Building Better Tissue Dr. Scott Hollister Leverages Engineering Tools to Save, Enrich Lives Scott Hollister first became interested in tissue engineering more than two decades ago, shortly after receiving his PhD in Bioengineering at the University of Michigan in Ann Arbor. He was looking for a way to build the complex porous scaffolds needed to grow human skin and bone when he turned to professor and mentor Noboru Kikuchi, a pioneer in what was then a novel technology, topology optimization. “His work made it possible to design some really extravagant structures that couldn’t be built with conventional manufacturing techniques,” Hollister said. “He was already exploring the use of 3D printing as a way to solve that limitation, and that in turn opened the door for the printing of biomaterials. The growth of those two technologies—topology optimization and 3D printing—has been very synergistic since that time.” Hollister’s credential list is impressive. While serving as a professor of Biomedical Engineering at his alma mater, his Scaffold Tissue Engineering Group (STEG) focused on “the computational design, manufacturing, and pre-clinical testing of degradable scaffold material systems.” He later moved to the Wallace H. Coulter Department of Biomedical Engineering—a joint department between the Georgia Institute of Technology College of Engineering and the Emory University School of Medicine—where he was appointed the first Patsy and Alan Dorris Chair in Pediatric Technology. Hollister also directs the Center for 3D Medical Fabrication as well as the Tissue Engineering and Mechanics Laboratory (TEM) at Georgia Tech. “3D printing has already had a huge impact on medicine, but the ability to computationally simulate how an implant will perform once its inside a specific patient is a game changer. It’s about to change even more—so far, we’ve only been using 3D printed biomaterials such as the polycaprolactone, but we look forward to actually printing other biomaterials with the cells themselves soon.” Scott Hollister Despite the highly technical nature of his chosen field, Hollister’s work is far from theoretical. Together with other university team members and colleagues from around the world, he has designed and built dozens of lifesaving devices, many of them for children: After securing emergency authorization from the Food and Drug Administration, Hollister and his colleague Glenn Green, an associate professor of pediatric otolaryngology at the University of Michigan, designed and printed the first bioresorbable tracheal splint, thereby saving the life of baby Kaiba Gionfriddo. The technology has since been used on nearly a dozen other infants, not only allowing them to go home to their families, but reducing hospitalization stays to days rather than months and even years. Hollister’s 3DMedFab center is currently developing advanced splint devices to reconstruct other airway defects. Hollister and pediatric cardiologist Martin Bocks from Case Western Reserve University are developing a shape memory bioresorbable polymer Poly(Glycerol Dodecannoate) (PGD) that they hope to 3D print to treat patients suffering from congenital structural heart defects. They have had initial success in pre-clinical models. In collaboration with pediatric otolaryngologist Dr. David Zopf at the University of Michigan, Hollister’s 3DMedFab Center and TEM lab has developed 3D-printed, patient-specific scaffolding, allowing them to perform craniofacial soft tissue reconstruction in pediatric and adult patients alike. Similar scaffolds have been built for patients with head injuries, congenital ear defects, and even periodontal disease. “One of the best things about what we’re doing is how well it works with kids,” Hollister said. “For example, consider a child born with microtia, where the ear canal and outer ear didn’t form correctly. In many cases, it's only one ear, so we can take an image of the good side, mirror it, and then build an exact replica. We’ll then fill the scaffold with stem cells or cartilage cells from the patient’s own body and implant it in the deformed area. In some cases, scaffolds might be placed temporarily inside a muscle or other blood-rich area of the patient’s body until sufficiently vascularized, then moved to the affected area. As with tracheal splints, the tissue grows in, gradually replacing the 3D printed material.” Hollister’s just getting started. Using multiscale computational simulation software together with other tools that he and his team have developed, they are able to utilize now mature topology optimization strategies as well as finite element analysis (FEA) to design structurally sound implants for young and old alike. “3D printing has already had a huge impact on medicine, but the ability to computationally simulate how an implant will perform once its inside a specific patient is a game changer,” Hollister said. “It’s about to change even more—so far, we’ve only been using 3D printed biomaterials such as the polycaprolactone, but we look forward to actually printing other biomaterials with the cells themselves soon. That’s going to open up a lot more possibilities.”
