The "printing," or layer-by-layer extrusion, of cell-laden hydrogels results in the fabrication of 3D tissue-like structures. These fabricated tissues have potential applications in regenerative medicine and as <i>in vitro </i>tissue prototypes for drug screening. Bioinks for 3D bioprinting of synthetic tissues must fulfill three criteria:  they must have rheological properties appropriate for extrusion printing, they must be cyto-compatible during the printing process, and they must include biological cues to control cell behavior after printing. Here we report on a recently developed family of bioinks that meet these requirements and can be further customized to achieve a range of mechanical properties. These hydrogel-based bioinks are produced from blends of engineered recombinant proteins and peptide-modified, naturally occurring biopolymers such as alginate. These materials undergo two-stages of crosslinking: (i) weak, peptide-based, supra-molecular assembly to homogeneously encapsulate cells in a shear-thinning hydrogel within the ink cartridge and (ii) stimuli-responsive crosslinking post-printing to rapidly stabilize the construct. Benefits of this two-stage crosslinking strategy include the prevention of cell sedimentation within the ink cartridge, mechanical shielding of the cell membrane from damaging extrusion forces during printing, rapid post-print self-assembly within an aqueous bath that prevents cell dehydration, and fine-tuning of the printed scaffold mechanical properties for optimal cell-matrix interactions. We demonstrate that tuning of the hydrogel material properties can be used to identify bioinks suitable as scaffolds for the large-scale expansion of neural stem cells.<br/>

Biomimetic polymers as custom bioinks for 3D printing

2019 Spring National Meeting

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