title: Additively Manufactured and Surface Biofunctionalized Porous Nitinol.
abstract: Enhanced bone tissue regeneration and improved osseointegration are among the most important goals in design of multifunctional orthopedic biomaterials. In this study, we used additive manufacturing (selective laser melting) to develop multifunctional porous nitinol that combines superelasticity with a rationally designed microarchitecture and biofunctionalized surface. The rational design based on triply periodic minimal surfaces aimed to properly adjust the pore size, increase the surface area (thereby amplifying the effects of surface biofunctionalization), and resemble the curvature characteristics of trabecular bone. The surface of additively manufactured (AM) porous nitinol was biofunctionalized using polydopamine-immobilized rhBMP2 for better control of the release kinetics. The actual morphological properties of porous nitinol measured by microcomputed tomography (e.g., open/close porosity, and surface area) closely matched the design values. The superelasticity originated from the austenite phase formed in the nitinol porous structure at room temperature. Polydopamine and rhBMP2 signature peaks were confirmed by X-ray photoelectron spectroscopy and Fourier transform infrared spectroscopy tests. The release of rhBMP2 continued until 28 days. The early time and long-term release profiles were found to be adjustable independent of each other. In vitro cell culture showed improved cell attachment, cell proliferation, cell morphology (spreading, spindle-like shape), and cell coverage as well as elevated levels of ALP activity and increased calcium content for biofunctionalized surfaces as compared to as-manufactured specimens. The demonstrated functionalities of porous nitinol could be used as a basis for deployable orthopedic implants with rationally designed microarchitectures that maximize bone tissue regeneration performance by release of biomolecules with adjustable and well-controlled release profiles.
authors.affiliation: Department of Mechanical Engineering, Kermanshah University of Technology , 63766-67178 Kermanshah, Iran.
authors.forename: Z
authors.identifier: http://orcid.org/0000-0003-2719-7192
authors.initials: Z
authors.lastname: Gorgin Karaji
authors.affiliation: PMA Division, Department of Mechanical Engineering, KU Leuven , 3001 Leuven, Belgium.
authors.forename: M
authors.identifier: http://orcid.org/0000-0002-2377-1671
authors.initials: M
authors.lastname: Speirs
authors.affiliation: PMA Division, Department of Mechanical Engineering, KU Leuven , 3001 Leuven, Belgium.
authors.forename: S
authors.identifier: http://orcid.org/0000-0003-4120-4790
authors.initials: S
authors.lastname: Dadbakhsh
authors.affiliation: PMA Division, Department of Mechanical Engineering, KU Leuven , 3001 Leuven, Belgium.
authors.forename: J-P
authors.identifier: http://orcid.org/0000-0003-0362-8875
authors.initials: JP
authors.lastname: Kruth
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology , 2628 CD Delft, The Netherlands.
authors.forename: H
authors.identifier: http://orcid.org/0000-0002-2275-6170
authors.initials: H
authors.lastname: Weinans
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology , 2628 CD Delft, The Netherlands.
authors.forename: A A
authors.identifier: http://orcid.org/0000-0003-3234-2112
authors.initials: AA
authors.lastname: Zadpoor
authors.affiliation: Department of Biomechanical Engineering, Delft University of Technology , 2628 CD Delft, The Netherlands.
authors.forename: S
authors.identifier: http://orcid.org/0000-0003-1677-5751
authors.initials: S
authors.lastname: Amin Yavari
mesh_terms: D000497:Alloys / Q000737:chemistry*; D001672:Biocompatible Materials; D008422:Materials Testing; D016062:Porosity; D013499:Surface Properties; D014025:Titanium; D055114:X-Ray Microtomography
chemical_list: D000497:Alloys; D001672:Biocompatible Materials; C013616:nitinol; D014025:Titanium
keywords: additive manufacturing; biomimetic topology; controlled release; osteogenic coatings; shape memory alloys