Effects of oxygen adsorption on the corrosion behavior of the Ti(0001) surface: a DFT investigation.

The electrochemical corrosion of Ti surfaces is significantly affected by O adsorption, yet the underlying mechanisms remain unexplored. Herein, density functional theory calculations are employed to examine the adsorption energies, structural properties, electronic structures, and thermodynamic stability of atomic O on Ti(0001) surfaces during initial oxidation. Additionally, the impact of O adsorption on Ti dissolution is assessed by introducing a Ti vacancy on the Ti(0001) surface. The passivation of the Ti(0001) surface is predominantly ascribed to the robust adsorption of O atoms. The thermodynamic results reveal that bulk TiO2 easily forms at 300 K, which explains the spontaneous passivation of the Ti(0001) surface. The formation of an O monolayer on the Ti(0001) surface increases the work function (Φ), positively shifting the equilibrium potential and reducing the corrosion rate. The surface vacancy formation energy of Ti on the Ti(0001)/O surface surpasses that on the clean surface. The electrode potential shift for a Ti atom dissolving from the Ti(0001)/O surface is positive, indicating that oxidation impedes the formation of Ti vacancies, rendering Ti atoms less soluble. This study enhances our comprehension of the corrosion mechanism in Ti metal.

DFT investigation of the dissolution trends of NiTi alloys with the B2 and B19' phases during the initial oxidation stage.

The selective corrosion of NiTi alloys was studied using density functional theory calculations, and the dissolution trends of the NiTi-B2 and NiTi-B19' phases in the initial oxidation stage were compared to predict their corrosion difference. The dissolution process of Ni and Ti was simulated by creating Ni or Ti vacancies on the unoxidized and oxidized NiTi alloy surfaces. The results show that the surface vacancy formation energy of Ti vacancies is higher than that of Ni vacancies, indicating that Ti is more difficult to dissolve than Ni. Furthermore, oxidation promotes and impedes the dissolution of Ni and Ti, respectively. This study improves the fundamental understanding of the corrosion mechanism of NiTi alloys.

A novel near-infrared polymethine dye biosensor for rapid and selective detection of lithocholic acid.

Lithocholic acid (LCA), a secondary bile acid, has emerged as a potential early diagnostic biomarker for various liver diseases. In this study, we introduce a novel near-infrared (NIR) polymethine dye-based biosensor, capable of sensitive and selective detection of LCA in phosphate buffer and artificial urine (AU) solutions. The detection mechanism relies on the formation of J-aggregates resulting from the interplay of 3,3-Diethylthiatricarbocyanine iodide (DiSC2(7)) dye molecules and LCA, which induces a distinctive red shift in both absorption and fluorescence spectra. The biosensor demonstrates a detection limit for LCA of 70 µM in PBS solution (pH 7.4), while in AU solution, it responds to an LCA concentration as low as ∼60 µM. Notably, the proposed biosensor exhibits outstanding selectivity for LCA, effectively distinguishing it from common interferents such as uric acid, ascorbic acid, and glucose. This rapid, straightforward, and cost-effective spectrometer-based method underscores its potential for early diagnosis of liver diseases by monitoring LCA concentrations.

Dealloyed nano-porous TiCu coatings with controlled copper release for cardiovascular devices.

TiCu coatings with controlled copper release and nano-porous structures were fabricated as biocompatible, blood-contacting interfaces through a two-step process. Initially, coatings with 58 % Cu were created using HiPIMS/DC magnetron co-sputtering, followed by immersion in a dilute HF solution for varying durations to achieve dealloying. The presence of Ti elements in the as-deposited TiCu coatings facilitated their dissolution upon exposure to the dilute HF solution, resulting in the formation of nanopores and increased nano-roughness. Dealloying treatment time correlated with higher Cu/(Ti + Cu) values, nanopore size, and nano-roughness in the dealloyed samples. The dealloyed TiCu coatings with 87 % Cu exhibited a controlled release of copper ions and displayed nanopores (approximately 80 nm in length and 31.0 nm in width) and nano-roughness (Ra roughness: 82 nm). These coatings demonstrated inhibited platelet adhesion and suppressed smooth muscle cell behavior, while supporting favorable endothelial cell viability and proliferation, attributed to the controlled release of copper ions and the extent of nanostructures. In contrast, the as-deposited TiCu coatings with 85 % Cu showed high copper ion release, leading to decreased viability and proliferation of endothelial cells and smooth muscle cells, as well as suppressed platelet adhesion. The TiCu coatings met medical safety standards, exhibiting hemolysis rates of <5 %. The technology presented here paves the way for the simple, controllable, and cost-effective fabrication of TiCu coatings, opening new possibilities for surface modification of cardiovascular devices such as vascular stents and inferior vena cava filters.

Metal-Driven Autoantifriction Function of Artificial Hip Joint.

The service life of an artificial hip joint is limited to 10-15 years, which is not ideal for young patients. To extend the lifespan of these prostheses, the coefficient of friction and wear resistance of metallic femoral heads must be improved. In this study, a Cu-doped titanium nitride (TiNX -Cu) film with "autoantifriction" properties is deposited on a CoCrMo alloy via magnetron sputtering. When delivered in a protein-containing lubricating medium, the Cu in TiNX -Cu quickly and consistently binds to the protein molecules in the microenvironment, resulting in the formation of a stable protein layer. The proteins adsorbed on the TiNX -Cu surface decompose into hydrocarbon fragments owing to the shear stress between the Al2 O3 /TiNX -Cu tribopair. The synergistic effect of the catalysis of Cu and shear stress between the Al2 O3 /TiNX -Cu tribopair transforms these fragments into graphite-like carbon tribofilms with an antifriction property. These tribofilms can simultaneously reduce the friction coefficient of the Al2 O3 /TiNX -Cu tribopair and enhance the wear resistance of the TiNX -Cu film. Based on these findings, it is believed that the autoantifriction film can drive the generation of antifriction tribofilms for lubricating and increasing the wear resistance of prosthetic devices, thereby prolonging their lifespan.

Diamond-like carbon films prepared by a low temperature periodic process for application in ventricular assist devices.

Due to the poor tribological properties of titanium (Ti) and its alloy Ti6Al4V (commonly used for ventricular assist devices manufacturing), diamond-like carbon (DLC) films with excellent anti-wear properties are pursued to improve the wear resistance of Ti and its alloys. Considering the effect of temperature on magnets inside pump impellers and workpiece deformation, DLC films are preferred to be prepared under low temperature. In this study, DLC films were prepared on Ti6Al4V alloys by periodic and continuous processes, and the corresponding maximum deposition temperature was 85 and 154°C, respectively. The periodic DLC films exhibited the feature of columnar structure, and the surface hillocks were less uniform than that of continuous DLC films. The periodic DLC films possessed more sp3 -bonded structures, and the accessorial sp3 -bonding mainly existed in the form of CH. Compared to continuous DLC films, the periodic DLC films had lower residual stress and better adhesion with Ti6Al4V substrates. Both DLC films could effectively reduce the friction coefficient and wear rate of Ti6Al4V alloys both in air and fetal bovine serum (FBS), and the periodic DLC films exhibited superior anti-wear properties to that of continuous DLC films in FBS. Haemocompatibility evaluation revealed that both DLC films presented similar levels of more human platelet adhesion and activation as compared with that of bare Ti6Al4V. However, both DLC films significantly prolonged plasma clotting time in comparison to bare Ti6Al4V. This study demonstrates the potential of low-temperature DLC films as wear-resistant surface modification for VADs.

Mechanical properties and electronic structure of Cu-doped tin: a first-principle study.

Metal doping is an effective method for improving the toughness of ceramic materials and reducing coating fractures. In this study, first-principle calculations based on density functional theory were performed to study the formation energy, elastic constant, and electronic structure of Cu-doped TiN. The results reveal that Cu tends to replace the Ti sites in TiN crystal cells; with an increase in Cu concentration, the formation energy of the Cu-doped TiN system decreases. This indicates that the structural stability of Cu-doped TiN decreases. From the calculated elastic constant and the Voigt-Reuss-Hill approximation, it is evident that the bulk modulus B and shear modulus G decrease as the Cu concentration increases. However, G decreases more rapidly, thus increasing the B/G ratio. According to Paugh's ratio, the increase in B/G indicates an increase in the ductility of TiN. The results of the band structure, density of states, charge density, and Mulliken bond population analysis reveal that Cu doping reduces the covalent bond strength of TiN, enhances metallicity, and reduces the structural stability of the system, enhancing the toughness of TiN. The results of this study will provide theoretical and experimental guidance for improving the toughness of TiN coatings.

[Study on immobilization of heparin on surface of Ti-O films and its antithrombogenicity].

Photoreactive heparin was synthesized by reaction of 4-azidoaniline and heparin. An organic layer was introduced on the surface of Ti-O by 3-aminopropylphosphonic acid assembling, and then the modified heparin was immobilized on the surface by UV irradiation. Water contact angle was used to characterize the hydrophilicity, quantitive assay was done by azure staining methods, and blood compatibility was evaluated by platelet adhesion experiment. Water contact angle of heparinized surface was smaller than that of Ti-O film, which indicated more hydrophilic property of heparinized surface. The surface density of heparin increased with the prolonging of irradiation time and the density was 2.1 microg/cm2 when irradiated for 300s. It showed the heparinized surface was effective in resisting platelets from adhesion and aggregation.

[Research on fibrinogen adsorption and its transformation response in hemocompatibility].

In this research,enzyme linked immunoassay (ELISA) was used to assay the fibrinogen (FIG) adsorbed on the Ti-O films and on the low temperature isotropic carbon (LTIC) films which were planted in the femoral arteries of 6 mongrel dogs for six months, respectively. The Ti-O films were planted in the dogs' left femoral arteries; the LTIC films as controls were planted in the dogs' right femoral arteries. The contents adsorbed in these two kinds of films were examined by scanning electron microscopy (SEM). The quantities of FIG adhered or denatured on the Ti-O films or LTIC films determined by ELISA, and the platelets adhered on the two kinds of films examined by SEM were of significant difference between the two groups. In the blood vessel, the amount of FIG adhered on biomaterial was related to its component and construction. FIG released electron to the biomaterial and induced the unfolding of C term of the gamma-chain of FIG, and the conjugation point and effect point were exposed. In conclusion, the biomaterial, which has the capability for resisting the electron release from FIG as well as for maintaining the invariable electric condition, will have excellent hemocompatibility.

Reactive magnetron co-sputtering of Ti-xCuO coatings: Multifunctional interfaces for blood-contacting devices.

Multifunctional interfaces that promote endothelialisation, suppress the viability of smooth muscle cells (SMCs), prevent the adhesion and activation of platelets, while demonstrating antibacterial activity are of great interest for surface engineering of blood-contacting devices. Here, we report for the first time the high-power pulsed magnetron sputtering (HPPMS)/DC magnetron sputtering (DCMS) co-sputtering of Ti-xCuO coatings that demonstrate this required multifunctionality. The Cu contents and surface chemistry of the coatings are optimized, and the critical role of copper release on the viability of endothelial cells (ECs) and SMCs, platelet adhesion, and antibacterial activities is elucidated. Rutile phase is formed for Ti-xCuO coatings with Cu atomic concentrations in the range of 1.9 to 13.7 at.%. Rutile and nanocrystalline/amorphous structures were determined for the coatings with 16.8 at.% Cu, while an amorphous phase was observed for the coating with 33.9 at.% Cu. The Ti-xCuO coatings with higher Cu contents were more susceptible to corrosion, and the release rates of Cu ions increased with increasing the Cu contents, maintaining a stable releasing state for up to 28 days. The Ti-xCuO coatings with optimum microstructure and Cu contents of 3.1 and 4.2 at.% promoted the viability and proliferation of ECs, suppressed the viability of smooth muscle cells, inhibited the platelet adhesion and activation, and showed excellent antibacterial activities. Such multifunctionality was achieved in one-pot through controlled copper ions release in the presence of titanium oxides such as TiO2 and Ti2O3 on the surface. The Ti-xCuO coatings developed through HPPMS/DCMS co-sputtering are attractive for surface modification of blood-contacting materials such as implantable cardiovascular devices.

Effective Strategy for Enhancing the Performance of Li4Ti5O12 Anodes in Lithium-Ion Batteries: Magnetron Sputtering Molybdenum Disulfide-Optimized Interface Architecture.

The interface between the current collector and active material is the primary interface of charge transfer. Herein, we designed an effective strategy to optimize the interface architecture by depositing molybdenum disulfide on the copper foil surface (Cu-MoS2) via magnetron sputtering. The Cu-MoS2 is directly used as a current collector and supports the Li4Ti5O12 anode (Cu-MoS2-LTO). Typically, after being cycled at 1 A g-1 for 300 cycles, the capacities of the Cu-LTO cell and Cu-MoS2 cell are about 114.94 and 128.35 mA h g-1, respectively, whereas the capacity of the Cu-MoS2-LTO cell is as high as 373.9 mA h g-1 with a capacity retention rate of 89.1%. The MoS2 not only optimizes the interfacial architecture but also provides an additional capacity contribution to the Cu-MoS2-LTO cell. Based on scanning electron microscopy and X-ray photoelectron spectroscopy test analysis, we propose a dual interface model. It is revealed that the molybdenum disulfide film can significantly improve the charge-transfer efficiency and uniformity of the interface, reduce internal resistance of the batteries, prevent oxidation of the copper foil, and thereby improve the chemical stability of the current collector. In addition, magnetron sputtering technology has large-scale productivity and greatly enhances the industrial application of this strategy.

Si/a-C Nanocomposites with a Multiple Buffer Structure via One-Step Magnetron Sputtering for Ultrahigh-Stability Lithium-Ion Battery Anodes.

Large volume expansion and serious pulverization of silicon are two major challenges for Si-based anode batteries. Herein, a high-mass-load (3.0 g cm-3) silicon-doped amorphous carbon (Si/a-C) nanocomposite with a hierarchical buffer structure is prepared by one-step magnetron sputtering. The uniform mixing of silicon and carbon is realized on the several-nanometer scale by cosputter deposition of silicon and carbon. The boundary of the primary particles, made up of nanocarbon and nanosilicon, and the boundary of the secondary particles aggregated by the primary particles can provide accommodation space for the volume expansion of silicon and effectively buffer the volume expansion of silicon. Meanwhile, the continuous and uniformly distributed amorphous carbon enhances the conductivity of the Si/a-C nanocomposites. Typically, the 20% Si/a-C cell shows a superior initial discharge capacity of 845.3 mAh g-1 and achieves excellent cycle performance of up to 1000 cycles (609.4 mAh g-1) at the current density of 1 A g-1. Furthermore, the 20% Si/a-C cell exhibits a high capacity of 602.8 mAh g-1 with the stable discharge/charge rate performance in several extreme conditions (-40-70 °C). In view of the validity and mass productivity of the magnetron sputtering, a potential route for the industrial preparation of the Si/a-C anode nanocomposites is therefore highlighted by this study.

Multifunctional Ti-xCu coatings for cardiovascular interfaces: Control of microstructure and surface chemistry.

Ti-xCu coatings with varied Cu contents were deposited by hybrid HiPIMS/DC magnetron co-sputtering to achieve optimum microstructures and surface chemistries for applications as multi-functional, blood-contacting interfaces. We have demonstrated that control over the chemistry and microstructure of the coatings provides interfaces that simultaneously exhibit antibacterial properties, show endothelial cell (EC) compatibility, and prevent smooth muscle cell (SMC) proliferation. Using XRD and HRTEM analyses, we identified distinct microstructures for coatings with various Cu/(Cu + Ti) atomic concentrations. The corrosion resistance was controlled by the microstructure of the Ti-xCu coatings and decreased with increases in the Cu atomic concentration. XPS and ICP-MS results provided evidence that copper ions are released from the coatings upon immersion in PBS solution. We have demonstrated that the Cu-containing phases are weak points that are attacked and corroded easily, resulting in the release of Cu ions from the coatings. The coatings with Cu/(Ti + Cu) ratios ranging from 3 to 65 at.% inhibited the viability of SMCs significantly. The optimized coating with Ti and Cu/CuTix crystals and Cu/(Ti + Cu) ratio of 16 at.% showed significant improvements in EC compatibility as well as reduced viability of SMCs, holding great promise for the surface modification of cardiovascular devices such as stents and coronary implants. The coatings with amorphous phases and Cu/(Ti + Cu) ratios of 55 and 65 at.% showed excellent antibacterial properties against Staphylococcus aureus bacteria. The coating with 55.0 at.% Cu is an encouraging material for the surface engineering of blood-contacting implant surfaces that have antibacterial properties but are not cytotoxic to SMCs.

[Study on a novel vascular stent material (titanium oxide, Ti-O) coated with albumin and heparin: is it hemocompatible with fibrinogen].

The functional hemocompatibility between fibrinogen (FIG) and a novel vascular stent material (Ti-O film fixed with albumin and heparin) was investigated as follows: (1) Preparing the new biologic material (Ti-O) film; (2) Coating albumin and heparin on the Ti-O film; (3) Testing platelets (PL) adsorption; (4) Determining FIG adhesion number by use of enzyme linked immunoassay (ELISA); (5) Implanting the films from the test group of Ti-O film and from the comparison group of stainless steel (SS) film into the left and right femoral arteries respectively in 4 dogs. It was proved that albumin and heparin were fixed on Ti-O film. After 6 months, the femoral arteries of the dogs were resected. In the test group of Ti-O film coated with albumin and heparin, few PL adhered to the coat, their form did not change, and no thrombus was found by scanning electron microscopy; the result was better than that of plain Ti-O film, and was much better than that of SS film. Ti-O maintained normal transformation condition of FIG, and no C terminal of gamma chain in FIG was revealed. As it is known whether the hemocompatibility of a biomaterial is good depends upon its adsorption of FIG, and Ti-O has excellent reaction on albumin and heparin by chemical processes. In this study, the Ti-O film coated with albumin and heparin further reduced the absorption of FIG and PL when compared against the plain Ti-O film. So the Ti-O film coated with albumin and heparin has the insistent and permanent anticoagulant character.

[The effect of surface free energy parameters of diamond-like carbon films deposited on medical polyethylene terephthalate on bacterial adhesion].

Diamond-like carbon (DLC) films were deposited by acetylene plasma immersion ion implantation-deposition (PIII-D) on biomedical polyethylene terephthalate (PET). The capacities of Staphylococcus aureus (SA), Staphylococcus epidermidis (SE), Escherichia coli (EC), Pseudomonas aeruginosa (PA) and Candida albicans (CA) for adhesion to PETs are quantitatively determined by the plate counting and Gamma-ray counting of 125I radio labeled bacteria in vitro. The results indicate that the capacities of five types of bacteria for adhesion to PETs are all suppressed by C2H2 PIII-D (P<0.05). The surface energy components of the various substrates and bacteria are calculated based on measurements in water, formamide and diiodomethane and Lifshitz-van del Waals/acid-base approach (LW-AB). The surface free energies obtained are used to calculate the interfacial free energies of adhesion (deltaF(adh)) of five kinds of bacteria on various substrates, and the results show that it is energetically unfavorable for bacterial adhesion to the DLC films already deposited on PET by C2H2 PIII-D.

[Research of plasma adsorption and action of platelet adhesion of Dacron modified by plasma surface modification].

In this paper, polyethylene glycol (PEG) of different molecular weight was grafted on the polyethylene terephthalate (PET, Dacron) films by plasma surface grafting modification. The competitive adsorption relation of plasma (fibrinogen and albumin) adsorbing on materials surface was analyzed in light of surface energy and interface free energy. The results indicated that the PET films grafted PEG long chain molecular possesses the characteristic of preferentially adsorbing albumin and this adsorption tendency of grafted PEG6000 sample is most distinct. The platelet adhesion tests of the PET films whose surfaces were pre-set in contact with fibrinogen and albumin indicated that the surface adsorbing albumin can distinctly inhibit platelet adhesion and aggregation and possess favorable blood compatibility, but the surface adsorbing fibrinogen can enhance platelet adhesion and aggregation.

Immobilization of selenocystamine on TiO2 surfaces for in situ catalytic generation of nitric oxide and potential application in intravascular stents.

Immobilization of selenocystamine on TiO(2) film deposited on silicon wafer and 316 stainless steel stents for catalytic generation of nitric oxide was described. Polydopamine was used as the linker for immobilization of selenocystamine to the TiO(2) surface. In vitro stability of the immobilized selenocystamine was investigated and the result shows surface selenium loss occurs mostly in the first four weeks. The selenocystamine immobilized surface possesses glutathione peroxidase (GPx) activity, and the activity increases with the amount of grafted polydopamine. Such selenocystamine immobilized surfaces show the ability of catalytically decomposing endogenous S-nitrosothiols (RSNO), generating NO; thus the surface displays the ability to inhibit collagen-induced platelet acitivation and aggregation. Additionally, smooth muscle cells are inhibited from adhering to the selenocystamine immobilized sample when RSNO is added to the culture media. ELISA analysis reveals that cGMP in both platelets and smooth muscle cells significantly increases with NO release on selenocystamine immobilized samples. Two months in vivo results show that selenocystamine immobilized stents are endothelialized, and show significant anti-proliferation properties, indicating that this is a favorable method for potential application in vascular stents.

Anticoagulant surface modification of titanium via layer-by-layer assembly of collagen and sulfated chitosan multilayers.

Extracellular matrix (ECM)-like biomimetic surface modification of cardiovascular implants is a promising method for improving hemocompatibility. In the present work, collagen (Col) and sulfated chitosan (SCS) multilayers were coated on pure titanium using a layer-by-layer (LBL) self-assembly technique. The Col-SCS multilayer growth was carried out by first depositing a single layer of positively charged poly-L-lysine (PLL) on the NaOH-treated titanium substrate (negatively charged surface), followed by alternate deposition of negatively charged SCS and positively charged Col, and terminated by an outermost layer of SCS. Platelet adhesion in vitro, partial activated thromboplastin time (APTT) and prothrombin time (PT) assays were used to evaluate the hemocompatibility of the Col-SCS multilayer coated titanium. The multilayer processed surfaces displayed reduced platelet adhesion and activation, and prolonged clotting time of APTT and PT compared with untreated titanium. Thus, the approach described here may provide a basis for the preparation of modified titanium surfaces for application in cardiovascular implants.