Interview

Microorganism repellent wrap

A team of researchers at McMaster University has developed a transparent wrap with self-cleaning properties. The wrap’s surface can even repel microorganisms such as antibiotic-resistant microbes. It can thus provide protection from these microorganisms in areas with high bacteria proliferation such as hospitals or kitchens when shrink-wrapped on often-touched surfaces such as door handles or railings. However, this transparent wrap is also suitable for food packaging, where it could prevent accidental transfer of harmful bacteria from raw packaged foods to their packaging during the packaging process.

The research was led by engineers Leyla Soleymani and Tohid Didar, who collaborated with colleagues from McMaster’s Institute for Infectious Disease Research and the McMaster-based Canadian Centre for Electron Microscopy. Their co-authors on the paper include Sara M. Imani, Roderick Maclachlan, Kenneth Rachwalski, Yuting Chan, Bryan Lee, Mark McInnes, Kathryn Grandfield and Eric D. Brown.1

Inspired by the water-repellent lotus leaf, the new surface works through a combination of nano-scale surface engineering and chemistry. The surface is textured with microscopic wrinkles that reject all external molecules. That is why any liquid, powder or germ will simply roll off this new surface. «We’re structurally tuning that plastic,» says Soleymani, an engineering physicist. «This material gives us something that can be applied to all kinds of things.» Chemical treatment supplements the wrap’s repellent properties, resulting in a barrier material that is supple, long-lasting and economical to reproduce. «We can see this technology being used in all kinds of institutional and domestic settings,» Didar says. «As the world confronts the crisis of anti-microbial resistance, we hope it will become an important part of the anti-bacterial toolbox.» This wrap is an easily applicable and effective cover for a variety of complex objects and that stands to make it superior to any substrate-specific surface modification or coating methods.

The researchers tested their material in collaboration with Brown and his colleagues at McMaster’s Institute for Infectious Disease Research. Their findings were that the development of biofilm by Gram-positive methicillin-resistant Staphylococcus aureus (MRSA) and Gram-negative Pseudomonas aeruginosa was reduced by 87 and 84%, respectively. Also, Gram-negative E. coli could not adhere to these surfaces. Electron microscope images captured by Grandfield verified the effectiveness of the surface by showing that virtually no bacteria had transferred to the wrap’s surface. The scientists involved established that the surfaces they had engineered repelled a large range of liquids and displayed fewer anchor points for bacterial adhesion.  The production process involves scalable bottom-up techniques.  

The researchers are hoping to work with a commercial partner to develop commercial applications for this product.

Leyla Soleymani, Associate Professor, Canada Research Chair in Miniaturized Biomedical Devices, McMaster University, Department of Engineering Physics, School of Biomedical Engineering was available for further questions:

1. You lead the team of researchers at McMaster University that has developed a self-cleaning surface that can repel all forms of bacteria. Please explain the concept and the technology behind this innovation.

We have discovered that combining multiple structural features having different length scales on a surface results in broad repellent and antimicrobial properties. These surfaces repel all kinds of liquid contamination and as a result contamination with deadly and drug-resistant bugs. In other words, due to the structure of these surfaces, it is not favourable for contaminants to stick to this surface.

2. Which contaminations can be repelled?

At this point, we have tested the surface against a broad range of liquids, water, oils, alcohol and bacteria. We are planning on our next series of tests with viruses.

3. How can this film be mass-produced?

These films are built on commercially available shrink films, these films are dipped in a solution and upon shrinking, the multi-length scale surface is developed

4. At the end of its shelf life, can this product be recycled?

We know that the product is stable for months. At this point, the wraps are not recycled but we are working on building them on biodegradable plastics.

Prof. Soleymani, thank you for explaining.

School of Biomedical Engineering, McMaster University, Hamilton, Ontario, Canada, L8S 4K1, www.geneticsensing.com

1  The work was published in ACS Nano: https://pubs.acs.org/doi/10.1021/acsnano.9b06287. The McMaster University reported on these findings at https://brighterworld.mcmaster.ca/articles/the-ultimate-non-stick-coating.

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