Bioink homogeneity control during 3D bioprinting of multicomponent micro/nanocomposite hydrogel for even tissue regeneration using novel twin screw extrusion system

The 3D bioprinting of an advanced multicomponent bioink requires the homogeneous distribution of bioink components to control the biological and structural properties of the printed tissue engineering construct. To ensure the homogeneous mixing of micro/nanomaterials in a bioink and then bioprinting, currently, multiple preparation steps must be followed before feeding the bioink to the conventional bioprinting extruder head. To overcome these limitations, a real-time one-step process was obtained by developing a semi-automated twin-screw extruder (TSE) head to synchronously perform systematic mixing and 3D bioprinting. In this study, as a proof of concept, the parameter optimizations for semi-automated mixing of bioink components and 3D bioprinting with the TSE head were demonstrated with an ionic gel (alginate), alpha-tricalcium phosphate (α-TCP) micro/nanoparticles, and osteoblast cells. The TSE-processed bioink samples showed better bioprintability, with better mechanical and biological properties than the conventional ones. The micro/nanoparticles were uniformly dispersed in the bioink within 60 s of screw mixing them inside the barrel (with the barrel outlet closed). The live cell distribution in the printed constructs was significantly superior to conventional mixing even with continuous feeding and extrusion-based bioink printing. This novel extrusion head ensured the control of uniform micro/nanomaterials and cell distribution throughout the directly mixed printable bioink with minimal cell damage. Further, they delivered increased batch consistency in real time mixing and bioink printing owing to its highly efficient variable screw pitch design. Higher repeatability than the conventional method of bioink component mixing and its subsequent 3D bioprinting was obtained through increased automation, as well as reduced processing time, demonstrating strong potential in tissue engineering applications through the controlled mixing of bioink components and its 3D bioprinting without damaging the cells.