Three-dimensional (3D) printing, known as the most promising approach for bioartificial organ manufacturing, has provided unprecedented versatility in delivering multi-functional cells along with other biomaterials with precise control of their locations in space. The constantly emerging 3D printing technologies are the integration results of biomaterials with other related techniques in biology, chemistry, physics, mechanics and medicine. Synthetic polymers have played a key role in supporting cellular and biomolecular (or bioactive agent) activities before, during and after the 3D printing processes. In particular, biodegradable synthetic polymers are preferable candidates for bioartificial organ manufacturing with excellent mechanical properties, tunable chemical structures, non-toxic degradation products and controllable degradation rates. In this review, we aim to cover the recent progress of synthetic polymers in organ 3D printing fields. It is structured as introducing the main approaches of 3D printing technologies, the important properties of 3D printable synthetic polymers, the successful models of bioartificial organ printing and the perspectives of synthetic polymers in vascularized and innervated organ 3D printing areas.

To investigate the osteogenesis of β-tricalcium phosphate nanoparticles-incorporated silk fibroin (SF/β-TCP) composite scaffolds, SF-based scaffolds with different β-TCP proportion (2/1, 1/1, and 1/2) were fabricated by freeze-drying technology in the present study. Structural and physicochemical properties of SF-based scaffolds were evaluated by using scanning electron microscope, X-ray diffraction, Fourier transformed infrared spectroscopy (ATR-FTIR) and transmission electron microscope. Biocompatibility and osteogenesis of SF/β-TCP scaffolds were investigated by using bone marrow mesenchymal stem cells (BMSCs). Eight New Zealand rabbits were selected, while four 8-mm-diameter calvarial defects were created in each rabbit to place SF/β-TCP scaffolds. The harvested specimens at 4 and 12 weeks were used to evaluate the bone forming ability by micro-CT and histological examination. The results suggested incorporation of β-TCP displayed flake-like pore morphology with proper pore sizes. With the increasing proportion of β-TCP, composite scaffolds exhibited higher compressive strength, lower swelling ratio and degradation rate, as well as enhanced biomineralization capacity. Alkaline phosphatase activity and collagen type I expression levels of BMSCs were significantly increased in the presence of β-TCP nanoparticles. All composite scaffolds with different β-TCP proportion had good bone formation ability at 12 weeks. Among them, SF/β-TCP (1/2) scaffold exhibited the favorable osteogenesis capability which had great potential for applications in bone regeneration.