z Materials Science inc. Nanomaterials & Polymers 3D Printing of Gelatine/Alginate/β-Tricalcium Phosphate Composite Constructs for Bone Tissue Engineering Cevriye Kalkandelen,* [a] Songul Ulag, [b] Burak Ozbek, [b] Gunes O. Eroglu, [c] Dilsad Ozerkan, [d] Serap E. Kuruca, [e] Faik N. Oktar, [b, f] Mustafa Sengor, [g] and Oguzhan Gunduz [b, h] Bone tissue engineering studies have brought three-dimen- sional scaffolds into focus that can provide tissue regeneration with designed porosity and strengthened structure. Current research has concentrated on the fabrication of natural and synthetic polymer-based complex structures that closely mimic biological tissues due to their superior biocompatibility and biodegradabilities. Gelatine/Sodium Alginate hydrogels rein- forced with different concentrations of β-Tricalcium Phosphate (TCP) (10, 13, and 15 wt.%) were studied to form 3D bone tissue. Physical, mechanical, chemical, morphological properties and biodegradability of the constructs were investigated. Furthermore, invitro biological assay with human osteosarco- ma cell line (SAOS-2) was performed to determine the biocompatibility of the constructs. It is found that cell viability rates for all constructs were increased and maximum cell viability rate was attained for 20%Gelatine/2%Alginate/10%TCP (wt.). The present work demonstrates that 3D printed Gelatine/ Alginate/TCP constructs with porous structures are potential candidates for bone tissue engineering applications. Introduction It is crucial to know bone structures and properties that can promote bone regeneration to fabricate bone tissues. [1] Bone defects which can be provoked by several pathological conditions (e.g., bone tumors, infections, major trauma with a bone stock loss) or by surgical procedures, have been treated with bone grafts. However, some limitations affect the active treatments, and bone grafts are insufficient to satisfy the clinical demand. Therefore, bone tissue engineering becomes a crucial area to regenerate bone by fabricating bioactive and biocompatible scaffolds which should be osteoconductive and osteoinductive to provide bone growth and create native invivo environment. [1,2] The most commonly used materials are; hydroxyapatite, tricalcium phosphate, (or phosphate com- pounds), collagen-structured hydrogels. [1–4] TCP is known as bone ash [Ca 3 (PO 4 ) 2 ], which is highly biocompatible and provides a resorbable substrate connection to promote healing. [2,5] Calcium phosphate is one of the main combustion products of bone. It can be used as a tissue replacement for repairing bony defects when an autogenous bone graft is not feasible or possible. [6,7] It may be used alone or in combination with a biodegradable, resorbable polymer. [8] It may also be combined with autologous materials for a bone graft. [9] Gelatine (Gel) is a denaturized version of collagen, which is abundant inside the bone tissue, water-soluble protein, and mechanical properties are very sensitive to temperature variations. It has excellent biocompatibility, biodegradability, and no immunogenicity in clinical applications. [3] Sodium alginate (NaC 6 H 7 O 6 ) is a linear polysaccharide derivative of alginic acid comprised of 1,4-β-d-mannuronic (M) and α-l- guluronic (G) acids. Sodium alginate is a cell wall component of marine brown algae and contains approximately 30–60% alginic acid. Conversion of alginic acid to sodium alginate promotes its solubility in water, which assists its extraction. [10] Alg has been extensively used for biomedical applications owing to its biocompatibility and cost-effectiveness. Nguyen et al. fabricated oxidized alginate-gelatine-BCP hydrogels and evaluated material properties, microstructure, and biocompatibility for bone tissue regeneration. Water [a] Dr.C.Kalkandelen Vocational School of Technical Sciences, Istanbul University-Cerrahpasa, Hadimkoy Campus, Center for Nanotechnology & Biomaterials Applica- tion and Research, Marmara University, Goztepe Campus, 34722 Istanbul, Turkey E-mail: cevriye.kalkandelen@gmail.com [b] S. Ulag, B. Ozbek, Prof. F. N. Oktar, O. Gunduz Center for Nanotechnology & Biomaterials Application and Research, Marmara University, Department of Metallurgical and Materials Engineer- ing, Marmara University, Goztepe Campus, 34722 Istanbul, Turkey [c] G.O.Eroglu Department of Molecular Medicine, Istanbul University, Turkey Capa Campus, 34093 Istanbul, Turkey [d] D. Ozerkan Faculty of Engineering & Architecture, Kastamonu University, Turkey Kastamonu Campus, 37150 Kastamonu, Turkey [e] Prof. S. E. Kuruca Istanbul Faculty of Physiology, Istanbul University, Istanbul, Turkey Capa Campus, 34093 Istanbul, Turkey [f] Prof.F.N.Oktar Center for Nanotechnology & Biomaterials Application and Research (NBUAM), Marmara University, Department of Bioengineering, Goztepe Campus, 34722 Istanbul, Turkey [g] Prof. M. Sengor Department of Mechanical Engineering, Faculty of Engineering, Bogazici University, North Campus, 34722 Istanbul, Turkey [h] O. Gunduz Center for Nanotechnology & Biomaterials Application and Research (NBUAM), Marmara University, Department of Metallurgical and Materials Engineering, Faculty of Technology, Goztepe Campus, Marmara Univer- sity, 34722 Istanbul, Turkey Supporting information for this article is available on the WWW under https://doi.org/10.1002/slct.201902878 Full Papers DOI: 10.1002/slct.201902878 12032 ChemistrySelect 2019, 4,12032–12036 © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim