3D Printing of Biodegradable Elastomers for Osteoarthritis Repair

3D Printing of Nor-PGS as Biodegradable Elastomer

Claude King III, Jonathan Galarraga, Dr. Yi-Cheun Yeh, Dr. Chris Highley, Dr. Jason Burdick

Abstract

The repair of cartilage defects is currently under an extensive amount of research; cartilage is avascular and aneural, making it difficult for self-repair to occur in vivo. There are a number of therapies that are currently employed to repair cartilage defects sites such as microfracture, autologous chondrocyte implantation, and mosaicplasty.¹ These options utilize stem cells or autologous cells/tissue from the host to repair defects. However, each of these approaches have only demonstrated limited success in clinical application. Engineered scaffolds are a more promising solution towards repairing cartilage defects because they can be designed with properties that mimic native cartilage. When designing scaffolds for applications in tissue engineering, properties such as material mechanics, biocompatibility, biodegradability, porosity, and surface chemistry should be engineered to support cell growth and regeneration of native tissue.² For example, the elastic moduli of implants should be sufficiently high to provide mechanical integrity to defects; in parallel, interconnected porosity is required to allow adequate space for tissue growth.² With a wide range of properties, scaffolds can be created through different methods; however, 3D printing will be utilized in the approach herein described because it allows full control over the scaffold fabrication process. 3D-printing is of growing interest in the cartilage repair field because it can be exploited to print patient-specific defect geometries. However, 3D-prinitng of biomaterials into free standing objects is a complicated barrier for the translation of this technology. In conventional extrusion-based printing, printed constructs require a base to print on and are restricted to layer-by-layer fabrication. Free-form embedded printing is necessary to create patient specific geometries that can be extruded in any direction without undergoing stress relaxation due to body forces such as gravity. To achieve this goal, a sacrificial support material that acts as a Bingham plastic may be employed to permits deposition of material with spatial control. Specifically, the use of support material allows for constructs to be printed anywhere in three-dimensional space such that a larger range of scaffold geometries are accessible. Towards translation, printing patient-specific geometries will consist of scanning a specific defect geometry to obtain an accurate 3D-model of the site. The 3D shape can then be processed via computer-aided design (CAD) and saved into an STL file so that it can be readily printed. The work herein described focuses on the development of a biodegradable elastomer (Nor-PGS) that can be printed into a Carbopol (Lubrizol) support to form clinically relevant scaffold geometries.

References

1.     Brittberg, M., Peterson, L., Sjouml;gren-Jansson, E., Tallheden, T., & Lindahl, A. (2003). Articular Cartilage Engineering with Autologous Chondrocyte Transplantation: A Review of Recent Developments . The Journal of Bone & Joint Surgery , 85(suppl_3), 109-115.

2.      Hutmacher, D. (2006). Scaffolds in tissue engineering bone and cartilage. The Biomaterials, 175-189. doi:10.1016/b978-008045154-1/50021-6