title: Hybrid Tissue Engineering Scaffolds by Combination of Three-Dimensional Printing and Cell Photoencapsulation.
abstract: Three-dimensional (3D) printing offers versatile possibilities for adapting the structural parameters of tissue engineering scaffolds. However, it is also essential to develop procedures allowing efficient cell seeding independent of scaffold geometry and pore size. The aim of this study was to establish a method for seeding the scaffolds using photopolymerizable cell-laden hydrogels. The latter facilitates convenient preparation, and handling of cell suspension, while distributing the hydrogel precursor throughout the pores, before it is cross-linked with light. In addition, encapsulation of living cells within hydrogels can produce constructs with high initial cell loading and intimate cell-matrix contact, similar to that of the natural extra-cellular matrix (ECM). Three dimensional scaffolds were produced from poly(lactic) acid (PLA) by means of fused deposition modeling. A solution of methacrylamide-modified gelatin (Gel-MOD) in cell culture medium containing photoinitiator Li-TPO-L was used as a hydrogel precursor. Being an enzymatically degradable derivative of natural collagen, gelatin-based matrices are biomimetic and potentially support the process of cell-induced remodeling. Preosteoblast cells MC3T3-E1 at a density of 10 × 106cells per 1 mL were used for testing the seeding procedure and cell proliferation studies. Obtained results indicate that produced constructs support cell survival and proliferation over extended duration of our experiment. The established two-step approach for scaffold seeding with the cells is simple, rapid, and is shown to be highly reproducible. Furthermore, it enables precise control of the initial cell density, while yielding their uniform distribution throughout the scaffold. Such hybrid tissue engineering constructs merge the advantages of rigid 3D printed constructs with the soft hydrogel matrix, potentially mimicking the process of ECM remodeling.
authors: Austrian Cluster for Tissue Regeneration, Institute of Materials Science and Technology, Technische Universität Wien (TU Wien), Getreidemarkt 9, Vienna 1060, Austria e-mail:  marica.markovic@tuwien.ac.at.
authors: Marica
authors: M
authors: Markovic
authors: Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S4-bis, Ghent 9000, Belgium; Brussels Photonics Team, Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, Elsene 1050, Belgium e-mail:  jasper.vanhoorick@ugent.be.
authors: Jasper
authors: J
authors: Van Hoorick
authors: Austrian Cluster for Tissue Regeneration, Institute of Materials Science and Technology, Technische Universität Wien (TU Wien), Getreidemarkt 9, Vienna 1060, Austria e-mail:  katja.hoelzl@tuwien.ac.at.
authors: Katja
authors: K
authors: Hölzl
authors: Austrian Cluster for Tissue Regeneration, Institute of Applied Synthetic Chemistry, Technische Universität Wien (TU Wien), Getreidemarkt 9, Vienna 1060, Austria e-mail:  maximilian.tromayer@tuwien.ac.at.
authors: Maximilian
authors: M
authors: Tromayer
authors: Austrian Cluster for Tissue Regeneration, Institute of Materials Science and Technology, Technische Universität Wien (TU Wien), Getreidemarkt 9, Vienna 1060, Austria e-mail:  peter.e308.gruber@tuwien.ac.at.
authors: Peter
authors: P
authors: Gruber
authors: Austrian Cluster for Tissue Regeneration, Medical University of Vienna, Department of Trauma Surgery, Währinger Gürtel 18-20, Vienna 1090, Austria e-mail:  sylvia.nuernberger@meduniwien.ac.at.
authors: Sylvia
authors: S
authors: Nürnberger
authors: Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S4-bis, Ghent 9000, Belgium e-mail:  peter.dubruel@UGent.be.
authors: Peter
authors: P
authors: Dubruel
authors: Polymer Chemistry and Biomaterials Research Group, Ghent University, Krijgslaan 281 S4-bis, 9000 Ghent, Brussels, Photonics Team, Department of Applied Physics and Photonics, Vrije Universiteit Brussel, Pleinlaan 2, Elsene 1050, Belgium e-mail:  sandra.vanvlierberghe@UGent.be.
authors: Sandra
authors: S
authors: Van Vlierberghe
authors: Austrian Cluster for Tissue Regeneration, Institute of Applied Synthetic Chemistry Division of Macromolecular Chemistry, Technische Universität Wien (TU Wien), Getreidemarkt 9, Vienna 1060, Austria e-mail:  robert.liska@tuwien.ac.at.
authors: Robert
authors: R
authors: Liska
authors: Austrian Cluster for Tissue Regeneration, Institute of Materials Science and Technology, Technische Universität Wien (TU Wien), Getreidemarkt 9, Vienna 1060, Austria e-mail:  aleksandr.ovsianikov@tuwien.ac.at.
authors: Aleksandr
authors: A
authors: Ovsianikov