Ion doping of 3D-plotted calcium deficient hydroxyapatite scaffolds

Abstract

Due to the increase of bone diseases caused by the ever-aging population, new biomaterials destined for bone regeneration need to be developed. New methods, such as robocasting are gaining interest as they allow printing of self-setting calcium phosphate (CaP) scaffolds. The control of the architecture by robocasting together with the control of composition using CaPhave resulted in the development of materials very similar to the structure and composition of natural bone. However, the mineral phase in bone is a calcium phosphate (hydroxyapatite) enriched with many ionic substitutions fundamental for bone growth. This project will focus on the incorporation of four different ions (Mg, Sr, Zn and Si) in hydroxyapatite scaffolds produced by robocasting. The incorporation of these ions is explored using two strategies, by incorporating the ion of interest during a post-printing treatment and by incorporation the ion of interest directly in the ink formulation. Different characterization techniques have been used to determine ion incorporation: X-ray powder diffraction, elemental analysis by energy-dispersive X-ray, Raman spectroscopy and electron diffraction by transmission electron microscopy (TEM). Among them, the most successful technique has been TEM. The results show that, in general, ion doping post printing is more successful than changing the ink formulation. In addition, ion concentration had a strong effect on scaffold purity and the degree of ion-doping.