The new hydrogels are highly versatile.
Image credit: Melanie Gonick/MIT.
The "smart wound dressing" releases medication as needed, in response to changes in skin temperature. It can even light up if the medication supply is running low.
The new dressing stretches with the body. Not only will it remain in place when the wearer bends the knee or the elbow, but its embedded structures and electronics also remain intact and functional when stretched.
The team that designed and created the new hydrogel dressing was led by Prof. Xuanhe Zhao, of the Massachusetts Institute of Technology (MIT) Department of Mechanical Engineering.
The research is published in Nature Materials.
What is a hydrogel?
Hydrogels feature in various everyday products, from soft contact lenses and condoms to disposable diapers. Hair gel, toothpaste and plant water crystals all make use of hydrogels. Alginate hydrogels combined with aloe vera provide a wound dressing that keeps the wound moist and allows for regeneration of cells.
- In industry, hydrogels are used in bulkhead seals and waste cleanup
- Consumer goods containing hydrogels include hair gel and cosmetics
- Medical applications include contact lenses, drug release, nerve guides, coatings, tissue bulking and nucleus replacement.
Gavin Braithwaite, of the Cambridge Polymer Group in Boston, MA, notes that hydrogels are hydrophilic, with the potential to contain 80% or more water, permeable and allowing solute transport. They can also be viscoelastic and lubricious. They are also environmentally sensitive. All these properties make them multi-functional.
Already meeting a wide range of functions, hydrogels are dreaming of a bright future, including a role in spinal cord regrowth, nerve and tissue engineering, and even organ generation.
The structure of hydrogel is the key to its success. Its physical or chemical cross linkages of hydrophilic polymer chains enable it to either contain or absorb water up to 99% of its volume.
To create hydrogels, the polymer chains that form their basis are either chemically synthesized or derived from natural polymers. These may be proteins, such as collagen and gelatin, or polysaccharides, such as starch, alginate and agarose. Natural sources of hydrogels include shrimp shell and seaweed.
The high water content makes them either soft, "squishy" and flexible, like contact lenses, or highly absorbent, as in babies' diapers. They can also be quite brittle. Their characteristics depend on their composition.
Materials scientists, who have for some time seen the potential of hydrogels for different applications, have been pushing the boundaries of this exceptional substance.
Hydrogel dressings are not new, with the first ones dating back to the 1950s. However, recent developments are producing some revolutionary concepts.
Soft contact lenses and wound dressings are among the many medical uses of hydrogels.
Familiar hydrogel dressings include free-flowing gels available in tubes and foil packets, preparations where hydrogel is saturated onto a gauze pad or strips, or a sheet of gel supported by a thin fiber mesh.
Hydrogel dressings provide moisture, promote healing and remove dead tissue from wounds. The high water content cools the wound and relieves pain relief. Hydrogels also prevent the dressing from sticking to the wound surface.
Hydrogels are strong and flexible, and they can be porous, allowing for diffusion, or dense, depending on composition. They can be adapted to meet different needs.
The University of Wollongong in Australia describe hydrogels as "some of the most biocompatible materials on the planet." In fact, animal bodies are mainly composed of hydrogels.
Body tissues and synthetic hydrogels have a lot in common, and the newest products have properties similar to body tissues, making them a good candidate for a growing range of medical applications.
Last year, Medical News Today reported on the development of a hydrogel that could stretch like skin.
Scientists have been working to harness these properties, in the hope of creating a "smart material" that will mimic biological tissue and function.
On the next page, we look at the characteristics of the new hydrogels developed by the team from MIT.