Additively manufactured biodegradable FeMn-based stents

J. Hufenbach1,2*, M. Otto1, A. Gebert1, A. Lode3, M. Gelinsky3, B. Paul1

1Leibniz Institute for Solid State and Materials Research Dresden, Institute for Complex Materials

2Technische Universität Freiberg, Institute of Materials Science

3University Hospital Carl Gustav Carus and Faculty of Medicine, Technische Universität Dresden, Centre for Translational Bone, Joint and Soft Tissue Research

*E-mail of presenting author: j.k.hufenbach@ifw-dresden.de

Additive manufacturing of biodegradable alloys for patient-specific implant applications is currently drawing increasing attention. Especially the combination of laser powder bed fusion (LPBF) and biodegradable metallic materials presents a promising approach. Among these materials, biodegradable FeMnC systems are attractive for, e.g., vascular implant applications, due to their high strength and ductility, excellent processability as well as adequate degradation rate. This work demonstrates that a novel Fe-30Mn-1C-0.02S twinning induced plasticity (TWIP) alloy can be successfully processed by LPBF [1]. The high solidification rate results in a fine austenitic microstructure with largely homogeneous element distribution resulting in an attractive mechanical integrity during corrosion besides promising mechanical properties under static loading in comparison to the corrosion resistant AISI 316L (1.4404) benchmark steel. For studying the initial cell-material interaction, degradable Fe-30Mn-1C-0.02S stent structures were compared with LPBF-processed references out of 316L [2]. Thereby, different corrosion stages of the as-built Fe-30Mn-1C-0.02S stent surfaces were simulated by pre-conditioning in Dulbecco´s Modified Eagle Medium (DMEM) under cell culture conditions for 2 hours, 7 days, and 28 days. Human umbilical vein endothelial cells (HUVECs) were directly seeded onto the pre-conditioned samples and cell viability, adherence and morphology were analyzed. To evaluate the influence of corrosion products on the cells, the study was accompanied by measurements of iron and manganese ion release by inductively coupled plasma optical emission spectrometry (ICP-OES) and Auger electron spectroscopy. The results display that after 2 hours pre-conditioning, HUVECs were able to attach, but the cell numbers decreased over the cultivation period of 14 days. After longer corrosion periods (7 and 28 days of pre-conditioning), the cells seemed to proliferate for up to 14 days. Concluding, it could be shown that the formation of a complex degradation layer due to pre-conditioning, led to a reduced ion release and therefore a positive effect on cell survival. In addition, our study suggests the suitability of Fe-30Mn-1C-0.02S for future in vivo studies and potential implant applications.

References:

[1] J. Hufenbach, J. Sander, F. Kochta, S. Pilz, A. Voß, U. Kühn, A. Gebert, Advanced Engineering Materials 22 (2020) 2000182.

[2] B. Paul, A. Lode, A.-M. Placht, A. Voß, S. Pilz, U. Wolff, S. Oswald, A. Gebert, M. Gelinsky, J. Hufenbach, Applied Materials & Interfaces 14 (2022) 439-451.