A novel Ti-Au alloy with strong antibacterial properties and excellent biocompatibility for biomedical application

On the design of low modulus Ti-Nb-Au alloys for biomedical applications

Developing new low modulus structures is important for reducing the risk of aseptic loosening during loading of implant materials. However, an alloy that may also confer some advantage at preventing septic loosening could dramatically improve the outcomes for patients. Nevertheless, the predictive power of current models remains limited to common alloying additions. As such, this study considers the mechanical properties of a range of Ti-Nb-Au superelastic alloys to elucidate the composition range for which low modulus structures can be achieved. These modulus values are compared to other critical design parameters such as strain recovery and strength. It was found that Au additions are effective at suppressing the formation of the ω phase and allow alloys with lower moduli to be achieved. It was also shown that low β phase stability is critical for achieving the lowest modulus, and that this susceptibility to transform to a martensite may enable higher strengths to be achieved. However, this low β phase stability also limits the strain recovery that may be achieved meaning these two properties are not necessarily independently tuneable. These data provide important context for the design of new systems containing unusual alloying additions such as Au.

Design and preparation of Ti-xFe antibacterial titanium alloys based on micro-area potential difference

Fe was selected as an alloying element for the first time to prepare a new antibacterial titanium alloy based on micro-area potential difference (MAPD) antibacterial mechanism. The microstructure, the corrosion resistance, the mechanical properties, the antibacterial properties and the cell biocompatibility have been investigated in detail by optical microscopy, scanning electron microscopy, electrochemical testing, mechanical property test, plate count method and cell toxicity measurement. It was demonstrated that heat treatment had a significant on the compressive mechanical properties and the antibacterial properties. Ti-xFe (x = 3,5 and 9) alloys after 850 °C/3 h + 550 °C/62 h heat treatment exhibited strong antimicrobial properties with an antibacterial rate of more than 90% due to the MAPD caused by the redistribution of Fe element during the aging process. In addition, the Fe content and the heat treatment process had a significant influence on the mechanical properties of Ti-xFe alloy but had nearly no effect on the corrosion resistance. All Ti-xFe alloys showed non-toxicity to the MC3T3 cell line in comparison with cp-Ti, indicating that the microzone potential difference had no adverse effect on the corrosion resistance, cell proliferation, adhesion, and spreading. Strong antibacterial properties, good cell compatibility and good corrosion resistance demonstrated that Ti-xFe alloy might be a candidate titanium alloy for medical applications.

Reduced TiO2 Nanotubes/Silk Fibroin/ZnO as a Promising Hybrid Antibacterial Coating

The current research aims to elucidate the influence of reduction process of TiO2 nanostructures on the surface properties of a bioinspired Ti modified implant, considering that the interface between a biomaterial surface and the living tissue plays an important role for this interaction. The production of reduced TiO2 nanotubes (RNT) with lower band gap is optimized and their performance is compared with those of simple TiO2 nanotubes (NT). The more conductive surfaces provided by the presence of RNT on Ti, allow a facile deposition of silk fibroin (SF) film using the electrochemical deposition method. This hybrid film is then functionalized with ZnO nanoparticles, to improve the antibacterial effect of the coating. The modified Ti surface is evaluated in terms of surface chemistry, morphology and roughness, wettability, surface energy, surface charge and antibacterial properties. Surface analysis such as SEM, AFM, FTIR and contact angle measurements were performed to obtain topographical features and wettability. FT-IR analysis confirms that SF was effectively attached to TiO2 nanotubes surfaces. The electrochemical deposition of SF and SF-ZnO reduced the interior diameter of nanotubes from ~85 nm to approx. 50-60 nm. All modified surfaces have a hydrophilic character.

Titanium alloys with varying surface micro-area potential differences have antibacterial abilities and a favorable cellular response

OBJECTIVES

Surface micro-area potential difference (MAPD) can achieve bacteriostatic performance independent of metal ion dissolution. To study the influence of MAPD on antibacterial properties and the cellular response, Ti-Ag alloys with different surface potentials were designed and prepared by changing the preparation and heat treatment processes.

MATERIALS AND METHODS

Ti-Ag alloys (T4, T6, and S) were prepared by vacuum arc smelting, water quenching, and sintering. Cp-Ti was set as a control group in this work. The microstructures and surface potential distributions of the Ti-Ag alloys were analyzed by SEM and energy dispersive spectrometry. Plate counting and live/dead staining methods were used to evaluate the antibacterial properties of the alloys, and the mitochondrial function, ATP levels, and apoptosis were assessed in MC3T3-E1 cells to analyze the cellular response.

RESULTS

Due to the formation of the Ti-Ag intermetallic phase in the Ti-Ag alloys, Ti-Ag (T4) without the Ti-Ag phase had the lowest MAPD, Ti-Ag (T6) with a fine Ti2Ag phase had a moderate MAPD, and Ti-Ag (S) with a Ti-Ag intermetallic phase had the highest MAPD. The primary results demonstrated that the Ti-Ag samples with different MAPDs exhibited different bacteriostatic effects, ROS expression levels, and apoptosis-related protein expression levels in cells. The alloy with a high MAPD exhibited a strong antibacterial effect. A moderate MAPD stimulated cellular antioxidant regulation (GSH/GSSG) and downregulated the expression of intracellular ROS. MAPD could also promote the transformation of the inactive mitochondria to biologically active mitochondria by increasing the ΔΨm and reducing apoptosis.

CONCLUSION

The results here indicated that moderate MAPD not only had bacteriostatic effects but also promoted mitochondrial function and inhibited cell apoptosis, which provides a new strategy to improve the surface bioactivity of titanium alloys and a new idea for titanium alloy design.

CLINICAL RELEVANCE

There are some limitations of the mechanism of MAPD. However, researchers will become increasingly aware of the advantages and disadvantages of MAPD and MAPD might provide an affordable solution of peri-implantitis.

Advanced surface engineering of titanium materials for biomedical applications: From static modification to dynamic responsive regulation

Titanium (Ti) and its alloys have been widely used as orthopedic implants, because of their favorable mechanical properties, corrosion resistance and biocompatibility. Despite their significant success in various clinical applications, the probability of failure, degradation and revision is undesirably high, especially for the patients with low bone density, insufficient quantity of bone or osteoporosis, which renders the studies on surface modification of Ti still active to further improve clinical results. It is discerned that surface physicochemical properties directly influence and even control the dynamic interaction that subsequently determines the success or rejection of orthopedic implants. Therefore, it is crucial to endow bulk materials with specific surface properties of high bioactivity that can be performed by surface modification to realize the osseointegration. This article first reviews surface characteristics of Ti materials and various conventional surface modification techniques involving mechanical, physical and chemical treatments based on the formation mechanism of the modified coatings. Such conventional methods are able to improve bioactivity of Ti implants, but the surfaces with static state cannot respond to the dynamic biological cascades from the living cells and tissues. Hence, beyond traditional static design, dynamic responsive avenues are then emerging. The dynamic stimuli sources for surface functionalization can originate from environmental triggers or physiological triggers. In short, this review surveys recent developments in the surface engineering of Ti materials, with a specific emphasis on advances in static to dynamic functionality, which provides perspectives for improving bioactivity and biocompatibility of Ti implants.

Deploying Gold Nanomaterials in Combating Multi-Drug-Resistant Bacteria

Antibiotic resistance has become a serious threat to human health due to the overuse of antibiotics. Different antibiotics are being developed to treat resistant bacteria, but the development cycle of antibiotics is hard to keep up with the high incidence of antibiotic resistance. Recent advances in antimicrobial nanomaterials have made nanotechnology a powerful solution to this dilemma. Among these nanomaterials, gold nanomaterials have excellent antibacterial efficacy and biosafety, making them alternatives to antibiotics. This review presents strategies that use gold nanomaterials to combat drug-resistant bacteria. We focus on the influence of physicochemical factors such as surface chemistry, size, and shape of gold nanomaterials on their antimicrobial properties and describe the antimicrobial applications of gold nanomaterials in medical devices. Finally, the existing challenges and future directions are discussed.

Construction of a Rough Surface with Submicron Ti2Cu Particle on Ti-Cu Alloy and Its Effect on the Antibacterial Properties and Cell Biocompatibility

Titanium-copper (Ti-Cu) alloy is an advanced antibacterial material with excellent mechanical properties, thermodynamic stability, corrosion resistance and biocompatibility. Sandblasting and acid-etching was applied to the Ti-3Cu alloy to construct a rough surface with Ti2Cu phase on the surface in order to improve the antibacterial properties and the osseointegration. The phase constitutes and the physical properties were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and confocal laser scanning microscope (CLSM), and the surface chemical properties were analyzed by X-ray photoelectron spectroscopy (XPS) and electrochemical testing. The antibacterial property was assessed by the plate-count method and the cell compatibility was evaluated by the CCK-8 test in order to reveal the effect of surface characteristics on the antibacterial ability and bioactivity. The results demonstrated a rough and lamellar surface structure with many submicron Ti2Cu particles on the surface of Ti-3Cu, which could enhance the antibacterial ability and promote the cell proliferation and the initial adhesion of osteoblasts. However, the surface treatment also reduced the corrosion resistance and accelerated the Cu ion release.