Modeling, fabrication and characterization of coated calcium phosphate scaffolds produced by 3D-Printing for tissue engineering application / Maria Touri

Maria , Touri (2020) Modeling, fabrication and characterization of coated calcium phosphate scaffolds produced by 3D-Printing for tissue engineering application / Maria Touri. PhD thesis, Universiti Malaya.

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Abstract

A fully interconnected 3-dimensional scaffold with pre-determined dimensions and porosity can be attained by design-dependent rapid prototyping techniques which possess precise control over the internal and external architecture of the scaffolds thus they can overcome the problems associated with the process-dependent classical approaches. Interruption of vascular flow with fracture or surgical osteotomy results in a transient hypoxic gradient within the wound and subsequent tissue necrosis. Tissue engineering scaffolds with oxygen generating elements have shown to be able to increase the level of oxygen and cell survivability. In this study, biphasic calcium phosphate (BCP) scaffolds with the composition of 60% hydroxyapatite and 40% beta-tricalcium phosphate, which have shown a great potential for bone tissue engineering applications, were fabricated by robocasting technique. Then, the three-dimensional-printed scaffolds were coated with different ratios (1, 3 and 5 wt%) of an oxygen producing biomaterial, calcium peroxide (CPO), which encapsulated within a polycaprolactone (PCL) matrix through dip-coating, and used for in situ production of oxygen in the implanted sites. 3D-printed BCP scaffolds with 70% porosity and large pore size (500 μm) showed a compressive strength of ~21 MPa. The oxygen release behaviour was sustained and dependant on the concentration of CPO encapsulated in the PCL coating matrix. It was also demonstrated that the coated scaffolds, having 3% CPO in the coating system, could provide an increase of approximately 50% in the oxygen concentration and a great potential for promoting bone ingrowth with improving osteoblast cells viability, function and proliferation. The finite element modelling was used to calculate the stress fields in scaffolds and the predicted compressive strength of the robocast scaffolds was ~24 MPa which is so close to the experimental result. Antimicrobial evaluations confirmed the inhibitory properties of the scaffolds on the growth of E. coli and S. aureus because of the release of calcium peroxide from the scaffolds. At in vivo part, a model of 15 mm segmental defect was made at the radius of rabbits. In the experimental group, defects were implanted using BCP scaffold coated with CPO. Control animals were implanted with uncoated BCP scaffolds. No implant was provided for the blank group. Bone repair was assessed by X-ray, biomechanical tests and histological observations at 3 and 6 months post-operation. The results showed that bone formation was increased at the interface and inside the inner pores of CPO coated scaffolds than those of uncoated scaffolds; biomechanical properties in the coated group were superior to those of the uncoated group. Our findings suggested CPO coated scaffolds had enhanced repairing ability in segmental bone defect in rabbit radius, and may serve as a potential material for repairing large bone defects.

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