Electro-active Scaffolds for Bone tissue engineering

UoM administered thesis: Phd

Abstract

Bone is a highly hierarchical tissue which is able to heal and remodel in case of small defects and damage. For critical-size defects, the most commonly used approach requires the use of synthetic grafts. These grafts, also known as scaffolds, are physical substrates designed for cell attachment, proliferation and differentiation. Scaffolds for bone applications must be biocompatible, biodegradable, and highly porous, presenting mechanical properties similar to bone and surface characteristics that promote cell-scaffold interactions. The final properties of a scaffold strongly depend on both material compositions and process conditions. This research project investigates different aspects related to the design fabrication and characterization of bioactive electro-active scaffolds. Scaffolds were produced using an extrusion-based additive manufacturing system and different material compositions based on Poly (ε-caprolactone) (PCL) mixed with hydroxyapatite (HA), β-tri-calcium phosphate (TCP) and multi-wall carbon nanotubes (MWCNTs) were investigated. HA and TCP are biocompatible and degradable ceramics related to improve the bioactivity of the scaffolds and MWCNTs were selected to improve mechanical properties and due to their excellent electrical conductivity characteristics, to promote both cell-cell and cell-substrate communication. Experimental work was conducted to characterize both pre-processed materials and produced scaffolds evaluating the rheological, mechanical, thermal, chemical and biological properties. Rheological tests show that printability strongly depends on the concentration of the inorganic fillers (MWCNTs, HA and TCP) and processing parameters such as temperature, screw rotational velocity and deposition velocity. The addition of MWCNTs, HA and TCP can enhance the compressive modulus of PCL scaffolds from 48 MPa to 75 MPa in the case of PCL/HA, or 88 MPa in the case of PCL/TCP and PCL/MWCNTs. Biological results show that all scaffolds containing MWCNTs, HA and TCP are biocompatible (more than 80% cell viability), bioactive (40% increase for TCP, 60% increase for HA and 86% increase for MWCNTs) and osteoconductive (significant increase of ALP activity). Results also show that the addition of MWCNTs improves the osteoinductive properties and the presence of nano-sized HA improves the mineralization process. This research shows that PCL/HA/MWCNTs can be viable scaffolds for bone tissue engineering, providing a promising way for bone tissue regeneration.

Details

Original languageEnglish
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Supervisors/Advisors
Award date31 Dec 2018