Modification of hydroxyapatite (HA) powder by carboxymethyl chitosan (CMCS) for 3D printing bioceramic bone scaffolds

The poor mechanical properties of 3D printed HA bone scaffold is always a challenge in tissue engineering, to address this issue, carboxymethyl chitosan (CMCS) was proposed to modify HA bone scaffolds by a physical blending method in this research. A series of HA and HA/CMCS composite ceramic scaffolds were printed by using piezoelectric inkjet 3D printing technology, and their properties were investigated in terms of forming quality, structural morphology, mechanical properties, degradability, cytotoxicity, and cell adhesion growth. The results of forming quality and structural morphology show that with the increase of CMCS content, the forming quality of the samples deteriorated, the pore size and porosity increased. However, when the content of CMCS reached 5 wt%, obvious cracks appeared on the surface of the sample, and the forming quality was relatively poor. The mechanical testing results indicated the toughness of composites could be enhanced by incorporating CMCS into HA, which was attributed to the higher strength connections of the CMCS polymer network between HA particles and the stronger interaction between HA and CMCS molecules. FTIR spectra further revealed the strong hydrogen bonding interaction between CMCS and HA. Moreover, the degradation rate and mineralization ability of the sample increased with the content of CMCS, but the compressive strength during degradation increased with the CMCS content, indicating that incorporating CMCS into HA cannot only improve the mechanical property and biological activity of the scaffold but also makes up the defect of slow degradation of pure HA scaffold. Finally, the cytotoxicity, cell adhesion, and cell proliferation tests show that HA and HA/CMCS composite samples had good cytocompatibility, HA/CMCS sample with 3 wt% CMCS possessed the best bioactivity. In summary, HA/CMCS composite powder with 3 wt% CMCS content is the optimal matrix material for 3D printing bone scaffolds.