In vitro evaluation of 3D bioprinted tri‐polymer network scaffolds for bone tissue regeneration

Abstract

In vitro evaluations provide vital information on the ability of tissue engineered scaffolds to support cell life and promote natural physiological behaviors in culture. Such assessments are necessary to conduct before implementation of the scaffolds for tissue healing in vivo. The scaffold extracellular matrix must provide the biochemical and mechanical cues necessary to promote cellular attachment, migration and proliferation before differentiation and new tissue deposition can occur. In this study, an in vitro evaluation was conducted to assess the ability of scaffolds three-dimensional (3D) printed with a previously developed alginate-polyvinyl alcohol-hydroxyapatite formulation to promote proliferation of encapsulated MC3T3 cells. A systematic investigation was conducted to increase cell proliferation, and it was determined that the concentration and duration of the calcium bath have a less effect on proliferation than the composition of the formulation itself. Collagen gel was incorporated into the formulation to provide cells with adhesion sites necessary to sufficiently attach to the matrix. Enhanced proliferation was achieved within scaffolds of increased collagen content and sufficient crosslinking. This highlighted the importance of the synergistic effect created as a result of sufficient ligand density coupled with appropriate scaffold mechanical rigidity to provide a suitable environment for proliferation. Thus, these 3D printed tri-polymer scaffolds have the ability to support cell proliferation and have potential to promote cell differentiation and new bone tissue deposition. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 3262-3272, 2017.

Chemical insights into bioinks for 3D printing

“…[57][58][59] Doping agents such as nanoparticles (e.g. hydroxyapatite [60][61][62][63][64] give robustness and can also improve cell differentiation into osteoblasts. Finally, micro carriers can be added for drug and growth factor delivery.…”

“…65 Organic and inorganic nanoparticles are used to improve cell differentiation (e.g. hydroxyapatite [60][61][62][63][64] ). and stiffness.…”

“…It is generally possible with the addition of another biopolymer to increase the viscosity of the bioink. 8,62,92,[139][140][141][142][143][144][145] Alginate-based bioinks So far, about one quarter of the bioinks described in the literature are composed of alginate, alone 92,136 or in combination with other biopolymers. Their popularity can be explained by the simplicity of the ionotropic gelation process, which does require neither chemical reagents, nor specific equipment (e.g.…”

“…nano-fibrillated cellulose 141,142 , methylcellulose 116 and ethylcellulose 143 ) or a combination of collagen and agarose 144 have also been reported to improve the alginate properties for extrusion printing, mainly viscosity, reinforcing thixotropy and stiffness. Along the same lines, polyvinyl alcohol (PVA) 61,62 has been sometimes added to improve the elasticity of the scaffold and to increase the resolution obtained by extrusion-based printing.…”

Three‐dimensional printing biotechnology for the regeneration of the tooth and tooth‐supporting tissues

“…To form gelatin‐based crosslinked hydrogels, gelatin was chemically modified. The methylation of gelatin results in the formation of methacrylate and methacrylamide groups in the gelatin structure without significantly influencing the RGD and MMP‐degradable motifs of gelatin and is called “gelatin methacryloyl” (Bendtsen & Wei, ). The synthesized polymer was crosslinked through photoinitiated radical polymerization at room temperature and neutral pH (Stratesteffen et al, ).…”