Smart hydrogels could contribute to biomedical applications

But traditional hydrogels, used in products such as facial masks and contact lenses, are made up of either synthetic polymers or biological extracts such as animal collagen, are likely to cause allergies. They cannot fully mimic the complex biological environment needed for cell growth and development.

Not only is the new smart hydrogel developed by Prof Sun's team suitable to act as a carrier for stem cells which are key components for regenerative medicine, but also can control the time and manner regarding drug delivery inside human body due to its light sensing function.

To create this novel hydrogel, the team assembled genetically-engineered proteins into molecular networks by stitching together the photoreceptor C-terminal adenosylcobalamin binding domain (CarHC) proteins at room temperature.

The synthesis relies solely on bacterial culturing - a process similar to fermentation. The composition of the resulting hydrogel resembles that of human tissues and thus can be used to deliver live cells into human bodies while potentially miniming allergies and body rejection.

As a drug carrier, this photo-responsive hydrogel can quickly switch from solid to liquid upon light exposure, thus allowing drugs to be released into the body in a controlled manner.

The strategy of creating entirely protein-based hydrogels represents a new way to design bioactive materials with precise control over their properties. The research findings were published in the journal PNAS.

"Demand for smart hydrogels is growing, the direct assembly of stimuli-responsive proteins into hydrogels opens up enormous opportunities not just for future material biology, but also medical treatment." Prof Sun said.

"In theory, hydrogels can serve as carriers for stem cells in regenerative medicine to promote the healing of damaged organs, which means organ transplantation may no longer be patients' only solution in the future."