Researchers use 3D printing to mimic functions of tissue


Professor talks advances in regenerative medicine, organ synthesis


In recent years, technological advancements in regenerative medicine and organ synthesis have led innovations in the health care industry. Now there is hope for new advancements from a seemingly unrelated field: three-dimensional printing.

Jordan Miller’s University of Pennsylvania research team is using the improved capabilities of three-dimensional printing to mimic the functionality of the human tissue, he said at a presentation on Feb. 18 at the Biomedical Engineering building on Busch campus.

“Cells outperform devices. The focus is now on regenerative medicine, which has proven invaluable throughout its brief history,” said Miller, a postdoctoral fellow in the Department of Bioengineering from the University of Pennsylvania.

The science began in the 1980s with the invention of skin grafting, which involves the transferring of a portion of a patient’s healthy skin to a damaged area to ease the healing process, he said.

Aside from skin grafting, regenerative medicine has been used in corneal repair and other surface operations, but has so far been limited to two-dimensional tasks. Miller said his work aims to break this limitation.

“Scientists have not yet recreated solid organs, because there is currently no way to ensure that the internal cells have a constant delivery of oxygen and nutrients,” Miller said.

All three-dimensional organs have complex vasculature composed of vein and arterial systems. These structures are difficult to emulate, he said.

Miller and his team are using three-dimensional printing technology to create lattice structures and surround these structures with various gels engineered to simulate the properties of organs.

“These structures will someday resemble the vasculature of organs,” Miller said.

The printing system, called RepRap, is an open-source project founded in February 2004, he said. The software and machinery are capable of printing complex three-dimensional structures, with diameters ranging from 200 to 1200 microns, precisely the size range needed to create vein and artery designs.

“I was definitely fascinated with the multi-disciplinary approach Dr. Miller took in his research —especially on applying things like 3D printing to a biomedical context like organ design,” said Sagar Singh, a graduate student in the Department of Biomedical Engineering.

Miller said he uses an unlikely material to make up his lattice structures — sugar. It has important biocompatible characteristics, such as the ability to dissolve without harming nearby cells and the rigidity to withstand the development process.

“Sugar is like glass physically, but not chemically,” Miller said.

Through architectural analysis of human organs and experimentation with gel characteristics, like stiffness and density, he hopes to someday be able to recreate organs simply by printing out their vasculature and surrounding them with the necessary cells and gel, he said.

“Our structures are robust enough to withstand the pumping of blood. This is extremely important, as weak organ structures would collapse under the combined forces of circulating blood and clustering cells,” Miller said.

In addition to new capabilities for printing, advancements in nanotechnology are proving to be useful for tissue engineers. Hongjun Wang, a post-doctoral fellow at Stevens Institute of Technology, is constructing scaffolds on the nanoscale and studying their effects on cells.

“When one vital organ stops, that ends a life,” Wang said. “If we can replace organs, we can make our lives longer.”

He said his goal is to create a more beneficial cellular environment.

“We want to recapture key features of the cellular environment,” Wang said.

Wang and his team use electrostatic forces to control the orientation of nanofibers in a three-dimensional matrix and then populate those matrices with cells.

“We can control the nanofibers’ orientation by manipulating the electric field,” Wang said.

He said the greater porosity and surface area of nanospun fiber matrices make them much more practical environments for cells compared to microscopic fibers.

“It is a more manipulative method that supports cell growth and spreading,” Wang said.

As the limits of technology are pushed and overcome, biomedical engineers will continue to innovate and develop new tissue-engineering methods to the benefit of people everywhere.

“Tissue engineering brings a lot of promise, but there are still a lot of challenges to tackle,” Wang said.

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