Nitinol Surface Research Articles

Exploring the potential of laser-textured metal alloys: Fine-tuning vascular cells responses through in vitro and ex vivo analysis

Medical stents are vital for treating vascular complications and restoring blood flow in millions of patients. Despite its widespread effectiveness, restenosis, driven by the complex interplay of cellular responses, remains a concern. This study investigated the reactions of vascular cells to nano/microscale wrinkle (nano-W and micro-W) patterns created on laser-textured nitinol (NiTi) surfaces by adjusting laser processing parameters, such as spot overlap ratio and line overlap ratio. Evaluation of topographical effects on endothelial and smooth muscle cells (SMCs) revealed diverse morphologies, proliferation rates, and gene expressions. Notably, microscale wrinkle patterns exhibited reduced monocyte adhesion and inflammation-related gene expression, demonstrating their potential applications in mitigating vascular complications after stent insertion. Additionally, an ex vivo metatarsal assay was utilized to bridge the gap between in vitro and in vivo studies, demonstrating enhanced angiogenesis on laser-textured NiTi surfaces. Laser-textured NiTi exhibits a guided formation process, emphasizing their potential to promote swift endothelialization. These findings underscore the efficacy of laser texturing for tailored cellular interactions on metallic surfaces and offer valuable insights into optimizing biocompatibility and controlling cellular responses, which may pave the way for innovative advances in vascular care and contribute to the ongoing improvement of stent insertion.

Fundamental characteristics of biomimetic superhydrophobic surface of nitinol alloy fabricated via laser cauterization and FAS modification

Biomimetic superhydrophobic surfaces draw inspiration from the biological realm, seeking to replicate and refine their superhydrophobic properties. Fabricating super-hydrophobic surface on nitinol has significant application value in medicine, biomedical science, industry, and micro electric system due to the special performance of this material with super-hydrophobicity. In this study, we achieved a super-hydrophobic surface on a laser-processed rough nitinol surface through FAS modification, and its corrosion resistance in salt electrolytes was evaluated using potentiodyjnamic polarization (PDP) and electrochemical impedance spectroscopy (EIS) measurements. The resulting indicated that the fabricated super-hydrophobic surface exhibited superior corrosion resistance performance. Besides, the mechanical properties of the material were also evaluated, revealing a reduction in contact angle by 2.04 and 2.82 times as well as enhanced wear its resistance. Furthermore, the promoting mechanism of chemical and abrasion stability were systematically elucidated based on scanning electron spectroscopy (SEM-EDS), 3D optical profiling, and X-ray photoelectron spectroscopy (XPS). These findings are anticipated to provide a deeper understanding of the fabrication of super-hydrophobic surfaces on nitinol alloys, thereby strengthening their potential for practical industrial and biomedical applications.

Mitigation of bio-corrosion characteristics of coronary artery stent by optimising fs-laser micromachining parameters

Cardiovascular diseases, particularly coronary artery disease, pose big challenges to human life. Deployment of the stent is a preferable treatment for the above-mentioned disease. However, stents are usually made up of shape memory alloy called Nitinol. The poorer surface finish on the machined nitinol stents accelerates the migration of Nickel ions from the implanted nitinol stent, which is considered toxic and can lead to stenosis. The current study deals with controlling surface quality by minimising surface roughness and improving corrosion resistance. Femtosecond laser (fs-laser 10−15 s) micromachining was employed to machine the Nitinol surface to achieve sub-micron surface roughness. The Grey relational analysis (GRA)-coupled design of the experimental technique was implemented to determine optimal levels of four micromachining parameters (laser power, pulse frequency, scanning speed, and scanning pattern) varied at three levels to achieve minimum surface roughness and to maximise the volume ablation. The results show that to yield minimum surface roughness and maximum volume ablation, laser power and scanning speed are in a higher range. In contrast, the pulse frequency is lower, and the scanning pattern is in a zig-zag manner. ANOVA results manifest that scanning speed is the predominant factor in minimising surface roughness, followed by pulse frequency. Furthermore, the corrosion behaviour of the machined nitinol specimens was evaluated, and the results show that specimens with lower surface roughness had lower corrosion rates.

Pro-endothelialization of nitinol alloy cardiovascular stents enhanced by the programmed assembly of exosomes and endothelial affinity peptide.

Stent implantation is one of the most effective methods for the treatment of atherosclerosis. Nitinol stent is a type of stent with good biocompatibility and relatively mature development; however, it cannot effectively achieve long-term anticoagulation and early endothelialization. In this study, nitinol surfaces with the programmed assembly of heparin, exosomes from endothelial cells, and endothelial affinity peptide (REDV) were fabricated through layer-by-layer assembly technology and click-chemistry, and then exosomes/REDV-modified nitinol interface (ACC-Exo-REDV) was prepared. ACC-Exo-REDV could promote the rapid proliferation and adhesion of endothelial cells and achieve anticoagulant function in the blood. Besides, ACC-Exo-REDV had excellent anti-inflammatory properties and played a positive role in the transformation of macrophage from the pro-inflammatory to anti-inflammatory phenotype. Ex vivo and in vivo experiments demonstrated the effectiveness of ACC-Exo-REDV in preventing thrombosis and hyperplasia formation. Hence, the programmed assembly of exosome interface could contribute to endothelialization and have potential application on the cardiovascular surface modification to prevent stent thrombosis and restenosis.

The effects of carbon ion implantation on wettability, abrasion, thermal and anti-corrosion stabilities of laser ablated super-hydrophobic Nitinol surface

Comparing with pure laser irradiation, the hybrid fabrication using laser ablation and chemical modification is one of the widely used techniques to obtain bio-inspired super-hydrophobic surface. Nevertheless, conventional surface chemical modification techniques have faced challenges including the detachment of micro-nano structures and the instability of super-hydrophobic surfaces. This research introduces an innovative method for creating extremely stable super-hydrophobic surfaces on NiTi alloy through a combination of laser exposure, carbon ion implantation, and modification with fluoroalkylsilane (FAS). Surface morphology and chemical component were systematically investigated to reveal the formation mechanism of super-hydrophobicity. Besides, its abrasion stability, thermal stability and corrosion resistance stability of this kind of super-hydrophobic surface were also investigated. And the corresponding stability improvement mechanisms were further revealed.

Corrigendum to “The effect of high temperature annealing on surface wettability, mechanical and chemical properties of laser ablated nitinol surface” [Opt. Laser Technol. 161 (2023) 109108

Corrigendum to “The effect of high temperature annealing on surface wettability, mechanical and chemical properties of laser ablated nitinol surface” [Opt. Laser Technol. 161 (2023) 109108

Nanodiamond Decorated PEO Oxide Coatings on NiTi Alloy.

Cardiovascular diseases (CVDs) remain a leading cause of death in the European population, primarily attributed to atherosclerosis and subsequent complications. Although statin drugs effectively prevent atherosclerosis, they fail to reduce plaque size and vascular stenosis. Bare metal stents (BMS) have shown promise in acute coronary disease treatment but are associated with restenosis in the stent. Drug-eluting stents (DES) have improved restenosis rates but present long-term complications. To overcome these limitations, nanomaterial-based modifications of the stent surfaces have been explored. This study focuses on the incorporation of detonation nanodiamonds (NDs) into a plasma electrolytic oxidation (PEO) coating on nitinol stents to enhance their performance. The functionalized ND showed a high surface-to-volume ratio and was incorporated into the oxide layer to mimic high-density lipoproteins (HDL) for reverse cholesterol transport (RCT). We provide substantial characterization of DND, including stability in two media (acetone and water), Fourier transmission infrared spectroscopy, and nanoparticle tracking analysis. The characterization of the modified ND revealed successful functionalization and adequate suspension stability. Scanning electron microscopy with EDX demonstrated successful incorporation of DND into the ceramic layer, but the formation of a porous surface is possible only in the high-voltage PEO. The biological assessment demonstrated the biocompatibility of the decorated nitinol surface with enhanced cell adhesion and proliferation. This study presents a novel approach to improving the performance of nitinol stents using ND-based surface modifications, providing a promising avenue for cardiovascular disease.

Parametric investigation of pulse frequency and microtool rotational speed for precise fabrication of microchannels on nitinol shape memory alloy through ECMM

Nitinol, a material with a unique combination of properties like shape memory effect, superelasticity, and biocompatibility, has become popular in the biomedical and micro-electro-mechanical systems (MEMS) industries. Electrochemical micromachining (ECMM) has emerged as an excellent method for micromachining Nitinol shape memory alloy (SMA) due to its ability to provide superior surface integrity and absence of any thermal effect. This study aimed at improving the surface integrity and the accuracy of the microfeatures on Nitinol fabricated through the ECMM process. The effects of process parameters like pulse frequency and microtool’s rotational speed on the diametral overcut of the microfeature were investigated at different inter-electrode gaps. The findings revealed that at 1 MHz pulse frequency and 500 rpm microtool rotating speed, the diametral overcut ranged from 0.163 µm at interelectrode gap (IEG) of 5 µm to 1.626 µm at IEG of 1 µm, indicating a precise microfeature fabrication. At the same parametric combination, the machined depth varied from 2.89 µm at IEG of 5 µm to 5.56 µm at IEG of 1 µm, suggesting a proportionate change in depth of the microfeature. Moreover, precise microchannels with average surface roughness values of 17.5 nm, 9.5 nm, and 12.4 nm were fabricated on the Nitinol surface at pulse frequencies of 1 MHz, 2 MHz, and 3 MHz, respectively.

The effect of high temperature annealing on surface wettability, mechanical and chemical properties of laser ablated nitinol surface

Nitinol shape memory alloys are widely used in medical devices due to their special properties. However, the release of nickel ions into human liquid during corrosion process would cause great harm to human body. It has been found that super-hydrophobic surface with superior anti-corrosion performance could greatly solve this issue. Therefore, the preparation of green and healthy super-hydrophobic layer on nickel-titanium alloy surface has significant medical value. In this work, we explored a newly method of fabricating healthy super-hydrophobic surface with contact angle (WCA) of 153.2° ± 1.5°, and roll angle (RA) of 6° ± 0.5°by combination of nitinol alloy laser irradiation. Particularly, high temperature annealing was firstly adopted in the fabrication procession of super-hydrophobic surface, which can bring great reference value to the research in this filed. Besides, the formation mechanism was also revealed via the analysis of scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). Furthermore, corrosion behavior was also investigated by electrochemical impedance (EIS) analysis to illustrate preventing nickel ions release performance. Unlike the traditional super-hydrophobic surface preparation methods, this method does not introduce any toxic substances, which has great application prospects in the medical field.

Performance of a Hydrogel Coated Nitinol with Oligonucleotide-Modified Nanoparticles Within Turbulent Conditions of Blood-Contacting Devices.

Hydrogels offer a wide range of applications in the antithrombotic modification of biomedical devices. The functionalization of these hydrogels with potentially drug-laden nanoparticles in the context of deviceassociated turbulence is critically under-studied. Thus, the purpose of this study was to use a hydrogel-coating nitinol surface as a model to understand the functions of hydrogels and the capture of nanoparticles under clinically relevant flow conditions. Nitinol was coated by an oligonucleotide (ON) functionalized hydrogel. Nanoparticles were functionalized with complementary oligonucleotides (CONs). The capture of CONfunctionalized nanoparticles by the ON-functionalized hydrogel surfaces was studied under both static and dynamic attachment conditions. Fluorescent-labelling of nanoparticles was utilized to assess capture efficacy and resistance to removal by device-relevant flow conditions. The specificity of the ON-CON bond was verified, exhibiting a dose-dependent attachment response. The hydrogel coating was resistant to stripping by flow, retaining >95% after exposure to one hour of turbulent flow. Attachment of nanoparticles to the hydrogel was higher in the static condition than under laminar flow (p < 0.01), but comparable to that of attachment under turbulent flow. Modified nitinol samples underwent one hour of flow treatment under both laminar and turbulent regimes and demonstrated decreased nanoparticle loss following static conjugation rather than turbulent conjugation (36.1% vs 53.8%, p < 0.05). There was no significant difference in nanoparticle functionalization by upstream injection between laminar and turbulent flow. The results demonstrate promising potential of hydrogelfunctionalized nitinol for capturing nanoparticles using nucleic acid hybridization. The hydrogel structure and ONCON bond integrity both demonstrated a resistance to mechanical damage and loss of biomolecular functionalization by exposure to turbulence. Further investigation is warranted to highlight drug delivery and antithrombogenic modification applications of nanoparticle-functionalized hydrogels.

Catechol-functionalized sulfobetaine polymer for uniform zwitterionization via pH transition approach

The study aims to develop a modification strategy to facilitate uniform catechol-assisted zwitterionization on nitinol alloy for bio-compatibility and fouling resistance. Catechol-functionalized polysulfobetaine methacrylate (pSBMA/DA) is synthesized via dopamine-initiated photo-polymerization. Under UV irradiation, semiquinone radicals from dopamine (DA) can be generated, and prevented loss of one electron to intramolecular cyclization and intermolecular dimerization in a solution at pH 2. Pseudo-first-order polymerization kinetics, and relations of apparent rate constant and number average molecular weight with the molar ratio of DA in photopolymerization for pSBMA/DA are unveiled. In a solution at pH 3, PSBMA/DA begins aggregation, kept catechol moieties from premature oxidization, and enabled even deposition on the nitinol substrate. After pH regulation to 8.5, pSBMA/DA extends, and concurrently catechol moieties are activated to interact with the nitinol surface via the formation of bidentate binding. X-ray photoelectron spectroscopy (XPS) analysis revealed that a shorter pSBMA/DA chain with higher catechol content provides more anchoring sites to enhance zwitterionic moieties coverage on substrates. Interestingly, atomic force microscopy (AFM) images revealed a smooth and uniform deposition of pSBMA/DA using the pH-transition method. Strong ionic hydration of pSBMA/DA coating on nitinol surface repels non-specific adsorption of bio-foulants, permitting excellent antifouling properties. Zwitterion-modified nitinol achieved a reduction rate of 99.9% against Escherichia coli and Staphylococcus aureus attachment. In addition, pSBMA/DA exhibits a robust antifouling performance to NIH 3T3 mouse fibroblasts in culture media after incubation for 24 h. Overall, the pSBMA/DA coating via pH transition approach opens up a promising strategy to facilitate uniform surface functionalization for antifouling and coating technology.

Structure, biocompatibility and corrosion resistance of the ceramic-metal surface of porous nitinol

One of the key aspects of the biochemical compatibility of medical alloys is the surface corrosion resistance in living organisms. This study discusses the structure of the ceramic-metal surface layer of a porous nickel-titanium alloy (nitinol) and the corrosion resistance in simulated physiological liquids. The structure of the protective layer and glass-ceramic non-metallic inclusions in the surface of the porous alloy have been studied. The formation of the surface ceramic-metal layer and crystallization of various glass-metal-ceramic phases as a result of chemisorption from reaction gases and epitaxial growth from the gas phase during the self-propagating high-temperature synthesis are observed.

Effect of Nitinol surface with nanotubes and/or ordered nanopores on cell behavior

AbstractRecent medical applications have specific requirements on materials and Nitinol can fulfill them due to its exceptional characteristics, which can be further improved by modifications of the material surface. Various surface nanostructuring methods are utilized to enhance characteristics of oxide layer, which naturally develops on the Nitinol surface, leading to improved biocompatibility and corrosion resistance. This review is focused on studies investigating the behavior of various cell types on surface nanotubes and ordered nanopores prepared by anodic oxidation, a technique allowing fabrication of nanostructures with defined parameters. Results showed that certain dimensions of nanotubes positively affect adhesion and viability of osteoblasts and endothelial cells on the surface, contrary to negative effect on smooth muscle cells, both required by the medical applications. Furthermore, increased antibacterial effect correlated with the nanostructure topography and release rates of Ni ions.

Identification of damage associated molecular patterns and extracellular matrix proteins as major constituents of the surface proteome of lung implantable silicone/nitinol devices

Lung implantable devices have been widely adopted as mechanical interventions for a wide variety of pulmonary pathologies. Despite successful initial treatment, long-term efficacy can often be impacted by fibrotic or granulation tissue formation at the implant sites. This study aimed to explore the lung-device interface by identifying the adhered proteome on lung devices explanted from patients with severe emphysema. In this study, scanning electron microscopy is used to visualize the adhesion of cells and proteins to silicone and nitinol surfaces of explanted endobronchial valves. By applying high-resolution mass-spectrometry, the surface proteome of eight explanted valves is characterized, identifying 263 unique protein species to be mutually adsorbed on the valves. This subset is subjected to gene enrichment analysis, matched with known databases and further validated using immunohistochemistry. Enrichment analyses reveal dominant clusters of functionally-related ontology terms associated with coagulation, pattern recognition receptor signaling, immune responses, cytoskeleton organization, cell adhesion and migration. Matching results show that extracellular matrix proteins and damage-associated molecular patterns are cardinal in the formation of the surface proteome. This is the first study investigating the composition of the adhered proteome on explanted lung devices, setting the groundwork for hypothesis generation and further exploration. Statement of significanceThis is the first study investigating the composition of the adhered proteome on explanted lung devices. Lung implantable devices have been widely adopted as mechanical interventions for pulmonary pathologies. Despite successful initial treatment, long-term efficacy can often be impacted by fibrotic or granulation tissue formation around the implant sites. We identified the adhered proteome on explanted lung devices using several techniques. We identified 263 unique protein species to be mutually adsorbed on explanted lung devices. Pathway analyses revealed that these proteins are associated with coagulation, pattern recognition receptor signaling, immune responses, cytoskeleton organization, cell adhesion and migration. Furthermore, we identified that especially extracellular matrix proteins and damage-associated molecular patterns were cardinal in the formation of the surface proteome.

The Effect of High Temperature Annealing on Surface Wettability, Mechanical and Chemical Properties of Laser Ablated Nitinol Surface

The Effect of High Temperature Annealing on Surface Wettability, Mechanical and Chemical Properties of Laser Ablated Nitinol Surface

Biological Property Investigation of Nitinol Surface Implanted with Tantalum

Biological Property Investigation of Nitinol Surface Implanted with Tantalum

Reduced thrombogenicity of surface-treated Nitinol implants steered by altered protein adsorption

Blood-contacting medical implants made of Nitinol and other titanium alloys, such as neurovascular flow diverters and peripheral stents, have the disadvantage of being highly thrombogenic. This makes the use of systemic (dual) anti-platelet/anticoagulant therapies inevitable with related risks of device thrombosis, bleeding and other complications. Meeting the urgent clinical demand for a less thrombogenic Nitinol surface, we describe here a simple treatment of standard, commercially available Nitinol that renders its surface ultra-hydrophilic and functionalized with phosphate ions. The efficacy of this treatment was assessed by comparing standard and surface-treated Nitinol disks and braids, equivalent to flow diverters. Static and dynamic (Chandler loop) blood incubation tests showed a drastic reduction of thrombus formation on treated devices. Surface chemistry and proteomic analysis indicated a key role of phosphate and calcium ions in steering blood protein adsorption and avoiding coagulation cascade activation and platelet adhesion. A good endothelialization of the surface confirmed the biocompatibility of the treated surface. STATEMENT OF SIGNIFICANCE: Titanium alloys such as Nitinol are biocompatible and show favorable mechanical properties, which led to their widespread use in medical implants. However, in contact with blood their surface triggers the activation of the intrinsic coagulation cascade, which may result in catastrophic thrombotic events. The presented results showed that a phosphate functionalization of the titanium oxide surface suppresses the activation of both coagulation cascade and platelets, avoiding the subsequent formation of a blood clot. This novel approach has therefore a great potential for mitigating the risks associated to either thrombosis or bleeding complications (due to systemic anticoagulation) in patients with cardiovascular implants.

Improvement corrosion resistance of Ni-Ti alloy by TiO2 coating and hydroxyaptite/TiO2 composite coating using micro arc oxidation process

Titanium oxide ceramic coatings were prepared by micro-arc oxidation (MAO) in galvanostatic regime on biomedical NiTi alloy produce via powder metallurgy, also the composite coating of HA/TiO2 was prepared on the surface of nitinol using a one-step micro-arc oxidation (MAO), the process time for each case at 280 V was 30 min. The surface of TiO2 coating exhibited a typical porous and rough structure. In this study, the hydroxyapatite, Ca–P precipitate it assisted to close the porous and the morphology of the surface coating showed a flower-like structure owing to the incidence of self-assembly because of the longtime of precipitate. Surface characterization of the coatings was determined utilizing SEM, XRD, and AFM. The surface morphology, topography and coating thickness were determined as well. In this study, the properties of corrosion were studied utilizing potentiostat test unit in Ringer's solution. Based on the results, the corrosion properties of NiTi alloys considerably improved due to the existence of TiO2 and HA/TiO2 coatings.

Physicochemical and biological characteristics of chitosan/κ-carrageenan thin layer-by-layer films for surface modification of nitinol

Thin films based on the natural polysaccharides κ-carrageenan (Carr) and chitosan (Chit) were formed by layer-by-layer deposition technique. Surface topography and mechanical characteristics (Young's modulus, adhesion strength) of the polymer films with different number of layers were determined using various modes of atomic force microscopy (AFM). Polymer films were used to deposit on the surface of nitinol (NiTi) plates. The creation of polysaccharide coatings on nitinol led to a change in surface properties, such as hydrophilicity and root mean square roughness. in vitro cytotoxicity assay for nitinol plates with and without polymer coating by the MG-63 osteoblast-like cell line was conducted and was shown that all the studied samples are not toxic. A decrease in cytotoxicity for samples with a polymer film consisting of 4 layers of chitosan and carrageenan was shown as compared to an uncoated nitinol plates.

A scanning electrochemical microscopy characterization of the localized corrosion reactions occurring on nitinol in saline solution after anodic polarization

Scanning electrochemical microscopy (SECM) in a combined amperometric/potentiometric operation was used to characterize the electrochemical activity of nitinol, before and after anodic treatment, in 0.1 M NaCl solution. The SECM operation in the feedback mode showed that the nitinol surface was homogeneously passive after surface finishing and storage under ambient conditions, while heterogeneous surface characteristics occurred after application of anodic polarization, even for a limited time. That is, the development of anodic and cathodic sites has been detected due to the onset of localized corrosion processes on the metal surface. The evolution of hydrogen gas from localized sites was monitored using SECM in the substrate generation/tip collection mode (SG/TC), while SECM operated in potentiometric mode was used to map the pH distribution in the electrolyte volume adjacent to the nitinol surface. Local acidification was observed around anodic spots associated with the Ni2+ discharge, as well as alkalinization above the cathodic zones.