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Three kinds of methods based on extrusion and 3D printing and different acidic solutions (formic acid (FA), acetic acid (AA), glycolic acid (GA) and lactic acid (LA)) were applied for manufacturing the CS ducts. The tensile properties and preliminary cytotoxicity were measured for selecting the optimal ratio of CS slurry. The 3D printability of CS slurry was also studied. The tensile strength, Young’s modulus, and fracture strain were tested for evaluating the degree of mechanical matching to soft-tissue. The optimal solvent to CS was 30 wt.% GA solution. The CS slurry possessing shear-thinning properties was suitable for 3D printing. The tensile strength, Young’s modulus, and fracture strain of the CS rods were 10.98 ± 0.61 MPa, 12.38 ± 1.19 MPa, and 146.03 ± 15.05 %, correspondingly. The CS ducts manufactured by 3D printing had an excellent mechanical matching to soft-tissue, outstanding biocompatibility and have great potential for soft-tissue restorations.

The purpose of this study was to enhance the compressive strength of 3D printed beta-tricalcium phosphate (β-TCP) scaffolds for bone tissue engineering. Ca10Li(PO4)7 (CLP) is acquired by doping Li into β-TCP. The optimum sintering temperature of CLP was determined by the compressive strength, relative density, microstructure, grain size and behaviors of cracks. The dense structure and porous scaffolds of CLP were manufactured by 3D printing. Cell viability and cell morphology of mouse osteoblast cell line (MC3T3-E1) were evaluated by the cell counter kit-8 assay (CCK-8) and fluorescence microscope, respectively. The mineralization effects and degradation property in vitro of CLP scaffolds were investigated as well. The optimal sintering temperature of CLP is 1000 °C. The pores size of scaffold is about 400 × 400 μm and 400 × 300 μm in the Z-axis and XY-axis direction, correspondingly. The compressive strength of the dense structure (332.24 ± 17.81 MPa) and porous scaffold (69.12 ± 20.62 MPa) of CLP is approximately three times as large as that of β-TCP (100.89 ± 9.33 MPa, 24.14 ± 5.01 MPa). There is no statistical difference in cytotoxicity between CLP and β-TCP at the diverse culture days (p > 0.05). The scaffolds of CLP have the closer mineralization effects and degradation property in vitro to β-TCP. Possessing higher strength and excellent biocompatibility, CLP scaffolds manufactured by 3D printing have significant clinical potentials in bone tissue engineering.

Sodium alginate (SA) hydrogels have a wide range of applications including tissue engineering, drug delivery and formulations for preventing gastric reflux. The dynamics of sodium ions during the gelation process of SA solution is critical for clarification of the gelation procedure. In this work, nuclear magnetic resonance (NMR) relaxometry and pulsed-field-gradient (PFG) NMR diffusometry were used to investigate the dynamics of the sodium ions during the gelation of SA alginate. We find that sodium ions are in two different states with the addition of divalent calcium ions, corresponding to Ca2+ crosslinked and un-crosslinked regions in the hydrogels. The sodium ions within the un-crosslinked regions are those released from the alginate chains without Ca2+ crosslinking. The relative content of sodium ions within the Ca2+ crosslinked regions decreased with the increase in the content of calcium ions in the system. The relaxation time T2 of sodium ions within the Ca2+ crosslinked and un-crosslinked regions shift to shorter and longer relaxation time with the increase in concentration of calcium ion, which indicates the closer package of SA chains and the larger space for the diffusion of free sodium ions. This work clarifies the dynamics of 23Na+ in a calcium alginate gel at the equilibrium state.