Solvent evaporation induced fabrication of porous polycaprolactone scaffold via low-temperature 3D printing for regeneration medicine researches

Liquid deposition modeling (LDM) is an evolving three-dimensional (3D) printing approach that mainly utilizes polymer solutions to enable the fabrication of biomedical scaffolds under mild conditions. A deep understanding of the rheological properties of polymer printing inks and the features of yielded scaffolds are critical for a successful LDM based fabrication of biomedical scaffolds. In this work, polymer printing inks comprised of Poly(epsilon-caprolactone) (PCL), sodium chloride (NaCl), and trichloromethane (CHCl3) were prepared. The rheological properties, including extrudability (shear stress, viscosity, and shear-thinning) and self-supporting ability (viscosity) of all printing inks were analyzed. Then printing performance was evaluated by measuring the die-swell ratio, 2D, and 3D printing fidelities. Finally, a series of porous PCL scaffolds were fabricated using printing inks comprised of different feed ratios (20:80, 40:60, 50:50, 60:40, and 80:20) of NaCl to PCL, and the porosity, mechanical properties, degradation behaviors, and biocompatibility were discussed. The results suggested that the printing ink formulation is greatly affected the printing performances. The increasing NaCl content in printing inks reduced shear force for extrusion, enhanced the shear-thinning behavior, increased the curing time. The dropping temperature and solvent evaporation both enhanced the self-supporting ability of the printing inks and solvent evaporation is a critical factor for the curing of the printing inks. The further evaluation demonstrated that the obtained fabricated porous PCL scaffolds were endowed with good biocompatibility and controllable porosity, mechanical features, and in vitro degradation behavior related to the NaCl content in the printing inks. This study built a fabricating method of porous polymer scaffolds by 3D printing at low temperatures for regeneration medicine researches.