Slapping on a Band-Aid is the easiest way to help a cut on your skin heal, but things aren't so simple for internal wounds. For one, it's obviously much harder to reach that surface to put a dressing on it, but even when its open, say during surgery, the slippery mucus lining prevents bandages sticking. Now, researchers from Harvard have developed spray-on hydrogels, produced by bacteria, that can help heal these internal wounds.

Hydrogels are emerging as a promising tool for wound healing for injuries to skin, organs, blood vessels or cartilage. They're particularly useful because they not only protect a wound from infection but can often actively pitch in to patch it up.

The newest such creation comes from researchers at two Harvard schools – the Wyss Institute for Biologically Inspired Engineering and the School of Engineering and Applied Sciences (SEAS). This hydrogel works a similar magic on the slimy surface of the intestines, and it's relatively simple to make by recruiting bacteria to do the hard work.

The Harvard team's new hydrogel contains a non-pathogenic strain of E. coli, and CsgA curli proteins. These curli proteins latch onto proteins called human trefoil factors (TFFs), which are present in the intestinal cells that create mucus. That lets the hydrogel stick to the normally-slippery surface, creating a water-tight seal that aids healing of the wound.

The CsgA curli proteins are produced by the E. coli, which has a few benefits. It's relatively easy to make, and keeping the bacteria in the hydrogel means the substance can replenish itself to last longer. But the team also made a "cell-free" version with no bacteria in it, for shorter-lived gels.

The team tested the material on a sample of colon tissue from a goat. By using different types of TFFs, they were able to get the hydrogel to selectively stick to either the inner or outer surfaces of the colon. Other TFFs increased the amount of time the hydrogel would stay in place, with some lasting more than five days.

The researchers envision that this hydrogel "bandage" could be sprayed onto a wound either during surgery, through an endoscopic procedure, or potentially even contained in a capsule that can be swallowed. In this last case, the team tested it on mice and found that the bacteria in the live gels survived long enough to reach the cecum, a pouch between the large and small intestines.

Interestingly, the team took inspiration for the project from the biofilms that bacteria build, which are often considered a nuisance to wound healing.

"Naturally produced biofilms are known to hinder wound healing processes up to a point where they need to be actively managed by health care practitioners," says Anna Duraj-Thatte, first author of the study. "We have essentially hacked one of the core machineries that produces them with the long-term goal to do exactly the opposite, to produce materials that could support wound healing in an environment that is inaccessible by other materials."

The research was published in the journal Advanced Materials.

Source: Harvard

