Significantly enhanced osteoblast response to nano-grained pure tantalum

Progress of research on the surface functionalization of tantalum and porous tantalum in bone tissue engineering

Tantalum and porous tantalum are ideal materials for making orthopedic implants due to their stable chemical properties and excellent biocompatibility. However, their utilization is still affected by loosening, infection, and peripheral inflammatory reactions, which sometimes ultimately lead to implant removal. An ideal bone implant should have exceptional biological activity, which can improve the surrounding biological microenvironment to enhance bone repair. Recent advances in surface functionalization have produced various strategies for developing compatibility between either of the two materials and their respective microenvironments. This review provides a systematic overview of state-of-the-art strategies for conferring biological functions to tantalum and porous tantalum implants. Furthermore, the review describes methods for preparing active surfaces and different bioactive substances that are used, summarizing their functions. Finally, this review discusses current challenges in the development of optimal bone implant materials.

Mechanically enhanced and osteobioactive synthetic periosteum via development of poly(ε-caprolactone)/microtantalum composite

Periosteum, the thin layer covering adjacent to bone containing specific architecture, is important for functional bone regeneration and remodeling. Synthetic periosteum investigated presently lacks the resemblance of natural periosteum, suffering from poor mechanical strength and cell attachment. Here, we report a newly-developed biomimetic film to function as synthetic periosteum. Based on poly(ε-caprolactone) (PCL), where surface wettability of the synthetic periosteum is enhanced by microtantalum (mTa) particle blending and after a cold drawing process, further obtains topographical anisotropy without any involvement of solvent. This new blend shows mechanical enhancement over pure PCL, with yield stress and elastic strain approaching the natural periosteum. A distinct degradation mechanism is proposed for the blend, and by seeding with mouse calvarial preosteoblasts, cell proliferation is promoted on surface of the drawn PCL but delayed on the mTa-blended PCL. However, cell mineralization is accelerated on the mTa-blended surface. This is less on the drawn PCL. The synergistical integration of cellular proliferation, alignment and osteogenic enhancement suggest that the cold drawn PCL/Ta blend has unique potential for developing into a synthetic periosteum and other tissue-engineering products.

Composite Nanocoatings of Biomedical Magnesium Alloy Implants: Advantages, Mechanisms, and Design Strategies

The rapid degradation of magnesium (Mg) alloy implants erodes mechanical performance and interfacial bioactivity, thereby limiting their clinical utility. Surface modification is among the solutions to improve corrosion resistance and bioefficacy of Mg alloys. Novel composite coatings that incorporate nanostructures create new opportunities for their expanded use. Particle size dominance and impermeability may increase corrosion resistance and thereby prolong implant service time. Nanoparticles with specific biological effects may be released into the peri-implant microenvironment during the degradation of coatings to promote healing. Composite nanocoatings provide nanoscale surfaces to promote cell adhesion and proliferation. Nanoparticles may activate cellular signaling pathways, while those with porous or core-shell structures may carry antibacterial or immunomodulatory drugs. Composite nanocoatings may promote vascular reendothelialization and osteogenesis, attenuate inflammation, and inhibit bacterial growth, thus increasing their applicability in complex clinical microenvironments such as those of atherosclerosis and open fractures. This review combines the physicochemical properties and biological efficiency of Mg-based alloy biomedical implants to summarize the advantages of composite nanocoatings, analyzes their mechanisms of action, and proposes design and construction strategies, with the purpose of providing a reference for promoting the clinical application of Mg alloy implants and to further the design of nanocoatings.

Biological Characteristics of Polyurethane-Based Bone-Replacement Materials

A study is presented on four polymers of the polyurethane family, obtained using a two-stage process. The first composition is the basic polymer; the others differ from it by the presence of a variety of fillers, introduced to provide radiopacity. The fillers used were 15% bismuth oxide (Composition 2), 15% tantalum pentoxide (Composition 3), or 15% zirconium oxide (Composition 4). Using a test culture of human fibroblasts enabled the level of cytotoxicity of the compositions to be determined by MTT (3-[4,5-dimethylthiazol-2-yl]-2,5 diphenyl tetrazolium bromide) assay, along with variations in the characteristics of the cells resulting from their culture directly on the specimens. The condition of cells on the surfaces of the specimens was assessed using fluorescence microscopy. It was shown that introducing 15% bismuth, tantalum, or zinc compounds as fillers produced a range of effects on the biological characteristics of the compositions. With the different fillers, the levels of toxicity differed and the cells' proliferative activity or adhesion was affected. However, in general, all the studied compositions may be considered cytocompatible in respect of their biological characteristics and are promising for further development as bases for bone-substituting materials. The results obtained also open up prospects for further investigations of polyurethane compounds.

Current Advances and Applications of Tantalum Element in Infected Bone Defects

Infected bone defects (IBDs) cause significant economic and psychological burdens, posing a huge challenge to clinical orthopedic surgeons. Traditional approaches for managing IBDs possess inevitable shortcomings; therefore, it is necessary to develop new functionalized scaffolds. Tantalum (Ta) has been widely used in load-bearing orthopedic implants due to its good biocompatibility and corrosion resistance. However, undecorated Ta could only structurally repair common bone defects, which failed to meet the clinical needs of bacteriostasis for IBDs. Researchers have made great efforts to functionalize Ta scaffolds to enhance their antibacterial activity through various methods, including surface coating, alloying, and micro- and nanostructure modifications. Additionally, several studies have successfully utilized Ta to modify orthopedic scaffolds for enhanced antibacterial function. These studies remarkably extended the application range of Ta. Therefore, this review systematically outlines the advances in the fundamental and clinical application of Ta in the treatment of IBDs, focusing on the antibacterial properties of Ta, its functionalization for bacteriostasis, and its applications in the modification of orthopedic scaffolds. This study provides researchers with an overview of the application of Ta in the treatment of IBDs.

Advances in surface modification of tantalum and porous tantalum for rapid osseointegration: A thematic review

After bone defects reach a certain size, the body can no longer repair them. Tantalum, including its porous form, has attracted increasing attention due to good bioactivity, biocompatibility, and biomechanical properties. After a metal material is implanted into the body as a medical intervention, a series of interactions occurs between the material’s surface and the microenvironment. The interaction between cells and the surface of the implant mainly depends on the surface morphology and chemical composition of the implant’s surface. In this context, appropriate modification of the surface of tantalum can guide the biological behavior of cells, promote the potential of materials, and facilitate bone integration. Substantial progress has been made in tantalum surface modification technologies, especially nano-modification technology. This paper systematically reviews the progress in research on tantalum surface modification for the first time, including physicochemical properties, biological performance, and surface modification technologies of tantalum and porous tantalum.

Nano tantalum-coated 3D printed porous polylactic acid/beta-tricalcium phosphate scaffolds with enhanced biological properties for guided bone regeneration

Bone defects caused by tumors section, traffic accidents, and surgery remain a challenge in clinical. The drawbacks of traditional autografts and allografts limit their clinical application. 3D printed porous scaffolds have monumental potential to repair bone defects but still cannot effectively promote bone formation. Nano tantalum (Ta) has been reported with effective osteogenesis capability. Herein, we fabricated 3D printed PLA/β-TCP scaffold by using the fused deposition modeling (FDM) technique. Ta was doped on the surface of scaffolds utilizing the surface adhesion ability of polydopamine to improve its properties. The constructed PLA/β-TCP/PDA/Ta had good physical properties. In vitro studies demonstrated that the PLA/β-TCP/PDA/Ta scaffolds considerably promote cell proliferation and migration, and it additionally has osteogenic properties. Therefore, Ta doped 3D printed PLA/β-TCP/PDA/Ta scaffold could incontestably improve surface bioactivity and lead to better osteogenesis, which may provide a unique strategy to develop bioactive bespoke implants in orthopedic applications.

Recent Progress on Nanocrystalline Metallic Materials for Biomedical Applications

Nanocrystalline (NC) metallic materials have better mechanical properties, corrosion behavior and biocompatibility compared with their coarse-grained (CG) counterparts. Recently, nanocrystalline metallic materials are receiving increasing attention for biomedical applications. In this review, we have summarized the mechanical properties, corrosion behavior, biocompatibility, and clinical applications of different types of NC metallic materials. Nanocrystalline materials, such as Ti and Ti alloys, shape memory alloys (SMAs), stainless steels (SS), and biodegradable Fe and Mg alloys prepared by high-pressure torsion, equiangular extrusion techniques, etc., have better mechanical properties, superior corrosion resistance and biocompatibility properties due to their special nanostructures. Moreover, future research directions of NC metallic materials are elaborated. This review can provide guidance and reference for future research on nanocrystalline metallic materials for biomedical applications.

Review on Grain Refinement of Metallic Materials to Regulate Cellular Behavior

Metallic materials have been widely used as orthopedic implants in clinics for their good mechanical, physical, and chemical properties, but their slow osseointegration rate is still one of the main issues causing implantation failure. Grain refinement has recently attracted wide attention for its effective improvement of cell–material interaction for biometals. In this review, the surface and bulk grain refinement mode and the influence of grain size reduction of various metallic materials including titanium, stainless steel, magnesium, zirconium, tantalum, and their alloys as well as NiTi shape memory alloys on the cell responses is summarized in detail. It is hoped that this review could help biomaterials-related researchers to understand the grain refinement of metallic materials in a timely manner, thus boosting the development of biomedical metals for clinical use.

Simultaneous incorporation of gallium oxide and tantalum microparticles into micro-arc oxidation coating of titanium possessing antibacterial effect and stimulating cellular response

Orthopedic implants with both osteogenesis and antibacterial functions are particularly promising for bone repair and substitutes. In this study, a micro-arc oxidation (MAO) coating containing titanium dioxide (TiO₂), gallium oxide (Ga₂O₃) and tantalum oxide (Ta₂O₅) on the titanium surface (MGT) was fabricated by dispersing Ga₂O₃ and Ta microparticles in the electrolyte. The results showed that the simultaneous incorporation of Ga₂O₃ and Ta microparticles into the MAO coating resulted in optimized surface performance (e.g., micro-topography, roughness, wettability, surface energy, and protein absorption) of MGT compared with pure titanium (pTi). In addition, MGT exhibited outstanding corrosion resistance owing to the presence of both Ga₂O₃ and Ta microparticles, which exhibit excellent corrosion resistance and their microparticles were incorporated into the micropores of the coating. Moreover, MGT with good cytocompatibility and optimized surface resulted in improved cellular responses (e.g., proliferation and osteogenic differentiation) of rat bone mesenchymal stem cells, which was attributed to Ta microparticles with outstanding osteogenic bioactivity. Furthermore, the excellent antibacterial effect of MGT was attributed to the slow release of Ga³⁺ from the coating. Thus, the simultaneous incorporation of Ga₂O₃ and Ta microparticles into the MAO coating of MGT exhibited excellent cytocompatibility, osteogenic bioactivity, antibacterial functions, and corrosion resistance, suggesting that MGT possesses great potential for bone repair applications.

EIS Characterization of Ti Alloys in Relation to Alloying Additions of Ta

The increased popularity of Ti and its alloys as important biomaterials is driven by their low modulus, greater biocompatibility, and better corrosion resistance in comparison to traditional biomaterials, such as stainless steel and Co-Cr alloys. Ti alloys are successfully used in severe stress situations, such as Ti-6Al-4V, but this alloy is related to long-term health problems and, in response, different Ti alloys composed of non-toxic and non-allergic elements such as Nb, Zr, Mo, and Ta have been developed for biomedical applications. In this context, binary alloys of titanium and tantalum have been developed and are predicted to be potential products for medical purposes. More than this, today, novel biocompatible alloys such as high entropy alloys with Ti and Ta are considered for biomedical applications and therefore it is necessary to clarify the influence of tantalum on the behavior of the alloy. In this study, various Ti-xTa alloys (with x = 5, 15, 25, and 30) were characterized using different techniques. High-resolution maps of the materials' surfaces were generated by scanning tunneling microscopy (STM), and atom distribution maps were obtained by energy dispersive X-ray spectroscopy (EDS). A thorough output of chemical composition, and hence the crystallographic structure of the alloys, was identified by X-ray diffraction (XRD). Additionally, the electrochemical behavior of these Ti-Ta alloys was investigated by EIS in simulated body fluid at different potentials. The passive layer resistance increases with the potential due to the formation of the passive layer of TiO₂ and Ta₂O₅ and then decreases due to the dissolution processes through the passive film. Within the Ti-xTa alloys, Ti-25Ta demonstrates excellent passive layer and corrosion resistance properties, so it seems to be a promising product for metallic medical devices.

Comparison of surface properties, cell behaviors, bone regeneration and osseointegration between nano tantalum/PEEK composite and nano silicon nitride/PEEK composite

Both tantalum (Ta) and silicon nitride (SN) exhibit osteogenic bioactivity and antibacterial property. In addition, as a biomaterial for bone repair, polyetheretherketone (PEEK) has outstanding biocompatibility and mechanical performances while it is biologically inert. In this study, by blending PEEK with Ta and SN nanoparticles, respectively, Ta/PEEK composite (TPC) and SN/PEEK composite (SPC) were fabricated for load-bearing bone repair. The surface roughness, hydrophilicity and surface energy of TPC containing Ta nanoparticles were higher than SPC containing SN nanoparticles and PEEK. In addition, TPC with Ta nanoparticles exhibited low antibacterial property while SPC with SN nanoparticles showed high bacterial property. Moreover, the MC3T3-E1 cells responses (e.g. proliferation and differentiation) to TPC was the highest while PEEK was the lowest in vitro. Furthermore, new bone formation and osseointegration for TPC was the highest while PEEK was the lowest in vivo. In conclusion, compared with PEEK, addition of Ta and SN nanoparticles into PEEK fabricated bioactive composites of TPC and SPC with optimized surface property, which played crucial roles in inducing cellular response/bone regeneration. Although the osteogenic activity of SPC was lower than TPC, SPC exhibited osteogenic activity and good antibacterial property, which could prevent infection from bacterial. Therefore, SPC would have better potential for bone substitute.

Assessment of tantalum nanoparticle-induced MC3T3-E1 proliferation and underlying mechanisms

OBJECTIVE

In our previous study, tantalum nanoparticle (Ta-NPs) was demonstrated to promote osteoblast proliferation via autophagy induction, but the specific mechanism remains unclear. In the present study, we will explore the potential mechanism.

METHODS

Ta-NPs was characterized by transmission electron microscopy, scanning electron microscopy, dynamic light scattering, and BET specific surface area test. MC3T3-E1 were treated with 0 or 20 μg/mL Ta-NPs with or without pretreatment with 10 μM LY294002, Triciribine, Rapamycin (PI3K/Akt/mTOR pathway inhibitors) for 1 h respectively. Western blotting was used to detect the expressions of pathway proteins and LC3B. CCK-8 assay was used to assess cell viability. Flow cytometry was used to detect apoptosis and cell cycle.

RESULTS

After pretreatment with LY294002, Triciribine and Rapamycin, the p-Akt/Akt ratio of pathway protein in Triciribine and Rapamycin groups decreased (P < 0.05), while the autophagy protein LC3-II/LC3-I in the Rapamycin group was upregulated obviously (P < 0.001). In all pretreated groups, apoptosis was increased (LY294002 group was the most obvious), G1 phase cell cycle was arrested (Triciribine and Rapamycin groups were more obvious), and MC3T3-E1 cells were proliferated much more (P < 0.01, P < 0.001, P < 0.05).

CONCLUSION

Pretreatment with Triciribine or Rapamycin has a greater effect on pathway protein Akt, cell cycle arrest, autophagy protein, and cell proliferation but with inconsistent magnitude, which may be inferred that the Akt/mTOR pathway, as well as its feedback loop, were more likely involved in these processes.

Enhanced spreading, migration and osteodifferentiation of HBMSCs on macroporous CS-Ta - A biocompatible macroporous coating for hard tissue repair

Macroporous tantalum (Ta) coating was produced on titanium alloy implant for bone repair by cold spray (CS) technology, which is a promising technology for oxygen sensitive materials. The surface characteristics as well as in vitro cytocompatibility were systematically evaluated. The results showed that a rough and macroporous CS-Ta coating was formed on the Ti6Al4V (TC4) alloy surfaces. The surface roughness showed a significant enhancement from 17.06 μm (CS-Ta-S), 27.48 μm (CS-Ta-M) to 39.21 μm (CS-Ta-L) with the increase of the average pore diameter of CS-Ta coatings from 138.25 μm, 198.25 μm to 355.56 μm. In vitro results showed that macroporous CS-Ta structure with tantalum pentoxide (Ta₂O₅) was more favorable to induce human bone marrow derived mesenchymal stem cells (HBMSCs) spreading, migration and osteodifferentiation than TC4. Compared with the micro-scaled structure outside the macropores, the surface micro-nano structure inside the macropores was more favorable to promote osteodifferentiation with enhanced alkaline phosphatase (ALP) activity and extracellular matrix (ECM) mineralization. In particular, CS-Ta-L with the largest pore size showed significantly enhanced integrin-α5 expression, cell migration, ALP activity, ECM mineralization as well as osteogenic-related genes including ALP, osteopontin (OPN) and osteocalcin (OCN) expression. Our results indicated that macroporous Ta coatings by CS, especially CS-Ta-L, may be promising for hard tissue repairs.

Coinciding significance of the crystallographic orientation and nanostructuring on the biocompatibility of TZNT-Ag1 .5 alloy deformed by the cold rolling process

In this study, the simultaneous significance of the crystallographic texture and nanostructuring on the cytocompatibility of as-cast (Ti₅₅ Zr₂₅ Nb₁₀ Ta₁₀ )_98.5 -Ag_1.5 alloy (at. %, TZNT-Ag_1.5 ), subjected to cold rolling up to 90% reduction, along with the changes of Young's modulus and hardness under cold rolling were investigated. For this purpose, the as-cast and cold-rolled TZNT-Ag_1.5 alloy test specimens were analyzed by XRD, TEM, HRTEM, SEM, contact angle, nanoindentation, and OM techniques. Moreover, to evaluate the effect of severe cold deformation on the biocompatibility, MG-63 osteoblastic cell was cultured on the surface of 90% cold-rolled and as-cast test specimens of TZNT-Ag_1.5 alloy. The results showed that severe cold deformation was led to fast grain refinement of β grains of the as-cast TZNT-Ag_1.5 alloy in the range of 50-100 nm. In addition to the nanostructuring, upon severe cold deformation, the <gamma>-fiber (<111>// normal direction) texture was formed and after 90% reduction, the (111)<1 1 ¯ 0 > γ_-fiber component was strengthened. The micro-hardness and reduced Young's modulus are 235 ± 5.29, 246 ± 1.73, 271 ± 4.0, and 283 ± 6.25 (HV); and 73.725 ± 1.70, 83.98 ± 5.10, 81.26 ± 6.55, and 88.66 ± 7.16 (GPa) for TZNT-Ag_1.5 (as-cast), TZNT-Ag_1.5 (20%CR), TZNT-Ag_1.5 (50%CR), and TZNT-Ag_1.5 (90%CR) test specimens, respectively. Further, with increasing the cold deformation degree, the dislocation density of TZNT-Ag_1.5 alloy increased as this parameter is 2.79 × 10¹⁵ (m^-2 ) for the 90%CR test specimen. On the other hand, the values of the contact angle for the 90%CR test specimen (46.2 ± 3.5°) exhibit a higher hydrophilic and wettable surface as compared to the other studied test specimens. After 5 days of incubation, osteoblastic cells on the surface of the 90% cold-rolled TZNT-Ag_1.5 test specimens revealed significant differences in cell proliferation and differentiation as compared to the as-cast alloy test specimens and/or CP-Ti. Finally, because the maximum orientation intensities were generally <3, it was deduced that grain refinement rather than the crystallographic texture plays a significant role in improving the surface biocompatibility of the new TZNT-Ag_1.5 alloy.

Tantalum and its derivatives in orthopedic and dental implants: Osteogenesis and antibacterial properties

Implant-associated infections and aseptic loosening are some of the main reasons for implant failure. Therefore, there is an urgent need to improve the osseointegration and antibacterial capabilities of implant materials. In recent years, a large number of breakthroughs in the biological application of tantalum and its derivatives have been achieved. Owing to their corrosion resistance, biocompatibility, osseointegration ability, and antibacterial properties, they have shown considerable potential in orthopedic and dental implant applications. In this review, we provide the latest progress and achievements in the research on osseointegration and antibacterial properties of tantalum as well as its derivatives, and summarize the surface modification methods to enhance their osseointegration and antibacterial properties.

[Research progress on the biological properties of the surface nanocrystals of typical medical metal materials]

Biomedical metal materials have always been a major biomedical material with a large and wide range of clinical use due to their excellent properties such as high strength and toughness, fatigue resistance, easy forming, and corrosion resistance. They are also the preferred implant material for hard tissues (bones and teeth that need to withstand higher loads) and interventional stents. And nano-medical metal materials have better corrosion resistance and biocompatibility. This article focuses on the changes and improvements in the properties of several typical medical metal materials surfaces after nanocrystallization, and discusses the current problems and development prospects of nano-medical metal materials.

A microporous surface containing Si3N4/Ta microparticles of PEKK exhibits both antibacterial and osteogenic activity for inducing cellular response and improving osseointegration

As an implantable biomaterial, polyetherketoneketone (PEKK) exhibits good mechanical strength but it is biologically inert while tantalum (Ta) possesses outstanding osteogenic bioactivity but has a high density and elastic modulus. Also, silicon nitride (SN) has osteogenic and antibacterial activity. In this study, a microporous surface containing both SN and Ta microparticles on PEKK (STP) exhibiting excellent osteogenic and antibacterial activity was created by sulfonation. Compared with sulfonated PEKK (SPK) without microparticles, the surface properties (roughness, surface energy, hydrophilicity and protein adsorption) of STP significantly increased due to the SN and Ta particles presence on the microporous surface. In addition, STP also exhibited outstanding antibacterial activity, which inhibited bacterial growth in vitro and prevented bacterial infection in vivo because of the presence of SN particles. Moreover, the microporous surface of STP containing both SN and Ta particles remarkably induced response (e.g., proliferation and differentiation) of rat bone mesenchymal stem (rBMS) cells in vitro. Furthermore, STP significantly improved new bone regeneration and osseointegration in vivo. Regarding the induction of cellular response in vitro and improvement of osseointegration in vivo, the microporous surface containing Ta was better than the surface with SN particles. In conclusion, STP with optimized surface properties activated cellular responses in vitro, enhanced osseointegration and prevented infection in vivo. Therefore, STP possessed the dual biofunctions of excellent osteogenic and antibacterial activity, showing great potential as a bone substitute.

•Microporous surface containing SN/Ta microparticles on PEKK (STP) was created.

•Surface performances (e.g., roughness) of STP were significantly increased.

•STP exhibited antibacterial activity in vitro and prevented infection in vivo.

•STP remarkably induced response of bone mesenchymal stem cells in vitro.

•STP obviously improved bone regeneration and osseointegration in vivo.

Implantable PEKK/tantalum microparticles composite with improved surface performances for regulating cell behaviors, promoting bone formation and osseointegration

Polyetherketoneketone (PEKK) exhibits admirable biocompatibility and mechanical performances but bioinert while tantalum (Ta) possesses excellent osteogenesis and osseointegration but high elastic modulus and density, and processing is too difficult and expensive. In the present study, combining of the advantages of both PEKK and Ta, implantable composites of PEKK/Ta were fabricated by blending PEKK with Ta microparticles of 20 v% (PT20) and 40 v% (PT40) content. In comparison with PT20 and PEKK, the surface hydrophilicity, surface energy, roughness and proteins adsorption as well as mechanical performances of PT40 significantly increased because of the higher Ta particles content in PEKK. Furthermore, PT40 exhibited the mechanical performances (e.g., compressive strength and modulus of elasticity) close to the cortical bone of human. Compared with PT20 and PEKK, PT40 with higher Ta content remarkably enhanced the responses (including adhesion, proliferation and osteogenic differentiation) of MC3T3-E1 cells in vitro. Moreover, PT40 markedly improved bone formation as well as osseointegration in vivo. In short, incorporation of Ta microparticles into PEKK created implantable composites with improved surface performances, which played key roles in stimulating cell responses/bone formation as well as promoting osseointegration. PT40 might have great potential for bear-loading bone substitute.

Local Cellular Responses to Metallic and Ceramic Nanoparticles from Orthopedic Joint Arthroplasty Implants

Over the last decades, joint arthroplasty has become a successful treatment for joint disease. Nowadays, with a growing demand and increasingly younger and active patients accepting these approaches, orthopedic surgeons are seeking implants with improved mechanical behavior and longer life span. However, aseptic loosening as a result of wear debris from implants is considered to be the main cause of long-term implant failure. Previous studies have neatly illustrated the role of micrometric wear particles in the pathological mechanisms underlying aseptic loosening. Recent osteoimmunologic insights into aseptic loosening highlight the important and heretofore underrepresented contribution of nanometric orthopedic wear particles. The present review updates the characteristics of metallic and ceramic nanoparticles generated after prosthesis implantation and summarizes the current understanding of their hazardous effects on peri-prosthetic cells.

Sol-gel-assisted micro-arc oxidation synthesis and characterization of a hierarchically rough structured Ta-Sr coating for biomaterials

Tantalum (Ta) is an element with high chemical stability and ductility that is used in orthopedic biomaterials. When utilized, it can produce a bioactive surface and enhance cell-material interactions, but currently, there exist scarce effective methods to introduce the Ta element onto the surface of implants. This work reported a sol-gel-assisted approach combined with micro-arc oxidation (MAO) to introduce Ta onto the surface of the titanium (TC4) substrate. Specifically, this technique produced a substrate with a hierarchically rough structured topography and introduced strontium ions into the film. The films were uniform and continuous with numerous crater-like micropores. Compared with the TC4 sample (196 ± 35 nm), the roughness of Ta (734 ± 51 nm) and Ta-Sr (728 ± 85 nm) films was significantly higher, and both films (Ta and Ta-Sr) showed increased hydrophilicity when compared with TC4, promoting cell attachment. Additionally, the in vitro experiments indicated that Ta and Ta-Sr films have the potential to enhance the recruitment of cells in the initial culture stages, and improve cell proliferation. Overall, this work demonstrated that the application of Ta and Ta-Sr films to orthopedic implants has the potential to increase the lifetime of the implants. Furthermore, this study also describes an innovative strategy to incorporate Ta into implant films.

Improvement of biohistological response of facial implant materials by tantalum surface treatment

Background

A compact passive oxide layer can grow on tantalum (Ta). It has been reported that this oxide layer can facilitate bone ingrowth in vivo though the development of bone-like apatite, which promotes hard and soft tissue adhesion. Thus, Ta surface treatment on facial implant materials may improve the tissue response, which could result in less fibrotic encapsulation and make the implant more stable on the bone surface. The purposes of this study were to verify whether surface treatment of facial implant materials using Ta can improve the biohistobiological response and to determine the possibility of potential clinical applications.

Methods

Two different and commonly used implant materials, silicone and expanded polytetrafluoroethylene (ePTFE), were treated via Ta ion implantation using a Ta sputtering gun. Ta-treated samples were compared with untreated samples using in vitro and in vivo evaluations. Osteoblast (MG-63) and fibroblast (NIH3T3) cell viability with the Ta-treated implant material was assessed, and the tissue response was observed by placing the implants over the rat calvarium (n = 48) for two different lengths of time. Foreign body and inflammatory reactions were observed, and soft tissue thickness between the calvarium and the implant as well as the bone response was measured.

Results

The treatment of facial implant materials using Ta showed a tendency toward increased fibroblast and osteoblast viability, although this result was not statistically significant. During the in vivo study, both Ta-treated and untreated implants showed similar foreign body reactions. However, the Ta-treated implant materials (silicone and ePTFE) showed a tendency toward better histological features: lower soft tissue thickness between the implant and the underlying calvarium as well as an increase in new bone activity.

Conclusion

Ta surface treatment using ion implantation on silicone and ePTFE facial implant materials showed the possibility of reducing soft tissue intervention between the calvarium and the implant to make the implant more stable on the bone surface. Although no statistically significant improvement was observed, Ta treatment revealed a tendency toward an improved biohistological response of silicone and ePTFE facial implants. Conclusively, tantalum treatment is beneficial and has the potential for clinical applications.

Nanolamellar Tantalum Interfaces in the Osteoblast Adhesion

The design of topographically patterned surfaces is considered to be a preferable approach for influencing cellular behavior in a controllable manner, in particular to improve the osteogenic ability of bone regeneration. In this study, we fabricated nanolamellar tantalum (Ta) surfaces with lamellar wall thicknesses of 40 and 70 nm. The cells attached to nanolamellar Ta surfaces exhibited higher protein adsorption and expression of β1 integrin, as compared to the nonstructured bulk Ta, which facilitated the initial cell attachment and spreading. We thus, as expected, observed significantly enhanced osteoblast adhesion, growth, and alkaline phosphatase activity on nanolamellar Ta surfaces. However, the beneficial effects of nanolamellar structures on osteogenesis became weaker as the lamellar wall thickness increased. The interaction between cells and Ta surfaces was examined through adhesion forces using atomic force microscopy. Our findings indicated that the Ta surface with a lamellar wall thickness of 40 nm exhibited the strongest stimulatory effect. The observed strongest adhesion force between the cell-attached tip and the Ta surface with a 40 nm thick lamellar wall encouraged the much stronger binding of cells with the surface and thus well-attached, -stretched, and -grown cells. We attributed this to the increase in the available contact area of cells with the thinner nanolamellar Ta surface. The increased contact area allowed the enhancement of the cell surface interaction strength and, thus, improved osteoblast adhesion. This study suggests that the thin nanolamellar topography shows immense potential in improving the clinical performance of dental and orthopedic implants.

What's Happening on the Other Side? Revealing Nano-Meter Scale Features of Mammalian Cells on Engineered Textured Tantalum Surfaces

Advanced engineered surfaces can be used to direct cell behavior. These behaviors are typically characterized using either optical, atomic force, confocal, or electron microscopy; however, most microscopic techniques are generally restricted to observing what's happening on the "top" side or even the interior of the cell. Our group has focused on engineered surfaces typically reserved for microelectronics as potential surfaces to control cell behavior. These devices allow the exploration of novel substrates including titanium, tungsten, and tantalum intermixed with silicon oxide. Furthermore, these devices allow the exploration of the intricate patterning of surface materials and surface geometries i.e., trenches. Here we present two important advancements in our research: (1) the ability to split a fixed cell through the nucleus using an inexpensive three-point bend micro-cleaving technique and image 3D nanometer scale cellular components using high-resolution scanning electron microscopy; and (2) the observation of nanometer projections from the underbelly of a cell as it sits on top of patterned trenches on our devices. This application of a 3-point cleaving technique to visualize the underbelly of the cell is allowing a new understanding of how cells descend into surface cavities and is providing a new insight on cell migration mechanisms.

Effects of laser shock peening on the corrosion behavior and biocompatibility of a nickel-titanium alloy

Nickel-titanium (NiTi) alloy is an attractive material for biomedical implant applications. In this study, the effects of laser shock peening (LSP) on the biocompatibility, corrosion resistance, ion release rate and hardness of NiTi were characterized. The cell culture study indicated that the LSP-treated NiTi samples had lower cytotoxicity and higher cell survival rate than the untreated samples. Specifically, the cell survival rate increased from 88 ± 1.3% to 93 ± 1.1% due to LSP treatment. LSP treatment was shown to significantly decrease the initial Ni ion release rate compared with that of the untreated samples. Electrochemical tests indicated that LSP improved the corrosion resistance of the NiTi alloy in simulated body fluid, with a decrease in the corrosion current density from 1.41 ± 0.20 μA/cm² to 0.67 ± 0.24 μA/cm² . Immersion tests showed that calcium deposition was significantly enhanced by LSP. In addition, the hardness of NiTi alloy increased from 226 ± 3 HV before LSP to 261 ± 3 HV after LSP. These results demonstrated that LSP is a promising surface modification method that can be used to improve the mechanical properties, corrosion resistance and biocompatibility of NiTi alloy for biomedical applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater 107B: 1854-1863, 2019.

Manipulating the degradation behavior and biocompatibility of Mg alloy through a two-step treatment combining sliding friction treatment and micro-arc oxidation

Manipulating the degradation rate of biomedical Mg alloys has always been a challenge. In this study, a two-step treatment including sliding friction treatment (SFT) and micro-arc oxidation (MAO) was adopted to acquire a unique Mg-based architecture containing three typical layers comprising a MAO coating/nanocrystalline (NC) layer/coarse-grained (CG) matrix. It was found that the modified topmost MAO coating possessed enhanced corrosion resistance, cytocompatibility and hemocompatibility. The intermediate NC layer sandwiched between the coating and CG matrix was an ideal transition layer capable of avoiding degradation rate upsurge caused by coating breakdown; meanwhile, it provided an effective reinforcing effect on the overall mechanical strength. More importantly, the corrosion resistance of these layers was ranked in the order: MAO coating > NC layer > CG matrix. This kind of gradually increasing corrosion rate of the three layers with depth renders the two-step treatment a promising approach to design Mg-based implants possessing controllable degradation rates.

Nanoscale-Textured Tantalum Surfaces for Mammalian Cell Alignment

Tantalum is one of the most important biomaterials used for surgical implant devices. However, little knowledge exists about how nanoscale-textured tantalum surfaces affect cell morphology. Mammalian (Vero) cell morphology on tantalum-coated comb structures was studied using high-resolution scanning electron microscopy and fluorescence microscopy. These structures contained parallel lines and trenches with equal widths in the range of 0.18 to 100 μm. Results showed that as much as 77% of adherent cell nuclei oriented within 10° of the line axes when deposited on comb structures with widths smaller than 10 μm. However, less than 20% of cells exhibited the same alignment performance on blanket tantalum films or structures with line widths larger than 50 μm. Two types of line-width-dependent cell morphology were observed. When line widths were smaller than 0.5 μm, nanometer-scale pseudopodia bridged across trench gaps without contacting the bottom surfaces. In contrast, pseudopodia structures covered the entire trench sidewalls and the trench bottom surfaces of comb structures with line-widths larger than 0.5 μm. Furthermore, results showed that when a single cell simultaneously adhered to multiple surface structures, the portion of the cell contacting each surface reflected the type of morphology observed for cells individually contacting the surfaces.

Pattern-Dependent Mammalian Cell (Vero) Morphology on Tantalum/Silicon Oxide 3D Nanocomposites

The primary goal of this work was to investigate the resulting morphology of a mammalian cell deposited on three-dimensional nanocomposites constructed of tantalum and silicon oxide. Vero cells were used as a model. The nanocomposite materials contained comb structures with equal-width trenches and lines. High-resolution scanning electron microscopy and fluorescence microscopy were used to image the alignment and elongation of cells. Cells were sensitive to the trench widths, and their observed behavior could be separated into three different regimes corresponding to different spreading mechanism. Cells on fine structures (trench widths of 0.21 to 0.5 μm) formed bridges across trench openings. On larger trenches (from 1 to 10 μm), cells formed a conformal layer matching the surface topographical features. When the trenches were larger than 10 μm, the majority of cells spread like those on blanket tantalum films; however, a significant proportion adhered to the trench sidewalls or bottom corner junctions. Pseudopodia extending from the bulk of the cell were readily observed in this work and a minimum effective diameter of ~50 nm was determined for stable adhesion to a tantalum surface. This sized structure is consistent with the ability of pseudopodia to accommodate ~4–6 integrin molecules.

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.

Enhanced Mechanical and Biological Performance of an Extremely Fine Nanograined 316L Stainless Steel Cell-Substrate Interface Fabricated by Ultrasonic Shot Peening

An extremely fine nanograined (NG) rough surface with the average grain size of 10 nm was successfully fabricated on 316L stainless steel (316L SS), which is a commonly used bioimplant metallic materials, via a simple physical therapy, namely, ultrasonic shot peening (USP). This extremely fine NG rough surface was proposed as the cell-substrate interface to enhance the mechanical and biological performance of 316L SS in orthopedic applications. Nanoindentation and micropillar compression tests indicated the significant improvement of the nanohardness and yield strength of the developed NG-316L SS, respectively, and the "in vitro" studies demonstrated that the developed extremely fine NG-316L SS rough surface could significantly enhance the attachment of the human osteoblast cells (Saos-2) compared with the as-received coarse-grained 316L SS surface. The observed mechanical and biological enhancement of the extremely fine NG-316L SS surface can be attributed to the ultrahigh-density nanosized grain boundaries, which could obstruct dislocation movement when the materials undergo plastic deformation and promote protein adsorption by providing a continuum of probable binding sites with partial surface coverage when the material encounters biological environments. In addition, aggregated protein particles were clearly observed on the proposed extremely fine NG-316L SS surface when it was used for the substrate of the human osteoblast cells. The findings and the advanced surface engineering technology utilized in this paper could promote the currently proposed concept that using nanograined/ultrafine grained cell-substrate interface for mechanical and biological enhancement of bioimplant materials from the current practice level of "hundreds of nanometers" to that of "tens of nanometers" or possibly even "several nanometers".

Electrochemical Impedance and Polarization Corrosion Studies of Tantalum Surface Modified by DC Plasma Electrolytic Oxidation

Tantalum has recently become an actively researched biomaterial for the bone reconstruction applications because of its excellent corrosion resistance and successful clinical records. However, a bare Ta surface is not capable of directly bonding to the bone upon implantation and requires some method of bioactivation. In this study, this was realized by direct current (DC) plasma electrolytic oxidation (PEO). Susceptibility to corrosion is a major factor determining the service-life of an implant. Therefore, herein, the corrosion resistance of the PEO coatings on Ta was investigated in Ringer’s solution. The coatings were formed by galvanostatic anodization up to 200, 300 and 400 V, after which the treatment was conducted potentiostatically until the total process time amounted to 5 min. Three solutions containing Ca(H₂PO₂)₂, Ca(HCOO)₂ and Mg(CH₃COO)₂ were used in the treatment. For the corrosion characterization, electrochemical impedance spectroscopy and potentiodynamic polarization techniques were chosen. The coatings showed the best corrosion resistance at voltages low enough so that the intensive sparking was absent, which resulted in the formation of thin films. The impedance data were fitted to the equivalent electrical circuits with two time constants, namely R(Q[R(QR)]) and R(Q[R(Q[RW])]). The inclusion of W in the circuit helped to fit the low-frequency part of the samples PEO-ed at 400 V, hinting at the important role of diffusion in the corrosion resistance of the PEO coatings described in the research.

Coating of Sandblasted and Acid-Etched Dental Implants With Tantalum Using Vacuum Plasma Spraying

PURPOSE

The objective was to prepare tantalum (Ta)-coated sandblasted and acid-etched (SLA) dental implants using vacuum plasma spraying (VPS) and to analyze their morphologies.

MATERIALS AND METHODS

Twelve SLA implants were coated with Ta using VPS. The topographies of the coatings and Ta/SLA surface interfaces were examined using scanning electron microscopy. The thickness at 4 locations for 6 Ta-coated and 6 uncoated SLA implants and pore sizes of the neck, central, and root areas of Ta-coated implants were measured. SPSS v20.0 was used for statistical analysis.

RESULTS

The Ta coatings were rough and consisted of pitted structures with various pore sizes; no cracks were observed. The Ta/SLA surface interface was tightly bonded. The 95% confidence interval of the Ta coating thickness was (114.0759, 129.3574). The maximal pore diameter was concentrated at 200 to 400 nm.

CONCLUSION

SLA dental implants were successfully coated with Ta using VPS. The nanoporous structure of these implants may facilitate osseointegration compared with uncoated SLA implants.

Involvement of autophagy in tantalum nanoparticle-induced osteoblast proliferation

Porous tantalum (Ta) implants are highly corrosion resistant and biocompatible, and they possess significantly better initial stability than that of conventional titanium (Ti) implants. During loading wear, Ta nanoparticles (Ta-NPs) that were deposited on the surface of a porous Ta implant are inevitably released and come into direct contact with peri-implant osteoblasts. The wear debris may influence cell behavior and implant stabilization. However, the interaction of Ta-NPs with osteoblasts has not been clearly investigated. This study aimed to investigate the effect of Ta-NPs on cell proliferation and their underlying mechanism. The Cell Counting Kit-8 (CCK-8) assay was used to measure the cell viability of MC3T3-E1 mouse osteoblasts and showed that Ta-NP treatment could increase cell viability. Then, confocal microscopy, Western blotting, and transmission electron microscopy were used to confirm the autophagy induced by Ta-NPs, and evidence of autophagy induction was observed as positive LC3 puncta, high-LC3-II expression, and autophagic vesicle ultrastructures. The CCK-8 assay revealed that the cell viability was further increased and decreased by the application of an autophagy inducer and inhibitor, respectively. In addition, pre-treatment with autophagy inhibitor 3-methyladenine (3-MA) inhibited the Ta-NP-induced autophagy. These results indicate that the Ta-NPs can promote cell proliferation, that an autophagy inducer can further strengthen this effect and that an autophagy inhibitor can weaken this effect. In conclusion, autophagy was involved in Ta-NP-induced cell proliferation and had a promoting effect.