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Biocompatibility of co-sputtered Si-Fe-C-N coatings
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Biomaterial systems)
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Material i medicin)ORCID iD: 0000-0001-9529-650X
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Engineering Sciences, Applied Materials Sciences. (Biomaterial Systems)ORCID iD: 0000-0001-6663-6536
2018 (English)Conference paper, Poster (with or without abstract) (Refereed)
Abstract [en]

INTRODUCTION: Hip joint arthroplasty is a common and increasingly frequent procedure that can relieve pain and restore mobility for individuals with e.g. severe osteoarthritis. While the procedure is common and to a large extent considered successful there is a need to prolong the lifespan of the implants to meet the need of a more active patient group, living longer. One of the main limiting factors behind the implant lifetime is the generation of particulate and ionic wear debris that causes an activation of the immune system. This debris originates in the articulating surfaces and one attempt to minimize the generation of debris is to deposit a ceramic coating on metal implant parts. The hard ceramic coatings, such as silicon nitride, could improve the wear resistance as well as act as a barrier for metal ion release.1,2 The silicon nitride coatings in this study were co-deposited with Fe and C in order to increase the deposition rate and tune the dissolution rate.

METHODS: The coatings were deposited using reactive magnetron sputtering onto silicon wafer substrates. The Si target (99.99% purity) was powered with pulsed DC at 200 W, 200 kHz and 2 µs. The Fe target (99.99% purity) and C target (99.99% purity) were powered by DC aggregates at 25 W and 65 W respectively. The targets were positioned at an angle (38.81˚) and no rotation was used during deposition. Nitrogen was introduced as a reactive gas in addition to the inert Ar at a ratio of 0.3. The deposition time was 10 000 s.

Based on the intended compositional gradients five points (4 corners in a square spaced 40 mm apart and the middle) on the sample were selected. No two points on the sample are identical and could be treated like individual samples.

The composition was determined using ERDA and the surface properties were estimated with atomic force microscopy (AFM) in non-contact mode.

The biocompatibility was assessed in vitro with osteo-progenitor cells from mouse (MC3T3)..

RESULTS: The ERDA investigation revealed clear compositional gradients. The Si content ranged from 26 at.% in point 4 to 34 at.% in point 1. The Fe content changed in a complementary manner with a maximum of 20 at.% in point 4 and a minimum of 10 at.% in point 1. The carbon content ranged from 8 at.% in point 1 to 14 in point 4. In addition to the expected gradients the N content ranged from 40 at.% to 47 at.%.

Despite the differences in composition the surface appearance and roughness remained similar for all the points (1-5) (Figure 1).

The cell study showed surviving cells that adhered to the Si-N-Fe-C surface for all five points.

DISCUSSION & CONCLUSIONS: Co-sputtering yielded compositional gradients along the silicon wafer. The unexpected gradient of N-content – N was present as a gas - is likely due to the ability of Si to form nitrides as seen from the low enthalpy of formation for Si3N4 (-743 kJ/mol). The low surface roughness is likely a consequence of the smooth Si-wafer substrate, it is however reasonable to assume that a polished metal substrate would also yield low surface roughness. The adhesion of the cells indicates biocompatibility. In summary the low surface roughness combined with the biocompatibility make the coatings interesting for further investigations.

 

REFERENCES

1.  Pettersson, M. et al. (2016) Mater. Sci. Eng. C. Mater. Biol. Appl. 62, 497–505 .

2.  Pettersson, M. et al. (2013) J. Mech. Behav. Biomed. Mater. 25, 41–7.

 

ACKNOWLEDGEMENTS: The research leading to these results has received funding from the European Union’s Seventh Framework Programme (FP7/2007-2013) under the LifeLongJoints Project, Grant Agreement no. GA-310477.

Place, publisher, year, edition, pages
2018.
National Category
Medical Materials Biomaterials Science
Research subject
Engineering Science with specialization in Materials Science
Identifiers
URN: urn:nbn:se:uu:diva-367366OAI: oai:DiVA.org:uu-367366DiVA, id: diva2:1267104
Conference
11th annual meeting, Scandinavian Society for Biomaterials, Gullmarsstrand, 25-27 April, 2018
Funder
EU, FP7, Seventh Framework Programme, GA-310477Available from: 2018-11-30 Created: 2018-11-30 Last updated: 2018-12-05

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Hulsart Billström, GryEngqvist, HåkanPersson, Cecilia

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