Functional gradient scaffolds play an important role in osteochondral tissue engineering because they can meet the essential requirement for a gradual transition of both physical and chemical properties in osteochondral tissue regeneration. There is a requirement for 3D composite osteochondral regeneration scaffolds with multiscale structures that are capable of controlling release of multiple biomolecules. To this end, this article describes a 3D bioprinting platform integrated forming system designed to produce various drug-loaded scaffolds. A novel scaffold was fabricated by the self-developed 3D bioprinting platform combining extrusion deposition with multi-nozzle electrospinning. For temporally controlled release of gentamycin sulfate (GS) and desferoxamine (DFO), blend electrospun GS/polyvinyl alcohol (PVA) and coaxial electrospun core (PVA-DFO)/shell (polycaprolactone; PCL) fibers were deposited in the scaffold. After a 25-day time-lapse release study in vitro, results showed GS released faster than DFO during the early stages and sustained release of DFO for long periods. For spatially controlled release of DFO, the vertically gradient gelatin/sodium alginate (SA) scaffolds presented to enable the release amount of DFO in a gradient mode. The experiment and test results demonstrate the validity of the 3D bioprinting platform integrated forming system and the excellent properties of such scaffolds for performing multidrug spatiotemporal release. POLYM. ENG. SCI., 171 FIG. 6. Release profiles of desferoxamine (DFO) from segments G1, G2, and G3 cut from the composite scaffold, based on (a) mass changes and (b) percentage release relative to the total amount loaded per scaffold. This release profile indicated the gradient release among G1, G2, and G3, respectively. *P < 0.05.

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It is found that Li2Sb compound can act as the nucleus of primary Mg2Si during solidification, by which the particle size of primary Mg2Si decreased from ~300 to ~15–25 μm. Owing to the synergistic effect of the Li2Sb nucleus and adsorption-poisoning of Li atoms, the effect of complex modification of Li-Sb on primary Mg2Si was better than that of single modification of Li or Sb. When Li-Sb content increased from 0 to 0.2 and further to 0.5 wt.%, coarse dendrite changed to defective truncated octahedron and finally to perfect truncated octahedral shape. With the addition of Li and Sb, ultimate compression strength (UCS) of Al-20Mg2Si alloys increased from ~283 to ~341 MPa and the yield strength (YS) at 0.2% offset increased from ~112 to ~179 MPa while almost no change was seen in the uniform elongation. Our study offers a simple method to control the morphology and size of primary Mg2Si, which will inspire developing new Al-Mg-Si alloys with improved mechanical properties.