Fe–Au and Fe–Ag composites as candidates for biodegradable stent materials

Abstract

In this study, Fe-Ag and Fe-Au composites were fabricated by powder metallurgy using spark plasma sintering. Their microstructures, mechanical properties, and biocorrosion behavior were investigated by using optical microscopy, X-ray diffraction, environment scanning electronic microscopy, compressive test, electrochemical measurements, and immersion tests. Microstructure characterization indicated that the as-sintered iron-based materials obtained much finer grains than that of as-cast pure iron. Phase analysis showed that the Fe-Ag composites were composed of α-Fe and pure Ag phases, and Fe-Au composites consisted of α-Fe and Au phases. Compressive test showed that the improved mechanical strengths were obtained in as-sintered iron-based materials, among which the Fe-5 wt %Ag exhibited the best mechanical properties. The electrochemical and immersion tests revealed that the addition of Ag and Au could increase the corrosion rate of the iron matrix and change the corrosion mode into more uniform one. Based on the results of cytotoxicity evaluation, it was found that all the experimental material extracts performed no significant toxicity on the L-929 cells and EA. hy-926 cells, whereas a considerable inhibition on the proliferation of vascular smooth muscle cells was observed. The hemocompatibility tests showed that the hemolysis of all the experimental materials was within the range of 5%, which is the criteria value of biomaterials with good hemocomaptibility. The amount of platelet adhered on the surface of as-sintered iron-based materials was lower than that of as-cast pure iron, and the morphology of platelets kept smoothly spherical on the surface of all the experimental materials.

Comparative corrosion behavior of Zn with Fe and Mg in the course of immersion degradation in phosphate buffered saline

“…Therefore, Zn exhibits more a uniform corrosion and the corrosion products present fine pebble-shaped morphology that may offer an extent of corrosion protection to the substrate, as evidenced by the increase of R ct and R p after 3 days of immersion. Other phases such as Zn 3 (PO 4 ) 2 (H 2 O) 4 , Zn 3 (PO 4 ) 2 (H 2 O) 4 , Na 6 Zn 6 (PO 4 ) 6 (H 2 O) 8 and KZn 2 (PO 4 ) 2 (H 2 O) 2 may also form with Zn(OH) 2 . Nonetheless, with the increasing of immersion time, the chloride ions constantly attack the formed product of Zn(OH) 2 , leading to localized damage of corrosion.…”

“…Any characteristic peak of ZnO and Zn(OH) 2 was absent, which may be attributed to their too small thickness that cannot be detected by XRD. It revealed that after 3 and 7 days immersion new peaks could be detected and identified as the characteristic peaks of Zn 3 (PO 4 ) 2 (H 2 O) 4 and Na 6 Zn 6 (PO 4 ) 6 (H 2 O) 8 . A new phase of KZn 2 (PO 4 ) 2 (H 2 O) 2 product was further detected after 21 days of immersion.…”

“…Magnesium, iron and zinc and their alloys have been considered as potential candidate materials for biodegradable metallic implants [1], such as internal bone fixation devices [2,3] and coronary stents [1,4]. This is because all the three metals are intrinsically prone to corrosion and therefore biodegradation in human body, and more importantly, they are alike in reputable bio-safety for they are all essential elements which participate in many metabolic reactions and biological mechanisms of the human body [3,[5][6][7].…”

Nanostructured Hydroxyapatite Coating on Bioalloy Substrates: Current Status and Future Directions

“…For orthopaedic applications, research results show that there are other alloys that have many advantages over Ti-6Al-4V, examples being 1) wrought Ti-13Zr-13Nb: (i) its modulus of elasticity is 45% lower and, as such, has lower potential for stress shielding and, hence, for ensuing osteolysis [66]; and (ii) having no Al, it has no potential for involvement in the etiology of Alzheimer's disease [67,68]; 2) porous Ti-(4-10) Mo alloys [69], and 3) porous Co-Cr alloy: its modulus of elasticity is 55% lower [70]. For the scaffold of a bioabsorbable coronary artery stent, new Mg-based alloys, such as wrought Mg-Nd-Sr-Zr, Mg-Gd-Nd-Zn-Zr, and Fe-35Mn alloys, powder-metallurgy Fe-Au and Fe-Ag alloys, and highly-porous Mg-Y and Mg-Y-Zn-Ca-Mn alloys are being evaluated [71][72][73][74]. New alloys that show good potential for applications as both bioresorbable TJRs and coronary artery stent scaffolds include Mg-0.63 Ca and Mg-0.89Ca [75].…”

Mechanical Properties and In Vitro Degradation of Sputtered Biodegradable Fe-Au Foils

“…In order to enhance the mechanical properties and the degradation performance, also the implementation of noble Pd [10,11], Pt [11], Au and Ag [12,13] were investigated. In the work [13] by Huang et al, they implemented the noble precipitates by using powder metallurgy and spark plasma sintering.…”