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