Extrusion-based 3D printing of gelatin methacryloyl with nanocrystalline hydroxyapatite

The particle shape and size distribution of inorganic fillers play a crucial role in the scaffold buildability when those are incorporated in the viscoelastic polymers. In order to address this issue, the phase pure rod-shaped nanocrystalline hydroxyapatite (HAp) powders with varying particle sizes and shapes were synthesized by a one-pot hydrothermal method without any regulatory surfactant at an initial solution pH of 9. As-synthesized nanocrystalline HAp particles (0-5 wt%) were incorporated into 15 wt% pre-cross-linked gelatin methacryloyl (GelMA) hydrogel matrix to fabricate a predesigned scaffold architecture using a custom-made 3D bioprinter. The printing parameters (nozzle diameter, extrusion pressure, and printing speed) were optimized for each composition. The biophysical properties (uniaxial compression behavior, swelling ratio, and in vitro degradation) of the composite hydrogel scaffolds were critically analyzed to unravel the role of nano-sized HAp addition. The compression strength and modulus were substantially improved, while the rate of water uptake and bio-enzymatic degradation significantly reduced with HAp content. We propose that the inorganic-organic nanocomposite hydrogel could be efficiently assembled to formulate a potential bioink for 3D bioprinting applications toward tissue regeneration.

Automated summary

The particle shape and size distribution of inorganic fillers are important in scaffold buildability when combined with viscoelastic polymers. By incorporating rod-shaped nanocrystalline HAp powders of varying sizes and shapes into GelMA hydrogel matrix, the mechanical properties of the composite hydrogel scaffolds were improved while water uptake rate and enzymatic degradation were reduced. The inorganic-organic nanocomposite hydrogel could be a potential bioink for 3D bioprinting applications in tissue regeneration.