Sep 8, 2017 | By Benedict

Engineers at Brown University have developed 3D printed biomaterials that can “degrade on demand.” The materials could be used to fabricate intricately patterned microfluidic devices or to make dynamic cell cultures.

Degradation of temporary 3D printed biostructure

One of the most exciting areas of 3D printing research is the development of materials that change after they are printed. Some like to call this “4D printing,” while others are too focused on the actual science at hand to care much about terminology. But however you categorize it, there is huge promise for dynamic 3D printed materials that go through changes after printing.

Engineers at Brown University are following the trend for changeable materials, having developed a technique for making 3D printed biomaterials that “degrade on demand.” This degradation can be brought about with a special chemical trigger, and could be useful in the fabrication of microfluidic devices, artificial tissue, and biomaterials that need to respond dynamically to stimuli.

“It’s a bit like Legos,” says Ian Wong, co-author of the research and an assistant professor in Brown’s School of Engineering. “We can attach polymers together to build 3D structures, and then gently detach them again under biocompatible conditions.”

But the 3D printing process behind the special biomaterials is, of course, much more complex than Lego. In fact, the Brown researchers have used a kind of stereolithography—the light-based resin printing method used by 3D System, Formlabs, and others—to make 3D printed structures with potentially reversible ionic bonds.

Wong and the other researchers say that nothing like this has ever been done before on an SLA machine, so the team had to figure out how to make the biomaterials completely on their own. To carry out the novel procedure, the scientists made solutions with sodium alginate, a compound derived from seaweed that is capable of ionic crosslinking.

By using different combinations of ionic salts, including magnesium, barium, and calcium, the Brown researchers were able to make 3D printed objects with varying stiffness levels, a factor which affected how quickly the structures dissolved.

SLA 3D printers like the Formlabs Form 2 can be used to print the degradable biomaterials

“The idea is that the attachments between polymers should come apart when the ions are removed, which we can do by adding a chelating agent that grabs all the ions,” Wong explains. “This way we can pattern transient structures that dissolve away when we want them to.”

So how can a 3D printed structure that dissolves on cue be useful? The researchers already have a few ideas.

For one, the alginate can be used as a template for making lab-on-a-chip devices with complex microfluidic channels.

“We can print the shape of the channel using alginate, then print a permanent structure around it using a second biomaterial,” says Thomas M. Valentin, a Ph.D. student in Wong’s lab and the study’s lead author. “Then we simply dissolve away the alginate and we have a hollow channel. We don’t have to do any cutting or complex assembly.”

The stereolithography technique can also be used to make dynamic environments for experiments with live cells. By surrounding alginate barriers with human mammary cells, the researchers found that cells migrate in specific ways when the barrier is dissolved away. They think this kind of work could even assist cancer research—one of Wong’s specialties—or the fabrication of artificial tissue and organs, since the alginate barrier did not add any toxicity to the human cells.

“We can start to think about using this in artificial tissues where you might want channels running through it that mimic blood vessels,” Wong says. “We could potentially template that vasculature using alginate and then dissolve it away like we did for the microfluidic channels.”

For now, however, the researchers plan to continue working on the project in order to achieve better control over the stiffness, strength, and degradation speed of the printed structures.

The researchers—Thomas M. Valentin, Susan E Leggett, Po-Yen Chen, Jaskiranjeet K. Sodhi, Lauren H. Stephens, Hayley D. McClintock, Jea Yun Sim and Ian Y Wong—have published their findings in the journal Lab on a Chip, in a paper titled “Stereolithographic Printing of Ionically-Crosslinked Alginate Hydrogels for Degradable Biomaterials and Microfluidics.”

 

 

Posted in 3D Printing Materials

 

 

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