title: Three-dimensional plotted hydroxyapatite scaffolds with predefined architecture: comparison of stabilization by alginate cross-linking versus sintering.
abstract: Scaffolds for bone tissue engineering are essentially characterized by porous three-dimensional structures with interconnected pores to facilitate the exchange of nutrients and removal of waste products from cells, thereby promoting cell proliferation in such engineered scaffolds. Although hydroxyapatite is widely being considered for bone tissue engineering applications due to its occurrence in the natural extracellular matrix of this tissue, limited reports are available on additive manufacturing of hydroxyapatite-based materials. In this perspective, hydroxyapatite-based three-dimensional porous scaffolds with two different binders (maltodextrin and sodium alginate) were fabricated using the extrusion method of three-dimensional plotting and the results were compared in reference to the structural properties of scaffolds processed via chemical stabilization and sintering routes, respectively. With the optimal processing conditions regarding to pH and viscosity of binder-loaded hydroxyapatite pastes, scaffolds with parallelepiped porous architecture having up to 74% porosity were fabricated. Interestingly, sintering of the as-plotted hydroxyapatite-sodium alginate (cross-linked with CaCl2 solution) scaffolds led to the formation of chlorapatite (Ca9.54P5.98O23.8Cl1.60(OH)2.74). Both the sintered scaffolds displayed progressive deformation and delayed fracture under compressive loading, with hydroxyapatite-alginate scaffolds exhibiting a higher compressive strength (9.5 ± 0.5 MPa) than hydroxyapatite-maltodextrin scaffolds (7.0 ± 0.6 MPa). The difference in properties is explained in terms of the phase assemblage and microstructure.
authors.affiliation: Translational Center on Biomaterials for Orthopedic and Dental Biomaterials, Materials Research Centre, Indian Institute of Science, Bangalore, India.
authors.forename: Alok
authors.initials: A
authors.lastname: Kumar
authors.affiliation: Centre for Translational Bone, Joint and Soft Tissue Research, Technische Universität Dresden, Germany.
authors.forename: Ashwini R
authors.initials: AR
authors.lastname: Akkineni
authors.affiliation: Translational Center on Biomaterials for Orthopedic and Dental Biomaterials, Materials Research Centre, Indian Institute of Science, Bangalore, India Center for Biosystems Science and Engineering, Indian Institute of Science, India *AK and AR contributed equally to this manuscript.
authors.forename: Bikramjit
authors.initials: B
authors.lastname: Basu
authors.affiliation: Centre for Translational Bone, Joint and Soft Tissue Research, Technische Universität Dresden, Germany michael.gelinsky@tu-dresden.de.
authors.forename: Michael
authors.initials: M
authors.lastname: Gelinsky
mesh_terms: D000464:Alginates / Q000737:chemistry*; D002122:Calcium Chloride / Q000737:chemistry; D019245:Compressive Strength; D003432:Cross-Linking Reagents / Q000737:chemistry; D017886:Durapatite / Q000737:chemistry*; D020723:Glucuronic Acid / Q000737:chemistry; D006603:Hexuronic Acids / Q000737:chemistry; D008422:Materials Testing; D016062:Porosity; D023822:Tissue Engineering / Q000379:methods; D054457:Tissue Scaffolds / Q000737:chemistry*
chemical_list: D000464:Alginates; D003432:Cross-Linking Reagents; D006603:Hexuronic Acids; D020723:Glucuronic Acid; D017886:Durapatite; D002122:Calcium Chloride
keywords: Three-dimensional plotting; additive manufacturing; direct plotting; hydroxyapatite; rapid prototyping; robocasting