Onionlike hydrogels

Interruptions in a gelation process have yielded the first hydrogel with a membrane architecture that resembles the distinct layers of an onion (Nature 2008, 452, 76). These onionlike hydrogels have potential uses in tissue engineering or regenerative medicine because, unlike other scaffolds, these materials could host various kinds of cells in separate compartments between the membrane layers. Laurent David and colleagues at the University of Lyon, in France, used the polysaccharide chitosan to form an alcohol gel. For this material to form a stable physical hydrogel, the alcohol gel must be completely neutralized with a basic solution. Prematurely removing the gel from this solution prevents base from completely permeating the material and creates a hydrogel membrane that encloses an alcohol gel core. David says the process was repeated up to 20 times to create a hydrogel with 20 separate membrane layers. He adds that the simple procedure can be used to generate multimembrane systems of various shapes from other polysaccharides.