Nano-coated ‘killer paper’ developed to extend food shelf life

The team from Institute of Nanotechnology and Advanced Materials, Bar-Ilan University, claim to have developed a “simple one-stop process” ​of coating paper with antimicrobial colloidal silver nanoparticles using ultrasonic radiation.

The study - Sonochemical Coating of Paper by Microbiocidal Silver Nanoparticles by Aharon Gedanken et al – notes that the antimicrobial properties of silver are well-established. Using silver nanoparticles, each one-50,000 the width of a human hair, lengthens their bacteria-fighting properties, said the paper published in the American Chemical Society’s journal Langmuir.

Method​

The process developed at the Kanbar Laboratory of Nanomaterials involves the in-situ generation of nanoparticles and their simultaneous application onto the paper substrate.

The group said it was able to control both the thickness of the silver coating and particle size through varying precursor concentrations and reaction times.

The nanomaterials were attached to the paper by a process of ultrasonication – which the group said is “one of the most attractive methods for coating applications involving nanomaterials”​.

The silver nanoparticles are anchored strongly to the surface either by physically embedding them in the surface or by forming chemical bonds or other interactions with the substrate to form a “remarkably study coating”.​

The coatings are also highly stable with loss of silver from the surface described as “minimal” - ​a key factor in making them suitable for long-life applications, added the researchers.

Gedanken said the coated paper showed potent antibacterial activity against foodborne disease-causing organisms such as E. coli​ and S. aureus​, killing all of the bacteria in just three hours.

“We believe that such coated paper has potential application in the food industry as a packing material with long shelf life and antifouling properties”, said the study authors.

Scaling up​

The simplicity of the process means it would be easy to scaled up to meet industry needs, said the research. It also noted that its technology could be use as another option to preservation processes.

“Developing coated paper with antimicrobial properties of silver nanoparticles could be an alternative to other food preservation methods employing radiation, heat treatment, low temperature storage, or the introduction of antimicrobial additives,”​ said the researchers.

Coating of Paper by Microbiocidal Silver Nanoparticles by ​Ronen Gottesman, Sourabh Shukla, Nina Perkas, Leonid A. Solovyov, Yeshayahu Nitzan, and Aharon Gedanken is published in Langmuir 2011, 27 (2), pp 720–726; ​DOI: 10.1021/la103401z​​