Poly-(l)-lactic acid and Hydroxyapatite nanopowder composite scaffold for bone regeneration in the biomedical field

Due to the aging population, the need for new materials for bone regenerations that can substitute natural bone is increasing. With the requirement of biodegradability and biocompatibility, many possibilities have been developed in recent years. In this thesis, a composite made with poly-(l)-lactic acid (PLLA) and hydroxyapatite has been developed and characterized. The amount of hydroxyapatite was chosen as a weight percentage of PLLA, in particular 1, 5 and 10 percent. The composite was made by solubilizing PLLA in chloroform and dispersing hydroxyapatite in the solution via bath sonication. The samples were ground and then dried in vacuum oven. Melt electro-writing 3D printing was then used to print square scaffolds with 1x1 cm size, 0.6 mm of thickness and a pore size of 200 μm. Laser microscope and SEM analyses were used to show the structure of the scaffold after printing and its change with the amount of hydroxyapatite. FT-IR, EDS and Raman techniques were used to verify the presence of hydroxyapatite and its distribution in the sample and after melt electro-writing, in conjunction with XPS. Contact angle was performed to investigate the hydrophobicity or hydrophilicity with water of the scaffolds. XRD has been applied to highlight any change in the crystallinity of the sample before and after printing. DSC and TGA techniques were used to respectively examine the melting temperature and degradation temperature of both the sample and scaffold. Finally, cytotoxicity test was performed to confirm the non-toxicity of the scaffolds, paired with bioactivity test to evaluate the diffusion, propagation and growth of cells in the presence of the final scaffolds. Optical characterization analysis show an overall good quality print of the scaffold, very dependent on the amount of hydroxyapatite, which influences the printing itself. Chemical characterizations showed a good quality dispersion sample, as well as the scaffold after printing, maintaining the percentage ratio of hydroxyapatite in relation to PLLA. The hydrophobicity of the scaffolds was confirmed by the contact angle, and non-toxicity has been observed with the WST-8 cytotoxicity test. Although further research would only improve the knowledge of this material and all of its properties, the overall results show promising results for a biocompatible and biodegradable composite that can positively impact in the bone regeneration area of biomedicine.