Peptides gel in the spotlight

US chemists have developed a peptide that self-assembles to form a hydrogel on exposure to ultra violet light. The hydrogel is rigid and non-toxic, and offers potential as an artificial tissue for treating wounds.

Hydrogels consist of networks of polymer chains that encapsulate a large amount of water. They are already used to create flexible contact lenses. The development of aqueous polymer solutions that transform into hydrogels on exposure to light has opened up the possibility of using them for tissue engineering. This type of hydrogel is usually produced by combining a macromolecular precursor with a photoactive compound, which is often toxic to human cells and is not very soluble in water.

Joel Schneider and colleagues from the University of Delaware, Newark, have been developing hydrogels from peptide precursors. They previously developed peptides that self-assembled into hydrogels in response to changes in solution pH, ionic strength or temperature. Now they have created a peptide that self-assembles on exposure to UV light.

The chemists took one of their previously designed peptides, containing 20 amino acids, and added a cysteine residue with a negatively charged side chain, which prevented the peptide from forming a hydrogel. Exposing a solution of this peptide to UV light caused the side chain to break away, allowing the peptides to self-assemble.

The hydrogel created from this novel peptide is quite rigid, said Schneider, whose team found that a type of human tissue cell known as a fibroblast could grow and spread over the gel’s surface. The researchers are now attempting to create a version of the hydrogel that allows cells to be incorporated within its structure. Jon Evans