Biological responses, cell viability and printability of biodegradable high-density collagen bioinks

Bioprinting is an emerging technique in the field of tissue engineering which combines the functionality of 3D-printing with the use of biocompatible materials. Therefore, bioprinting can be used to print structurally complex scaffolds that mimics the body’s native tissues and microenvironments where cells can attach and proliferate to promote tissue regeneration. However, achieving optimal scaffold architecture while maintaining mechanical integrity and cell viability remains a significant challenge. Using extrusion-based bioprinting, scaffolds were printed from high-density collagen bioink enhanced with hydroxyapatite and crosslinking agents to evaluate their printability, cell viability and biocompatibility in mice. The printability study demonstrated that higher extrusion pressure and slower printing speed resulted in thicker filaments and reduced pore size, whereas lower pressure and faster speed produced larger and more stable pores. Adjustments to nozzle size further influenced filament thickness, with smaller nozzles achieving finer resolution of pores. The cell viability assay showed that intermediate pore sizes in collagen scaffolds enhance mouse mesenchymal stem cell viability and uniformity of cell distribution. In contrast, larger pores resulted in cell aggregation and nutrient diffusion limitations. The in vivo study showed no signs of rejection or any harmful reaction. Additionally, it demonstrated differences in biodegradation rates based on bioink composition and scaffold architecture. Overall, this study highlights the interplay between scaffold architecture, printing parameters and bioink properties in scaffold performance. By advancing our understanding of collagen type I scaffold properties and their interactions in biological systems, the efficacy of regenerative therapies in future clinical applications may be improved.