Influence of bovine serum albumin on corrosion behaviour of pure Zn in phosphate buffered saline

Zinc (Zn) and its alloys have received increasing attention as new alternative biodegradable metals. However, consensus has not been reached on the corrosion behaviour of Zn. As cardiovascular artery stent material, Zn is supposed to contact with plasma that contains inorganic salts and organic components. Protein is one of the most important constitute in the plasma and could adsorb on the material surface. In this paper, bovine serum albumin (BSA) was used as a typical protein. Influences of BSA on pure Zn corrosion in phosphate buffered saline is investigated as a function of BSA concentrations and immersion durations by electrochemical techniques and surface analysis. Results showed that pure Zn corrosion was progressively accelerated with BSA concentrations (ranging from 0.05 to 5 g L−1) at 0.5 h. With time evolves, formation of phosphates as corrosion product was delayed by BSA adsorption, especially at concentration of 2 g L−1. Within 48 h, the corrosion of pure Zn was alleviated by BSA at concentration of 0.1 g L−1, whereas the corrosion was enhanced after 168 h. Addition of 2 g L−1 BSA has opposite influence on the pure Zn corrosion. Furthermore, schematic corrosion behaviour at protein/Zn interfaces was proposed. This work encourages us to think more about the influence of protein on the material corrosion and helps us to better understand the corrosion behaviour of pure Zn.

Effect of Biodegradable Magnesium Alloy Biomaterials on Neurological Rehabilitation of Cerebrovascular Diseases

Elements such as Mg, Zn, and Sr were selected in this research, and the Zn content was set to 3.8%. The relative content of Sr was determined to be 1.0% after the influence of Sr on the microstructure and properties of Mg–Sr alloys was explored. Then, the Mg–3.8Zn–1.0Sr alloy material was prepared, and the uniformity and tensile strength of the material were further increased through solution treatment and aging treatment. When the biodegradation test was performed and the biocompatibility of the material was analyzed, the material was used in the rehabilitation treatment of intracranial wide-necked aneurysms. In the test, the addition of Zn and Sr helped to form the passivation film on the surface of the magnesium alloy, and the second phase of the cross-section generated can prevent the expansion of corrosion. The corrosion rate continued to decrease with time (P < 0.05), and the pH of the DMEM solution participating in the experiment also showed a rising trend (P < 0.05). The hemolysis rate of Mg–3.8Zn–1.0Sr (wt.%) alloy was only 4.54%, indicating that it had a good anti-hemolytic function and showed low toxicity in the cytotoxicity test of the extract. The lateral wall type aneurysm model was constructed in white rabbits, and Mg–3.8Zn–1.0Sr (wt.%) was set as the stent material. Postoperative follow-up showed that the material implantation in the model promoted the complete occlusion of the aneurysm and the unobstructed common carotid artery. The molybdenum target test showed that the prepared magnesium alloy stent gradually degraded with time, and most of it degraded after 12 months. Moreover, clinical trials of intracranial wide-necked aneurysms suggested that alloy stent materials based on the preparation of Mg–3.8Zn–1.0Sr can help patients realize complete embolization. Although there was residual tumor, no recurrence of aneurysm occurred in the re-examination, which proved that the stent material was effective.

Fluid-Structure Interaction in Coronary Stents: a Discrete Multiphysics Approach

Stenting is a common method for treating atherosclerosis. A metal or polymer stent is deployed to open the stenosed artery or vein. After the stent is deployed, the blood flow dynamics influence the mechanics by compressing and expanding the structure. If the stent does not respond properly to the resulting stress, vascular wall injury or re-stenosis can occur. In this work, Discrete Multiphysics is used to study the mechanical deformation of the coronary stent and its relationship with the blood flow dynamics. The major parameters responsible for deforming the stent are sort in terms of dimensionless numbers and a relationship between the elastic forces in the stent and pressure forces in the fluid is established. The blood flow and the stiffness of the stent material contribute significantly to the stent deformation and affect the rate of deformation. The stress distribution in the stent is not uniform with the higher stresses occurring at the nodes of the structure.

Uropathogens Preferrentially Interact with Conditioning Film Components on the Surface of Indwelling Ureteral Stents Rather than Stent Material

Despite routine implementation in urology, indwelling ureteral stents pose as a nidus for infection. Conditioning film accumulates on stents, which prime pathogen adhesion, promoting infectious biofilm formation. However, the extent to which conditioning film components play a role in facilitating bacterial adhesion and biofilm formation remains largely unknown. Here, we examined the interaction of previously identified stent-bound conditioning film components (fibrinogen, uromodulin, and albumin) with bacterial uropathogens. Cytoscopically removed stents were incubated with common uropathogens (Escherichia coli, Enterococcus faecalis, and Staphylococcus aureus). Immunofluorescent double staining was performed to study the localization of uropathogens relative to stent-bound conditioning film proteins. Conditioning film components were identified on the external stent surface with some deposition in the inner lumen. Bacteria co-localized with fibrinogen, uromodulin, and albumin, suggesting a potential mechanism for stent-associated infections. Here, we determine strong co-localization between common uropathogenic bacterial species with prominent conditioning film components on ureteral stents. Further functional validation of interactions amongst these uropathogens and conditioning film proteins may enhance clinical management for stent-associated infections and development of improved stent technologies.

Conjugating heparin, Arg–Glu–Asp–Val peptide, and anti-CD34 to the silanic Mg–Zn–Y–Nd alloy for better endothelialization

Magnesium alloy is generally accepted as a potential cardiovascular stent material due to its good mechanical properties, biocompatibility, and biodegradability, and has become one of the research hotspots in this field. However, too fast degradation rate and delayed surface endothelialization have been the bottleneck of further application of magnesium alloy stent. In this study, we selected Mg–Zn–Y–Nd, a kind of biodegradable magnesium alloy for cardiovascular stent, and passivated its surface by alkali heat treatment and silane treatment to improve the corrosion resistance, subsequently conjugated Arg–Glu–Asp–Val (REDV) peptide and anti-CD34 to promote endothelial cells adhesion and capture endothelial progenitor cells respectively, further improving surface endothelialization. In addition, the heparin was also immobilized to the Mg–Zn–Y–Nd surface for the consideration of anti-coagulation and anti-inflammation. Systematic material characterization and biological evaluation show that we have successfully developed this composite surface on Mg–Zn–Y–Nd alloy, and achieved multiple functions such as corrosion resistance, promoting endothelialization, and inhibiting platelet/macrophage adhesion.