Microwave sintering and characterization of robocasted HA, CNT-HA scaffold structures for bone regeneration applications

Abstract

The application of additive manufacturing in the field of biomedical medical research is being widely explored, in the development of bone scaffolds with different architectures and desired properties. Robocasting, an extrusion-based additive manufacturing technique that can print a wide range of materials at a relatively lower cost has been adopted in this study. The 3D structure was realized by robocasting of hydroxyapatite (HA) incorporated with different loading percentages (0.5, 1, and 2 wt%) of multiwalled carbon nanotubes (MWCNTs). Carboxymethyl cellulose (CMC) is used as a binder for the development of ceramic slurries with desired viscoelastic properties. Microwave sintering of the developed scaffold structures in the argon (Ar) atmosphere was performed at different sintering temperatures, with a 5 min soaking time, and 3 LPM Ar flow rate. FESEM/EDS imaging and Raman spectroscopy analysis confirmed the retention of incorporated MWCNTs post-sintering. With an increase in sintering temperature, physical properties of the developed scaffold structures such as density and shrinkage were observed to increase whereas porosity was reduced. The better compressive strength was observed in samples sintered at 1100 °C. And a maximum compressive strength of 21.86 MPa was recorded for 0.5HAIF100 scaffold structures in comparison to other reported groups. The in vitro cell studies confirmed that the adopted percentages of MWCNTs were biocompatible and also capable of promoting osteogenic differentiation. The developed scaffolds also remained stable for about 28 days without undergoing degradation.