Direct-write printing is a versatile platform for fabricating micro-scale devices in which shear-thinning viscous inks are extruded from small-diameter print-heads that then retain filamentary shape following printing. Integration of diverse hydrogel chemistries into ink compositions facilitates fabrication of biocompatible classes of devices that can be used to direct and study cellular growth. To print bio-active hydrogel scaffolds, we first design a custom collinear disposable print-head that can be fabricated with a commercial 3D printer and assembled with glass capillaries to co-extrude inks of interest at a variety of diameters under 500um. We then develop a new direct-write hydrogel ink chemistry consisting of an aqueous solution of hydroxyethyl methacrylate monomer, an acrylate cross-linker, a radical initiator, dimethyl sulfoxide for enhanced solvent polarity, and a commercial clay to induce ink gelation prior to printing. Optional replacement of a portion of water with hydroxyapatite yields a bone mimetic crystalline dispersion within the clear gel matrix. Incorporation of protein solutions into the ink can further diversify the biochemical profiles of the final inks. 3D micro-scale periodic scaffolds can then be readily printed and uv-cured due to the high geometric retention and gap spanning of the hydrogel ink pre-polymers. Use of the collinear print-head allows distinct ink chemistries to be printed selectively and continuously within a single printed structure, yielding spatial gradients of function. NIH/3T3 embryonic murine fibroblasts cultured on the cured hydrogels do not require any additional protein surface treatments to induce biocompatibility, a property attributed to the charged micro-domains of the laponite particles within the hydrogel matrices. These materials and devices present a foundational approach to fabricating 4D bio-scaffolds that exhibit dynamic spatial and temporal activity.

4D printing for spatially and temporally dynamic bioscaffolds

249th National Meeting (2015)

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