Porous iron-silver nanocomposites as biodegradable load-bearing scaffolds in medical applications
A.Sharipova1,2, S.G. Psakhie 2,3, S. K. Swain1, R. Unger4, D. Starosvetsky1, I. Gotman1,2 and E.Y. Gutmanas1,3
1Department of Materials Science and Engineering, Techion-Israel Institute of Technology, Haifa, 32000, Israel
2Tomsk Polytechnic University, Tomsk 634050, Russian Federation
3Institute of Strength Physics and Materials Science SB RAS, Tomsk 634055, Russian Federation
4 REPAIR-lab, Institute of Pathology, University Medical Center of the Johannes Gutenberg University, 55101 Mainz, Germany
Presenting Author: firstname.lastname@example.org
The application of iron-based alloys as possible biodegradable medical implants is hindered by low degradation rate in biological environment. In this research, silver nanoparticles were added as the cathodic second phase to increase the corrosion rate of iron. The known antibacterial activity of Ag gives it an additional medicinal value. Dense pure iron and Fe-Ag nanocomposites containing 10 to 30 vol.% Ag were fabricated employing high energy attrition milling of Fe and Ag2O micron-submicron powders followed by cold sintering/high pressure consolidation at ambient temperature. Post-consolidation, some specimens were heat treated at 600, 800 or 900°C. Macroporous scaffolds with 50 to 75% open porosity were prepared employing the combination of cold sintering and the modified salt-leaching method, using precompacted Fe-Ag granules (200-400 ?m) and water soluble Na2SO4 or K2CO3 porogen particles of the comparable size. The dense and porous materials obtained were characterized by X-ray diffraction, scanning electron microscopy (SEM) and high resolution SEM with EDS analysis. Mechanical properties were tested in compression and corrosion behavior was investigated by potentiodynamic polarization technique. The permeability of porous scaffolds was measured using Darcy's law. 50%, 55% and 75% porous scaffolds exhibited high compressive strengths of 25, 20 and 12 MPa, correspondingly. Annealing at 800 and 900°C led to an increase in both strength and ductility, without significant coarsening of the nano/submicron scale microstructure. The permeability was in the range of the trabecular bone, even for the 50% porous scaffolds (2x10-10 m2). The corrosion current of cold sintered Fe-10Ag nanocomposites was 3-fold that of the pure Fe and at least 25 times higher than the literature-reported data for Fe-10Ag with 25 ?m grainsize . In vitro tests in human osteoblast monocultures and osteoblast-endothelial cell co-cultures indicated that Fe-Ag nanocomposites are biocompatible for the growth and survival of both cell types. The proposed processing approach allows for drug and/or protein delivery, via incorporation into the open nanopores of the Fe-Ag nanocomposites, during implant fabrication  or post-processing, e.g., under vacuum.
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Keywords: Fe-Ag, Nanocomposite, Porous Scaffold, Bioresorbable, Permeability, Strength, Corrosion, Cell culture