Development of new Ti_(50)Zr_(25)Nb_(20)Cu_(5-x)Ag_(x)high-entropy alloys with excellent antibacterial property,osteo-conductivity and biocompatibility in vitro and in vivo

A new series of medical antibacterial high-entropy alloys(HEAs)with composition Ti 50 Zr 25 Nb 20 Cu 5-x Ag x(x=0 at.%,1 at.%,and 2.5 at.%)were developed by arc-melting the mixture of pure elements under a high-purity argon atmosphere.The cytotoxicity,osteo-conductivity,and antibacterial properties of these HEAs were systematically investigated in vitro,along with their in vivo biocompatibility and antibacte-rial properties.These HEAs,especially Ti_(50)Zr_(25)Nb_(20)Cu_(2.5)Ag_(2.5),showed better antibacterial ability against Staphylococcus aureus than Ti-6Al-4V,which has a nearly 99%antibacterial rate in vitro.Moreover,ion release and cytotoxicity tests showed that these HEAs had excellent biosafety,similar to or better than that of Ti-6Al-4V.Osteoblasts were used to evaluate the osteogenic activity of these HEAs,and good osteo-conductivity was observed in vitro.In a Sprague-Dawley rat infection model,Ti_(50)Zr_(25)Nb_(20)Cu_(2.5)Ag_(2.5)showed remarkable antibacterial properties compared to Ti-6Al-4V.The in vivo biocompatibility results showed that Ti_(50)Zr_(25)Nb_(20)Cu_(2.5)Ag_(2.5)did not increase biotoxicity compared to Ti-6Al-4V.The excellent bio-compatibility and antibacterial properties of the Ti-Zr-Nb-Cu-Ag HEAs are expected to enable the pre-vention of periprosthetic/peri-implant infections in the future.

The Effect of Material Surface Microstructure on the Enhancement of Bone-Bonding Ability of a Hydroxyapatite-Implant by Low-Intensity Pulsed Ultrasound (LIPUS)

Excellent firm bonding between the biomaterials and bone tissue (osseointegration and osteo-conductivity) has been desired for the stability in vivo of dental implants and artificial joints. Much has been learned about this concept, which has led to significant improvements in the design and surface modification of implants in the field of implant dentistry, orthopedic surgery. We have already reported that low-intensity pulsed ultrasound (LIPUS) irradiation can accelerate the bone bonding ability of the bio-conductive materials such as bioactive titanium and hydroxyapatite implant. However, it is still unclear whether the LIPUS could have same effect to different types of the bioactive-materials. Therefore, in this study, the differences of bone-like hydroxyapatite formation on some kind of hydroxyapatite surface in simulated body fluid (SBF) under the LIPUS irradiation were investigated. Two kinds of hydroxyapatite samples immersed in SBF was exposed to ultrasound waves, the bone-like apatite on the surface was analyzed by Scanning electron microscopy and X-ray diffraction. As a result, the enhancement of hydroxyapatite formation on the surface by LIPUS was confirmed, the initial epitaxial nucleation and crystal growth of apatite depended on crystal structure of the surface of matrix materials.

Magnesium based implants for functional bone tissue regeneration–A review

Magnesium(Mg)has emerged as one of the third-generation biomaterials for regeneration and support of functional bone tissue.Mg is a better choice over permanent implants such as titanium,stainless steel,cobalt-chrome as magnesium is biodegradable and does not require a second surgery for its removal after bone tissue recovery.It also reduces the risk of stress shielding as its elastic modulus is closer to human bone in comparison to permanent implants and other biodegradable metallic implants based on Iron and Zinc.Most importantly,Mg is osteoconductive thus stimulates new bone formation and possess anti-bacterial properties hence reducing the risk of failure due to infection.Despite its advantages,a major concern with pure Mg is its rapid bio-corrosion in presence of body fluids due to which the mechanical integrity of the implant deteriorates before healing of the tissue is complete.Mechanical properties of Mg-based implants can be enhanced by mechanical processing,alloying,and topology optimization.To reduce the corrosion/degradation rate,Mg has been alloyed with metals,reinforced with ceramics,and surface coatings have been applied so that the degradation rate of Mg-based implant matches with that of healing rate of bone tissue.The present review discusses the effect of alloying elements and reinforcing ceramics on microstructure,mechanical,and corrosion properties of Mg-based orthopedic implants.In addition,the biocompatibility of Mg-based alloys,composites,and coatings applied on Mg implants has been highlighted.Further,different methods of fabricating porous implants have been highlighted as making the implant porous facilitates the growth of new bone tissue through the pores.