Second-phase-dependent grain refinement in Ti-25Nb-3Mo-3Zr-2Sn alloy and its enhanced osteoblast response

Nanotexture and crystal phase regulation for synergistic enhancement in re-endothelialization on medical pure titanium surface

Re-endothelialization has been recognized as a promising strategy to address the tissue hyperplasia and subsequent restenosis which are major complications associated with vascular implant/interventional titanium devices. However, the uncontrollable over-proliferation of smooth muscle cells (SMCs) limits the clinical application of numerous modified strategies. Herein, a novel modified strategy involving with a two-step anodic oxidation and annealing treatment was proposed to achieve rapid re-endothelialization function regulated by regular honeycomb nanotexture and specific anatase phase on the titanium surface. Theoretical calculation revealed that the presence of nanotexture reduced the polar component of surface energy, while the generation of anatase significantly enhanced the polar component and total surface energy. Meanwhile, the modified surface with regular nanotexture and anatase phase produced positive effect on the expression of CD31, VE-Cadherin and down-regulated α-SMA proteins expression, indicating excellent capacity of pro-endothelial regeneration and inhibition of SMCs proliferation and migration. One-month in vivo implantation in rabbit carotid arteries further confirmed that modified tube implant surface effectively accelerated confluent endothelial monolayer formation and promoted native-like endothelium tissue regeneration. By contrast, original titanium tube implant induced a disorganized tissue proliferation in the lumen with a high risk of restenosis. Collectively, this study opens us an alternative route to achieve the function that selectively promotes endothelial cells (ECs) growth and suppresses SMCs on the medical titanium surface, which has a great potential in facilitating re-endothelialization on the surface of blood-contacting titanium implant.

Preliminary Results on Preparation and Performance of a Self-Emulsifying Waterborne Epoxy Curing Agent at Room Temperature

Polyethylene glycol 1000 (PEG1000) and epoxy resin E20 were used to synthesize the E20/PEG1000 polymer (EP1K), which was later transformed into a self-emulsifying water-based epoxy curing agent by reacting with m-Xylylenediamine (MXDA). The effects of molecular weight, the molar ratio of the raw materials, the catalyst dosage, and the different co-solvents on the properties of the prepared curing agent were systematically explored. The infrared absorption spectra of E20, EP1K, and the water-based epoxy curing agent were compared and analyzed. The coating properties of the waterborne epoxy varnish, which was based on water-based epoxy curing agents to emulsify and cure the resin E44, were systematically tested. The results demonstrated that with a molar ratio of 1:1:4 of PEG1000, E20, and MXDA, the boron trifluoride etherate (BF3·Et2O) as catalyst accounts for 0.3% of the total mass of E20 and PEG1000, and an applicable period of 3 h for the prepared varnish, the anti-corrosion performance, and mechanical properties of the coatings were excellent.

Advancing dental implants: Bioactive and therapeutic modifications of zirconia

Zirconium-based implants have gained popularity in the dental implant field owing to their corrosion resistance and biocompatibility, attributed to the formation of a native zirconia (ZrO₂) film. However, enhanced bioactivity and local therapy from such implants are desirable to enable the earlier establishment and improved long-term maintenance of implant integration, especially in compromised patient conditions. As a result, surface modification of zirconium-based implants have been performed using various physical, chemical and biological techniques at the macro-, micro-, and nano-scales. In this extensive review, we discuss and detail the development of Zr implants covering the spectrum from past and present advancements to future perspectives, arriving at the next generation of highly bioactive and therapeutic nano-engineered Zr-based implants. The review provides in-depth knowledge of the bioactive/therapeutic value of surface modification of Zr implants in dental implant applications focusing on clinical translation.

Using a two-step method of surface mechanical attrition treatment and calcium ion implantation to promote the osteogenic activity of mesenchymal stem cells as well as biomineralization on a β-titanium surface

Combination of the SMAT technique and Ca-ion implantation produced a β-titanium alloy with a bioactive surface layer, which was proved to effectively promote the osteogenic activity of MSCs and Ca–P mineral deposition in vitro.

Review of recent developments in surface nanocrystallization of metallic biomaterials

Metallic materials are widely used to prepare implants for both short-term and long-term use in the human body. The performance of these implants is greatly influenced by their surface characteristics, which has motivated the development of several surface modification techniques. Surface severe plastic deformation (S2PD) techniques have emerged as promising strategies to enhance the performance of metallic biomaterials. They do not involve chemical modification of the surface and impart minimal changes to the surface topography. S2PD processes are based on the principle of generating nanocrystals at the surface, which can improve performance metrics, such as fatigue, wear, corrosion resistance, and biocompatibility through various mechanisms, such as surface hardening and alterations to the surface oxide layer. This review presents the state of the art on the development of different S2PD processes and their applications on metallic biomaterials. Brief descriptions of the different processes have been provided, followed by a discussion on the microstructural changes induced by these processes for different generations of biomaterials. The effect of S2PD on surface and bulk characteristics of the biomaterials and their performance is critically reviewed. As an emerging class of surface engineering techniques in biomaterials science, more work is needed to fully leverage their potential in this field, and these opportunities are discussed in this review.

Improved osteogenic differentiation of human amniotic mesenchymal stem cells on gradient nanostructured Ti surface

Titanium (Ti) and Ti-based alloys are widely used in the manufacture of dental and orthopedic implants. However, how to improve their osteogenic differentiation ability is still a key issue to be resolved. In this study, gradient nanostructured surface (GNS) samples were prepared by surface mechanical grinding treatment, and coarse-grained (CG) samples were obtained by recrystallization annealing, making sure that the two kinds of specimens had similar roughness. Then, human amniotic mesenchymal stem cells (hAMSCs) were cocultured with the two kinds of Ti to investigate the material effects on the cellular functions. The results demonstrated that the grains with size ~56 nm were formed on the surface of the GNS Ti, and the grain size gradually increases from the sample surface to interior. Compared to the CG samples, the GNS ones could make the adhesion effect of the hAMSCs better, and promote the cell proliferation and osteogenic differentiation more significantly, the preliminary mechanism of which might be due to their specific nanostructure, the thicker oxide layer formed on their surface and the enhanced hardness. Our results indicated that the gradient nanostructured Ti materials could enhance both osteogenic differentiation and mechanical properties, which may possess broader applications in bone tissue engineering and clinical implanting.

Enhanced in-vitro osteoblastic functions on β-type titanium alloy using surface mechanical attrition treatment

To improve the osseointegration of titanium based implants, we herein modified Ti-25Nb-3Mo-2Sn-3Zr, a β-type titanium alloy by means of surface mechanical attrition treatment (SMAT). X-ray diffraction and transmission electron microscope results jointly indicate that SMAT process refined the average grain size of β phase in the surface layer of the alloy from about 110 μm to 26 nm. Besides, the surface properties and in-vitro cell culture tests of the SMAT-processed samples were investigated compared to those on the non-treated samples. Atomic force microscope and hydrophilicity tests revealed that the SMAT-processed surface was much rougher and hydrophilic than the non-treated surface. In vitro experimental results showed that SMAT-processed surface promoted adsorption of total protein as well as anchoring proteins such as vitronectin and fibronectin on its surface from cell culture medium, furthermore, significant improvements of osteoblast adhesion, proliferation, differentiation and extracellular mineralization were also found on the SMAT-processed surface compared to the non-treated surface. This could be attributed to the grain refinement as well as increased surface hydrophilicity and roughness after SMAT process. Our study provides a promising means of surface modification for future use in biomedical application.

In vitro corrosion behavior and biocompatibility of nanostructured Ti6Al4V

Ti6Al4V (TC4) alloy has long been used as a bone interfacing implant material in dentistry and orthopedics due to its excellent biocompatibility and mechanical properties. The performance of TC4 can be further tailored by altering its grain structures. In this study, by means of sliding friction treatment (SFT), a nano-grained (NG) surface layer with an average grain size of ≤100 nm on the topmost surface was successfully generated on coarse-grained (CG) TC4 alloy sheet. It was shown that the NG surface possessed notably enhanced corrosion resistance in physiological solution compared to the CG surface, due to the formation of thicker and denser passive film facilitated by surface nanocrystallization. Additionally, the NG surface with stronger hydrophilicity favorably altered the absorption of anchoring proteins such as fibronectin (Fn) and vitronectin (Vn) that can mediate subsequent osteoblast functions. The in vitro results indicated that the NG surface exhibited remarkable enhancement in osteoblast adherence, spreading and proliferation, and obviously accelerated the osteoblast differentiation as compared to CG surface. Moreover, the NG surface also demonstrated good hemocompatibility. These findings suggest that SFT can endure bio-metals with advanced multifunctional properties for biomedical applications.

Significantly enhanced osteoblast response to nano-grained pure tantalum

Tantalum (Ta) metal is receiving increasing interest as biomaterial for load-bearing orthopedic applications and the synthetic properties of Ta can be tailored by altering its grain structures. This study evaluates the capability of sliding friction treatment (SFT) technique to modulate the comprehensive performances of pure Ta. Specifically, novel nanocrystalline (NC) surface with extremely small grains (average grain size of ≤20 nm) was fabricated on conventional coarse-grained (CG) Ta by SFT. It shows that NC surface possessed higher surface hydrophilicity and enhanced corrosion resistance than CG surface. Additionally, the NC surface adsorbed a notably higher percentage of protein as compared to CG surface. The in vitro results indicated that in the initial culture stages (up to 24 h), the NC surface exhibited considerably enhanced osteoblast adherence and spreading, consistent with demonstrated superior hydrophilicity on NC surface. Furthermore, within the 14 days culture period, NC Ta surface exhibited a remarkable enhancement in osteoblast cell proliferation, maturation and mineralization as compared to CG surface. Ultimately, the improved osteoblast functions together with the good mechanical and anti-corrosion properties render the SFT-processed Ta a promising alternative for the load-bearing bone implant applications.

Biological Behaviour and Enhanced Anticorrosive Performance of the Nitrided Superelastic Ti-23Nb-0.7Ta-2Zr-0.5N Alloy

The influence of gas nitriding surface treatment on the superelastic Ti-23Nb-0.7Ta-2Zr-0.5N alloy was evaluated. A thorough characterization of bare and nitrided Ti-based alloy and pure Ti was performed in terms of surface film composition and morphology, electrochemical behaviour, and short term osteoblast response. XPS analysis showed that the nitriding treatment strongly influenced the composition (nitrides and oxynitrides) and surface properties both of the substrate and of the bulk alloy. SEM images revealed that the nitrided surface appears as a similar dotted pattern caused by the formation of N-rich domains coexisting with less nitrided domains, while before treatment only topographical features could be observed. All the electrochemical results confirmed the high chemical stability of the nitride and oxynitride coating and the superiority of the applied treatment. The values of the corrosion parameters ascertained the excellent corrosion resistance of the coated alloy in the real functional conditions from the human body. Cell culture experiments with MG63 osteoblasts demonstrated that the studied biomaterials do not elicit any toxic effects and support cell adhesion and enhanced cell proliferation. Altogether, these data indicate that the nitrided Ti-23Nb-0.7Ta-2Zr-0.5N alloy is the most suitable substrate for application in bone implantology.

Increased osteoblast function in vitro and in vivo through surface nanostructuring by ultrasonic shot peening

Surface topography has significant influence on good and fast osseointegration of biomedical implants. In this work, ultrasonic shot peening was conducted to modify titanium to produce nanograined (NG) surface. Its ability to induce new bone formation was evaluated using an in vivo animal model. We demonstrated that the NG surface enhanced osteoblast adhesion, proliferation, differentiation, and mineralization in in vitro experiments compared to coarse-grained titanium surface. Push-out test, histological observations, fluorescent labeling, and histomorphometrical analysis consistently indicated that the NG surfaces developed have the higher osseointegration than coarse-grained surfaces. Those results suggest that ultrasonic shot peening has the potential for future use as a surface modification method in biomedical application.

Effect of thermomechanical treatment on the superelasticity of Ti-7.5Nb-4Mo-2Sn biomedical alloy

Effects of thermomechanical treatment on the microstructure and superelasticity of Ti-7.5Nb-4Mo-2Sn biomedical alloy were investigated by using XRD measurement, optical microscope (OM), transmission electron microscope (TEM) and tensile tests. The titanium alloy samples were prepared by annealing at a temperature in the range of 600 to 1000°C after severe cold rolling; and the samples that were annealed at 800°C were further aged at 600 and 700°C. The volume fraction of α phases decreased while that of ω phases increase with increasing annealing temperature. The α→β transformation temperature of the alloy was determined to be between 700 and 800°C. The alloy that was annealed at 700°C exhibited a high level of superelasticity with relatively high first yield stress (σSIM) at room temperature because it contained a fine α phase. A certain amount of ω phases also resulted in an increase in σSIM, leading to an improvement in the superelasticity of the alloys that were annealed at 900 and 1000°C. Aging treatment led to the precipitations of α and ω phases in the alloy after annealing at 800°C; and the volume fraction of α phases decreased while that of ω phases increased with increasing aging temperature. Excellent superelasticity with high recovered strain (εrecoverable) and strain recovery rate (η) were obtained in the aged alloy due to the reinforcement of α and ω phases induced by aging treatment. The alloy annealed at 700°C for 0.5h exhibited the best superelasticity in all the thermomechanically treated alloys due to the strengthening from the subgrain refining and the precipitating of fine α phases.