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

Rajesh R. Naik and colleagues explain that in adverse conditions, bacteria of the Bacillus species, which includes anthrax, become dormant spores, 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 silk 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 anthrax 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.

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

Abstract
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.

Provided by American Chemical Society (news : web)

Nano detector for deadly anthrax

An automatic and portable detector that takes just fifteen minutes to analyze a sample suspected of contamination with anthrax is being developed by US researchers. The technology amplifies any anthrax DNA present in the sample and can reveal the presence of just 40 microscopic cells of the deadly bacteria Bacillus anthracis.

B. anthracis, commonly known as anthrax, is a potentially lethal microbe that might be used intentionally to infect victims through contamination of food and water supplies, aerosolized particles, or even dried powders, such as those used in bioterrorist attacks in the USA. Detection is crucial to preventing widespread fatalities in the event of an anthrax attack. However, the complexity of the microbe's biology have so far made it difficult to build a portable system that can be employed quickly in the field. That said, there are several systems available that use PCR to amplify a particular component of the genetic material present in anthrax and then to flag this amplified signal. These systems are fast and sensitive but do not integrate sample preparation and so are not as convenient as a single detector unit would be.

Writing in the International Journal of Biomedical Nanoscience and Nanotechnology this month, Nathaniel Cady of the College of Nanoscale Science and Engineering (CNSE) of the University at Albany and colleagues there and at Cornell University, New York, explain how they have constructed nanofabricated fluidic cartridges that can be used to carry out detection of anthrax. The device is a so-called "lab-on-a-chips" device, or more properly a 3D microfluidic network that contains nanofabricated pillar structures.

The device has fluidic inputs for adding sample and reagents, removing waste, for carrying out DNA purification, and critically an integrated chamber for amplifying only the target DNA in the sample using the polymerase chain reaction (PCR) system. The chip also contains a wave guide for the fluorescence-based identification of the amplified DNA and thus the target microbe. Importantly, the system works without manual intervention other than loading a droplet of sample into the detector.

"The average time required for DNA purification during these experiments was approximately 15 min, and when combined with real-time PCR analysis, this resulted in an average time to detection of 60 min," the team says. The system can detect as few as 40 B. anthracis cells. "Due to its small size and low power requirements, this system can be further developed as a truly portable, hand-held device," the researchers conclude.

More information: "PCR-based detection of Bacillus anthracis using an integrated microfluidic platform" in Int. J. Biomed. Nanosci. Nanotechnol., 2011, 2, 152-166

Provided by Inderscience Publishers (news : web)

Science review casts doubt on 2001 anthrax case (Update 2)

There was insufficient scientific evidence to support the FBI's assertion that anthrax sent to politicians and journalists in the wake of the September 11 attacks originated in Ivins' lab, said the National Academy of Sciences.

"It is not possible to reach a definitive conclusion about the origins of the B. anthracis in the mailings based on the available scientific evidence alone," said the NAS report.

The anthrax mailings, which killed five people and injured 17, rattled an already jittery American public just days after Al-Qaeda militants hijacked passenger jets and plunged them into the World Trade Center and the Pentagon.

The review found that anthrax contained in a flask, known as RMR-1029, in Ivins' lab shared genetic similarities with spores in the mailed letters but "was not the immediate source of spores used in the letters."

"One or more derivative growth steps would have been required to produce the anthrax in the attack letters," the report said, adding that the letters sent to Washington had different characteristics than those sent to New York.

"They have enough physical and chemical differences between the two that they must have come from separate batches," said lead author of the report Alice Gast.

The FBI concluded that the mailed anthrax must have come from a single flask of parent spores that Ivins had created and which he alone had maintained.

The type of anthrax contained in the letters, mailed to NBC anchor Tom Brokaw, the New York Post and senators Tom Daschle and Patrick Leahy, was correctly identified as the Ames strain of B. anthracis, which originated from a cow in Texas in 1981 and was shared with labs worldwide, the report said.

But a key problem arose from the way the FBI attempted to narrow down the source of the anthrax by creating a repository of potential samples provided by the labs that maintain them.

The repository was incomplete, leaving the possibility that other sources could remain unexamined, and also relied on scientists to provide their own samples, allowing for manipulation by potential suspects.

"Standards of custody of evidence would dictate that agents of the FBI should have obtained the samples," the report said.

"The sender could have been the instigator and may not have complied with instructions, as the FBI alleges with respect to Dr. Ivins."

Ivins, a bio-defense researcher at the US Army's Medical Research Institute of Infectious Diseases, committed suicide by taking drugstore medications in July 2008 as FBI agents were about to bring charges against him.

Investigators began focusing on Ivins in 2007 after new forensic scientific methods traced the anthrax back to him.

The NAS report was delayed in November 2010 when the FBI, which had just received the final draft for security review, decided to release more, previously classified information for the panel to consider.

FBI investigators had looked at anthrax evidence from "an undisclosed overseas site at which a terrorist group's anthrax program was allegedly located," the report said.

"The information indicates that there was inconsistent evidence of Ames strain DNA in some of these samples, but no culturable B. anthracis," it said, adding that the late-arriving information "deserves a more thorough scientific review."

The NAS reviewers also noted that their analysis of evidence was limited to "the biological, physical, and chemical sciences," and did not consider other traditional forensic science methods.

The FBI, which commissioned the NAS report, highlighted the panel's assertion that a definitive conclusion based on science alone "was not possible" and said a combination of factors led investigators to Ivins.

"The FBI has long maintained that while science played a significant role, it was the totality of the investigative process that determined the outcome of the anthrax case," it said in a statement.

Some lawmakers called for a new, independent probe of the government's response.

"The National Academy of Sciences report released today shows that the science is not necessarily a slam dunk," said Senator Chuck Grassley.

"There are no more excuses for avoiding an independent review and assessment of how the FBI handled its investigation in the anthrax case."

Congressman Rush Holt said he was re-introducing a 2008 bill to establish a legislative commission to investigate.