocoon stalk of the cave spider Meta menardi is the most stretchable egg sac silk yet tested, according to a study published Feb. 8 in the open access journal PLoS ONE.

Recommended for you

New polymer creates safer fuels

October 1, 2015

Before embarking on a transcontinental journey, jet airplanes fill up with tens of thousands of gallons of fuel. In the event of a crash, such large quantities of fuel increase the severity of an explosion upon impact. Researchers ...

Researchers print inside gels to create unique shapes

September 30, 2015

(—A team of researchers at the University of Florida has taken the technique of printing objects inside of a gel a step further by using a highly shear-rate sensitive gel. In their paper published in the journal ...

How a molecular motor untangles protein

October 1, 2015

A marvelous molecular motor that untangles protein in bacteria may sound interesting, yet perhaps not so important. Until you consider the hallmarks of several neurodegenerative diseases—Huntington's disease has tangled ...

Anti-aging treatment for smart windows

October 1, 2015

Electrochromic windows, so-called 'smart windows', share a well-known problem with rechargeable batteries – their limited lifespan. Researchers at Uppsala University have now worked out an entirely new way to rejuvenate ...

1 comment

Adjust slider to filter visible comments by rank

Display comments: newest first

5 / 5 (1) Mar 14, 2012
Please send this research to the University of Oklahoma and other forensic science departments around the nation. Might be helpful for victims of bioterrorism who have been given Dioxin, Morgellon's disease and other toxins. GOOD RESEARCH!

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.