Design and characterization of nano and bimodal structured biodegradable Fe-Mn-Ag alloy with accelerated corrosion rate

Researchers in biodegradable metals have been putting efforts to accelerate the corrosion of iron-based biodegradable metals. These include by alloying iron with manganese and noble elements such as silver, but further increase to the corrosion rate is still needed. In this study, a set of bimodal nano/microstructured Fe-30Mn-1Ag alloys was prepared through mechanical alloying and spark plasma sintering. The alloys were characterized and tested for their corrosion behavior in Hanks' solution at 37 °C and for their mechanical properties. The bimodal-structured alloy possessed a mixture of austenitic (γ-FeMn) and ferritic (α-Fe) phases, while the nano- and macro-structured ones were essentially composed of γ-FeMn and α-Fe phases, respectively. Addition of 1–3 wt.% of silver into the nanostructured alloy increased its corrosion rate from 0.24 mm/year to 0.33 and 0.58 mm/year for Fe-30Mn-1Ag and Fe-30Mn-3Ag, respectively. Whilst, the bimodal Fe-30Mn-1Ag alloy corroded at a higher rate of 0.88 mm/year. This alloy also possessed an interesting combination of high and low micro-hardness phases that contributed to high shear strength of 417 MPa and shear strain of 0.66. Detailed discussion on the relationship of microstructure with corrosion behavior and mechanical properties is presented in this manuscript

Fatigue behaviour of load-bearing polymeric bone scaffolds: A review

Bone scaffolds play a crucial role in bone tissue engineering by providing mechanical support for the growth of new tissue while enduring static and fatigue loads. Although polymers possess favourable characteristics such as adjustable degradation rate, tissue-compatible stiffness, ease of fabrication, and low toxicity, their relatively low mechanical strength has limited their use in load-bearing applications. While numerous studies have focused on assessing the static strength of polymeric scaffolds, little research has been conducted on their fatigue properties. The current review presents a comprehensive study on the fatigue behaviour of polymeric bone scaffolds. The fatigue failure in polymeric scaffolds is discussed and the impact of material properties, topological features, loading conditions, and environmental factors are also examined. The present review also provides insight into the fatigue damage evolution within polymeric scaffolds, drawing comparisons to the behaviour observed in natural bone. Additionally, the effect of polymer microstructure, incorporating reinforcing materials, the introduction of topological features, and hydrodynamic/corrosive impact of body fluids in the fatigue life of scaffolds are discussed. Understanding these parameters is crucial for enhancing the fatigue resistance of polymeric scaffolds and holds promise for expanding their application in clinical settings as structural biomaterials. Statement of Significance: Polymers have promising advantages for bone tissue engineering, including adjustable degradation rates, compatibility with native bone stiffness, ease of fabrication, and low toxicity. However, their limited mechanical strength has hindered their use in load-bearing scaffolds for clinical applications. While prior studies have addressed static behaviour of polymeric scaffolds, a comprehensive review of their fatigue performance is lacking. This review explores this gap, addressing fatigue characteristics, failure mechanisms, and the influence of parameters like material properties, topological features, loading conditions, and environmental factors. It also examines microstructure, reinforcement materials, pore architectures, body fluids, and tissue ingrowth effects on fatigue behaviour. A significant emphasis is placed on understanding fatigue damage progression in polymeric scaffolds, comparing it to natural bone behaviour

Novel antibacterial biodegradable Fe-Mn-Ag alloys produced by mechanical alloying

Various compositions and synthesis methods of biodegradable iron-based alloys have been studied aiming for the use of temporary medical implants. However, none is focused on nano-structured alloy and on adding antibacterial property to the alloy. In this study, new Fe-30Mn-(1–3)Ag alloys were synthesized by means of mechanical alloying and assessed for their microstructure, mechanical properties, corrosion rate, antibacterial activity and cytotoxicity. Results showed that the alloy with 3 wt% Ag content displayed the highest relative density, shear strength, micro hardness and corrosion rate. However, optimum cytotoxicity and the antibacterial activity were reached by the alloy with 1 wt% Ag content. The compositional and processing effects of the alloys' properties are further discussed in this work

In vitro degradation, hemocompatibility and cytocompatibility of nanostructured absorbable Fe-Mn-Ag alloys for biomedical application

The addition of noble elements such as Ag was shown as a successful method to accelerate the corrosion rate of absorbable Fe-based alloys. One major concern of Ag addition is its effect on hemocompatibility and biocompatibility. In this study, in vitro degradation and surface analysis of Fe-30Mn-xAg (x= 0, 1 and 3 wt.%) alloys as well as their effects on hemocompatibility and cell viability of human umbilical vein endothelial cells (HUVECs) were investigated. The static degradation rate of the alloys was 4.97, 4.69 and 4.49 mg/cm2 for Fe-30Mn, Fe-30Mn-1Ag, and Fe-30Mn-3Ag, respectively. The surface analysis after degradation showed that γ-FeOOH was formed on Fe-30Mn-3Ag, while α-FeOOH was more dominant on Fe-30Mn and Fe-30Mn1Ag. As γ-FeOOH is more soluble than α-FeOOH, it assists further degradation of Fe-30Mn3Ag alloy. The high amount of Ag, induced hemolysis ratio however, inhibited coagulation by decreasing the platelet adhesion. Fe-30Mn-1Ag and Fe-30Mn-3Ag alloys shown improved cell viability compared to that of Fe-Mn alloy. Shear yield strength and shear elastic modulus of the samples after immersion tests were increased while the ultimate shear strength was not affected. Based on acceptable hemolysis rate, low platelet adhesion, acceptable cell viability, and appropriate mechanical properties after degradation Fe-30Mn-1Ag can be considered as a suitable blood-contacting Fe-based absorbable alloy