Northwestern-invented biomaterials technology moves from lab bench to orthopedic market


Northwestern biomedical engineer Guillermo A. Ameer has achieved a rare and major achievement. An application based on a new material invented in his laboratory will be widely available for use in musculoskeletal reconstructive surgeries for the direct benefit of patients.

The biomaterial technology, called CITREGEN ™, developed by start-up Acuitive Technologies, Inc., is featured in Stryker Corporation’s CITRELOCK ™, an innovative device that will debut this week at the American Orthopedic Foot Annual Meeting and Ankle Society in Charlotte, NC The CITRELOCK ™ Tendon Fixation Device System is used to attach soft tissue grafts to bone in reconstructive surgeries and offers surgeons a differentiated design using Ameer’s biomaterial.

CITREGEN ™ has unique chemical and mechanical properties for orthopedic surgical applications which aid in the healing of transplanted tissues. The polymer contains organic molecules and includes citrate, phosphate and calcium, materials essential for healthy bone growth. CITREGEN ™ is the first thermoset biodegradable synthetic polymer ever used in implantable medical devices.

CITREGEN ™ is Northwestern Technology’s third medical technology company that Stryker has released. A robotic arm invented by Michael Peshkin in 1997 hit the orthopedic markets after Stryker bought his medical device company, Mako, in 2013. And the cement mixer from former Northwestern Dental School teacher Richard Wixson was also purchased and developed by Stryker.

The ceramic implantable device, CITRELOCK ™, received approval from the Food and Drug Administration (FDA) last year. The CITRELOCK ™ device has compressive strength comparable to cortical bone and maintains structural integrity during the healing phase, while allowing the implant to be reshaped by host tissue over time.

Founding director of Northwestern’s Center for Advanced Regenerative Engineering (CARE) and director of a newly created regenerative engineering training program funded by the National Institutes of Health, Ameer’s mission is to utilize engineering and training of the hand -Works to enable the practice of regenerative medicine to improve surgical outcomes and benefit patients. But generally, medical technologies derived from academic research take years to be adopted by a company, and more than a decade to receive clearance or approval from regulatory agencies such as the FDA.

Activated by collaboration

Guillermo Ameer

Ameer, Daniel Hale Williams Professor of Biomedical Engineering at the McCormick School of Engineering at Northwestern and Professor of Surgery at the Feinberg School of Medicine at Northwestern, looks back on the nearly 20 years he and his teams have spent developing the innovative technology of biomaterials.

“When I started my lab years ago here at Northwestern, one of my main goals was to use engineering to positively impact patient care. This objective has been the common thread of my research. I have sought to work with surgeons to fully understand medical issues, patient needs, constraints and find solutions, ”Ameer said.

“We first developed our citrate-based polymers about 18 years ago and first looked for applications in vascular and orthopedic tissue engineering. For the latter, we have created composites that are a blend of polymer and ceramic, the foundation of CITREGEN. ™ The first publication of these composites for bone regeneration, in collaboration with orthopedic surgeon Dr Jason Koh, was in the journal Biomaterials in 2006. Our work was developed by other researchers around the world, perhaps most notably Jian Yang, my former postdoctoral fellow and the current Dorothy Foehr Huck and J. Lloyd Huck Chair in Regenerative Engineering at Pennsylvania State University .

“A decade later, thanks to collaborations with industry, we were able to initiate the translation process to use our polymer technology in innovative bioresorbable orthopedic devices. Even though 20 years seems like a long time to see our technology come to market, we are fortunate to take this important step in my academic career. “

On the search for new materials: “What has motivated the development of polymers and citrate-based composites is the need to work with elastic materials such as rubber, easy to adapt, capable of supporting cellular functions, but also to dissolve safely in the body while being replaced by normal tissue, as no such material existed at the time. Working with an excellent team of students and post-docs, we invented a material from the start that took into account a variety of requirements. These included the body’s breakdown mechanism, the ability to synthesize easily and with safe components, and modularity to control material properties for a variety of potential applications. Over the years, we and others have shown that the citrate-based polymer can be incorporated into devices that help regenerate blood vessels, skin, heart, cartilage, bones, bladder, and tissues. muscle.

On demand for better devices: “There is a demand from surgeons and patients for better bioabsorbable devices, those that promote tissue regeneration or at least do not interfere with it. It is not easy to introduce new devices constructed with new bioresorbable polymers to the market due to issues with implants made from traditional biodegradable polymers and the scrutiny of regulatory agencies when reviewing. new bioabsorbable devices. It was a long process, but it was worth it to bring new solutions to market through established medical device companies. “

On Risk Taking: “Although we have been pioneering and working on this biomaterials technology for almost 20 years, great credit goes to visionaries in the industry, especially Acuitive Technologies and Stryker, for recognizing the potential of our technology and invested resources for its development and validation. It took Acuitive six years to develop CITREGEN ™ into useful products. The collaborations and partnerships that CARE has formed are important, replicating the success of CITREGEN ™ in other healthcare applications and translating other types of regenerative engineering technologies into clinical practice in the future.

Ameer’s work was recently recognized with the 2021 Clemson Prize for his contributions to literature and numerous other honors, including his election to the Fellowship of the Biomedical Engineering Society, American Institute of Chemical Engineers, Materials Research Society, American Institute of Medical and Biological Engineering. , American Association for the Advancement of Science and National Academy of Inventors.

Ameer is also a member of the Simpson Querrey Institute, the Chemistry of Life Processes Institute, and the International Institute for Nanotechnology.

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