Development of 3D calcium phosphate scaffolds produced using additive manufacturing technology with solvent free inks

Abstract

This thesis seeks to advance the development of calcium phosphate (CP) bioceramics inks for use in Additive Manufacturing (AM) of Tissue Engineered (TE) scaffolds for the treatment of orthopaedic bone defects. The aim of the study was to create bespoke, patient-specific bioactive scaffold systems that can support bone tissue regeneration in vivo. The central focus of the work reported here is provision to the key structural and mechanical properties that such biological bone scaffolds must have in the context of the clinical requirements concerned. This thesis presents an innovative non-aqueous based formulation for the creation of Calcium Phosphate (CaP) based ink systems for 3D
extrusion printing using a solventless triglyceride binder carrier, capable of producing inks with up to 82.5% w/w CaP solid loading. A value greater than anything previously reported in the literature to date.


Adjustments to theses CaP ink formulation have resulted in effective printing of
interwoven filamentary pre-forms that can withstand subsequent high temperature sintering to create robust, open pore 3D isotropic structures. A detailed assessment of the mechanical properties of the 3D structures shows that their ability to withstand compressive forces is dependent upon the structural design, the Calcium Phosphate (CaP) material and the processing conditions. For examples the scaffold designs G1 (Sr13%-(𝛽 − 𝑇𝐶𝑃) 𝐶𝑟𝑜𝑠𝑠 ℎ𝑎𝑡𝑐ℎ ) reported an Ultimate Compressive Strength (UCS) value in the region of 11.68Mpa, which is suitable for the most demanding of critical defect sites.

The developed 3D printed scaffolds can match their mechanical properties to those of the intended bone implant site, by adjusting the design and CaP material choice. Chemical characterisation indicates that the resulting sintered 3D scaffolds are free from any cytotoxic residues that may cause adverse interactions with biological cells. There biocompatibility has been confirmed by a focused cell culture study and biological assessment using the U20s cell line. It can be suggested that the new knowledge gained from the findings reported within thesis provide a significant advancement towards adopting additive technology to producing the next generation of personalised bone scaffolds. Which in turn can be used to treat critical sized bone defects, offering an alternative to the current treatment approach, e.g. autologous grafting.

Date of Award	Jun 2024
Original language	English
Sponsors	Department for the Economy
Supervisor	Brian Meenan (Supervisor) & George Burke (Supervisor)