Unexpected beauty, powerful antimicrobial effect

A team of McMaster researchers who regularly work with bacteriophages—viruses that eat bacteria—had a pleasant and potentially very important surprise when preparing slides for viewing under a powerful microscope.

After processing samples of the so-called phages so they could be seen alive under an electron microscope, the researchers were surprised to see that they had coalesced into three-dimensional shapes similar to sunflowers, but only two-tenths of a millimeter in diameter.

With a little guidance, nature created the very structure that experts in their field have been trying to create artificially for decades—a structure that turns out to be 100 times more effective than unrelated phages at finding elusive bacterial targets.

The ability to create such structures opens up the possibility of detecting and treating many forms of disease using natural materials and processes, the researchers say.

Their work is explained in a recently published journal article. Advanced functional materials.

The initial discovery was a fluke, the result of routine laboratory work.

Rather than subjecting the phage samples to conventional preparation processes that involve heat or solvents that kill viruses, lead author Lei Tian and his colleagues decided to treat them with high-pressure carbon dioxide instead. Tian, ​​now a principal investigator at Southeast University in China, led the study while he was a graduate student and then a research fellow at McMaster.

Although the researchers were used to seeing microscopic viruses do amazing things, after treatment they were stunned to see the phages clustering into such complex, natural and highly beneficial forms.

“We tried to protect the structure of this beneficial virus,” says Tian. “It was a technical problem that we were trying to solve. We got this amazing design created by nature itself.”

The researchers imaged the formations using facilities at the Canadian Electron Microscopy Center at McMaster and have spent the last two years uncovering the process and showing how the new structures can serve very useful purposes in science and medicine.

“This was an accidental discovery,” says the paper’s corresponding author, Tohid Didar, a mechanical engineer who holds the Canada Research Chair in Nanobiomaterials. “When we took them out of the pressure chamber and saw these beautiful flowers, it absolutely amazed us. It took us two years to understand how and why this happened, and to open up the possibility of creating similar structures with other protein-based materials.”

Q. In recent years, researchers in the laboratory of senior author Zeinab Hosseinidust, a chemical and biomedical engineer and Canada Research Chair in Bacteriophage Bioengineering, have made significant advances in phage research, making it possible to induce beneficial viruses to associate with each other like living, microscopic tissue. and even form a gel visible to the naked eye, opening up new prospects for their applications – especially for detecting and fighting infections.

However, until the recent discovery, it was impossible to give the material the shape and depth it now has through the folds, ridges and crevices of flower-like structures.

“It’s really about building with nature,” says Hosseinidoust. “Such a beautiful wrinkled structure is found everywhere in nature. The mechanical, optical and biological properties of these types of structures have inspired engineers for decades to create similar structures artificially in the hope of obtaining the same properties from them.”

Now that they have triggered such a transformation and have successfully duplicated the process, the researchers are amazed at the collective efficiency that phages achieve when banding together and taking on these forms, and are exploring ways to exploit the same properties.

Porous, flower-like phage structures are 100 times better than their unbound counterparts at detecting dispersed, diffuse targets, even in complex environments. The authors were able to prove this fact by mixing them with DNAzymes created by their infectious disease research colleagues and using the color-like formations to detect low concentrations of Legionella bacteria in commercial cooling tower water.

Bacteriophages are re-emerging as treatments for many forms of infection because they can be programmed to target specific bacteria while leaving others alone.

Work in this area stalled with the introduction of penicillin in the middle of the last century, but as antimicrobial resistance continues to reduce the effectiveness of existing antibiotics, engineers and scientists, including McMaster researchers, are turning their attention back to phages.

Discovering the process that causes them to coalesce into flower forms could enhance their already impressive properties, both in finding and killing target bacteria and as a scaffold for other beneficial microorganisms and materials.

“Nature is so powerful and so intelligent. Our job as engineers is to study how it works so that we can use similar processes and put them into practice,” says Hosseinidoust.

“The possibilities are endless because we can now create structures using biological building blocks.”