Development of three-dimensional printing polymer-ceramic scaffolds with enhanced compressive properties and tuneable resorption

Zuoxin Zhou,Eoin Cunningham,Alex Lennon,Helen O Mccarthy,Fraser Buchanan,Nicholas Dunne

doi:10.1016/j.msec.2018.08.048

Abstract

In this study, bone tissue engineered scaffolds fabricated via powder-based 3D printing from hydroxyapatite (HA) and calcium sulphate (CaSO4) powders were investigated. The combination of using a fast resorbing CaSO4 based powder and the relatively slower HA powder represents a promising prospect for tuning the bioresorption of 3D printed (3DP) scaffolds. These properties could then be tailored to coincide with tissue growth rate for different surgical procedures. The manufactured scaffolds were infiltrated with poly(ε‑caprolactone) (PCL). The PCL infiltrated the inter-particle spacing within the 3DP structures due to the nature of a loosely-packed powder bed and also covered the surface of ceramic-based scaffolds. Consequently, the average compressive strength, compressive modulus and toughness increased by 314%, 465% and 867%, respectively. The resorption behaviour of the 3DP scaffolds was characterised in vitro using a high-throughput system that mimicked the physiological environment and dynamic flow conditions relevant to the human body. A rapid release of CaSO4 between Day 0 and 28 was commensurate with a reduction in scaffold mass and compressive properties, as well as an increase in medium absorption. In spite of this, HA particles, connected by PCL fibrils, remained within the microstructure after 56 days resorption under dynamic conditions. Consequently, a high level of structural integrity was maintained within the 3DP scaffold. This study presented a porous PCL-HA-CaSO4 3DP structure with the potential to encourage new tissue growth during the initial stages of implantation and also offering sufficient structural and mechanical support during the bone healing phase.

Highlights

Additive Manufacturing (AM) has been highly recognised as a promising tool to fabricate patient-specific bone substitutes for the replacement and restoration of lost or irreparable bone tissues due to its unique ability to fully control the complex external shape and internal porous network for the printed scaffold
Previous studies have used biopolymers as infiltration materials to improve the mechanical properties of 3D printed (3DP) bioceramic scaffolds [26,32,33]
PCL infiltrating the micropores of the ceramic scaffold increased the interfacial contact area providing a corresponding increase in the compressive properties of the scaffold

Summary

Introduction

Additive Manufacturing (AM) has been highly recognised as a promising tool to fabricate patient-specific bone substitutes for the replacement and restoration of lost or irreparable bone tissues due to its unique ability to fully control the complex external shape and internal porous network for the printed scaffold. A precise construction of a three-dimensional (3D) structure allows prediction and monitoring of biomechanical behaviour of the scaffold and ensures that it provides sufficient support to the surrounding tissues and dynamic resorption to match the rate of newly-formed tissue ingrowth. Such de velopments are crucial for the future of the interdisciplinary field of bone tissue engineering. A setting reaction occurred between CaSO4⁠ and water-based binder, which solidified surrounding powders and, offered high green strength for the printed structure

Methods

Results

Conclusion