Jun 3, 2015 | By Simon

Although there have been many new additive manufacturing technologies, material developments and 3D printing applications announced within the last six months, among those that have been gathering the most attention include applications and technologies for 3D bioprinting. 

While the ability to 3D bioprint an entire functional organ - such as a liver or even skin implants -  is still a few years off, many developments have been focused on smaller-scale 3D bioprinting applications, such as those that function at the molecular level.  

Recently, Xuanhe Zhao, an MIT associate professor of mechanical engineering, along with colleagues at MIT, Duke University, and Columbia University published a paper in the industry journal Advanced Materials describing the process of 3D printing highly-stretchable and tough hydrogels into complex cellularized structures.    

The tough biocompatible hydrogels are capable of being printed into complex and intricately patterned shapes that could ultimately lead to injectable materials for delivering drugs or cells into the human body.  Additionally, the unique process could lead to the creation of scaffolds for regenerating load-bearing tissues; or tough but flexible actuators for future robots, the researchers say.  Previously, we’ve seen how medical researchers have been experimenting with something similar to create 3D bioprinted scaffolding for slowly introducing cells for a diabetic treatment process.  This new process could enable them to further optimize the design of the scaffolding structure as needed.  

According to Zhao, who led the experiments,  the new process can produce complex hydrogel structures that are “extremely tough and robust,” and compatible with the encapsulation of cells in the structures.

One of the challenges in creating usable hydrogels has been in finding the right consistency that both allows for the material to break down as needed within the human body while also being able to maintain its shape while going through the printing process.  Hydrogels, which are defined by water molecules that are encased in rubbery polymer networks that provide shape and structure, can be used by the body as a natural shock absorber and are often compared to the biological structure of cartilage.  

While the development of the 3D printable hydrogels is certainly a breakthrough for Zhao and the rest of the team, they were also able to produce a hydrogel that is capable of synthesizing together with living cells.  Previous hydrogels were made in “harsh chemical environments” and thus, killed living cells that were encapsulated within them.  The newer ‘recipe’ will allow for stem cells or other types of living cells to be synthesized into the formula and be placed within the body using the hydrogel as a vehicle and support structure.  

Among other shapes that Zhao and the team were able to print with the new hydrogel include a hollow cube, a hemisphere, a pyramid, a twisted bundle, a multilayer mesh and even physiologically relevant shapes including a human nose and an ear.

“The innovation is really about the material ... a new ink for 3D printing of biocompatible-tough hydrogel,” explains Zhao.  

“Each material individually is very weak and brittle, but once you put them together, it becomes very tough and strong. It’s like steel-reinforced concrete.”

In addition to being able to be synthesized with living cells, the hydrogels have also proven to have incredible elastic properties; the pyramid shape is able to be compressed by 99 percent and still retain its intended printed shape.  Additionally, it is also able to be stretched to five times its original size and still conform back to its original shape.  According to Zhao and the researchers, these are great properties for replacing body parts that are cartilage-dense including noses and ears or even load-bearing joints that are in need of extra cartilage.  Zhao is so confident about the material that he believes it could even be used for soft robotic applications.    

“This is really beautiful work that demonstrates major advances in the utilization of tough hydrogels,” added David Mooney, a professor of bioengineering at Harvard University.

“This builds off earlier work using other polymer systems, with some of this earlier work done by Dr. Zhao, but the demonstration that one can achieve similar mechanical performance with a common biomedical polymer is a substantial advance … iIt is also quite exciting that these new tough gels can be used for 3D printing, as this is new for these gels, to my knowledge.”



Posted in 3D Printing Applications


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