Wear-Resistant, Hemocompatible Ti-Nb-Zr and Zr-Nb Alloys to Improve Blood Pump Design and Performance

Control of Blood Coagulation by Hemocompatible Material Surfaces-A Review

Hemocompatibility of biomaterials in contact with the blood of patients is a prerequisite for the short- and long-term applications of medical devices such as cardiovascular stents, artificial heart valves, ventricular assist devices, catheters, blood linings and extracorporeal devices such as artificial kidneys (hemodialysis), extracorporeal membrane oxygenation (ECMO) and cardiopulmonary bypass. Although lower blood compatibility of materials and devices can be handled with systemic anticoagulation, its side effects, such as an increased bleeding risk, make materials that have a better hemocompatibility highly desirable, particularly in long-term applications. This review provides a short overview on the basic mechanisms of blood coagulation including plasmatic coagulation and blood platelets, as well as the activation of the complement system. Furthermore, a survey on concepts for tailoring the blood response of biomaterials to improve the hemocompatibility of medical devices is given which covers different approaches that either inhibit interaction of material surfaces with blood components completely or control the response of the coagulation system, blood platelets and leukocytes.

Recent Progress on Wear-Resistant Materials: Designs, Properties, and Applications

There has been tremendous interest in the development of different innovative wear-resistant materials, which can help to reduce energy losses resulted from friction and wear by ≈40% over the next 10-15 years. This paper provides a comprehensive review of the recent progress on designs, properties, and applications of wear-resistant materials, starting with an introduction of various advanced technologies for the fabrication of wear-resistant materials and anti-wear structures with their wear mechanisms. Typical strategies of surface engineering and matrix strengthening for the development of wear-resistant materials are then analyzed, focusing on the development of coatings, surface texturing, surface hardening, architecture, and the exploration of matrix compositions, microstructures, and reinforcements. Afterward, the relationship between the wear resistance of a material and its intrinsic properties including hardness, stiffness, strength, and cyclic plasticity is discussed with underlying mechanisms, such as the lattice distortion effect, bonding strength effect, grain size effect, precipitation effect, grain boundary effect, dislocation or twinning effect. A wide range of fundamental applications, specifically in aerospace components, automobile parts, wind turbines, micro-/nano-electromechanical systems, atomic force microscopes, and biomedical devices are highlighted. This review is concluded with prospects on challenges and future directions in this critical field.

Hemocompatibility of Super-Repellent surfaces: Current and Future

Virtually all blood-contacting medical implants and devices initiate immunological events in the form of thrombosis and inflammation. Typically, patients receiving such implants are also given large doses of anticoagulants, which pose a high risk and a high cost to the patient. Thus, the design and development of surfaces with improved hemocompatibility and reduced dependence on anticoagulation treatments is paramount for the success of blood-contacting medical implants and devices. In the past decade, the hemocompatibility of super-repellent surfaces (i.e., surfaces that are extremely repellent to liquids) has been extensively investigated because such surfaces greatly reduce the blood-material contact area, which in turn reduces the area available for protein adsorption and blood cell or platelet adhesion, thereby offering the potential for improved hemocompatibility. In this review, we critically examine the progress made in characterizing the hemocompatibility of super-repellent surfaces, identify the unresolved challenges and highlight the opportunities for future research on developing medical implants and devices with super-repellent surfaces.

Comparison of the Use of Titanium–Zirconium Alloy and Titanium Alloy in Dental Implants: A Systematic Review and Meta-Analysis

The aim of this study was to compare the values of bone-implant contact (BIC) and removal torque (RTQ) reported in different animal studies for titanium–zirconium (TiZr) and titanium (Ti) dental implants. This review has been registered at PROSPERO under number CRD42016047745. We undertook an electronic search for data published up until November 2017 using the PubMed/Medline, Embase, and The Cochrane Library databases. Eligibility criteria included in vivo studies, comparisons between Ti and TiZr implants in the same study, and studies published in English that evaluated BIC and RTQ. After inclusion criteria, 8 studies were assessed for eligibility. Of the 8 studies, 7 analyzed BIC outcome and 3 analyzed RTQ outcome. Among such studies, 6 studies were considered for meta-analysis of quantitative for BIC and 2 studies for RTQ. There was no significant difference for BIC analysis (P = .89; random ration [RR]: −0.21; 95% confidence interval [CI]: −3.14 to 2.72). The heterogeneity of the primary outcome studies was considered low (7.19; P = .21; I2: 30%). However, the RTQ analysis showed different results favoring the TiZr dental implants (P = .001; RR: 23.62; 95%CI: 9.15 to 38.10). Low heterogeneity was observed for RTQ (χ2: 1.25; P = .26; I2: 20%). Within the limitations of this study, there was no difference between TiZr and Ti alloys implants in terms of BIC. However, TiZr implants had higher RTQ than Ti alloys.

Device thrombosis and pre-clinical blood flow models for assessing antithrombogenic efficacy of drug-device combinations

Thrombosis associated with blood-contacting devices is a complex process involving several component interactions that have eluded precise definition. Extensive investigations of individual biological modules such as protein adsorption, coagulation cascade activation and platelet activation/adhesion/aggregation have provided an initial foundation for developing biomaterials for blood-contacting devices, but a material that is intrinsically non-thrombogenic is yet to be developed. The well-recognized association between fluid dynamics parameters such as shear stress, vortices, stagnation and thrombotic processes such as platelet aggregation and coagulation aggravate thrombosis on most device geometries that elicit these flow disturbances. Thus, antithrombotic drugs that were developed to treat thrombosis associated with vascular diseases such as atherosclerosis have also been adapted to mitigate the risk of device thrombosis. However, balancing the risk of bleeding with the antithrombotic efficacy of these drugs continues to be a challenge, and surface modification of devices with these drug molecules to mitigate device thrombosis locally has been explored. Pre-clinical blood flow models to test the effectiveness of these drug-device combinations have also evolved and several in-vitro, ex-vivo, and in-vivo test configurations are available with their attendant merits and limitations. Despite considerable efforts toward iterative design and testing of blood contacting devices and antithrombogenic surface modifications, device thrombosis remains an unsolved problem.

Screening on binary Zr-1X (X = Ti, Nb, Mo, Cu, Au, Pd, Ag, Ru, Hf and Bi) alloys with good in vitro cytocompatibility and magnetic resonance imaging compatibility

In this study, the microstructures, mechanical properties, corrosion behaviors, in vitro cytocompatibility and magnetic susceptibility of Zr-1X alloys with various alloying elements, including Ti, Nb, Mo, Cu, Au, Pd, Ag, Ru, Hf and Bi, were systematically investigated to explore their potential use in biomedical applications. The experimental results indicated that annealed Zr-1X alloys consisted entirely or primarily of α phase. The alloying elements significantly increased the strength and hardness of pure Zr and had a relatively slight influence on elastic modulus. Ru was the most effective enhancing element and Zr-1Ru alloy had the largest elongation. The results of electrochemical corrosion indicated that adding various elements to Zr improved its corrosion resistance, as indicated by the reduced corrosion current density. The extracts of the studied Zr-1X alloys produced no significant deleterious effects on osteoblast-like cells (MG 63), indicating good in vitro cytocompatibility. All except for Zr-1Ag alloy showed decreased magnetic susceptibility compared to pure Zr, and Zr-1Ru alloy had the lowest magnetic susceptibility value, being comparable to that of α' phase Zr-Mo alloy and Zr-Nb alloy and far lower than that of Co-Cr alloy and Ti-6Al-4V alloy. Among the experimental Zr-1X alloys, Zr-1Ru alloy possessing high strength coupled with good ductility, good in vitro cytocompatibility and low magnetic susceptibility may be a good candidate alloy for medical devices within a magnetic resonance imaging environment.