This paper presents a proof-of-concept study on the biocolonization of 3D-printed hydroxyapatite scaffolds with mesenchymal stem cells (MSCs). Three-dimensional (3D) printed biomimetic bone structure made of calcium deficient hydroxyapatite (CDHA) intended as a future bone graft was made from newly developed composite material for FDM printing. The biopolymer polyvinyl alcohol serves in this material as a thermoplastic binder for 3D molding of the printed object with a passive function and is completely removed during sintering. The study presents the material, the process of fused deposition modeling (FDM) of CDHA scaffolds, and its post-processing at three temperatures (1200, 1300, and 1400 °C), as well it evaluates the cytotoxicity and biocompatibility of scaffolds with MTT and LDH release assays after 14 days. The study also includes a morphological evaluation of cellular colonization with scanning electron microscopy (SEM) in two different filament orientations (rectilinear and gyroid). The results of the MTT assay showed that the tested material was not toxic, and cells were preserved in both orientations, with most cells present on the material fired at 1300 °C. Results of the LDH release assay showed a slight increase in LDH leakage from all samples. Visual evaluation of SEM confirmed the ideal post-processing temperature of the 3D-printed FDM framework for samples fired at 1300 °C and 1400 °C, with a porosity of 0.3 mm between filaments. In conclusion, the presented fabrication and colonization of CDHA scaffolds have great potential to be used in the tissue engineering of bones.
Partially hydrophobized particles of α-Al 2 O 3 were used to prepare the alumina foams. Dodecylbenzenesulfonic acid (DBSA) was applied to the hydrophobized surface of alumina particles. The infrared spectroscopy provided the evidence of the interaction (adsorption) of DBSA on the alumina surface. The quantity of DBSA adsorbed on the alumina particles was determined using Lambert-Beer law by measuring UV-VIS spectra. The mechanisms of DBSA adsorption on the surface of alumina particles may be attributed to (1) electrostatic interactions or (2) specific chemical reactions between the surfactant and the surface hydroxyl groups. Adsorption of DBSA on the alumina particles is strongly influenced by the pH of suspensions. The quantity of DBSA is not sufficient to hydrophobize alumina particles at pH up to about pH 9.5, as the electrostatic repulsion forces between the sulfonic group of DBSA and the alumina surface prevailed and the DBSA acts only as a surfactant. The foams were sintered at 1400, 1450, 1500, 1550 and 1600°C. The optimal sintering temperature was found to be 1550°C. The maximal compressive strength of the alumina foams was ~300 kPa while its porosity was relatively high (96.7 %).
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