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Stretchable, biocompatible hydrogels with complex patterning for tissue engineering

Researchers have developed a new way of making tough — but soft and wet — biocompatible materials, called “hydrogels,” into complex and intricately patterned shapes. The process might lead to injectable materials for delivering drugs or cells into the body; scaffolds for regenerating load-bearing tissues; or tough but flexible actuators for future robots, the researchers say.The new process is described in a paper in the journal Advanced Materials, co-authored by MIT associate professor of mechanical engineering Xuanhe Zhao and colleagues at MIT, Duke University, and Columbia University.

Zhao says the new process can produce complex hydrogel structures that are “extremely tough and robust,” and compatible with the encapsulation of cells in the structures. That could make it possible to 3D-print complex hydrogel structures — for example, implants to be infused with cells and drugs and then placed in the body.Hydrogels, defined by water molecules encased in rubbery polymer networks that provide shape and structure, are similar to natural tissues such as cartilage, which is used by the body as a natural shock absorber. The new 3-D printing process could eventually make it possible to produce tough hydrogel structures artificially for repair or replacement of load-bearing tissues, such as cartilage.

While synthetic hydrogels are commonly weak or brittle, a number of them that are tough and stretchable have been developed over the last decade. However, previous ways of making tough hydrogels have usually involved “harsh chemical environments” that would kill living cells encapsulated in them, Zhao says.The new materials are benign enough to synthesize together with living cells — such as stem cells — which could then allow high viability of the cells, says Zhao, who holds a joint appointment in MIT’s Department of Civil and Environmental Engineering

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