title: Morphological characterization and in vitro biocompatibility of a porous nickel-titanium alloy.
abstract: Disks consisting of macroporous nickel-titanium alloy (NiTi, Nitinol, Actipore) are used as implants in clinical surgery, e.g. for fixation of spinal dysfunctions. The morphological properties were studied by scanning electron microscopy (SEM) and by synchrotron radiation-based microtomography (SRmuCT). The composition was studied by X-ray diffractometry (XRD), differential scanning calorimetry (DSC), and energy-dispersive X-ray spectroscopy (EDX). The mechanical properties were studied with temperature-dependent dynamical mechanical analysis (DMA). Studies on the biocompatibility were performed by co-incubation of porous NiTi samples with isolated peripheral blood leukocyte fractions (polymorphonuclear neutrophil granulocytes, PMN; peripheral blood mononuclear leukocytes, PBMC) in comparison with control cultures without NiTi samples. The cell adherence to the NiTi surface was analyzed by fluorescence microscopy and scanning electron microscopy. The activation of adherent leukocytes was analyzed by measurement of the released cytokines using enzyme-linked immunosorbent assay (ELISA). The cytokine response of PMN (analyzed by the release of IL-1ra and IL-8) was not significantly different between cell cultures with or without NiTi. There was a significant increase in the release of IL-1ra (p<0.001), IL-6 (p<0.05), and IL-8 (p<0.05) from PBMC in the presence of NiTi samples. In contrast, the release of TNF-alpha by PBMC was not significantly elevated in the presence of NiTi. IL-2 was released from PBMC only in the range of the lower detection limit in all cell cultures. The material, clearly macroporous with an interconnecting porosity, consists of NiTi (martensite; monoclinic, and austenite; cubic) with small impurities of NiTi2 and possibly NiC(x). The material is not superelastic upon manual compression and shows a good biocompatibility.
authors.affiliation: Institute for Inorganic Chemistry, University of Duisburg-Essen, Universitaetsstr. 5-7, D-45117 Essen, Germany.
authors.forename: Oleg
authors.initials: O
authors.lastname: Prymak
authors.forename: Denise
authors.initials: D
authors.lastname: Bogdanski
authors.forename: Manfred
authors.initials: M
authors.lastname: Köller
authors.forename: Stefan A
authors.initials: SA
authors.lastname: Esenwein
authors.forename: Gert
authors.initials: G
authors.lastname: Muhr
authors.forename: Felix
authors.initials: F
authors.lastname: Beckmann
authors.forename: Tilmann
authors.initials: T
authors.lastname: Donath
authors.forename: Michel
authors.initials: M
authors.lastname: Assad
authors.forename: Matthias
authors.initials: M
authors.lastname: Epple
mesh_terms: D001672:Biocompatible Materials / Q000737:chemistry*; D016207:Cytokines / Q000378:metabolism; D004797:Enzyme-Linked Immunosorbent Assay; D006098:Granulocytes / Q000166:cytology; D066298:In Vitro Techniques; D007249:Inflammation; D053590:Interleukin 1 Receptor Antagonist Protein; D016209:Interleukin-8 / Q000378:metabolism; D007963:Leukocytes, Mononuclear / Q000166:cytology / Q000378:metabolism; D008422:Materials Testing; D008855:Microscopy, Electron, Scanning; D009532:Nickel / Q000737:chemistry*; D012795:Sialoglycoproteins / Q000378:metabolism; D013499:Surface Properties; D013696:Temperature; D013718:Tensile Strength; D014025:Titanium / Q000737:chemistry*; D014961:X-Ray Diffraction
chemical_list: D001672:Biocompatible Materials; D016207:Cytokines; D053590:Interleukin 1 Receptor Antagonist Protein; D016209:Interleukin-8; D012795:Sialoglycoproteins; C040654:titanium nickelide; D009532:Nickel; D014025:Titanium