Coated Ti Substrates Research Articles

Dielectric Performance of Forsterite-Coated Titanium Substrate-Based Medical Implant

Forsterite solutions with variable concentrations of tetra ethyl ortho-silicate (TEOS) and magnesium nitrate hexahydrate (MNH) are prepared using the sol-gel method. The dip coating method is applied to coat forsterite solution on a titanium (Ti) substrate. Forsterite coated Ti substrates are subjected to structural analysis and phase identification using the X-ray Diffraction (XRD) technique. Surface morphology and elemental composition of coated Ti substrates are also investigated using scanning electron microscopy (SEM) and energy dispersive X-ray (EDX) techniques. An extensive study is also conducted with the help of a vector network analyzer (VNA) assembly to determine the dielectric properties (dielectric constant, dielectric loss, alternating current conductivity, and loss tangent) and their relationship with frequency at room temperature in the frequency range of 200 MHz - 20 GHz. Furthermore, focusing on their use in medical implants, the impact of TEOS and MNH on the surface morphology and dielectric characteristics of forsterite coated Ti substrate is also examined in detail. Results proved that forsterite coated Ti substrate with a higher composition of TEOS and MNH performs better than others.

Imparting bioactivity to CP−Titanium with sputtered TiBN interlayer and electrophoretically grown bioglass overlay

Surface-modified implant materials with improved physicochemical properties and biocompatibility are vital for determining osseointegration and to enhance bone anchorage. Herein, titanium boron nitride (TiBN) thin films of thickness 3.4 μm were coated as an interlayer on sandblasted Ti plates by confocal D.C. magnetron sputtering using Ti and TiB2 targets. Nanoindentation tests showed a hardness of 27 GPa for the thin film. The bioactivity of the as-prepared coatings was enriched by introducing bioglass (BG), 45S5, overlay via electrophoretic deposition. The nanocrystalline microstructure with lattice parameter 4.2 Å, surface topology and vibration modes/surface chemistry of the coatings were comprehensively studied using microscopic and spectroscopic techniques. Swab inoculation assay, cellular viability assay and hemocompatibility studies revealed that bioglass overlaid thin films exhibited antibacterial property and cytocompatibility with no clot formation. Contact angle measurements showed that 45S5 bioglass-coated substrates were hydrophilic. Biocorrosion studies of the prepared implant materials in simulated body fluid (SBF) revealed the corrosion resistance of bioglass overlaid specimens with the corrosion potential (Ecorr) shifting towards a relatively positive value and the corrosion current density (Icorr) decreasing in the order bare Ti > TiBN >45S5/TiBN coated Ti substrates. Obtained experimental results suggests that the as-prepared 45S5 glass-coated TiBN/Ti plates could be a potential implantable candidate with synergistic cytocompatibility and corrosion resistance.

Natural prokaryotic antimicrobial peptide coated titanium discs prevent Staphylococcus auerus growth and biofilm formation – Implications on peri-implant infections

Staphylococcus auerus (S. aureus) biofilms are a frequently associated cause of artificial implant infections and failures. Surface coating of titanium (Ti), a widely used implant biomaterial with antimicrobial agents may appear a promising approach to prevent and reduce the periimplant infections and associated failures. Natural antimicrobial peptides (AMPs) viz laterosporulins (LS) from soil bacteria Brevibacillus spp. were bound on titanium (Ti) substrates using a simple, time and cost effective chemical processing technique. Resistance of the AMP coated Ti substrates against biofilm formation of the bacterium S. aureus was determined by crystal violet staining, in vitro. Further the antibiofilm activity was visualized in replicate experiments on Hydroxyapatite (HA) discs also to simulate enamel surfaces consistently layered by saliva in oral cavity to ascertain the biofilm inhibition assessment. AMP coated Ti substrates showed marked reduction in the biofilm formation by S. aureus, in vitro compared against the control-Ti surfaces. Further, Coated HA discs also substantiated the findings in a similar trend compared with control-Ti substrates. The findings suggested a promising potential for laterosporulins as effective antibiofilm agents for coating titanium surfaces for various applications, including dental implants used in oral cavity.

Alkali-Treated Titanium Coated with a Polyurethane, Magnesium and Hydroxyapatite Composite for Bone Tissue Engineering.

The aim of this study was to form a functional layer on the surface of titanium (Ti) implants to enhance their bioactivity. Layers of polyurethane (PU), containing hydroxyapatite (HAp) nanoparticles (NPs) and magnesium (Mg) particles, were deposited on alkali-treated Ti surfaces using a cost-effective dip-coating approach. The coatings were assessed in terms of morphology, chemical composition, adhesion strength, interfacial bonding, and thermal properties. Additionally, cell response to the variably coated Ti substrates was investigated using MC3T3-E1 osteoblast-like cells, including assessment of cell adhesion, cell proliferation, and osteogenic activity through an alkaline phosphatase (ALP) assay. The results showed that the incorporation of HAp NPs enhanced the interfacial bonding between the coating and the alkali-treated Ti surface. Furthermore, the presence of Mg and HAp particles enhanced the surface charge properties as well as cell attachment, proliferation, and differentiation. Our results suggest that the deposition of a bioactive composite layer containing Mg and HAp particles on Ti implants may have the potential to induce bone formation.

Bioinspired polydopamine/graphene oxide/collagen nanofilms as a controlled release carrier of bioactive substances

A single functional coating is far from enough to meet the high requirements of complex bone microenvironments for titanium (Ti)-based implants. In this study, multilayered polydopamine (PDA)/graphene oxide (GO)/type I collagen (Col I) (PGC) nanofilms on the basis of bioinspired design make it possible to develop a versatile, personalized, and biocompatible Ti-based implant. The nanofilms were successfully prepared by layer by layer (LBL) self-assembly of PDA, GO, and Col I, which was confirmed by surface physical and chemical characterization. In vitro biological assessments demonstrated the outstanding biological properties of PGC nanofilms coated Ti substrates, including enhanced protein adsorption, excellent biocompatibility, and accelerated osteogenic differentiation of rat bone marrow-derived mesenchymal stem cells (rBMSCs). Importantly, the more layers of PGC nanofilms were, the more significant osteogenic differentiation of rBMSCs was. In addition, PGC nanofilms displayed a powerful capacity of controllably releasing bioactive substances. And the encapsulated amount and release rate of bioactive substances (e.g., silver (Ag) ions and bovine serum albumin (BSA)) could be precisely controlled by the layer number of PGC nanofilms. The work provides a fairly feasible approach for developing a multifunctional bioactive coating on the surfaces of Ti-based implants.

Investigation of Ag/a-C:H Nanocomposite Coatings on Titanium for Orthopedic Applications.

One of the leading causes of failure for any bone implant is implant-associated infections. The implant-bone interface is in fact the crucial site of infection where both the microorganisms and cells compete to populate the newly introduced implant surface. Most of the work dealing with this issue has focused on the design of implant coatings capable of preventing infection while ignoring cell proliferation or vice versa. The present study is therefore focused on investigating the antibacterial and biological properties of nanocomposite coatings based on an amorphous hydrocarbon (a-C:H) matrix containing silver nanoparticles (AgNPs). a-C:H coatings with varying silver concentrations were generated directly on medical grade titanium substrates using a combination of a gas aggregation source (GAS) and a plasma-enhanced chemical vapor deposition (PE-CVD) process. The obtained results revealed that the surface silver content increased from 1.3 at % to 5.3 at % by increasing the used DC magnetron current in the GAS from 200 to 500 mA. The in vitro antibacterial assays revealed that the nanocomposites with the highest number of silver content exhibited excellent antibacterial activities resulting in a 6-log reduction of Escherichia coli and a 4-log reduction of Staphylococcus aureus after 24 h of incubation. An MTT assay, fluorescence live/dead staining, and SEM microscopy observations of MC3T3 cells seeded on the uncoated and coated Ti substrates also showed that increasing the amount of AgNPs in the nanocomposites had no notable impact on their cytocompatibility, while improved cell proliferation was especially observed for the nanocomposites possessing a low amount of AgNPs. These controllable Ag/a-C:H nanocomposites on Ti substrates, which simultaneously provide an excellent antibacterial performance and good biocompatibility, could thus have promising applications in orthopedics and other biomedical implants.

Adhesion, biological corrosion resistance and biotribological properties of carbon films deposited on MAO coated Ti substrates

A thin diamond-like carbon (DLC) film, a graphite-like carbon (GLC) film and a thick diamond-like carbon (PE-DLC) film are deposited on the micro arc oxidation (MAO) coated pure titanium substrates using a hybrid ion beam deposition system, magnetron sputtering and plasma enhanced chemical vapor deposition, respectively. The microstructure, adhesion, biological corrosion resistance and biotribological properties were determined. The results showed that the three duplex coatings presented uneven surface features and increased binding force. The binding force of the duplex coatings was strongly affected by the bonding strength between the MAO coating and Ti substrate. Although the roughness Ra of the three duplex coatings was high, their friction coefficients were small (under 0.22) in the SBF solution. The MAO/DLC and MAO/GLC coatings showed an excellent tribological behavior and corrosion resistance in the SBF solution.

Assessment of synergistic effects of LP-MOCVD TiO2 and Ti surface finish for dental implant purposes

Three differently treated titanium substrates to be used in dental implant applications and with different surficial morphology were coated with titanium dioxide (TiO 2 ) films by using Low-Pressure Metal Organic Chemical Vapor Deposition (MOCVD). No literature references were found on the performance evaluation of the TiO 2 MOCVD coatings on substrates with different pristine morphology; in this work the influence of the pristine Ti surface characteristics on TiO 2 crystalline structure, morphology, wettability as well as on ion release, electrochemical behavior, tribocorrosion performance, and nano-mechanical properties were studied and discussed. It was shown that the pristine substrate influenced both the crystalline phases' formation and crystallite size. Scanning electron microscopy analyses and roughness evaluation showed the optimal conformal coverage of all the MOCVD coatings for all substrates, with grain size depending on the substrate morphology and topography. The wettability of the TiO 2 coated Ti substrates highlighted a superhydrophilic behavior and, if stored in air, decreased as a function of the time aging. Ions release tests, nanoindentation measurements, tribocorrosion, and potentiodynamic polarization experiments suggest the enhancement of functional properties of the coated samples. Titania sandblasted/acid etched coated Ti substrates generally showed the best performance of the functional properties for their use in dental implant fabrications. • TiO 2 coated samples allow better wettability in aqueous media. • Titania surface functionalization is a good strategy to reduce ion release. • Tribocorrosion studies indicate better behavior for TiO 2 coated samples. • TiO 2 surface functionalization improves the mechanical properties of bulk titanium.

Self-assembled phase-transited lysozyme/heparin coating on titanium surfaces for improved hemocompatibility

To further improve the hemocompatibility of titanium (Ti) biomaterials, a bioactive coating was prepared by self-assembly of phase-transited lysozyme (PTL) and heparin (Hep). Scanning electron microscopy (SEM), atomic force microscopy (AFM), X-ray photoelectron spectroscopy (XPS), and water contact angle (WCA) measurement systematically confirmed the successful preparation of PTL/Hep coating on pure Ti surfaces. Blood compatibility assays showed that the platelet-repellent effect of the coating was significantly better than that of pure Ti surfaces. Also, the coating significantly extended the blood clotting time to 40.8 min. Besides, the hemolysis rate of PTL/Hep coated Ti substrates was only 0.39 ± 0.13%. These results confirmed the exceedingly excellent blood-compatibility of Ti surfaces modified by the self-assembled PTL/Hep coating.

Surface functionalization of titanium implants with chitosan-catechol conjugate for suppression of ROS-induced cells damage and improvement of osteogenesis.

Oxidative stress induced by reactive oxygen species (ROS) overproduction would hinder bone healing process at the interface of bone/implant, yet underlying mechanism remains to be explored. To endow titanium (Ti) substrates with antioxidant activity for enhanced bone formation, multilayered structure composing of chitosan-catechol (Chi-C), gelatin (Gel) and hydroxyapatite (HA) nanofibers was constructed on Ti substrates. Surface wettability and topography of multilayer coated Ti substrates were characterized by water contact angle measurement, scanning electron microscopy and atomic force microscopy, respectively. Chi-C containing multilayer on Ti surface effectively protected osteoblasts from ROS damage, which was revealed by high level of intracellular ROS scavenging activity and reduced oxidative damage on cellular level by regulating the expression of cell adhesion related genes (integrin αv, β3, CDH11 and CDH2). Moreover, it regulated the production of cell adhesive and anti-apoptotic related proteins (p-MYPT1, p-FAK, p-Akt and Bcl-2) and pro-apoptotic critical executioners (Bax and cleaved caspase 3). Beside, the composite multilayer of Chi-C/Gel/HA nanofibers on Ti substrates promoted osteoblasts differentiation, which was evidenced by high expression levels of alkaline phosphatase activity, collagen secretion, ECM mineralization and osteogenesis-related genes expression invitro. The invivo experiments of μ-CT analysis, push out test and histochemistry staining further confirmed that Chi-C multilayered implant had great potential for improved early bone healing. Overall, the study offers an effective strategy for the exploration of high quality Ti implants for orthopedic applications.

Bio-inspired YSZ coated titanium by EB-PVD for biomedical applications

Abstract Yttria stabilized zirconia (YSZ) was deposited onto titanium (Ti) substrates using electron beam physical vapor deposition (EB-PVD) method. The crystalline nature of as-deposited YSZ coating was evaluated using X-ray diffraction (XRD) technique and cubic phase was noticed. Smooth and uniform surface topography was observed by atomic force microscopy (AFM) analysis. The hardness and scratch resistance of the coating was determined by nanoindentation and scratch test analysis respectively. Wettability studies exhibited more hydrophilic nature on YSZ coating and least hydrophilic on uncoated Ti substrate. Anti-adhesion and antibacterial efficiency were performed against gram (-)ve ( E.coli ) and gram (+)ve ( S. aureus ) bacterial strains and revealed that YSZ coating effectively protected bacterial invasion. Hemocompatibility was evaluated by platelets adhesion and their activation behavior was studied onto uncoated and YSZ coated Ti substrates. YSZ coating exhibited less activated platelets; whereas, platelets activation (large number of pseudopods) were seen on uncoated Ti substrates. Furthermore, superior in vitro biomineralization behavior with increased weight gain, higher protein adsorption and superior biocompatible nature with NIH 3T3 fibroblast cells were observed on YSZ coating. Overall results indicated that surface modification by YSZ coating could become a promising material for biomedical applications.

Facile Synthesis of Photofunctional Nanolayer Coatings on Titanium Substrates.

We developed a two-step chemical bonding process using photosensitizer molecules to fabricate photofunctional nanolayer coatings on hematoporphyrin- (HP-) coated Ti substrates. In the first step, 3-aminopropyltriethoxysilane was covalently functionalized onto the surface of the Ti substrates to provide heterogeneous sites for immobilizing the HP molecules. Then, HP molecules with carboxyl groups were chemically attached to the amine-terminated nanolayer coatings via a carbodiimide coupling reaction. The microstructure and elemental and phase composition of the HP-coated Ti substrates were investigated using field-emission scanning electron microscopy and energy-dispersive X-ray spectrometry. The photophysical properties of the photofunctional nanolayer coatings were confirmed using reflectance ultraviolet-visible absorption and emission spectrophotometry. The singlet oxygen generation efficiency of the photofunctional nanolayer coatings was determined using the decomposition reaction of 1,3-diphenylisobenzofuran. The HP-coated Ti substrates exhibited good biocompatibility without any cytotoxicity, and these nanolayer coatings generated singlet oxygen, which can kill microorganisms using only visible light.

Covalent immobilization of antimicrobial agents on titanium prevents Staphylococcus aureus and Candida albicans colonization and biofilm formation.

Biofilm-associated implant infections represent a serious public health problem. Covalent immobilization of antimicrobial agents on titanium (Ti), thereby inhibiting biofilm formation of microbial pathogens, is a solution to this problem. Vancomycin (VAN) and caspofungin (CAS) were covalently bound on Ti substrates using an improved processing technique adapted to large-scale coating of implants. Resistance of the VAN-coated Ti (VAN-Ti) and CAS-coated Ti (CAS-Ti) substrates against in vitro biofilm formation of the bacterium Staphylococcus aureus and the fungal pathogen Candida albicans was determined by plate counting and visualized by confocal laser scanning microscopy. The efficacy of the coated Ti substrates was also tested in vivo using an adapted biomaterial-associated murine infection model in which control-Ti, VAN-Ti or CAS-Ti substrates were implanted subcutaneously and subsequently challenged with the respective pathogens. The osseointegration potential of VAN-Ti and CAS-Ti was examined in vitro using human bone marrow-derived stromal cells, and for VAN-Ti also in a rat osseointegration model. In vitro biofilm formation of S. aureus and C. albicans on VAN-Ti and CAS-Ti substrates, respectively, was significantly reduced compared with biofilm formation on control-Ti. In vivo, we observed over 99.9% reduction in biofilm formation of S. aureus on VAN-Ti substrates and 89% reduction in biofilm formation of C. albicans on CAS-Ti substrates, compared with control-Ti substrates. The coated substrates supported osseointegration in vitro and in vivo. These data demonstrate the clinical potential of covalently bound VAN and CAS on Ti to reduce microbial biofilm formation without jeopardizing osseointegration.

Improved contact damage resistance of hydrogenated diamond-like carbon (DLC) with a ductile α-Ta interlayer

Local contact damage as well as cohesive and adhesive failure can limit the lifetime and applicability of hydrogenated diamond-like carbon (DLC) films on metallic substrates. DLC on titanium (Ti) is very interesting for industrial applications (e.g. biomedical applications), while also an excellent model system for the general understanding of hard and brittle films on ductile metallic substrates. Interlayers deposited between the DLC film and the Ti substrate have been shown to affect failure of such DLC coated Ti substrates. In this study, the effect of interlayer structure on contact damage and cohesive and adhesive failure is studied with tantalum (Ta) in its α- and β-phase. In all investigated cases the more ductile α-Ta provides improved results over the hard and brittle β-Ta interlayer. Due to plastic deformation effects, the resistance to contact damage is significantly increased with an α-Ta interlayer. Delamination occurs at the interface between the Ti substrate and the Ta interlayer. Compared to DLC on Ti without a Ta interlayer no enhancement in onset strain of fragmentation and delamination was achieved. A finite-element analysis shows that stress concentrations can be distributed over both interfaces if the Young's modulus of the interlayer material is of the order of the Young's modulus of the DLC.

CHARACTERIZATION AND EVALUATION OF TITANIUM SUBSTRATES COATED WITH GELATIN/HYDROXYAPATITE COMPOSITE FOR CULTURING RAT BONE MARROW DERIVED MESENCHYMAL STROMAL CELLS

Titanium (Ti) is widely used for making tissue engineering implants, due to its good corrosion resistance, biocompatibility and mechanical properties. However, bare Ti does not integrate well with natural bone tissue and releases ions and particles that are harmful to the extracellular matrix. To overcome these problems, the Ti substrate could be coated with various biocompatible materials including a composite of gelatin and hydroxyapatite (HA). However, few have characterized and evaluated the coating of gelatin/HA on Ti substrate and its effect on bone related cells. In this study, samples of Ti substrate coated with gelatin/HA composite were fabricated with gelatin concentration ranging from 0 to 200 mg/L. The porous surface structure of gelatin/HA composite formed on the Ti substrate was then examined and characterized for its composition and topography by X-ray diffraction (XRD), scanning electron microscopy (SEM), atomic force microscopy (AFM), and image processing and analysis software (ImageJ), respectively. Subsequently, rat bone marrow-derived mesenchymal stromal cells (BMMSC) were cultured on the surface of gelatin/HA composite on Ti substrate, and evaluated for cell morphology, proliferation, and osteo-differentiation using SEM, MTT assay, and alkaline phosphatase (ALP) assay, respectively. It is shown that gelatin enhanced binding of HA onto Ti substrate, and the topography of the porous surface structures was influenced by gelatin concentration only for the large pore sizes. Furthermore, the results indicate that the porous surface structures of gelatin/HA on Ti substrate promoted proliferation and osteo–differentiation as compared to the naked pure Ti substrate, particularly on that with concentration of gelatin at 100 mg/L. These findings, taken together, suggest that Ti substrate can be coated with different porous surface structures of gelatin/HA composite with gelatin solution of different concentrations. Such coated Ti substrates can promote cytocompitibility and osteo-differentiation of BMMSC, and thus may be of potential in development of implants and devices for bone tissue engineering.

Synthesis and tribological properties of diamond-like carbon films by electrochemical anode deposition

Diamond-like carbon films (DLC) are deposited on Ti substrate by electrochemical anodic deposition at room temperature in pure methanol solution using a pulsed DC voltage at a range from 200V to 2000V. Raman spectroscopy analysis of the films reveals two broaden characteristic absorption peaks centred at ∼1350cm−1 and 1580cm−1, relating to D- and G-band of typical DLC films, respectively. A broad peak centred at 1325–1330cm−1 is observed when an applied potential is 1200V, which can confirm that the deposited films contained diamond structure phase. Tribological properties of the coated Ti substrates have been measured by means of a ball-on-plate wear test machine. A related growth mechanism of DLC films by the anodic deposition mode has also been discussed.

Surface properties and cell response of fluoridated hydroxyapatite/TiO2 coated on Ti substrate

Abstract Dense and well-crystallized TiO 2 and fluoridated hydroxyapatite (FHAp) films with TiO 2 as a buffer layer were deposited on Ti substrates using a sol–gel spin-coating technique. X-ray diffraction showed a positive correlation between the level of F − incorporation into the HAp structure and the crystallinity of the HAp phase and the concentration of the FHAp phase. The decrease in water contact angle was attributed mainly to the increase in total surface energy of the FHAp/Ti and FHAp/TiO 2 /Ti as well as the increased polar component in FHAp. The FTIR spectra of the FHAp coated samples showed a weak absorption band at PO 4 3 - (1040 and 1092 cm −1 ) and P–O (875 cm −1 ), and several strong absorption bands between 3450 and 3550 cm −1 due to F–OH and OH − . The critical load values measured by the scanning scratch tester showed that the adhesion strength of the FHAp/TiO 2 coated Ti substrate was 1.2–1.7 times higher than that of the HAp and FHAp coated Ti substrate. The level of cell attachment on FHAp and FHAp/TiO 2 coated Ti substrates were 1.4 and 1.7 times higher than that on the HAp coated Ti substrate, respectively.

Electrode erosion and coating properties in pulsed air arc deosition of WC-based hard alloys

WC-based hard alloys were deposited from a slab source anode on to low carbon steel and pure Ti substrates using a pulsed air arc. The depositions were conducted with a series of pulses with current amplitudes of 75 A, 300 A, and 500 A, a pulse duration of 150 μs, and a pulse repetition rate of 100 Hz. The influence of the electrode material, discharge energy and deposition time on the electrode erosion rate, mass transfer direction, and the wear resistance and friction coefficient of the coatings was investigated. Anodic and cathodic mass change characteristics depended on both the anode and cathode materials. Using a steel cathode and a WC anode, depositions of the anode material always formed on the cathode. For the same WC anode but a Ti cathode, coatings only formed locally in the craters of the eroded cathode. The anodic mass loss when using the steel cathodes was about a factor of 3 larger than when using the Ti cathodes. The microhardness of the coated substrates was larger by factors of 5–12 than the uncoated Ti and low carbon steel substrates. The coatings increased the wear resistance of the steel and Ti substrates by factors of 4.3 and 1.4, respectively. The poorer performance of the coated Ti substrates is attributed to the intensive erosion of the Ti cathodes (compared to the steel cathodes) and the discontinuous nature of the coatings (i.e. only in the erosion caters).