Functionalization Of Titanium Surfaces Research Articles

Strontium/zinc phytate-based self-assembled monolayers on titanium surfaces enhance osteogenesis and antibacterial performance in vitro

The accumulation of bacteria over implant surfaces is still the first cause of failure, and the development of antimicrobial surfaces constitutes a first line in implant research. Besides, the durability and mechanical performance of implants, in special in the dental area, are mainly determined by their osseointegration capacity into the maxillofacial bone and the appearance of infections. Consequently, implant osseointegration and infection prophylaxis remain as big challenges to attain so a huge investigation is being developed on the production of bioactive surfaces to achieve improvements in these aspects. In this work we propose the functionalization of titanium surfaces (Ti Cp) with self-assembled monolayers (SAMs) of bioactive organophosphate compounds: phytic acid (Ti-PA) and its metallic phytate derivatives bearing Sr2+ and/or Zn2+ (Ti-SrPhy, Ti-ZnPhy and Ti-SrPhy/ZnPhy) which exhibited tunable in vitro osteogenic, antimicrobial and antioxidant properties in a previous work. Thus, phytate compounds are chemically anchored onto Ti discs through a simple procedure consisting of a condensation reaction promoted by heat treatment. EDS and XPS spectroscopies confirm the obtaining of the modified surfaces and the topographic properties and wettability analysed by SEM, AFM, profilometry and contact angle measurements, respectively, are explored. Additionally, phytate-SAMs do not release any cytotoxic compound after 14 days and stimulate in vitro adhesion and proliferation of human osteoblast cells after 14 days of culture. The osteogenic ability of the modified surfaces evaluated by the quantification of ALP activity and matrix mineralization degree shows a significant improvement with respect to unmodified surfaces. Furthermore, the antimicrobial activity of phytate-SAMs against Streptococcus mutans cultures is evaluated. The count of viable cells and the quantification of produced biofilm are significantly reduced by all phytate-SAMs groups (p < 0.001). Cell membrane integrity studies by LIVE/DEAD staining and SEM imaging confirm a decreased viability of adhered bacteria when phytate-based surfaces are tested, due to a disruption in the function and permeability of the cell membrane. Therefore, phytate-SAMs exhibit suitable in vitro features suggesting their promising potential as bioactive coatings of dental implants.

In vitro and in vivo evaluation of surface functionalization of titanium with H2 O2 hydrothermal treatment and FGF-2.

The goals of the study were to investigate the effects on bone bioactivity of a titanium dioxide layer formed by hydrothermal oxidation of a titanium surface with hydrogen peroxide (H2 O2 ) and loading with fibroblast growth factor-2 (FGF-2) in vitro and in vivo. Ti-6Al-4V discs were hydrothermally oxidized with H2 O2 and then loaded with FGF-2. After cytotoxicity testing, Ti-6Al-4V mini-implants were subjected to the same treatment, and their osteogenic potential was evaluated histologically in a rat model. H2 O2 hydrothermal oxidation resulted in a dense porous network structure and hydrophilic changes, which improved retention of FGF-2. Morphologically, the cell density was higher, cell elongation was more pronounced, and the cell adhesion area was significantly higher in FGF-2-loaded cells than in those without FGF-2. In a cell proliferation assay using mouse osteoblast-like cells, absorbance tended to increase over time, especially in the FGF-2 group after 7 and 14 days, and in a bone differentiation assay based on ALP activity, there was a significant increase in the FGF-2 group after 14 days. In the rat model, H2 O2 hydrothermal oxidation and FGF-2 loading both resulted in more laminar bone tissue in the bone marrow around the mini-implant. These results suggest that titanium surface functionalization by H2 O2 hydrothermal oxidation and FGF-2 may promote initial cell adhesion, proliferation, and osteodifferentiation, and enhance bone bioactivity. These effects all contribute to early bonding of an implant with the surrounding bone.

Bone Response to Osteopontin-Functionalized Carboxyethylphosphonic Acid-Modified Implants. Experimental Study in a Minipig Model

Currently, dental implants have become a common and reliable treatment for restoring masticatory function in edentulous patients. Their surface topography is of great importance for the adhesion and remodeling of bone cells, both in the initial phases and over time, and different strategies have been proposed to improve the biological performance of conventional sandblasted, large-grit, acid-etched implant surfaces. Corrosion has been identified as one of the causes of implant failure due to contact with oral fluids. Carboxyethylphosphonic acid is a potent anticorrosive that would form stable bonds with titanium oxide, generating an organic layer on which modifications could be made to improve cell adhesion. Osteopontin is considered a molecule capable of improving the osseointegration of titanium. Our study evaluated the osseointegration capacity of titanium implants modified with carboxyethylphosphonic acid and functionalized with osteopontin in a minipig model. A total of 16 implants were inserted in the tibial diaphysis of two minipigs, 8 implants modified with carboxyethylphosphonic acid and functionalized with osteopontin from the experimental group and 8 from the control group with sandblasted, large-grit, acid-etched surface treatment. After 4 weeks, the animals were sacrificed and the samples were analyzed by histomorphometric analysis, assessing bone-implant contact, cortical bone-implant contact, percentage of new bone, peri-implant bone density and interthread bone area interthread. Statistical analysis was performed using SPSS v.18. Statistical significance was found between groups for the percentage of new bone (p = 0.04) and for interthread bone area interthread (p = 0.01). Functionalization of titanium surfaces by osteopontin may be of interest for conditioning bone remodeling in the early stages of osseointegration, although more in vivo studies are needed to determine its real influence in this aspect.

Customizing the extracellular vesicles release and effect by strategizing surface functionalization of titanium.

Metallic material functionalization with Extracellular Vesicles (EVs) is a desirable therapeutic approach to improve regenerative procedures. Among the different functionalization strategies available, here we have compared drop casting on machined Ti surfaces, drop casting on nanostructured TiO2 surfaces and polymeric entrapment with polydopamine. EVs are a heterogeneous population of communication nanovesicles released by cells that are being intensively investigated for their use in therapeutics. We have selected platelet derived EVs for Ti surface coating due to their demonstrated osteoinductive properties. Our results show that each functionalization strategy leads to differences in the size of EV populations attached to and released from the metallic implants, which, in turn, leads to variations in their osteogenic capability measured through alkaline phosphatase activity and calcium deposition. In conclusion, the functionalization strategy used has an important effect on the resulting implant functionality, probably due to the heterogeneous EVs nature. Thus, the methodological approach to metallic material functionalization should be carefully chosen when working with extracellular vesicles in order to obtain the desired therapeutic application.

Principal Physics of Oblique Sputtering of Calcium Phosphate Coatings Using RF-Magnetron Discharge Plasma

A possibility in principle is determined for the titanium surface functionalization by oblique sputtering of nanostructured bioactive calcium phosphate coatings. The coatings are deposited by the RF magnetron sputtering of the targets based on hydroxyapatite and antibacterial zinc-substituted hydroxyapatite. The coating morphology and their growth characteristics are studied as a function of such process parameters as the specimen tilt angle with respect to the particle flux from the source, the supplied power, and the distance from the target plane to the specimen surface. As the tilt angle is increased, the coating surface morphology significantly changes and represents nanosized structural elements oriented towards the particle source and ordered in accordance with the substrate surface morphology prior to sputtering. The inner coating structure consists of columnar elements tilted to the substrate plane.

Физические основы наклонного напыления фосфатов кальция из плазмы ВЧ-магнетронного разряда

The possibility of titanium surface functionalization by an oblique angle deposition of nanostructured bioactive calcium phosphate coatings is shown in the present work. The coatings were obtained by an RF magnetron sputtering of hydroxyapatite and antibacterial zinc-substituted hydroxyapatite-based targets. The morphology and growth features of coatings were studied in relation to the process parameters, such as the angle of substrates inclination relative to the particle flux, an RF power supplied to the target, and the distance from the target surface to the surface of the substrates. With an increase in the angle of inclination, the surface morphology of the coating’s changes significantly. It resulted inappearance of nanoscale structural elements tilted towards the source of the material flux. The arrangement of surface features is ordered in accordance with the initial surface of the substrate before sputtering. The internal structure of the coatings is represented by columnar elements inclined relative to the plane of the substrate.

Liquid-Infused Structured Titanium Surfaces: Antiadhesive Mechanism to Repel Streptococcus oralis Biofilms.

To combat implant-associated infections, there is a need for novel materials which effectively inhibit bacterial biofilm formation. In the present study, the antiadhesive properties of titanium surface functionalization based on the "slippery liquid-infused porous surfaces" (SLIPS) principle were demonstrated and the underlying mechanism was analyzed. The immobilized liquid layer was stable over 13 days of continuous flow in an oral flow chamber system. With increasing flow rates, the surface exhibited a significant reduction in attached biofilm of both the oral initial colonizer Streptococcus oralis and an oral multispecies biofilm composed of S. oralis, Actinomyces naeslundii, Veillonella dispar, and Porphyromonas gingivalis. Using single cell force spectroscopy, reduced S. oralis adhesion forces on the lubricant layer could be measured. Gene expression patterns in biofilms on SLIPS, on control surfaces, and expression patterns of planktonic cultures were also compared. For this purpose, the genome of S. oralis strain ATCC 9811 was sequenced using PacBio Sequel technology. Even though biofilm cells showed clear changes in gene expression compared to planktonic cells, no differences could be detected between bacteria on SLIPS and on control surfaces. Therefore, it can be concluded that the ability of liquid-infused titanium to repel S. oralis biofilms is mainly due to weakened bacterial adhesion to the underlying liquid interface.

Bioinspired Surface Functionalization of Titanium for Enhanced Lubrication and Sustained Drug Release.

Titanium and its alloys have long been used as implantable biomaterials in orthopedics; however, to the best of our knowledge, few studies were reported to investigate surface functionalization of titanium for enhanced lubrication and sustained drug release. In the present study, titania nanotube arrays (TNTs) were prepared by anodization as effective drug nanocarriers, using titanium as the substrate. Meanwhile, motivated by articular cartilage-inspired superlubricity and mussel-inspired adhesion, a copolymer containing both dopamine methacrylamide and 2-methacryloyloxyethyl phosphorylcholine was synthesized (DMA-MPC) and spontaneously grafted onto the TNT surface, which was validated by characterization techniques such as scanning electron microscopy, water contact angle measurements, and X-ray photoelectron spectroscopy. Additionally, the lubrication test showed that copolymer-grafted TNTs have remarkably reduced friction coefficients compared with bare TNTs. Furthermore, the drug release test demonstrated that copolymer-grafted TNTs inhibited burst drug release and achieved sustained drug release in comparison with bare TNTs. In conclusion, the bioinspired surface functionalization strategy developed here, namely DMA-MPC copolymer-grafted TNTs, can be applied to modify orthopedic biomaterials (such as titanium) for enhanced lubrication and sustained drug release.

Can We Further Improve Titanium Implant Surfaces at Nanoscale to Enhance Osseointegration?

The main aim of this review study was to report the state of art on the technological improvements of titanium implant surfaces to accelerate the osseointegration process.Several methods of surface modification are chronologically described bridging ordinary methods (e.g. grit blasting and etching) and novel physicochemical approaches such as 3D-laser printing and biomimetic modification. Advanced functionalization procedures by using proteins, peptides, and bioactive ceramics have provided an enhancement of wettability and bioactivity of implant surfaces. Furthermore, recent findings have revealed a combined beneficial effect of micro- and nano-scale modification and biomimetic functionalization of titanium surfaces. However, some technological developments of implant surfaces are not commercially available yet due to costs and a lack of clinical validation of the novel surfaces. Further in vitro and in vivo studies are necessary to endorse of the use of enhanced biomimetic implant surfaces.

Surface functionalization of titanium with silver nanoparticles

This study aims to investigate the most efficient ways for metallic samples functionalization with silver nanoparticles (AgNPs). Three different techniques of surface functionalization have been used for the coating of titanium metal, i.e. the sessile drop method (evaporation), dip-coating and electrophoretic deposition (EPD). AgNPs stabilized with polyvinylpyrrolidone had a spherical shape and the metallic core diameter, charge and polydispersity index were 70 ± 20 nm, -15 mV and 0.192, respectively. SEM analysis revealed that AgNPs were homogeneously distributed over the entire surface and did not form the particle agglomerates only in case of EPD. Thus, EPD method and spherical AgNPs can be used for further investigation concerning the preparation of biocomposites with antibacterial and bioactive properties.

Surface functionalization of titanium with zinc/strontium-doped titanium dioxide microporous coating via microarc oxidation

Deficient osseointegration and implant-related infections are pivotal issues for the long-term clinical success of titanium (Ti) implants. Zinc (Zn) and strontium (Sr) serve dual functions by promoting osteogenesis and inhibiting bone destruction, and Zn has good antibacterial activity. As such, this study examined the preparation of a Zn/Sr-doped titanium dioxide microporous coating (MT-Zn/Sr) on a Ti surface using microarc oxidation (MAO), with Zn and Sr evenly distributed throughout the coating. In vitro, the coating could promote the adhesion, proliferation, differentiation and mineralization of osteoblasts, showing good biological activity. Antibacterial testing demonstrated the good antibacterial activity of the coating, as it inhibited the proliferation of Staphylococcus. In vivo, MT-Zn/Sr promoted early osseointegration between the Ti substrate and the bone tissue. This work is expected to provide a new method for improving the biological activity of Ti implants and thus has important theoretical significance and great clinical prospects.

Effect of titanium surface functionalization with bioactive glass on osseointegration: An experimental study in dogs.

The purpose of this study was to evaluate the effect of surface functionalization with bioactive glass BSF18 on the osseointegration of sandblasted and dual acid-etched surface (AE) implants. Forty Morse taper implants with an AE surface as controls (C) or with an AE surface functionalized with BSF18 (BF) were placed in the mandibles of 10 beagles. Implants were analyzed after 2 and 4weeks of healing. Implant stability quotient (ISQ) values were registered immediately after installation and prior to sacrifice. Samples were analyzed for bone-to-implant contact (BIC) and bone density (BD). The characterization of BF implants included surface roughness analysis with atomic force microscopy and contact angle (CA) analysis to evaluate wettability. Data were analyzed using two-way ANOVA followed by Tukey's test (p<0.05). Surface roughness was not affected by BF treatment. CA was lower in the BF group compared to the C group. No significant difference was observed in ISQ values between surfaces (p=0,231), irrespective of time. Significantly higher ISQ values were observed for both implants after 4weeks when compared with baseline (p=0.04). Significantly higher BIC (p=0.011) and BD (p=0.025) values were observed for the BF compared to the C group at 2weeks. Significantly higher BIC (p=0.030) and BD (p=0.015) values for the C group were observed at 4weeks compared to 2weeks. No significant difference was observed in the BF group between 2 and 4weeks. Implant functionalization with BSF18 improved the wettability of the implant surface; enhancing BIC and BD at 2weeks.

Functionalization of Titanium Surfaces with Lysine: A Micro Raman Study of the Intermolecular Interactions of Lysine-TiO2

Raman scattering (RS) was used as a powerful, efficient, and sensitive technique for studying intermolecular interactions between an organic ligand adsorbate and a metallic substrate. Functionalization of titanium (TiO2[Formula: see text]Ti) surfaces was performed using lysine (Lys) as adsorbate and later developing a hydroxyapatite (HA) layer onto this functionalized surface. The functionalization process was performed at different pH values of the interacting chemical species. Chemisorption onto the TiO2Ti substrates through the Lys carboxylic group was demonstrated spectroscopically. Analysis of vibrational spectra showed that the CH side chain of Lys was relatively distant from the (TiO2[Formula: see text]Ti) surface, preventing direct contact with the surface. Additionally, the signals corresponding to the unbound [Formula: see text]-NH2 group indicate that it is available for additional complexation. In vitro bioactivity of the Lys–TiO2[Formula: see text]Ti surface was achieved by developing an HA layer onto already functionalized TiO2[Formula: see text]Ti surfaces at various pH values. Spectroscopic data using the spectral markers of HA and Lys provided a decisive role in establishing the necessary baseline data for evidencing the intermolecular bonding. The functionalized TiO2[Formula: see text]Ti surface reactivity is linked to the specific intermolecular interactions of –COO− (pH 7.0) with Ca[Formula: see text] ions, as well as the –COOH (pH 2.0 and 12.0) groups of Lys, with the –OH groups of PO[Formula: see text] belonging to HA.

Highly Stabilized Nanoparticles on Poly-l-Lysine-Coated Oxidized Metals: A Versatile Platform with Enhanced Antimicrobial Activity

The increasing incidence of infections in implantable devices has encouraged the search for biocompatible antimicrobial surfaces. To inhibit the bacterial adhesion and proliferation on biomaterials, several surface functionalization strategies have been developed. However, most of these strategies lead to bacteriostatic effect and only few of these are able to reach the bactericidal condition. In this work, bactericidal surfaces were designed through the functionalization of titanium surfaces with poly-l-lysine (PLL) as the mediator for the incorporation of antimicrobial silver nanoparticles (AgNPs). This functionalization influences the adsorption of the particles on the substrate impeding the agglomeration observed when bare titanium surfaces are used, leading to a homogeneous distribution of AgNPs on the surfaces. The antimicrobial activity of this surface has been tested against two different strains, namely, Staphylococcus aureus and Pseudomonas aeruginosa. For both strains and different AgNPs sizes, the surface modified with PLL and AgNPs shows a much enhanced antimicrobial activity in comparison with AgNPs deposited on bare titanium. This enhanced antibacterial activity is high enough to reach bactericidal effect, a condition hard to achieve in antimicrobial surfaces. Importantly, the designed surfaces are able to decrease the bacterial viability more than 5 orders with respect to the initial bacterial inoculum. That means that a relative low load of AgNPs on the PLL-modified titanium surfaces reaches 99.999% bacterial death after 24 h. The results of the present study are important to avoid infections in indwelling materials by reinforcing the preventive antibiotic therapy usually dosed throughout the surgical procedure and during the postoperative period.

Titanium surface functionalization with coatings of chitosan and polyphenol-rich plant extracts

Coating biomedical implant surfaces with biopolymers is an easy and inexpensive way to impart functionalities. Numerous biocompatible biopolymers, including cationic crustacean-derived chitosans, have been used. Here, substrates of Titanium (Ti), commonly used for bone contact applications, were coated with chitosan and one of three polyphenol-rich plant extracts (PPrPE) and characterized physicochemically. Hela cell adhesion and growth of methicillin-resistant Staphylococcus aureus (MRSA) were studied. Chitosan and PPrPE on surfaces were detected by FTIR and XPS. Chitosan coatings, both with and without PPrPE functionalization, did not inhibit MRSA growth and promoted Hela cell adhesion. The effect of PPrPE functionalization remained unclear.

In Vitro and In Vivo Evaluation of Tetracycline Loaded Chitosan-Gelatin Nanosphere Coatings for Titanium Surface Functionalization.

Owing to the biocompatibility of titanium surface, titanium implants are suitable substrates for microbial colonization and biofilm formation, which is still a serious clinical threat. Current research trends have been focused on the development of antibacterial coatings on titanium substrate or adhesion resistant surface. In our previous study, tetracycline (Tc) loaded chitosan-gelatin (CSG) nanosphere coatings are successfully fabricated on titanium substrates via electrophoretic deposition. These coatings show nanosphere structure, and excellent antibacterial property in vitro. However, further in vitro and in vivo evaluation of the coatings is required for the future application. Therefore, in the present study, the authors investigate the coatings' mechanical, swelling and degradation property, in vitro cellular response to preosteoblast cells, and the antibacterial property in rabbits. Results show that Tc incorporation can improve the tensile bond strength of the coating, decrease the swelling ratio, and accelerate the degradation of the coating. Although high Tc concentration group exhibits cytotoxicity to MC3T3-E1 cells, its in vivo antibacterial property is preferred, and shows better outcome than the prophylactic administration of Tc. Tc loaded CSG nanosphere coatings are suitable antibacterial coatings for titanium surface functionalization.

Self-assembled monolayers of alendronate on Ti6Al4V alloy surfaces enhance osteogenesis in mesenchymal stem cells.

Phosphonates have emerged as an alternative for functionalization of titanium surfaces by the formation of homogeneous self-assembled monolayers (SAMs) via Ti-O-P linkages. This study presents results from an investigation of the modification of Ti6Al4V alloy by chemisorption of osseoinductive alendronate using a simple, effective and clean methodology. The modified surfaces showed a tailored topography and surface chemistry as determined by SEM microscopy and RAMAN spectroscopy. X-ray photoelectron spectroscopy revealed that an effective mode of bonding is created between the metal oxide surface and the phosphate residue of alendronate, leading to formation of homogenous drug distribution along the surface. In-vitro studies showed that alendronate SAMs induce differentiation of hMSC to a bone cell phenotype and promote bone formation on modified surfaces. Here we show that this novel method for the preparation of functional coatings on titanium-based medical devices provides osseoinductive bioactive molecules to promote enhanced integration at the site of implantation.

Fabrication and characterization of Mg-doped chitosan–gelatin nanocompound coatings for titanium surface functionalization

Titanium and its alloys have been widely used in clinic and achieved great success. Due to the bio-inertness of titanium surface, challenges still exit in some compromised conditions. The present study aimed to functionalize titanium surface with magnesium (Mg)-doped chitosan/gelatin (CS/G) nanocompound coatings via electrophoretic deposition (EPD). CS/G coatings loaded with different amount of magnesium were successfully prepared on titanium substrate via EPD. Physicochemical characterization of the coatings confirmed that magnesium ions were loaded into the coatings in a dose-dependent manner. XRD results demonstrated that co-deposition of magnesium influenced the crystallinity of the coatings, and a new crystalline substance presented, namely hydrated basic magnesium carbonate. Mechanical tests showed improved tensile and shear bond strength of the magnesium-doped coatings, while the excessively high magnesium concentration could eventually decrease the bonding strength. Sustained release of magnesium ion was detected by ICP-OES within 28 days. TEM images also displayed that nanoparticles could be released from the coatings. In vitro cellular response assays demonstrated that the Mg-doped nanocompound coatings could enhance the proliferation and osteogenic differentiation of MC3T3-E1 cells compared to CS/G coatings. Therefore, it could be concluded that Mg-doped CS/G nanocompound coatings were successfully fabricated on titanium substrates via EPD. It would be a promising candidate to functionalize titanium surface with such organic–inorganic nanocompound coatings.

Surface functionalization of titanium with tetracycline loaded chitosan–gelatin nanosphere coatings via EPD: fabrication, characterization and mechanism

Tetracycline loaded chitosan–gelatin nanosphere coating has been fabricated on titanium substrate via electrophoretic deposition.

Surface functionalization of titanium surfaces grafted with hyaluronic acid through alendronate self-assembling monolayers

Surface functionalization of titanium surfaces grafted with hyaluronic acid through alendronate self-assembling monolayers