A new process patent for adding biodegradable silver nanoparticles to the naturally occurring plant protein lignin has been described in a recent Nature Nanotechnology paper out of NC State University, exciting researchers who see antimicrobial potential for this technology in everything from preventing food poisoning to coating medical devices.

The technique involves the lignin polymer of plants, a biodegradable strengthening portion of cells that has little economic value outside of uses involving wood.  Isolated lignin is converted to nanoparticles and infused with silver ions.  These nanoparticles are then coated in polyelectrolytes, long strings of molecules that assist the nanoparticles in attaching to pathogenic bacteria.  When the bacteria ingest the lignin, the silver ions are released and, after being incorporated into the bacteria, kill the offending microbe.

Importantly, the silver becomes biodegradable.  Other studies, both from Dr. Orlin Velev’s lab (who was the lead investigator of this study) and others, have shown that pure metals are very good antimicrobial agents but do not readily biodegrade after killing the microbes.  By converting their metals to ions, the researchers showed that the bacteria incorporate the silver into their membranes, and leached it into the environment after death with no increased environmental toxicity.  Normal use of metals for antimicrobial purposes resulted in accumulated environmental stores that at higher concentrations could have significant and detrimental impacts.

“We expect this method to have a broad impact,” said Alexander P. Richter, PhD Candidate and lead author of the paper.  Indeed, they showed in their study that by tailoring the polyelectrolyte layer on the nanoparticles, they can target various bacteria such as Ralstonia, a bacterial genus containing soil-borne pathogen species, and Staphylococcus epidermis, a pathogenic bacteria that can form biofilms on medical plastics such as catheters.  Mr. Richter and Dr. Velev have started a company, Benenova Inc., to commercialize this technology and expand on the promising results.

Edward Marks is a PhD student at the University of Delaware.  His research involves the healing of myocardial tissue after major cardiac events using nanomedicine techniques, with the goal of pushing any advancement directly into the clinic.  Edward received his BS from Rutgers University and Masters from the University of Delaware.