Biomedical Metallic Materials Research Articles

Effect of Surface Morphologies on the In Vitro and In Vivo Properties of Biomedical Metallic Materials.

Metallic biomaterials, including traditional bioinert materials (such as stainless steel, cobalt-chromium alloys, pure titanium, and titanium alloys), novel biodegradable metals (such as pure magnesium and magnesium alloys, pure zinc and zinc alloys, and pure iron and iron alloys), and biomedical metallic glasses, have been widely used and studied as various biomedical implants and devices. Many scientists and researchers have investigated their superior biomechanical properties, corrosion behavior, and biocompatibility. However, their surface characteristics are of extreme importance due to continuing interactions between the surface/interface of an implanted metallic biomaterial and the surrounding physiological environment. Surface morphologies on these metallic biomaterials can modulate their in vitro and in vivo biological responses. In this review, we have summarized and investigated the effect of various surface morphologies on the corrosion behavior, cellular response, antibacterial activity, and osteogenesis of biomedical metallic materials. In addition, future research directions and challenges of surface morphologies on biomedical metallic materials have been elaborated. This review can lay a theoretical and practical foundation for further research and development on biomedical metallic materials.

Synchronous improvement in strength and ductility of Cu-bearing stainless steels through formation of bimodal grain structure induced by short-time electric pulses

Excellent strength and favorable formability are two important mechanical properties of stainless steel, but there is usually a trade-off between both properties. However, it has been suggested in recent studies that preparing microstructures with a non-homogeneous structure can effectively achieve strength-ductility synergy. Given these facts, a microstructure with bimodal grain structures was prepared in this study by short-time electric pulse treatment (EPT). Besides, the evolution of microstructures and mechanical properties of Cu-bearing stainless steel during EPT was analyzed. The results demonstrated that the non-uniform heating in the EPT process can rapidly promote localized grain growth, thus forming a bimodal grain structure compared with conventional heat treatment. The microstructure of the fine grains formed random textures, while the coarsened grains showed stronger textures. After EPT, the amount of S {123} < 634 < 634 >-type textures increased significantly, with the proportion reaching up to 30.1 %. There was also a certain amount of brass {110} < 112 >- and copper {112} < 111 >-type textures. Compared with the solution-treated samples, the best overall mechanical properties were detected under the optimal electric pulse parameters, which ultimately realized a synergistic increase of 11.8 % and 10.2 % in the ultimate tensile strength and ductility. The excellent strength-ductility synergy was closely related to heterogeneous deformation-induced (HDI) strengthening and textures induced by the bimodal grain structure. This finding may provide novel insights for enhancing the formability of biomedical metallic materials.

New Powder Metallurgy Titanium Alloys with Built-In Antibacterial Capability

Amongst biomedical metallic materials, titanium alloys are normally used as structural permanent implants due to their favourable combination of mechanical properties and biocompatibility. However, commonly implanted titanium alloys are expensive and, unless purposely surface treated, generally cannot prevent surgical infections related to bacteria. Specifically, bacterial infection in biomedical protheses leads to inflammation, obstruction of the healing process, prevention of osteogenesis and, eventually, premature failure of the implant. This work therefore analysis the development of new ternary Ti-based alloys with built-in antibacterial capability as pathogenic bacterial infection occurring during surgery is a raising issue of metallic biomedical implants. The new Ti-based alloys were designed to be manufactured via powder metallurgy, which permits to successfully produce chemically homogeneous materials, key for a uniform antibacterial response, at lower cost. It is found that, primarily due to the stabilisation of the beta phase, the amount of the selected β stabilising alloying elements directly increases the mechanical performance and the antibacterial capability. Consequently, new ternary Ti-based alloys are promising candidates for structural prosthesis functionalised with antibacterial capability.

Study on Corrosion Resistance and Biological Properties of the Double Glow Plasma Nb-Zr Biological Implantation Alloying Layers

In order to improve the corrosion resistance of implant materials and understand the corrosion mechanisms, we prepared a biomedical Nb-Zr alloying layer on 316L stainless steel using double-layer glow plasma surface-alloying technology and investigated the effects of gas pressures on its surface structure, mechanical properties, and corrosion behavior. In particular, the surface states of the substrate and alloying layers were investigated using 3D confocal micrographs, the water contact angle, and UV reflectance, which aims to study the effect of the surface quality on corrosion resistance and discuss the corrosion mechanisms. The results show that the working pressure has an effect on the current density, the sputtering amount of the alloying elements, and the diffusion process of the alloying elements during glow discharge. The Nb-Zr alloying layer prepared under a pressure of 40 Pa had a uniform and dense surface structure, and the distribution was island-like. A Nb-Zr alloying layer with a thickness of 15 μm was successfully obtained, including the diffusion layer and the deposition layer. Simultaneously, the elements Nb and Zr were gradually distributed along the depth, and a high Nb concentration formed in the Nb-Zr alloying layer. The solid solution formed by Zr in the Nb layer significantly improved the microhardness and corrosion resistance of the substrate. The Nb-Zr alloying layer prepared under a pressure of 40 Pa had the lowest corrosion current density and excellent corrosion resistance, which originated from the passive film formed by the Nb-Zr alloying layer that could inhibit the invasion of corrosive ions and improve the corrosion resistance. In addition, the Nb-Zr alloying layer could promote cell proliferation during long-term use and had good biocompatibility. Our study provides an efficient, high-quality processing method for the surface modification of biomedical metallic materials to form thicker Nb-Zr alloying layers as a cost-effective alternative to bulk Nb-based alloys.

Recent advances in tribological and wear properties of biomedical metallic materials

Recent advances in tribological and wear properties of biomedical metallic materials

Nutrient alloying elements in biodegradable metals: a review.

As a new generation of biomedical metallic materials, biodegradable metals have become a hot research topic in recent years because they can completely degrade in the human body, thus preventing secondary surgery, and reducing the pain and economic burden for patients. Clinical applications require biodegradable metals with adequate mechanical properties, corrosion resistance, and biocompatibility. Alloying is an important method to create biodegradable metals with required and comprehensive performances. Since nutrient elements already have important effects on various physiological functions of the human body, the alloying of nutrient elements with biodegradable metals has attracted much attention. The present review summarizes and discusses the effects of nutrient alloying elements on the mechanical properties, biodegradation behavior, and biocompatibility of biodegradable metals. Moreover, future research directions of biodegradable metals with nutrient alloying elements are suggested.

Evaluation of some properties of polyetheretherketone composites used for biomedical applications

Polyetheretherketone is considered to be a prime candidate with the potential to replace biomedical metallic materials as an orthopedic and dental implant on account of its elastic modulus similar to that of human cortical bone. This study presents the effect of polyetheretherketone specimens incorporated with different nano titanium dioxide and nano hydroxyapatite loading up to (1.5 wt%) have been prepared through a series of processing stages involving melt compounding, granulating and hot pressing. Following analysis of mechanical and chemical interactions by flexural, surface roughness and fourier transform infrared spectroscopy respectively. The results showed that the nano titanium dioxide and nano hydroxyapatite particles were uniformly disperse into polyetheretherketone, so the flexural modulus, flexural strength and surface roughness of polyetheretherketone biocomposites obviously increased with the addition of nano powder. On the other hand, break strain decreased with the rise of the total nano titanium dioxide and nano hydroxyapatite content. Furthermore, the best properties obtained when reinforced with nano hydroxyapatite.

Additive Manufacturing of Customized Metallic Orthopedic Implants: Materials, Structures, and Surface Modifications

Metals have been used for orthopedic implants for a long time due to their excellent mechanical properties. With the rapid development of additive manufacturing (AM) technology, studying customized implants with complex microstructures for patients has become a trend of various bone defect repair. A superior customized implant should have good biocompatibility and mechanical properties matching the defect bone. To meet the performance requirements of implants, this paper introduces the biomedical metallic materials currently applied to orthopedic implants from the design to manufacture, elaborates the structure design and surface modification of the orthopedic implant. By selecting the appropriate implant material and processing method, optimizing the implant structure and modifying the surface can ensure the performance requirements of the implant. Finally, this paper discusses the future development trend of the orthopedic implant.

PEGylated Tantalum Nanoparticles: A Metallic Photoacoustic Contrast Agent for Multiwavelength Imaging of Tumors.

Elemental tantalum is a well-known biomedical metal in clinics due to its extremely high biocompatibility, which is superior to that of other biomedical metallic materials. Hence, it is of significance to expand the scope of biomedical applications of tantalum. Herein, it is reported that tantalum nanoparticles (Ta NPs), upon surface modification with polyethylene glycol (PEG) molecules via a silane-coupling approach, are employed as a metallic photoacoustic (PA) contrast agent for multiwavelength imaging of tumors. By virtue of the broad optical absorbance from the visible to near-infrared region and high photothermal conversion efficiency (27.9%), PEGylated Ta NPs depict high multiwavelength contrast capability for enhancing PA imaging to satisfy the various demands (penetration depth, background noise, etc.) of clinical diagnosis as needed. Particularly, the PA intensity of the tumor region postinjection is greatly increased by 4.87, 7.47, and 6.87-fold than that of preinjection under 680, 808, and 970 nm laser irradiation, respectively. In addition, Ta NPs with negligible cytotoxicity are capable of eliminating undesirable reactive oxygen species, ensuring the safety for biomedical applications. This work introduces a silane-coupling strategy for the surface engineering of Ta NPs, and highlights the potential of Ta NPs as a biocompatible metallic contrast agent for multiwavelength photoacoustic image.

Enhanced osteogenic activity of phosphorylated polyetheretherketone via surface-initiated grafting polymerization of vinylphosphonic acid.

Polyetheretherketone (PEEK) is considered to be a prime candidate with the potential to replace biomedical metallic materials as an orthopedic and dental implant on account of its elastic modulus similar to that of human cortical bone. Unfortunately, its biomedical application is impeded by the bioinert surface property and inferior osteogenic activity. In this work, phosphate groups were incorporated onto the PEEK surface through a single-step UV-initiated graft polymerization of vinylphosphonic acid. Diffuse reflectance Fourier transform infrared spectroscopy (DRFTIR), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM) revealed that phosphate groups were successfully introduced onto the PEEK surface without apparently altering its surface topographical feature and roughness. Water contact angle measurements diclosed the increasing hydrophilia after surface phosphonation. In vitro cell adhesion, spreading, proliferation, alkaline phosphatase activity, extracellular matrix mineralization, and real-time PCR analyses showed enhanced adhesion, spreading, proliferation and osteogenic differentiation of MC3T3-E1 osteoblast on the surface-phosphorylated PEEK. An in vivo biological evaluation in the rabbit tibiae proximal defect model by means of a histological analysis confirmed that the surface-phosphorylated PEEK had improved bone-implant contact. The obtained results indicate that enhanced osteogenic activity to surface-phosphorylated PEEK, which gives positive information of its potential applications in orthopedic and dental implants.

The effect of molybdenum on titanium’s castability in dental prosthesis applications: A numerical analysis

The ISO 22674 standard categorizes metallic materials that are suitable for dental appliances and restoration fabrication. Nickel, cadmium, and beryllium are classified as hazardous elements in this international standard. However, many alloys containing nickel and beryllium are used in dentistry as biomedical metallic materials. Numerous studies on the toxicity of nickel and beryllium have led to serious doubts about the biological reliability of these alloys. Titanium therefore attracts great interest due to its potential use in dental prostheses. Commercially pure titanium has biocompatibility, low density, great corrosion resistance, and mechanical strength at room temperature. In spite of its numerous desirable properties, it is hard to cast titanium because of its high melting temperature. In this study, the microstructure and castability of binary Ti–Mo alloys (2%, 4%, 6%, 8%) was investigated using numerical methods to evaluate their potential use in dentistry. ProCAST software was used to model the casting behavior.

Engineered Functional Surfaces by Laser Microprocessing for Biomedical Applications

Abstract Metallic biomaterials are increasingly being used in various medical applications due to their high strength, fracture resistance, good electrical conductivity, and biocompatibility. However, their practical applications have been largely limited due to poor surface performance. Laser microprocessing is an advanced method of enhancing the surface-related properties of biomaterials. This work demonstrates the capability of laser microprocessing for biomedical metallic materials including magnesium and titanium alloys, with potential applications in cell adhesion and liquid biopsy. We investigate laser-material interaction, microstructural evolution, and surface performance, and analyze cell behavior and the surface-enhanced Raman scattering (SERS) effect. Furthermore, we explore a theoretical study on the laser microprocessing of metallic alloys that shows interesting results with potential applications. The results show that cells exhibit good adhesion behavior at the surface of the laser-treated surface, with a preferential direction based on the textured structure. A significant SERS enhancement of 6 × 103 can be obtained at the laser-textured surface during Raman measurement.

Progress in selective laser melting equipment, related biomedical metallic materials and applications

This paper introduces the latest achievements of the South China University of Technology in basic research on selective laser melting (SLM), applications of SLM manufacturing equipment, and biomedical metallic materials manufactured by SLM. First, we describe the use of DiMetal-100 equipment to study the process parameters, microstructure, and mechanical properties of three kinds of metal medical materials manufactured by SLM, including 316L stainless steel, CoCrMo, and Ti6Al4V. Second, we describe the application of 316L stainless steel manufactured by SLM to personalized lingual orthodontic brackets and surgical guide plates, the application of CoCrMo manufactured by SLM to knee prostheses and dental crowns and bridges, and the research results of Ti6Al4V manufactured by SLM in the treatment of pelvic fracture bone plates and personalized cranial prostheses. Finally, we introduce the development directions and research plans for SLM technology at the South China University of Technology, including the manufacture of a new porous structure by SLM directly, the manufacture by SLM of various material products simultaneously, SLM + material-reducing hybrid manufacturing, improving the negative feedback systems of SLM equipment, and developing SLM manufacturing processes using ceramics and new metals.

Corrosion Behavior of Titanium Implant with different Surface Morphologies

As one of vital biomaterials to implants, titanium (Ti) is widely used in the orthopedic and dentistry fields. In order to improve the interaction of biomaterial surfaces with tissues, various surface structures were fabricated by surface medication methods in previous researches. However, the corrosion of biomedical metallic materials is inevitable, and the ions released from their surfaces would lead to toxicity and allergen. Therefore, to achieve satisfied osseointegration, good corrosion resistance is necessary. In this paper, four groups of samples (smooth surface (P), microstructure surface (M), micro/nanostructure surface (MN) and functionalized micro/nanostructure surface (Ag-PDA)) were prepared, and the corrosion behavior of them was evaluated by electrochemical workstation in Ringer's solution. Through comparing to the electrochemical parameters of different samples, the corrosion resistance of the Ag-MN samples is the best, while that of the M samples is the worst. The results showed that treated samples displayed out good corrosion resistance except for M samples and the order of their corrosion resistance was Ag-PDA>MN>P>M. It was indicated that the suitable surface morphologies were important to improve the corrosion resistance of Ti via applying surface modification methods. In particular, the corrosion resistance of Ti would be significantly increased after covering a layer of barrier.

Microstructure and mechanical properties of stainless steel/calcium silicate composites manufactured by selective laser melting

Selective laser melting (SLM) is raised as one kind of additive manufacturing (AM) which is based on the discrete-stacking concept. This technique can fabricate advanced composites with desirable properties directly from 3D CAD data. In this research, 316L stainless steel (316L SS) and different fractions of calcium silicate (CaSiO3) composites (weight fractions of calcium silicate are 0%, 5%,10% and 15%, respectively) were prepared by SLM technique with a purpose to develop biomedical metallic materials. The relative density, tensile, microhardness and elastic modulus of the composites were tested, their microstructures and fracture morphologies were observed using optical microscope (OM), scanning electron microscopy (SEM) and X-ray diffraction (XRD). It was found that the addition of CaSiO3 particles influenced the microstructure and mechanical properties of specimens significantly. The CaSiO3 precipitates from the overlap of adjacent tracks and became the origin of the defects. The tensile strength of specimens range 320–722MPa. The microhardness and elastic modulus are around 250HV and 215GPa respectively. These composites were ductile materials and the fracture mode of the composites was mixed mode of ductile and brittle fracture. The 316L SS/CaSiO3 composites can be a potential biomedical metallic materials in the medical field.

Manufacturing of high-strength Ni-free Co–Cr–Mo alloy rods via cold swaging

The strengthening of biomedical metallic materials is crucial to increasing component durability in biomedical applications. In this study, we employ cold swaging as a strengthening method for Ni-free Co–Cr–Mo alloy rods and examine its effect on the resultant microstructures and mechanical properties. N is added to the alloy to improve the cold deformability, and a maximum reduction in area (r) of 42.6% is successfully obtained via cold swaging. The rod strength and ductility increase and decrease, respectively, with increasing cold-swaging reduction r. Further, the 0.2% proof stress at r=42.6% eventually reaches 1900MPa, which is superior to that obtained for the other strengthening methods proposed to date. Such significant strengthening resulting from the cold-swaging process may be derived from extremely large work hardening due to a strain-induced γ (fcc)→ε (hcp) martensitic transformation, with the resultant intersecting ε-martensite plates causing local strain accumulation at the interfaces. The lattice defects (dislocations/stacking faults) inside the ε phase also likely contribute to the overall strength. However, excessive application of strain during the cold-swaging process results in a severe loss in ductility. The feasibility of cold swaging for the manufacture of high-strength Co–Cr–Mo alloy rods is discussed.

Research progress of self-assembled monolayer in biomedical metallic materials

Because of the excellent mechanical properties, biocompatibility and reasonable prices, biomedical metallic materials are widely used in the manufacture of vascular stents, heart valve membrane, artificial joints and other body implants. However, the physiological environment in the body is very complex, the long-term embedding of the metal implants may result in corrosion or some nonspecific effects. The properties of medical metal surfaces may decay, which can cause serious injury to human body. By means of the self-assembled monolayer(SAM) technology, the physical and chemical properties of the medical metal surfaces can be modified, and through the SAM medium, some functional materials can be grafted on the metal surfaces, which can largely improve the stability and compatibility of implants in the body, and find wide applications in promoting cell adhesion, improving hemocompatibility, inhibiting bacteria growth, and constructing drug delivery coatings. This paper reviews the progress in the application of SAM in biomedical metallic materials.

A Potential Biodegradable Metallic Material with Shape Memory Effect Based on Iron

FeMnSi alloys are promising shape memory alloys which have been used for pipe joints but no previous work pays any attention to their biomedical application. Following the outline of the aforementioned development of biodegradable Fe-based alloys, we believe that it is worthwhile to investigate the feasibility of FeMnSi alloy as biodegradable metal candidate, since element Si is widely used in biomedical metallic materials as an alloying element. A shape memory metallic material based on FeMnSi was obtained through classical melting method. The material was analyzed as cast and plastic deformed through rolling concerning materials microstructure (scanning electrons microscopy - SEM), chemical analyses (X-ray analyze by EDAX) and corrosion resistance (or biodegradation rate) in an artificial saliva electrolytic solutions (Fusayama) artificial aerated by linear and cyclic curves determination (potentiometry - VoltaLab).

The Ultrafine-Grained Titanium and Biomedical Titanium Alloys Processed by Severe Plastic Deformation (SPD)

The ultrafine-grained materials processed by severe plastic deformation (SPD) can be tailored to achieve superior properties and performances. Recently, the SPD methods, emerging as an effective way to grain refinement, have become attractive for fabrication of the ultrafine-grained biomedical materials, which can be adjusted to possess both favorable mechanical properties and excellent biocompatibility. Biomedical titanium alloys have become one of the most promising biomedical metallic materials, due to their high strength, low density, good biocompatibility and excellent corrosion resistance. Compared with traditional titanium alloys, the ultrafine-grained biomedical titanium alloys possess higher strength, better corrosion resistance and fatigue performance. Moreover, the ultrafine-grained biomedical titanium alloys, which are usually used for orthopedic and dental implants, can induce in-growth of bone tissues, increase the interfacial strength and accelerate the repair process. This review examines recent developments related to fabricating ultrafine-grained titanium and biomedical titanium alloys by various kinds of SPD methods, such as equal channel angular pressing (ECAP), high pressure torsion (HPT), accumulative roll bonding (ARB) and friction stir processing (FSP). More specifically, the mechanical properties and performances of biomedical titanium alloys processed by ECAP, HPT, ARB and FSP have been investigated. It can be expected that in the near future, these techniques will be utilized as methods for continuous productions of the UFG biomaterials in large scale industrial applications.

Surface engineering of biomedical metallic materials by plasma-based low-energy ion implantation

Abstract Plasma-based low-energy ion implantation, including plasma source ion nitriding/carburizing and plasma source low-energy ion enhanced deposition of thin films, for surface engineering of metallic materials was emerged as low-temperature, low-pressure surface modification technique. Plasma source ion nitriding onto AISI 316L austenitic stainless steel produced a high nitrogen face-centered-cubic phase (γ N ) layer about 10 μm thick at the temperature of 380 °C during 4 h with the high microhardness of HK 0.1 N 22.0 GPa. The microhardness of the nitrided surface from the titanium nitride phase [(Ti, Al, V)N] layer on Ti6Al4V alloy at 750 °C during 4 h achieved up to about HK 0.1 N 15.5 GPa. No pitting corrosion in the Ringer’s solution at 37 °C was detected by electrochemical polarization measurement for the nitrided AISI 316L stainless steel and Ti6Al4V alloy, respectively. Plasma source ion nitriding of the metallic materials provided the engineering surfaces with combined improvement in hardness and corrosion resistance.