Porous iron scaffolds with the addition of manganese and copper—physicochemical characteristics and biocompatibility analysis

Background: Biodegradable iron scaffolds are potential biomaterials which can be used for the needs of modern cardiology. The primary criterion for biodegradable implants is corrosion time, and pure iron has a relatively low corrosion rate in the physiological environment, which can be a limitation for materials that require faster biodegradation. The introduction of manganese (Mn) and copper (Cu) as alloying elements into iron could increase the corrosion rate through changes in the microstructure and electrochemical potentials of the material. Methods: The materials investigated in this study were pure iron scaffolds ferrite (Fe) and scaffolds with the addition of manganese (35 % w/w) and copper (1 % w/w): Fe35Mn, Fe1Cu, and Fe35Mn1Cu, subsequently referred to as Fe, FeMn, FeCu, and FeMnCu, respectively. They were obtained by applying the template method and sintering procedure, using the polyurethane (PU) and melamine (Mel) polymeric templates. Samples have been characterized in terms of their structure and morphology. Their electrochemical corrosion has been carried out with the use of potentiodynamic polarization. The biological in vitro studies were conducted using four cell lines: human aortic smooth muscle cells (HASMC), human umbilical vein endothelial cells (HUVEC), murine fibroblasts (L929), and murine macrophages (RAW 264.7). Results: Depending on the template used, we obtained iron scaffolds with larger pores and higher porosity for the PU template (0.7–1.6 mm, porosity 97 %) and smaller pores with lower porosity for the Mel template (0.1–0.35 mm, porosity 21 %). Additives of manganese (35 wt %) and copper (1 wt %) in the samples result in differences in orphology and composition. Analysis of the polarisation curves clearly indicates that the type of alloy used significantly determines the degradation of the scaffold, while the type of scaffold used (PU-based or Mel-based) has less influence. FeMn-Mel scaffolds exhibited Ecorr = −475.5 mV and Icorr = 11.5 μA, FeMnCu-Mel Ecorr = −443.5 mV and Icorr = 8.67 μA, while FeCu-Mel showed Ecorr = −369.4 mV and Icorr = 8.11 μA. Among PU-based samples, FeMn-PU showed Ecorr = −576.6 mV and Icorr = 9.44 μA, FeMnCu-PU Ecorr = −526.8 mV and Icorr = 7.56 μA, whereas FeCu-PU reached Ecorr = −479.2 mV and Icorr = 19.61 μA. When comparing the toxic effects of scaffolds based on polyurethane and melamine, all materials made based on a melamine template are less toxic to HASMC, HUVEC, and L929 cells than their polyurethane-based counterparts. Conclusions: Considering the impact on the viability of key cells essential for the proper implantation of cardiovascular devices, such as endothelial cells, aortic smooth muscle cells, and fibroblasts, as well as the assessment of potential inflammatory induction, melamine-based scaffolds containing Mn or Cu demonstrate the greatest application potential. Additionally, these materials also show significant anti-inflammatory effects, further supporting their suitability for use in cardiovascular implants.