Three dimensional printing of bone tissue engineering scaffold: Design, structure, and mechanical properties / Mitra Asadi-Eydivand
Techniques to restore and replace bones in large fractures are still a major clinical need in the field of orthopedic surgery. Thus, tissue engineering is one of the most hopeful approaches for developing engineered alternatives for damaged bones. Scaffolds are important part of bone tissue engin...
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| Format: | Thesis |
| Published: |
2016
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| Online Access: | http://studentsrepo.um.edu.my/6964/1/Mitra_Asadi_KHA130005.pdf http://studentsrepo.um.edu.my/6964/ |
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| Summary: | Techniques to restore and replace bones in large fractures are still a major clinical
need in the field of orthopedic surgery. Thus, tissue engineering is one of the most hopeful
approaches for developing engineered alternatives for damaged bones. Scaffolds are
important part of bone tissue engineering (BTE). They are three-dimensional (3D) porous
structures that are expected to, at least, partially imitate the extracellular matrix (ECM)
of natural bone. Due to the natural properties of bone that are similar to calcium-based
ceramics, the fabrication of scaffolds with the same properties as patient’s bone and
adaptability to fracture defect are still a matter of concern and have remained a
challenging area in the BTE field. Since the microarchitecture of a scaffold, like its pore
size, and interconnectivity cannot be fully controlled by conventional techniques,
recently, the additive manufacturing (AM) techniques have drawn the attention among
tissue engineering experts. Other than that, solid freeform fabrication (SFF) is a wellestablished
AM technique that can be employed to produce prototypes from complex 3D
data sets. Moreover, the ability of inkjet-based 3D printing (3DP) to fabricate
biocompatible ceramics has made it one of the most favorable techniques to build BTE
scaffolds. Furthermore, calcium sulfates, which exhibit various beneficial characteristics,
can be used as a promising biomaterial in BTE and it is a low-cost material for 3DP.
Hence, this project had designed and developed the optimal processing parameters based
on the design of the experimental approach and evolutionary algorithms to evaluate the
ability of commercial 3D printers for making calcium sulfate-based or in other words,
commercial-materials-based scaffold prototypes. Besides the simple design to fulfill the
BTE requirements and to study the printing parameters, a library of triply periodic
minimal surfaces (TPMS) based unit cells was subjected to finite element analysis and
computational fluid dynamic (CFD) simulations. Elastic modulus, compressive strength, as well as permeability, were characterized for different volume fractions of TPMS
structures to develop structure-property correlations with emphasis on describing the
architectural features of optimum models. The major printing parameters examined in
this study for the simple design were layer thickness, delayed time of spreading the next
layer, and build orientation of the specimens. However, low mechanical performance
caused by the brittle character of ceramic materials had been the main weakness of the
3DP calcium sulfate scaffolds. Moreover, the presence of certain organic matters in the
starting commercial powder and binder solution caused the products to have high toxicity
levels. So, after fabrication, post-processing treatments were employed upon optimal
specimens to further improve the physical, the chemical, and the biological behaviors of
the printed samples. The first post-processing technique was heat treatment, while the
second one was phosphate treatment of 3D-printed specimens to convert the calcium
sulfate-based prototypes to calcium phosphate ones solely to improve their properties. |
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