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Northwestern U Doctors, Scientists Outline New AM Materials for Medicine

Brett Brune
By Brett Brune Editor in Chief, Smart Manufacturing

PITTSBURGH—Doctors and scientists at Northwestern University have been working diligently for about seven years to bring new materials to clinics that handle plastic and reconstructive surgery, as well as transplants, Sue Jordan, chief resident in plastic and reconstructive surgery at Northwestern Memorial Hospital, told a crowd gathered to hear her speak today at the RAPID + TCT show.

Reconstructive surgeons every day face challenges that additive manufacturing can help address, she said. “For decades, plastic surgeons have been coming up with innovative techniques to solve challenging 3-dimensional conditions that are oftentimes inflicted by cancer and other trauma. Now it’s time for new ideas.”

Ramille Shah of the Shah Tissue Engineering and Additive Manufacturing (TEAM) Lab at Northwestern University spoke yesterday at RAPID + TCT in Pittsburgh. (Photo by Michael Drazdzinski)

Custom implants “have really skyrocketed in the past couple of years,” Jordan said. Many companies have solutions for cranioplasty, for example, that have been “extremely useful.”

Jordan showed slides taken during the treatment of a 9-year-old girl who, after a tumor, had much of her calvarium missing. To protect her brain, she had to wear a helmet.

She was outfitted with a custom PEEK (polyether-etherketone) implant— “and now she … can go without a helmet,” Jordan said.

The world is “ready for the next generation of custom … implants,” she added.

Ramille Shah of the Shah Tissue Engineering and Additive Manufacturing (TEAM) Lab at Northwestern University spoke about some of the materials experts are working with to advance custom implants.

That work happens where 3D printing and regenerative engineering interface, said Shah, who is also an assistant professor in materials science and engineering and surgery at the school. “Regenerative engineering is a paradigm where we’re trying to regenerate tissues with cells, and manipulating those cells within different material scaffolding systems—with or without stimulating factors.”

The people building regenerative implants of the future focus on scaffolds: The materials that make up artificial environments for cells, she said. “With these materials we are able to control the bioactivity, the architectural features, and the mechanical and degradation properties that can significantly influence how cells behave and how tissue successfully regenerates.”

The innovators are developing “more sophisticated scaffolding systems, to recreate and regenerate multiple, different types of tissues—from the soft more complex organ structures to ones that are more load bearing such as musculoskeletal tissues,” Shah said.

“Ideally, it would be great to have one printer that could print everything,” she said. “But its’ really hard to print a variety of different tissues with just a small number of available biomaterials that are printable.”

In her lab, scientists are working to “expand the biomaterial palette to be able to tune the systems that are 3D printed in order to regenerate a variety of different tissue types,” Shah said. Those include inks that include cells (“bioinks”) and those that do not. With the latter, cells are seeded on top.

“One of the main challenges associated with bioink development is that we have to be able to tune and optimize material properties without compromising printability,” Shah said.

The world needs materials that are “self-supporting once they are printed,” she added. “And ideally, … we want to make inks that are compatible when they are printed together.”

“This is the ideal scenario – where we have multiple different inks, different cell types, different material and bioactivity that can be printed in one construct, similar to what we see in natural tissues and organs.”

Shah and her associates have developed two main platforms.

One is based off of partially cross-linked hydrogels. “These are materials that can be used for soft tissue regeneration,” she said. “This is a platform that enables us to print cells and different types of materials.”

Shah and partners developed the first single bioink method using polyethylene glycol cross-linkers (PEGX) for the synthesis of hydrogel inks for cell printing that can be easily manipulated to tune hydrogel mechanical, degradation, nanostructural, and bioactive properties without compromising printability, she said.

PEG is commercially available and biocompatible, she said. It’s been used in several FDA-approved clinical products. It has variations in physical and chemical properties, and it’s relatively inexpensive. “We are able to use different types of polymers, and we can cross-link it lightly with or without the addition of cells. It [becomes] extrudable and yet self-supporting to maintain a well-defined porous architecture.”

The main challenge in bioinks is to be able to print materials that are cell compatible and can maintain the 3D architecture that you designed.

The other platform is particle-laden inks.

“We call them ‘3D paints’ because they have very similar composition to household paint,” Shah said. “These are acellular materials, but they have a great amount of functionality.”  Examples of Shah TEAM lab 3D paints include, Hyperelastic Bone, 3D Graphene, and metal and metal oxide- based inks that can be transformed into sintered metal parts after a post-printing thermal process.

“We focus on developing material platforms and processes that can be used to 3D print multiple different types of materials,” she said.  “This has significantly expanded what we can print using extrusion-based 3D printing.”

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