Self-healing gel could seal wounds and deliver drugs
22 March 2012
A self-healing gel that binds in seconds, as easily as Velcro,
and forms a bond strong enough to withstand repeated stretching, has
been developed by bioengineers at the University of California, San
The material has numerous potential applications, including
medical sutures, targeted drug delivery, industrial sealants and
self-healing plastics, a team of UC San Diego Jacobs School of
Engineering researchers reported March 5 in the online Early Edition
of the Proceedings of the National Academy of Sciences.
Hydrogels are made of linked chains of polymer molecules that
form a flexible, jello-like material similar to soft-tissues. Until
now, researchers have been unable to develop hydrogels that can
rapidly repair themselves when a cut was introduced, limiting their
potential applications. The team, led by Shyni Varghese, overcame
this challenge with the use of “dangling side chain” molecules that
extend like fingers on a hand from the primary structure of the
hydrogel network and enable them to grasp one another.
Self-healing hydrogel made from polymer with
dangling side chain
“Self-healing is one of the most fundamental properties of living
tissues that allows them to sustain repeated damage,” says Varghese.
“Being bioengineers, one question that repeatedly appeared before us
was if one could mimic self-healing in synthetic, tissue-like
materials such as hydrogels. The benefits of creating such an
aqueous self-healing material would be far-reaching in medicine and
To design the side chain molecules of the hydrogel that would
enable rapid self-healing, Varghese and her collaborators performed
computer simulations of the hydrogel network. The simulations
revealed that the ability of the hydrogel to self-heal depended
critically on the length of the side chain molecules, or fingers,
and that hydrogels having an optimal length of side chain molecules
exhibited the strongest self-healing.
When two cylindrical pieces of gels featuring these optimized
fingers were placed together in an acidic solution, they stuck
together instantly. Varghese’s lab further found that by simply
adjusting the solution’s pH levels up or down, the pieces weld (low
pH) and separate (high pH) very easily. The process was successfully
repeated numerous times without any reduction in the weld strength.
Ameya Phadke, a fourth year PhD student in Varghese’s lab said
the hydrogel’s strength and flexibility in an acidic environment,
similar to that of the stomach, makes it ideal as an adhesive to
heal stomach perforations or for controlled drug delivery to ulcers.
Such healing material could also be useful in the field of energy
conservation and recycling where self-healing materials could help
reduce industrial and consumer waste, according to Varghese.
Additionally, the rapidity of self-healing in response to acids
makes the material a promising candidate to seal leakages from
containers containing corrosive acids. To test this theory, her lab
cut a hole in the bottom of a plastic container, “healed” it by
sealing the hole with the hydrogel and demonstrated that it
prevented any leakage of acid through the hole.
Moving forward, Varghese and her lab hope to test the material in
its envisioned applications on a larger scale. The team also hopes
to engineer other varieties of hydrogels that self-heal at different
pH values, thereby extending the applications of such hydrogels
beyond acidic conditions.