Abstract
Background: One of the main challenges for extrusion 3D bioprinting is the identification of non-synthetic bioinks with suitable rheological properties and biocompatibility. Our aim was to optimize and compare the printability of crystal, fibril and blend formulations of novel pulp derived nanocellulose bioinks and assess biocompatibility with human nasoseptal chondrocytes. Methods: The printability of crystalline, fibrillated and blend formulations of nanocellulose was determined by assessing resolution (grid-line assay), post-printing shape fidelity and rheology (elasticity, viscosity and shear thinning characteristics) and compared these to pure alginate bioinks. The optimized nanocellulose-alginate bioink was bioprinted with human nasoseptal chondrocytes to determine cytotoxicity, metabolic activity and bioprinted construct topography. Results: All nanocellulose-alginate bioink combinations demonstrated a high degree of shear thinning with reversible stress softening behavior which contributed to post-printing shape fidelity. The unique blend of crystal and fibril nanocellulose bioink exhibited nano- as well as micro-roughness for cellular survival and differentiation, as well as maintaining the most stable construct volume in culture. Human nasoseptal chondrocytes demonstrated high metabolic activity post printing and adopted a rounded chondrogenic phenotype after prolonged culture. Conclusions: This study highlights the favorable rheological, swelling and biocompatibility properties of nanocellulose-alginate bioinks for extrusion-based bioprinting.
Highlights
The ability to print biological ‘inks’ rather than traditional 3D printing of metals and plastic has resulted in the birth of the new bioprinting research field [1,2,3,4] which is gaining interest in engineering customized tissues for reconstructive surgery [5,6,7]
The printability of crystalline, fibrillated and blend formulations of nanocellulose was determined by assessing resolution, post-printing shape fidelity and rheology and compared these to pure alginate bioinks
It is easier to tailor the biomechanical properties of synthetic bioinks such as polyacrylamides and polyethylene glycols to suit extrusion techniques, their biocompatibility and tissue regenerative potential are inferior to non-synthetic bioinks such as gelatin, agarose, alginate, hyaluronic acid and collagen, which mimic the natural extracellular matrix environment [12]
Summary
The ability to print biological ‘inks’ rather than traditional 3D printing of metals and plastic has resulted in the birth of the new bioprinting research field [1,2,3,4] which is gaining interest in engineering customized tissues for reconstructive surgery [5,6,7]. Of the three-main 3D bioprinting technologies: extrusion, inkjet and laser-assisted, extrusion is the most versatile, fast, scalable and cost-effective [9, 10]. This technique relies on extruding bioinks with suitable mechanical properties (viscosity, elasticity, shear thinning) through a nozzle using either mechanical (piston or screw driven) or pneumatic forces. It is easier to tailor the biomechanical properties of synthetic bioinks such as polyacrylamides and polyethylene glycols to suit extrusion techniques, their biocompatibility and tissue regenerative potential are inferior to non-synthetic bioinks such as gelatin, agarose, alginate, hyaluronic acid and collagen, which mimic the natural extracellular matrix environment [12]
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