Frontiers Of Biology

Developments in Tissue Engineering and Bioprinting

In recent years, developments have been made in 3D printing to allow for rapid 3D printing of hydrogel tissue scaffolds to help support the tissue building process within the human body once implanted. The two main methods of 3D printing that have been used in the past 5 years are stereolithography and extrusion based. Stereolithography is a type of 3D printing that creates solid physical models directly from computer data. Usually, Computed Tomography (CT) is used to create the computerized 3D model but Magnetic Resonance Imaging (MRI) can be used in similar way. Stereolithography has been a great tool for making large, durable material quickly but at an expensive cost.

Developments in Tissue Engineering and Bioprinting

Though stereolithography has been a great asset to many research projects, it could not be used in this study. “Stereolithography creates a solid material by catalyzing a polymerization process within a liquid medium.” Dr. Butcher, one of the authors of this paper, explains, “This requires that the platform be submerged within the medium, and therefore must be a significant volume (many liters). While fine for making a tissue scaffold, this is untenable for live cell encapsulation, which is our ultimate goal.” Recently, extrusion based printing has come to replace stereolithography. Extrusion based printing, commonly referred to as fused deposition modeling, functions by melting a ribbon of material through a computer controlled nozzle deposition unit. The material flows through the nozzle under pressure to ensure a constant rate of flow. It is possible to build stronger material with greater geometric complexity using extrusion based methods than by using stereolithography. The ultimate goal of these type of experiments is to create hydrogels to function as the desired tissue scaffold.

The process of 3D printing has been done before on numerous occasions, but still proved to be a major obstacle given the complexity of the aortic valve tissue scaffold. Dr. Butcher explains that throughout the process, “Just figuring out how to print the materials was the toughest part. Most people think this technology is just pushing a button, but it took us nearly 4 years to get right. We “printed” hundreds of shapes that didn’t come out at all like they were supposed to, with many computer and device errors that needed debugging. Until we figured out the direct crosslinking method, it took 14 hours to print just one. Now we can do it in 45 minutes.” Even though the procedures can be grueling, Butcher and his coworkers stay focused on the task at hand knowing their study can help open the doors for many other research opportunities down the line.

“My desire to get involved in science was an evolution from originally wanting to be an architect, then a design engineer.”

Butcher responds when asked about his inspiration to continue his work in scientific research, “I realized that few people actually got to design their own technology (rather, they fixed others crazy ideas). I found out that creating knowledge was a powerful enabler to designing technology to take advantage of that knowledge to benefit society. Ultimately, I found that the process of becoming someone who can create knowledge and technology that utilizes that knowledge was most exciting to me, so I chose to become a professor to help people realize that transformation in themselves.”

When asked about his future goals, Butcher noted that he hopes, “one day to develop an implantable living valve for children suffering from heart defects. I also hope to develop a biologically based diagnostic and therapeutic for aortic valve disease. These are particularly needed on a global scale, as the cases of valve disease in the developing world are much more legion.”

Even with the recent developments made in tissue engineering, it will take much more research before these type of hydrogels will be ready for implantation as tissue scaffolds. Dr. Butcher and his coworkers have help lay down the framework for rapid 3D printing that could later help cure patients with certain tissue defects around the world.

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