Year

2019

Degree Name

Master of Philosophy

Department

Intelligent Polymer Research Institute

Abstract

Three-dimensional (3D) printing of one or more material, herein referred to as 3D hybrid printing, enables a promising fabrication method for complex tissue engineering (TE). The combination of different materials opens up the possibilities to design scaffolds for specific applications with matching or tailored properties. For the regeneration of the auricular cartilage, an ear shaped scaffold with a structural support layer is needed. The structural support needs to be mechanically robust but also cell friendly. In this regard, an advanced 3D hybrid printing method with three different materials is presented in this work. The hybrid printing strategy includes two main materials, the supporting materials and the hydrogel. As supporting material polycaprolactone (PCL) is used to deliver the structure similar to the mechanical characteristics of the human ear. The hydrogel ink is a combination of gelatin methacrylate (GelMa) and hyaluronic acid with methacylate (HAMa) (later called: GelMa-HAMa). GelMa-HAMa is expected to provide the biological environment, as well as to facilitate cell growth and differentiation of adipose stem cells (ASCs). In addition, depending on the geometry of the construct a sacrificial material is needed to achieve an optimal shape of the printed structure. In this work Pluronic F127 is used as sacrificial material and as model-gel for the pre-studies of the scaffold design. The printing conditions and parameters for all three materials were established and optimized. The hybrid scaffolds consisting of polycaprolactone (PCL) and the hydrogel GelMa-HAMa were found to be suitable to mimic the mechanical properties of the native auricular cartilage by varying the pattern design. It was possible to get a range of compression moduli from 2.5 to 10.0 MPa. In addition, the influence of the pattern design on the bending behavior was studied. The stiffness and the bending behavior of the hybrid scaffolds was mainly given though the PCL and the environment for the cells is provided with the hydrogel GelMa-HAMa, which is printed in-between the PCL strands. Furthermore, an enzymatic degradation study of PCL scaffolds was conducted and showed a uniform mass loss throughout the porous scaffolds.

Thus, a platform was established for 3D printed auricular cartilage using a combination of materials that is of clinically relevant sizes with matching mechanical properties for each part of the cartilage.

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Unless otherwise indicated, the views expressed in this thesis are those of the author and do not necessarily represent the views of the University of Wollongong.