The most numerous of organisms on Earth, bacteriophages are viruses that infect and kill bacteria. Now, scientists have grown enough of them to create a self-healing hydrogel that's made almost entirely of the things. It could have important applications in medicine, and in other fields.

Led by chemical engineer Zeinab Hosseini-Doust, researchers at Canada's McMaster University grew bacteriophages in the lab, extracted them from their growth medium, and then packed them together within a confined space. This caused the "phages" to self-assemble into liquid crystals, to which a chemical binder was added.

The result was a gelatin-like hydrogel, that heals back together when cut. Just a single milliliter of the substance contains approximately 300 trillion phages. And by modifying their DNA, it's possible to tweak the viruses to attack different types of bacteria or other targets. What's more, the gel should work against antibiotic-resistant bacteria.

One of the most obvious places in which the material could be used is the field of medicine, where it may be utilized as a wound dressing, an antibacterial coating for implants, or a sterile three-dimensional scaffold for growing biological tissue. The phages might even be made to attack cancer cells.

Amongst its uses in other fields, the gel could be utilized to clean up the environment, as the viruses can be altered to target plastics or other pollutants.

"Phages are bacteria's natural predators," says Hosseini-Doust. "Wherever there are bacteria, there are phages. What is unique here is the concentration we were able to achieve in the lab, to create a solid material."

A paper on the research was recently published in the journal Chemistry of Materials.