Preparation of tantalum-containing coatings on NiTi shape memory alloys with enhanced in vitro cytocompatibility and antibacterial effectiveness

In this work, the magnetron sputtering method is used to deposit tantalum-containing coatings on NiTi shape memory alloys under various sputtering atmospheres including (i) 100% argon, (ii) 16.6% oxygen and 83.4% argon, and (iii) 16.6% nitrogen and 83.4% argon. This research examines how the sputtering atmosphere can impact surface morphology, roughness, wettability, biocompatibility, in vitro cytocompatibility, and antibacterial performance of tantalum-containing coatings. The calculation of nickel ions release by coupled inductively coupled plasma-optical emission spectrometry displayed that none of the coated samples showed any traces of nickel, unlike the bare NiTi substrate. This has led to an improvement in biocompatibility. Topographical measurements demonstrated the formation of a smooth surface under the argon-oxygen atmosphere, whereas the deposited layer in the argon-nitrogen atmosphere exhibited irregular ups and downs. The coatings deposited under the argon-nitrogen atmosphere result in a hydrophobic surface with many hills and valleys which can considerably enhance protein and cellular absorption. Besides, the samples coated under an argon-oxygen atmosphere with a smooth surface exhibited excellent antibacterial efficiency only as early as 6 h of incubation. This is probably due to the formation of amorphous tantalum pentoxide

Synthesis and Characterization of Nano-Hydroxyapatite/mPEG-b-PCL Composite Coating on Nitinol Alloy

In this study the bioactivity of hydroxyapatite/poly(ε-caprolactone)–poly(ethylene glycol) bilayer coatings on Nitinol superelastic alloy was investigated. The surface of Nitinol alloy was activated by a thermo-chemical treatment and hydroxyapatite coating was electrodeposited on the alloy, followed by applying the polymer coating. The surface morphology of coatings was studied using FE-SEM and SEM. The data revealed that the hydroxyapatite coating is composed of one-dimensional nano sized flakes and the polymer coating is uniformly covered the sublayer. Also, High resolution TEM studies on the hydroxyapatite samples revealed that each flake contains nano-crystalline grains with a diameter of about 15 nm. The hydroxyapatite monolayer coating was rapidly covered by calcium phosphate crystals (Ca/P=1.7) after immersion in simulated body fluid confirming the bioactivity of the nanostructured flakes. However, the flakes were weak against applied external forces because of their ultra-fine thickness. Scratch test was applied on hydroxyapatite/polymer coating to evaluate delamination of the coating from substrate. It was shown that, the polymer coating has a great influence on toughening the hydroxyapatite coating. To assess the degradation effect of the polymer layer on hydroxyapatite coating, samples were immersed in phosphate-buffered saline at 37 ᵒC. SEM studies on the samples revealed that the beneath layer of hydroxyapatite appears after 72 h without any visible change in morphology. It seems that, application of a biodegradable polymer film on the nanostructured hydroxyapatite coating is a good way to support the coating during implantation processe

Effect of sputtering rate on morphological alterations, corrosion resistance, and endothelial biocompatibility by deposited tantalum oxide coatings on NiTi using magnetron sputtering technique

The Magnetron sputtering method was utilized to apply tantalum-oxide coatings on NiTi shape memory alloys, and this was done under 16.6 vol% oxygen, 83.4 vol% argon atmospheres at a substrate temperature of 300 °C. In the present article, the influence of sputtering rate on surface morphology, roughness, corrosion behavior, and biological response of tantalum oxide coatings has been investigated via FESEM, AFM, potentiodynamic polarization method, and MTT assay, respectively. FESEM studies demonstrated the positive effect of sputtering rate on forming a uniform and dense layer under 0.8 Å s−1 sputtering rate. GI-XRD patterns depicted amorphous coatings in all samples, meaning 300 °C was not sufficient for the formation of crystallized TaxOy. The XPS results revealed that stoichiometric tantalum pentoxide formed at the top of the layer under 0.8 Å s−1 sputtering rate as there was enough oxygen to support the reaction. AFM 3D images of surface topographies suggested that all coatings possessed almost similar roughness values, but their line graphs showed irregular peaks and valleys for lower and higher sputtering rates. Electrochemical measurements indicated the expected results of supremacy in corrosion resistance for the sample sputtered under 0.8 Å s−1 with the most uniform morphology. Finally, the biocompatibility of the coatings was studied using specific human endothelial cells (HUVECs) to evaluate their potential for vascular applications. Unlike other results, the sample, which sputtered at the highest rate with lots of hills and valleys, showed the greatest cell viability and cellular activity on its surface

Progress in Niobium Oxide-Containing Coatings for Biomedical Applications: A Critical Review

: Typically, pure niobium oxide coatings are deposited on metallic substrates, such as commercially pure Ti, Ti6Al4 V alloys, stainless steels, niobium, TiNb alloy, and Mg alloys using techniques such as sputter deposition, sol-gel deposition, anodizing, and wet plasma electrolytic oxidation. The relative advantages and limitations of these coating techniques are considered, with particular emphasis on biomedical applications. The properties of a wide range of pure and modified niobium oxide coatings are illustrated, including their thickness, morphology, microstructure, elemental composition, phase composition, surface roughness and hardness. The corrosion resistance, tribological characteristics and cell viability/proliferation of the coatings are illustrated using data from electrochemical, wear resistance and biological cell culture measurements. Critical R&D needs for the development of improved future niobium oxide coatings, in the laboratory and in practice, are highlighted

Surface modified NiTi smart biomaterials: surface engineering and biological compatibility

NiTi metallic biomaterials have a broad spectrum of clinical applications from heart stents to orthopedic implants. Recently, the use of NiTi smart biomaterials has received growing attention due to their striking features, including a low elastic modulus, shape memory behavior and acceptable biocompatibility. However, leaching of Ni ions from the surface of NiTi, the need for decreased elastic modulus and the desire for improved biological properties, including better material-cell interactions, biomineralization, and antibacterial activity, have provided the driving force for a wide variety of surface-modification techniques to address these problems before using NiTi in vivo. Depending on the target application, both dry and wet coating techniques have been employed to deposit biocompatible and bioactive layers over NiTi smart biomaterials. The influence of such coatings on the biological characteristics of the NiTi is illustrated. R&D activities have proved fruitful but much work needs to be done before clinical use of coated-NiTi

Additive Manufacturing: An Opportunity for the Fabrication of Near-Net-Shape NiTi Implants

Nickel–titanium (NiTi) is a shape-memory alloy, a type of material whose name is derived from its ability to recover its original shape upon heating to a certain temperature. NiTi falls under the umbrella of metallic materials, offering high superelasticity, acceptable corrosion resistance, a relatively low elastic modulus, and desirable biocompatibility. There are several challenges regarding the processing and machinability of NiTi, originating from its high ductility and reactivity. Additive manufacturing (AM), commonly known as 3D printing, is a promising candidate for solving problems in the fabrication of near-net-shape NiTi biomaterials with controlled porosity. Powder-bed fusion and directed energy deposition are AM approaches employed to produce synthetic NiTi implants. A short summary of the principles and the pros and cons of these approaches is provided. The influence of the operating parameters, which can change the microstructural features, including the porosity content and orientation of the crystals, on the mechanical properties is addressed. Surface-modification techniques are recommended for suppressing the Ni ion leaching from the surface of AM-fabricated NiTi, which is a technical challenge faced by the long-term in vivo application of NiTi

Enhanced in vitro immersion behavior and antibacterial activity of NiTi orthopedic biomaterial by HAp-Nb2O5 composite deposits

Abstract NiTi is a class of metallic biomaterials, benefit from superelastic behavior, high biocompatibility, and favorable mechanical properties close to that of bone. However, the Ni ion leaching, poor bioactivity, and antibacterial activity limit its clinical applications. In this study, HAp-Nb2O5 composite layers were PC electrodeposited from aqueous electrolytes containing different concentrations of the Nb2O5 particles, i.e., 0–1 g/L, to evaluate the influence of the applied surface engineering strategy on in vitro immersion behavior, Ni2+ ion leaching level, and antibacterial activity of the bare NiTi. Surface characteristics of the electrodeposited layers were analyzed using SEM, TEM, XPS, and AFM. The immersion behavior of the samples was comprehensively investigated through SBF and long-term PBS soaking. Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus) infective reference bacteria were employed to address the antibacterial activity of the samples. The results illustrated that the included particles led to more compact and smoother layers. Unlike bare NiTi, composite layers stimulated apatite formation upon immersion in both SBF and PBS media. The concentration of the released Ni2+ ion from the composite layer, containing 0.50 g/L Nb2O5 was ≈ 60% less than that of bare NiTi within 30 days of immersion in the corrosive PBS solution. The Nb2O5-reinforced layers exhibited high anti-adhesive activity against both types of pathogenic bacteria. The hybrid metallic-ceramic system comprising HAp-Nb2O5-coated NiTi offers the prospect of a potential solution for clinical challenges facing the orthopedic application of NiTi