Biocompatibility assessments of 316L stainless steel substrates coated by Fe-based bulk metallic glass through electro-spark deposition method

Study on the Properties of TiC Coating Deposited by Spark Discharge on the Surface of AlFeCoCrNiCu High-Entropy Alloy

Titanium carbide (TiC) coatings were prepared on the surface of AlFeCoCrNiCu high-entropy alloy blocks using electro-spark deposition (ESD). The microhardness and corrosion resistance of the TiC coatings prepared under different voltage and capacitance process parameters were studied. The research shows that the maximum microhardness of the TiC coating on sample 4 (working voltage of 20 V, working capacitance of 1000 μF) is 844.98 HV, which is 81.5% higher than the microhardness of the substrate. This is because the deposition energy increases with the increase in voltage, and the adhesion and aggregation between the coating and the substrate are enhanced, increasing the hardness of the coating. It is worth noting that excessive deposition energy can increase surface defects and reduce the microhardness of the coating surface. Electrochemical testing analysis shows that the corrosion current density of the TiC coating is the lowest (9.475 × 10-7 ± 0.06 × 10-7), and the coating impedance is the highest (2.502 × 103 Ω·com2). The absolute phase angle value is the highest (about 72°). The above indicates that the TiC coating prepared with a working voltage of 20 V and a working capacitance of 1000 μF has better microhardness and corrosion resistance.

Enhanced Hemocompatibility and Cytocompatibility of Stainless Steel

The present study introduces an advanced surface modification approach combining electrochemical anodization and non-thermal plasma treatment, tailored for biomedical applications on stainless steel grade 316L (SS316L) surfaces. Nanopores with various diameters (100-300 nm) were synthesized with electrochemical anodization, and samples were further modified with non-thermal oxygen plasma. The surface properties of SS316L surfaces were examined by scanning electron microscopy, atomic force microscopy, X-ray photoemission spectroscopy, and Water contact angle measurements. It has been shown that a combination of electrochemical anodization and plasma treatment significantly alters the surface properties of SS316L and affects its interactions with blood platelets and human coronary cells. Optimal performance is attained on the anodized specimen featuring pores within the 150-300 nm diameter range, subjected to subsequent oxygen plasma treatment; the absence of platelet adhesion was observed. At the same time, the sample demonstrated good endothelialization and a reduction in smooth muscle cell adhesion compared to the untreated SS316L and the sample with smaller pores (100-150 nm). This novel surface modification strategy has significant implications for improving biocompatibility and performance of SS316L in biomedical applications.

Effectiveness of laser welding in cerclage wiring fixation: a biomechanical study

Introduction

Cerclage wiring is a common orthopedic procedure for fracture fixation. However, previous studies reported wiring-related perioperative complications, such as wire loosening or breakage, with an incidence rate of up to 77%. Recently, the use of laser welding on medical implants was introduced to connect biomedical materials. This study used laser technology to weld between wires after conventional cerclage fixation. We hypothesized that the laser welding could significantly increase the biomechanical properties of cerclage wiring fixation.

Materials and methods

Twenty-five wiring models underwent biomechanical tests in five cerclage wiring configurations (five models per group), namely, (1) single loop, (2) single loop with laser welding, (3) double loop, (4) double loop with one-side laser welding, and (5) double loop with two-side laser welding. Characteristics such as load to failure, mode of failure, and wiring failure were compared between groups. The biocompatibility for a 316L stainless steel wire with laser welding was evaluated via an in vitro hemolysis test.

Results

Mean load to failure of the double loop with one-side and two-side laser welding groups were 3,596 ± 346 N and 3,667 ± 240 N, which were significantly higher than for the double-loop group (2,919 ± 717 N) (p = 0.012 and p = 0.044, respectively). Conversely, no significant difference was shown in the comparison of the mean load to failure between the single loop and the single loop with laser-welded cerclage wire (1,251 ± 72 N, 1,352 ± 122 N, and p = 0.12). Untwisted wire and wire breakage were the most common mode of failure. All welding specimens revealed non-hemolytic effects from in vitro hemolysis test.

Conclusion

Laser welding on cerclage wiring significantly increases the biomechanical property of double cerclage wire fixation. However, further biocompatibility tests and clinical studies are still recommended.

Production and Characterization of a 316L Stainless Steel/β-TCP Biocomposite Using the Functionally Graded Materials (FGMs) Technique for Dental and Orthopedic Applications

Metallic biomaterials are widely used for implants and dental and orthopedic applications due to their good mechanical properties. Among all these materials, 316L stainless steel has gained special attention, because of its good characteristics as an implantable biomaterial. However, the Young’s modulus of this metal is much higher than that of human bone (~193 GPa compared to 5–30 GPa). Thus, a stress shielding effect can occur, leading the implant to fail. In addition, due to this difference, the bond between implant and surrounding tissue is weak. Already, calcium phosphate ceramics, such as beta-tricalcium phosphate, have shown excellent osteoconductive and osteoinductive properties. However, they present low mechanical strength. For this reason, this study aimed to combine 316L stainless steel with the beta-tricalcium phosphate ceramic (β-TCP), with the objective of improving the steel’s biological performance and the ceramic’s mechanical strength. The 316L stainless steel/β-TCP biocomposites were produced using powder metallurgy and functionally graded materials (FGMs) techniques. Initially, β-TCP was obtained by solid-state reaction using powders of calcium carbonate and calcium phosphate. The forerunner materials were analyzed microstructurally. Pure 316L stainless steel and β-TCP were individually submitted to temperature tests (1000 and 1100 °C) to determine the best condition. Blended compositions used to obtain the FGMs were defined as 20% to 20%. They were homogenized in a high-energy ball mill, uniaxially pressed, sintered and analyzed microstructurally and mechanically. The results indicated that 1100 °C/2 h was the best sintering condition, for both 316L stainless steel and β-TCP. For all individual compositions and the FGM composite, the parameters used for pressing and sintering were appropriate to produce samples with good microstructural and mechanical properties. Wettability and hemocompatibility were also achieved efficiently, with no presence of contaminants. All results indicated that the production of 316L stainless steel/β-TCP FGMs through PM is viable for dental and orthopedic purposes.

Review of the Recent Development in Metallic Glass and Its Composites

Metallic glasses are known for their mechanical properties but lack plasticity. This could be prevented by combining them with other materials or by inducing a second phase to form a composite. These composites have enhanced thermo-physical properties. The review paper aims to outline a summary of the current research done on metallic glass and its composites. A background in the history, properties, and their applications is discussed. Recent developments in biocompatible metallic glass composites, fiber-reinforced metallic glass, ex situ and in situ, are discussed.