Deposition of thin titanium–copper films with antimicrobial effect by advanced magnetron sputtering methods

Effect of Co-Sputtered Copper and Titanium Oxide Coatings on Bacterial Resistance and Cytocompatibility of Osteoblast Cells

One of the primary risk factors for implant failure is thought to be implant-related infections during the early healing phase. Developing coatings with cell stimulatory behaviour and bacterial adhesion control is still difficult for bone implants. This study proposes an approach for one-step deposition of biocompatible and antimicrobial Cu-doped TiO2 coatings via glow-discharge sputtering of a mosaic target. During the deposition, the bias of the Ti6Al4V substrates was changed. Structure examination, phase analysis, and surface morphology were carried out using X-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), atomic force microscopy (AFM), and X-ray photoelectron spectroscopy (XPS). The hardness values and hydrophilic and corrosion performance were also evaluated together with cytocompatible and antibacterial examinations against E. coli and S. aureus. The results show great chemical and phase control of the bias identifying rutile, anatase, CuO, or ternary oxide phases. It was found that by increasing the substrate bias from 0 to -50 V the Cu content increased from 15.3 up to 20.7 at% while at a high bias of -100 V, the copper content reduced to 3 at%. Simultaneously, apart from the Cu2+ state, Cu1+ is also found in the biased samples. Compared with the bare alloy, the hardness, the water contact angle and corrosion resistance of the biased coatings increased. According to an assessment of in vitro cytocompatibility, all coatings were found to be nontoxic to MG-63 osteoblast cells over the time studied. Copper release and cell-surface interactions generated an antibacterial effect against E. coli and S. aureus strains. The -50 V biased coating combined the most successful results in inhibiting bacterial growth and eliciting the proper responses from osteoblastic cells because of its phase composition, electrochemical stability, hydrophilicity, improved substrate adhesion, and surface roughness. Using this novel surface modification approach, we achieved multifunctionality through controlled copper content and oxide phase composition in the sputtered films.

Coatless modification of 3D-printed Ti6Al4V implants through tailored Cu ion implantation combined with UV photofunctionalization to enhance cell attachment, osteogenesis and angiogenesis

The three-dimensional-printed Ti6Al4V implant (3DTi) has been widely accepted for the reconstruction of massive bone defects in orthopedics owing to several advantages, such as its tailored shape design, avoiding bone graft and superior bone-implant interlock. However, the osteoinduction activity of 3DTi is inadequate when applied clinically even though it exhibits osteoconduction. This study developes a comprehensive coatless strategy for the surface improvement of 3DTi through copper (Cu) ion implantation and ultraviolet (UV) photofunctionalization to enhance osteoinductivity. The newly constructed functional 3DTi (UV/Ti-Cu) achieved stable and controllable Cu doping, sustained Cu2+ releasing, and increased surface hydrophilicity. By performing cellular experiments, we determined that the safe dose range of Cu ion implantation was less than 5×1016 ions/cm2. The implanted Cu2+ enhanced the ALP activity and the apatite formation ability of bone marrow stromal cells (BMSCs) while slightly decreasing proliferation ability. When combined with UV photofunctionalization, cell adhesion and proliferation were significantly promoted and bone mineralization was further increased. Meanwhile, UV/Ti-Cu was conducive to the migration and angiogenesis of human umbilical vein endothelial cells (HUVECs) in vitro, theoretically facilitating vascular coupling osteogenesis. In conclusion, UV/Ti-Cu is a novel attempt to apply two coatless techniques for the surface modification of 3DTi. In addition, it is considered a potential bone substrate for repairing bone defects.

Improving antibacterial ability of Ti-Cu thin films with co-sputtering method

Due to the resistance of some bacteria to antibiotics, research in the field of dealing with bacterial infections is necessary. A practical approach utilized in this study involves the preparation of an antibacterial thin film on the surfaces, which can effectively inhibit and reduce biofilm formation and bacterial adherence. In this study, we report the fabrication of bactericidal titanium (Ti) and copper (Cu) surfaces which involves a powerful co-sputtering method. This method provides a situation in which constituent elements are deposited simultaneously to control the composition of the thin film. Prepared samples were examined by energy-dispersive X-ray spectroscopy (EDX), scanning electron microscopy (SEM), X-ray diffraction (XRD), atomic force microscopy (AFM), and contact angle measurements. To evaluate antibacterial behavior, we used two bacterial strains Gram-negative Escherichia coli (E. coli) and Gram-positive Staphylococcus aureus (S. aureus). Antibacterial activity of the prepared sample was assessed by determining the number of colony-forming units per milliliter (CFU/ml) using a standard viable cell count assay. Results indicated that as the Cu concentration increased, the nanoscale surfaces became rougher, with roughness values rising from 11.85 to 49.65 nm, and the contact angle increased from 40 to 80 degrees, indicating a hydrophilic character. These factors play a significant role in the antibacterial properties of the surface. The Ti-Cu films displayed superior antibacterial ability, with a 99.9% reduction (equivalent to a 5-log reduction) in bacterial viability after 2 h compared to Ti alone against both bacterial strains. Field emission scanning electron microscopy (FE-SEM) images verified that both E. coli and S. aureus cells were physically deformed and damaged the bacterial cell ultrastructure was observed. These findings highlight that adding Cu to Ti can improve the antibacterial ability of the surface while inhibiting bacterial adherence. Therefore, the Ti14-Cu86 sample with the highest percentage of Cu had the best bactericidal rate. Investigation of toxicity of Cu-Ti thin films was conducted the using the MTT assay, which revealed their biocompatibility and absence of cytotoxicity, further confirming their potential as promising biomaterials for various applications.

In Vitro and In Vivo Studies of Antibacterial Coatings on Titanium Alloy Implants for Veterinary Application

The aim of this work was the evaluation of biological properties of hybrid coatings modified with Ag, Cu, and Zn nanoparticles (NPs) applied on TPLO medical implants by the sol-gel process. The implant coatings enriched with various concentrations of metallic NPs were investigated in the in vitro bactericidal efficacy tests against Gram+ and Gram- bacteria and pathogenic yeast. Next, the designed materials were tested on human osteosarcoma cell lines. The cells adhesion, proliferation, viability, and differentiation were investigated. The cell growth wasevaluated using SEM, and the metallic ion release was measured. The results revealed that the NPs concentration in the hybrid layers decreased with the incubation time. In the last stage, the implants were tested in vivo on six canine patients. Three months after the operation, the radiological evaluation of the performed anastomosis was carried out as well as the histopathological evaluation of tissue regeneration. The strongest bactericidal efficacy was observed for the layers containing AgNPs. Along with an increased concentration of metallic additives, a growing toxic effect was clearly observed. The most pronounced toxic effect was especially evident with the AgNPs concentration exceeding 1 mol %. In all the operated patients, no deviations were found during the follow-up examinations in the postoperative period. The low dose of AgNPs in the hybrid layer facilitated the tissue healing process. It was proven that silver nanoparticles may accelerate the bone healing process. The correct tissue reparation was observed.

Functionalized TiCu/TiCuN coating promotes osteoporotic fracture healing by upregulating the Wnt/β-catenin pathway

Osteoporosis results in decreased bone mass and insufficient osteogenic function. Existing titanium alloy implants have insufficient osteoinductivity and delayed/incomplete fracture union can occur when used to treat osteoporotic fractures. Copper ions have good osteogenic activity, but their dose-dependent cytotoxicity limits their clinical use for bone implants. In this study, titanium alloy implants functionalized with a TiCu/TiCuN coating by arc ion plating achieved a controlled release of copper ions in vitro for 28 days. The coated alloy was co-cultured with bone marrow mesenchymal stem cells and showed excellent biocompatibility and osteoinductivity in vitro. A further exploration of the underlying mechanism by quantitative real-time polymerase chain reaction and western blotting revealed that the enhancement effects are related to the upregulation of genes and proteins (such as axin2, β-catenin, GSK-3β, p-GSK-3β, LEF1 and TCF1/TCF7) involved in the Wnt/β-catenin pathway. In vivo experiments showed that the TiCu/TiCuN coating significantly promoted osteoporotic fracture healing in a rat femur fracture model, and has good in vivo biocompatibility based on various staining results. Our study confirmed that TiCu/TiCuN-coated Ti promotes osteoporotic fracture healing associated with the Wnt pathway. Because the coating effectively accelerates the healing of osteoporotic fractures and improves bone quality, it has significant clinical application prospects.

High Performance of Metallic Thin Films for Resistance Temperature Devices with Antimicrobial Properties

Titanium-copper alloy films with stoichiometry given by Ti1-xCux were produced by magnetron co-sputtering technique and analyzed in order to explore the suitability of the films to be applied as resistive temperature sensors with antimicrobial properties. For that, the copper (Cu) amount in the films was varied by applying different DC currents to the source during the deposition in order to change the Cu concentration. As a result, the samples showed excellent thermoresistivity linearity and stability for temperatures in the range between room temperature to 110 °C. The sample concentration of Ti0.70Cu0.30 has better characteristics to act as RTD, especially the αTCR of 1990 ×10-6°C-1. The antimicrobial properties of the Ti1-xCux films were analyzed by exposing the films to the bacterias S. aureus and E. coli, and comparing them with bare Ti and Cu films that underwent the same protocol. The Ti1-xCux thin films showed bactericidal effects, by log10 reduction for both bacteria, irrespective of the Cu concentrations. As a test of concept, the selected sample was subjected to 160 h reacting to variations in ambient temperature, presenting results similar to a commercial temperature sensor. Therefore, these Ti1-xCux thin films become excellent antimicrobial candidates to act as temperature sensors in advanced coating systems.

Recent Advances in Copper-Doped Titanium Implants

Titanium (Ti) and its alloys have been extensively used as implant materials in clinical practice due to their high corrosion resistance, light weight and excellent biocompatibility. However, the insufficient intrinsic osteogenic capacity of Ti and its alloys impedes bone repair and regeneration, and implant-related infection or inflammation remains the leading cause of implant failure. Bacterial infections or inflammatory diseases constitute severe threats to human health. The physicochemical properties of the material are critical to the success of clinical procedures, and the doping of Cu into Ti implants has been confirmed to be capable of enhancing the bone repair/regeneration, angiogenesis and antibacterial capability. This review outlines the recent advances in the design and preparation of Cu-doped Ti and Ti alloy implants, with a special focus on various methods, including plasma immersion implantation, magnetron sputtering, galvanic deposition, microarc oxidation and sol-gel synthesis. More importantly, the antibacterial and mechanical properties as well as the corrosion resistance and biocompatibility of Cu-doped Ti implants from different methods are systematically reviewed, and their prospects and limitations are also discussed.

Investigation on Blood Compatibility of Cu/Ti Metal Coating Prepared via Various Bias Voltages and Copper Content

Surface modification of some metal coatings is usually used to improve the blood compatibility of biomaterials; however, some aspects of the bological properties of metal coatings cannot be adjusted via the content of each component. In this work, Cu/Ti metal coatings with various amounts of copper content were prepared by the physical vapor deposition (PVD) method, and the influence of deposition bias was further investigated. Phase structure, element composition and surface morphology were investigated by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy, respectively. The hemolysis ratio, platelet adhesion and protein adsorption were applied to evaluate the blood compatibility. The results show that a Cu/Ti coating of uniform quality can be obtained; the dispersion of the deposition and copper content is regulated by the number of copper sheets, but the deposition bias does not obviously affect the copper content of the Cu/Ti coating. The hemolysis rate of the Cu/Ti coating is less than 0.4%, the degree of platelet adhesion is significantly reduced on Cu/Ti coatings compared to control samples, and the contact angle of all coatings is greater than that of pure titanium. The largest adsorption capacity of BSA was found on the coating with the deposition bias voltage of −40 V. The number of copper flakes is increased, and the adsorption of FIB on the Cu/Ti coating surface is reduced. Therefore, Cu/Ti coatings prepared via this deposition method have potential for applications to regulate blood compatibility and surface performance.

Thermal activation of Ti(1-x)Au(x) thin films with enhanced hardness and biocompatibility

The lifetime of orthopaedic implants can be extended by coating the softer Ti₆Al₄V alloy with harder biocompatible thin films. In this work, thin films of Ti_(1-x)Au_(x) are grown on Ti₆Al₄V and glass substrates by magnetron sputtering in the entire x = 0–1 range, before their key biomechanical properties are performance tuned by thermal activation. For the first time, we explore the effect of in-situ substrate heating versus ex-situ post-deposition heat-treatment, on development of mechanical and biocompatibility performance in Ti–Au films. A ∼250% increase in hardness is achieved for Ti–Au films compared to bulk Ti₆Al₄V and a ∼40% improvement from 8.8 GPa as-grown to 11.9 and 12.3 GPa with in-situ and ex-situ heat-treatment respectively, is corelated to changes in structural, morphological and chemical properties, providing insights into the origins of super-hardness in the Ti rich regions of these materials. X-ray diffraction reveals that as-grown films are in nanocrystalline states of Ti–Au intermetallic phases and thermal activation leads to emergence of mechanically hard Ti–Au intermetallics, with films prepared by in-situ substrate heating having enhanced crystalline quality. Surface morphology images show clear changes in grain size, shape and surface roughness following thermal activation, while elemental analysis reveals that in-situ substrate heating is better for development of oxide free Ti₃Au β-phases. All tested Ti–Au films are non-cytotoxic against L929 mouse fibroblast cells, while extremely low leached ion concentrations confirm their biocompatibility. With peak hardness performance tuned to >12 GPa and excellent biocompatibility, Ti–Au films have potential as a future coating technology for load bearing medical implants.

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Combined study on biocompatibility and mechanical performance of Ti–Au films.

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Reports on effect of varying of thermal activation on quality of Ti–Au film structure.

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Clear development of super-hard β-Ti₃Au phase with in-situ thermal activation.

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Peak hardness value > 12 GPa attained for Ti rich films with ex-situ thermal activation.

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All Ti–Au films highly biocompatible with safe cytotoxic profile against L929 cells.

Flexible TiCux Thin Films with Dual Antimicrobial and Piezoresistive Characteristics

The eradication of microorganisms from high traffic surfaces to prevent either viral or bacterial infections represents an urgent need, mainly in the scope of the present pandemic scenario. In this context, this work explores the dual functionality of titanium-copper thin films as pressure elements with antimicrobial properties, aiming for the implementation of touch and sensing capabilities in high traffic surfaces. Copper was employed as the antibacterial agent within a titanium matrix. The film's geometry and deposition parameters were varied in order to optimize antimicrobial and piezoresistive response. A considerable antimicrobial response has been obtained, increasing the copper amount (from 23 to 63 at. %) in the titanium matrix, leading to an outstanding 8 log₁₀ CFU bacterial reduction in the case of Escherichia coli. Moreover, for the same amount of copper, the piezoresistive sensibility of the thin films increases up to a maximum gauge factor of 5.18 ± 0.09, which indicates an adequate electromechanical behavior for sensing applications. Our findings demonstrate the best combined antimicrobial and piezoresistive characteristics for the films with a Cu content of 63 at. %, indicating a potential use of these films for electromechanical sensor applications.

Inhibition efficiency of 304-Cu stainless steel against oral bacterial biofilm

PURPOSE

This study aims to evaluate the antibacterial properties of 304 Cu-bearing stainless steel (SS) with different Cu contents (0, 2.5, 4.5 wt.%) against oral biofilms of Streptococcus mutans (S. mutans), Streptococcus sanguinis (S. sanguinis), and their mixture.

METHODS

Bacterial biofilms on the surface of 304-Cu SS were characterized by plate counting, 4', 6-diamidino-2-phenylindole (DAPI) staining with aid of sanning electron microscopy (SEM) and 2, 3-bis (2-methoxy-4-nitro-5-sulfophenyl)-2H-tetrazolium-5-carboxanilide inner salt (XTT). In addition, the inhibition zone method was also employed to evaluate the antibacterial properties of 304-Cu SS. Cell Counting Kit-8 (CCK-8) and flow cytometry were used to assess the cytotoxicity and apoptosis rate of 304-Cu SS, respectively.

RESULTS

304-4.5Cu SS could effectively inhibit the attachment, formation, activity, and metabolism of bacterial biofilm, possessing the best antibacterial properties exceeding 99.9% of antibacterial rate against S. mutans, S. sanguinis, and their mixture. The diameters of inhibition zones to S. mutans and S. sanguinis on the surface of 304-4.5Cu SS were 21.7 and 14.7 mm, respectively. The results of cell experiments in vitro showed that both 304-2.5Cu SS and 304-4.5Cu SS had no evident cytotoxicity with an identical grade 1. The apoptosis rate exhibited a gradually increased tendency with increase of the Cu content in 304 SS.

CONCLUSIONS

304-4.5Cu SS without cytotoxic effect on NIH3T3 cells has obvious antibacterial activity against S. mutans, S. sanguinis and their mixture.

CLINICAL SIGNIFICANCE

The Cu-bearing stainless steel provides a new solution to be used as oral orthodontic devices for inhibiting oral microflora imbalance and enamel demineralization.

Cellulose acetate fibres loaded with daptomycin for metal implant coatings

Multifunctional polymeric coatings containing drug delivery vehicles can play a key role in preventing/reducing biofilm formation on implant surfaces. Their requirements are biocompatibility, good adhesion, and controllable drug release. Although cellulose acetate (CA) films and membranes are widely studied for scaffolding, their applications as a protective coating and drug delivery vehicle for metal implants are scarce. The reason is that adhesion to stainless steel (SS) substrates is non-trivial. Grinding SS substrates enhances the adhesion of dip-coated CA films while the adhesion of electrospun CA membranes is improved by an electrosprayed chitosan intermediate layer. PMMA microcapsules containing daptomycin have been successfully incorporated into CA films and fibres. The released drug concentration of 3 × 10^-3 mg/mL after 120 min was confirmed from the peak luminescence intensity under UV radiation of simulated body fluid (SBF) after immersion of the fibres.

Inorganic material based macrophage regulation for cancer therapy: basic concepts and recent advances

Macrophages with the M1 phenotype are a type of immune cell with exciting prospects for cancer therapy; however, when these macrophages infiltrate into tumours, many of them are induced by the tumour microenvironment to transform into the M2 type, which can enable tumour defence against external therapeutic strategies, assisting in tumour development. Macrophages have strong plasticity and functional heterogeneity, and their phenotypic transformation is complex and still poorly understood in relation to cancer therapy. Recent material advances in inorganic nanomaterials, especially inorganic elements in vivo, have accelerated the development of macrophage regulation-based cancer treatments. This review summarizes the basics of recent research on macrophage phenotype transformation and discusses the current challenges in macrophage type regulation. Then, the current achievements involving inorganic material-based macrophage regulation and the related anticancer effects of induced macrophages and their extracellular secretions are reviewed systematically. Importantly, inorganic nanomaterial-based macrophage phenotype regulation is flexible and can be adapted for different types of cancer therapies, presenting a possible novel approach for the generation of immune materials for cancer therapy.

Surface Stoichiometry and Depth Profile of Tix-CuyNz Thin Films Deposited by Magnetron Sputtering

We report the surface stoichiometry of Tix-CuyNz thin film as a function of film depth. Films are deposited by high power impulse (HiPIMS) and DC magnetron sputtering (DCMS). The composition of Ti, Cu, and N in the deposited film is investigated by X-ray photoelectron spectroscopy (XPS). At a larger depth, the relative composition of Cu and Ti in the film is increased compared to the surface. The amount of adventitious carbon which is present on the film surface strongly decreases with film depth. Deposited films also contain a significant amount of oxygen whose origin is not fully clear. Grazing incidence X-ray diffraction (GIXD) shows a Cu3N phase on the surface, while transmission electron microscopy (TEM) indicates a polycrystalline structure and the presence of a Ti3CuN phase.

Vapor-Deposited Biointerfaces and Bacteria: An Evolving Conversation

At the biointerface where materials and microorganisms meet, the organic and synthetic worlds merge into a new science that directs the design and safe use of synthetic materials for biological applications. Vapor deposition techniques provide an effective way to control the material properties of these biointerfaces with molecular-level precision that is important for biomaterials to interface with bacteria. In recent years, biointerface research that focuses on bacteria-surface interactions has been primarily driven by the goals of killing bacteria (antimicrobial) and fouling prevention (antifouling). Nevertheless, vapor deposition techniques have the potential to create biointerfaces with features that can manipulate and dictate the behavior of bacteria rather than killing or deterring them. In this review, we focus on recent advances in antimicrobial and antifouling biointerfaces produced through vapor deposition and provide an outlook on opportunities to capitalize on the features of these techniques to find unexplored connections between surface features and microbial behavior.

Development of Antibacterial Ti-Cux Alloys for Dental Applications: Effects of Ageing for Alloys with Up to 10 wt% Cu

Peri-implantitis, a disease caused by bacteria, affects dental implants in patients. It is widely treated with antibiotics, however, with growing antibiotic resistance new strategies are required. Titanium-copper alloys are prospective antibacterial biomaterials, with the potential to be a remedy against peri-implantitis and antibiotic resistance. The aim of this study was to investigate Ti-Cu_x alloys, exploring how Cu content (up to 10 wt%) and ageing affect the material properties. Electron microscopy, X-ray diffraction, hardness testing, bacteriological culture, and electrochemical testing were employed to characterize the materials. It was found that alloys with above 3 wt% Cu had two phases and ageing increased the volume fraction of Ti₂Cu. An un-aged alloy of 5 wt% Cu showed what could be Ti₃Cu, in addition to the α-Ti phase. The hardness gradually increased with increased Cu additions, while ageing only affected the alloy with 10 wt% Cu (due to changes in microstructure). Ageing resulted in faster passivation of the alloys. After two hours the aged 10 wt% Cu alloy was the only material with an antibacterial effect, while after six hours, bacteria killing occurred in all alloys with above 5 wt% Cu. In conclusion, it was possible to tune the material and antibacterial properties of Ti-Cu_x alloys by changing the Cu concentration and ageing, which makes further optimization towards an antibacterial material promising.

Surface Stoichiometry and Optical Properties of Cux–TiyCz Thin Films Deposited by Magnetron Sputtering

Ternary carbide in metal matrix composites constitute a big challenge in the industry, and in this regard their surface treatment is one of the most important issues. Ternary carbide (CuxTiyCz, where x, y and z are integers) thin films are synthesized by magnetron sputtering and characterized with respect to the film depth. X-ray photoelectron spectroscopy (XPS) of Cu-2p and Ti-2p peaks shows the associated shake-up satellite peaks at a smaller film depth; the peak intensity is reduced at a higher depth. The relative intensity of Cu and Ti increases at a larger film depth. The optical band gap varies from 1.83 to 2.20 eV at different film depths.

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/CuTi_x 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.

Antibacterial properties and biocompatibility in vivo and vitro of composite coating of pure magnesium ultrasonic micro-arc oxidation phytic acid copper loaded

Bone infection and implant secondary removal remains a clinical challenge. We used ultrasonic micro-arc oxidation (UMAO) and conversion of phytic acid copper plating to prepare a pure magnesium polyhydric biofilm; we evaluated the surface microstructures, phase, element composition, and wettability of the film in vitro. The antibacterial activity of films with different Cu contents was confirmed by coating method, imaging examination, and microbiological cultures in vitro. The biocompatibility of biofilms was confirmed by cell proliferation, vitality, and morphology assays in vitro and histological evaluation in vivo. MC3T3-E1 cells were co-cultured with different films to assess cell viability on the films. The results showed that the mass fraction of Cu increased with increasing time of copper plating, and the surface of the Cu group was more dense and uniform. Additionally, copper coating significantly inhibited the growth of E. coli and Staphylococcus aurous. We also found that the adhesion, proliferation, and differentiation of the cells on the surface of copper plating were enhanced. Copper implantation of animals in vivo showed fine ability to promote bone growth. Antibacterial activity and biocompatibility of pure magnesium UMAO-phytic acid-Cu3min implant film are excellent, so the film has potential application value in the treatment of bone implantation.

Surface Characterization and Copper Release of a-C:H:Cu Coatings for Medical Applications

This paper focuses on the surface properties of a-C:H:Cu composite coatings for medical devices and how the release of Cu2+ ions from such coatings can be controlled. The released Cu ions have the potential to act as a bactericidal agent and inhibit bacterial colonization. A PVD–PECVD hybrid process was used to deposit a-C:H:Cu composite coatings onto Ti6Al4V substrates. We examine the layer surface properties using atomic force microscopy and static contact angle measurements. An increasing surface roughness and increasing contact angle of Ringer’s solution was measured with increasing copper mole fraction (XCu) in the coatings. The contact angle decreased when a supplementary bias voltage of −50 V was used during the a-C:H:Cu deposition. These findings are in line with earlier published results regarding these types of coatings. The release of Cu2+ ions from a-C:H:Cu coatings in Ringer’s solution was measured by anodic stripping voltammetry. Different layer structures were examined to control the time-resolved Cu release. It was found that the Cu release depends on the overall XCu in the a-C:H:Cu coatings and that an additional a-C:H barrier layer on top of the a-C:H:Cu layer effectively delays the release of Cu ions.

Antibacterial Silicon Oxide Thin Films Doped with Zinc and Copper Grown by Atmospheric Pressure Plasma Chemical Vapor Deposition

Zn-doped and Cu-doped SiO_x films were synthesized by atmospheric pressure plasma chemical vapor deposition to study their antibacterial efficiency against Gram-negative Escherichia coli and their cytotoxic effect on the growth of mouse cells. Zn-rich and Cu-rich particles with diameters up to several microns were found to be homogeneously distributed within the SiO_x films. For both doping elements, bacteria are killed within the first three hours after exposure to the film surface. In contrast, mouse cells grow well on the surfaces of both film types, with a slight inhibition present only after the first day of exposure. The obtained results indicate that the films show a high potential for use as effective antibacterial surfaces for medical applications.

A critical review of multifunctional titanium surfaces: New frontiers for improving osseointegration and host response, avoiding bacteria contamination

Evolution of metal implants progressively shifted the focus from adequate mechanical strength to improved biocompatibility and absence of toxicity and, finally, to fast osseointegration. Recently, new frontiers and challenges of Ti implants have been addressed to improvement of bioactivity, fighting of bacterial infection and biofilm formation, as well as modulation of inflammation. This is closely related to the clinical demand of multifunctional implants able to simultaneously have a number of specific responses with respect to body fluids, cells (osteoblasts, fibroblasts, macrophages) and pathogenic agents (bacteria, viruses). This complex system of multiple biological stimuli and surface responses is a major arena of the current research on biomaterials and biosurfaces. This review covers the strategies explored to this purpose since 2010 in the case of Ti and Ti alloys, considering that the number of related papers doubled about in the last seven years and no review has comprehensively covered this engaging research area yet. The different approaches followed for producing multifunctional Ti-based surfaces involve the use of thick and thin inorganic coatings, chemical surface treatments, and functionalization strategies coupled with organic coatings.

STATEMENT OF SIGNIFICANCE

According to the clinical demand of multifunctional implants able to simultaneously have a number of specific responses with respect to body fluids, cells and pathogenic agents, new frontiers of Ti implants have been addressed to improvement of bioactivity, fighting of bacterial infection and biofilm formation, as well as modulation of inflammation. Literature since 2010 is here reviewed. Several strategies for getting bioactive and antibacterial actions on Ti surfaces have been suggested, but they still need to be optimized with respect to several concerns. A further step will be to combine on the same surface a proven ability of modulation of inflammatory response. The achievement of multifunctional surfaces able to modulate inflammation and to promote osteogenesis is a grand challenge.

Copper as an alternative antimicrobial coating for implants - An in vitro study

AIM

To investigate osteoconductive and antimicrobial properties of a titanium-copper-nitride (TiCuN) film and an additional BONIT^® coating on titanium substrates.

METHODS

For micro-structuring, the surface of titanium test samples was modified by titanium plasma spray (TPS). On the TPS-coated samples, the TiCuN layer was deposited by physical vapor deposition. The BONIT^® layer was coated electrochemically. The concentration of copper ions released from TiCuN films was measured by atomic absorption spectrometry. MG-63 osteoblasts on TiCuN and BONIT^® were analyzed for cell adhesion, viability and spreading. In parallel, Staphylococcus epidermidis (S. epidermidis) were cultivated on the samples and planktonic and biofilm-bound bacteria were quantified by counting of the colony-forming units.

RESULTS

Field emission scanning electron microscopy (FESEM) revealed rough surfaces for TPS and TiCuN and a special crystalline surface structure on TiCuN + BONIT^®. TiCuN released high amounts of copper quickly within 24 h. These release dynamics were accompanied by complete growth inhibition of bacteria and after 2 d, no planktonic or adherent S. epidermidis were found on these samples. On the other hand viability of MG-63 cells was impaired during direct cultivation on the samples within 24 h. However, high cell colonization could be found after a 24 h pre-incubation step in cell culture medium simulating the in vivo dynamics closer. On pre-incubated TiCuN, the osteoblasts span the ridges and demonstrate a flattened, well-spread phenotype. The additional BONIT^®coating reduced the copper release of the TiCuN layer significantly and showed a positive effect on the initial cell adhesion.

CONCLUSION

The TiCuNcoating inhibits the formation of bacterial biofilms on orthopedic implants by influencing the “race for the surface” to the advantage of osteoblasts.

Flexible Antibacterial Coatings

This article reviews the present state of the art in the field of flexible antibacterial coatings which efficiently kill bacteria on their surfaces. Coatings are formed using a reactive magnetron sputtering. The effect of the elemental composition and structure of the coating on its antibacterial and mechanical properties is explained. The properties of Cr–Cu–O, Al–Cu–N, and Zr–Cu–N antibacterial coatings are used as examples and described in detail. The efficiency of killing of bacteria was tested for the Escherichia coli bacterium. The principle of the formation of thick, flexible antibacterial coatings which are resistant to cracking under bending is explained. It is shown that magnetron sputtering enables production of robust, several-micrometer thick, flexible antibacterial coatings for long-term use. The antibacterial coatings produced by magnetron sputtering present huge potential for many applications.

Investigation of Structural, Compositional and Anti-Microbial Properties of Copper Thin Film Using Direct Current Magnetron Sputtering for Surgical Instruments

Surgical instruments and other bioimplant devices, owing to their importance in the biomedical industry require high biocompatibility to be used in the human body. Nevertheless, issues of compatibility, bacterial infections are quite common in such devices. Hence development of surface coatings on various substrates for implant applications is a promising technique to combat the issues arising in these implant materials. The present investigation aims at coating copper on stainless steel substrate using DC Magnetron sputtering which is used to achieve film of required thickness (0.5–8[Formula: see text][Formula: see text]m). The deposition pressure, substrate temperature, power supply, distance between the specimen and target are optimized and maintained constant, while the sputtering time (30–110[Formula: see text]min) is varied. The sputtered copper thin film’s morphology, composition are characterized by SEM and EDAX. X-ray diffraction analysis shows copper oriented on (111) and (002) and copper oxide on (111) planes. The contact angle of copper thin film is 92[Formula: see text] while AISI 316L shows 73[Formula: see text]. The antimicrobial studies carried in Staphylococcus aureus, Escherichia Coli, Klebsiella pneumonia and Candida albicans show that the maximum reduction was seen upto 35, 26, 54, 39[Formula: see text]CFU/mL, respectively after 24[Formula: see text]h. The cell viability is studied by MTT assay test on Vero cell line for 24[Formula: see text]h, 48[Formula: see text]h and 72[Formula: see text]h and average cell viability is 43.85%. The copper release from the thin film to the culture medium is 6691[Formula: see text][Formula: see text]g/L (maximum) is estimated from AAS studies. The copper coated substrate does not show much reaction with living Vero cells whereas the bacteria and fungi are found to be destroyed.

Influence of Cu, Au and Ag on structural and surface properties of bioactive coatings based on titanium

In this work influence of copper, silver and gold additives on structural and surface properties of biologically active thin films based on titanium have been described. Coatings were prepared by magnetron sputtering method. During each process metallic discs (targets) - Ti and the additive (Cu, Ag or Au) were co-sputtered in argon atmosphere. Structural investigation of as-deposited coatings was performed with the aid of XRD and SEM/EDS method. It was found that all prepared thin films were homogenous. Addition of Cu, Ag and Au resulted in nanocrystalline structure. Moreover, influence of these additives on hardness and antibacterial activity of titanium coatings was also studied. Ti-Cu, Ti-Ag and Ti-Au films had lower hardness as-compared to Ti. According to AAS results the difference of their activity was related to the ion migration process. It was found that Ti-Ag and Ti-Au coatings had biocidal effect related to direct contact of their surface with microorganisms. In the case of Ti-Cu antimicrobial activity had direct and indirect nature due to efficient ion migration process from the film surface to the surrounding environment. Functional features of coatings such as wettability and corrosion resistance were also examined and included in the comprehensive analysis.

Antibacterial Metallic Touch Surfaces

Our aim is to present a comprehensive review of the development of modern antibacterial metallic materials as touch surfaces in healthcare settings. Initially we compare Japanese, European and US standards for the assessment of antimicrobial activity. The variations in methodologies defined in these standards are highlighted. Our review will also cover the most relevant factors that define the antimicrobial performance of metals, namely, the effect of humidity, material geometry, chemistry, physical properties and oxidation of the material. The state of the art in contact-killing materials will be described. Finally, the effect of cleaning products, including disinfectants, on the antimicrobial performance, either by direct contact or by altering the touch surface chemistry on which the microbes attach, will be discussed. We offer our outlook, identifying research areas that require further development and an overview of potential future directions of this exciting field.

In vitro study on an antibacterial Ti-5Cu alloy for medical application

Health of human beings is subjected to severe threats from the spread of harmful bacteria and the implant-associated infection remains a serious problem in clinic. In this study, a copper-bearing antibacterial titanium alloy, Ti-5Cu, has been developed for dental and orthopedic implant applications. The microstructure, mechanical property, electrochemical corrosion behavior, in vitro antibacterial performance, cytocompatibility and hemocompatibility of the alloy are systematically investigated. The results reveal that the Ti-5Cu alloy which consists of α-phase matrix and intermetallic compound Ti2Cu not only possesses strong antibacterial activity against both E. coli and S. aureus, but also exhibits better mechanical properties than the commercial pure titanium. It is confirmed that the release of trace amount of Cu ions from the alloy plays an important role in killing bacteria. In spite of the ion release, Ti-5Cu alloy still reveals excellent corrosion resistance. Moreover, good cytocompatibility and superior hemocompatibility make Ti-5Cu alloy to be a potential solution that could prevent the peri-implant infection in dental and orthopaedic applications.

One-step method for the preparation of poly(methyl methacrylate) modified titanium-bioactive glass three-dimensional scaffolds for bone tissue engineering

A novel three-dimensional (3D) titanium (Ti)-doping meso-macroporous bioactive glasses (BGs)/poly(methyl methacrylate) (PMMA) composite was synthesised using PMMA and EO20PO70EO20 (P123) as the macroporous and mesoporous templates, respectively. Unlike the usual calcination method, the acid steam technique was used to improve the polycondensation of Ti-BGs, and then PMMA was partially extracted via chloroform to induce the macroporous structure. Simultaneously, the residual PMMA which remained in the wall enhanced the compressive strength to 2.4 MPa (0.3 MPa for pure BGs). It is a simple and green method to prepare the macro-mesoporous Ti-BGs/PMMA. The materials showed the 3D interconnected hierarchical structure (250 and 3.4 nm), making the fast inducing-hydroxyapatite growth and the controlled drug release. Besides mentioned above, the good antimicrobial property and biocompatible of the scaffold also ensure it is further of clinical use. Herein, the fabricated materials are expected to have potential application on bone tissue regeneration.

Novel Cu@SiO2/bacterial cellulose nanofibers: Preparation and excellent performance in antibacterial activity

The antibacterial composite based on bacterial cellulose (BC) was successfully prepared by in-situ synthesis of SiO2 coated Cu nanoparticles (Cu@SiO2/BC) and its properties were characterized. Its chemical structures and morphologies were evaluated by Fourier transformation infrared spectrum (FTIR), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The results demonstrated that the SiO2 coated Cu particles were well homogeneously precipitated on the surface of BC. The Cu@SiO2/BC was more resistant to oxidation than the Cu nanoparticles impregnated into BC (Cu/BC) and then Cu@SiO2/BC could prolong the antimicrobial activity against Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli).

Influence of Cu-Ti thin film surface properties on antimicrobial activity and viability of living cells

The paper describes properties of thin-film coatings based on copper and titanium. Thin films were prepared by co-sputtering of Cu and Ti targets in argon plasma. Deposited coatings consist of 90at.% of Cu and 10at.% of Ti. Characterization of the film was made on the basis of investigations of microstructure and physicochemical properties of the surface. Methods such as scanning electron microscopy, x-ray microanalysis, x-ray diffraction, x-ray photoelectron spectroscopy, atomic force microscopy, optical profilometry and wettability measurements were used to assess the properties of deposited thin films. An impact of Cu-Ti coating on the growth of selected bacteria and viability of the living cells (line L929, NCTC clone 929) was described in relation to the structure, surface state and wettability of the film. It was found that as-deposited films were amorphous. However, in such surroundings the nanocrystalline grains of 10-15nm and 25-35nm size were present. High surface active area with a roughness of 8.9nm, had an effect on receiving relatively high water contact angle value (74.1°). Such wettability may promote cell adhesion and result in an increase of the probability of copper ion transfer from the film surface into the cell. Thin films revealed bactericidal and fungicidal effects even in short term-contact. High activity of prepared films was directly related to high amount (ca. 51 %) of copper ions at 1+ state as x-ray photoelectron spectroscopy results have shown.

Persistent effectivity of gas plasma-treated, long time-stored liquid on epithelial cell adhesion capacity and membrane morphology

Research in plasma medicine includes a major interest in understanding gas plasma-cell interactions. The immediate application of gas plasma in vitro inhibits cell attachment, vitality and cell-cell contacts via the liquid. Interestingly, in our novel experiments described here we found that the liquid-mediated plasma effect is long-lasting after storage up to seven days; i. e. the liquid preserves the characteristics once induced by the argon plasma. Therefore, the complete Dulbecco's Modified Eagle cell culture medium was argon plasma-treated (atmospheric pressure, kINPen09) for 60 s, stored for several days (1, 4 and 7 d) at 37°C and added to a confluent mouse hepatocyte epithelial cell (mHepR1) monolayer. Impaired tight junction architecture as well as shortened microvilli on the cell membrane could be observed, which was accompanied by the loss of cell adhesion capacity. Online-monitoring of vital cells revealed a reduced cell respiration. Our first time-dependent analysis of plasma-treated medium revealed that temperature, hydrogen peroxide production, pH and oxygen content can be excluded as initiators of cell physiological and morphological changes. The here observed persisting biological effects in plasma-treated liquids could open new medical applications in dentistry and orthopaedics.

In vivo evaluation of copper release and acute local tissue reactions after implantation of copper-coated titanium implants in rats

Copper (Cu) based coatings can reduce infections for titanium (Ti) implants. However, Cu is also cytotoxic. To examine the balance of antibacterial versus adverse tissue effects, this study aimed at evaluating a Cu coating regarding in vivo Cu release and local inflammatory reactions for 72 h. TiAl6V4 plates received either plasma electrolytic oxidation only (Ti), or an additional galvanic Cu deposition (Ti-Cu). No Staphylococcus aureus were found in vitro on Ti-Cu after 24 h. Following simultaneous intramuscular implantation of two Ti and two Ti-Cu plates into nine rats, serum Cu was elevated until 48 h and residual Cu on explanted samples reduced accordingly after 48 h. Total and tissue macrophages around implants increased until 72 h for both series, and were increased for Ti-Cu. As numbers of total and tissue macrophages were comparable, macrophages were probably tissue-derived. MHC-class-II-positive cells increased for Ti-Cu only. T-lymphocytes had considerably lower numbers than macrophages, did not increase or differ between both series, and thus had minor importance. Tissue reactions increased beyond Cu release, indicating effects of either surface-bound Cu or more likely the implants themselves. Altogether, Ti-Cu samples possessed antibacterial effectiveness in vitro, released measurable Cu amounts in vivo and caused a moderately increased local inflammatory response, demonstrating anti-infective potential of Cu coatings.

In vivo examination of the local inflammatory response after implantation of Ti6Al4V samples with a combined low-temperature plasma treatment using pulsed magnetron sputtering of copper and plasma-polymerized ethylenediamine

Copper (Cu) could serve as antibacterial coating for Ti6Al4V implants. An additional cell-adhesive layer might compensate Cu cytotoxicity. This study aimed at in vitro and in vivo evaluation of low-temperature plasma treatment of Ti6Al4V plates with Ti/Cu magnetron sputtering (Ti6Al4V-Ti/Cu), plasma-polymerized ethylenediamine (Ti6Al4V-PPEDA), or both (Ti6Al4V-Ti/Cu-PPEDA). Ti6Al4V-Ti/Cu and Ti6Al4V-Ti/Cu-PPEDA had comparable in vitro Cu release and antibacterial effectiveness. Following intramuscular implantation of Ti6Al4V-Ti/Cu, Ti6Al4V-PPEDA, Ti6Al4V-Ti/Cu-PPEDA and Ti6Al4V controls for 7, 14 and 56 days with 8 rats/day, peri-implant tissue was immunohistochemically examined for different inflammatory cells. Ti6Al4V-PPEDA had more mast cells and NK cells than Ti6Al4V, and more tissue macrophages, T lymphocytes, mast cells and NK cells than Ti6Al4V-Ti/Cu-PPEDA. Ti6Al4V-Ti/Cu had more mast cells than Ti6Al4V and Ti6Al4V-Ti/Cu-PPEDA. Results indicate that PPEDA-mediated cell adhesion counteracted Cu cytotoxicity. Ti6Al4V-Ti/Cu-PPEDA differed from Ti6Al4V only for mast cells on day 56. Altogether, implants with both plasma treatments had antibacterial properties and did not increase inflammatory reactions.

Analysis of the release characteristics of cu-treated antimicrobial implant surfaces using atomic absorption spectrometry

New developments of antimicrobial implant surfaces doped with copper (Cu) ions may minimize the risk of implant-associated infections. However, experimental evaluation of the Cu release is influenced by various test parameters. The aim of our study was to evaluate the Cu release characteristics in vitro according to the storage fluid and surface roughness. Plasma immersion ion implantation of Cu (Cu-PIII) and pulsed magnetron sputtering process of a titanium copper film (Ti-Cu) were applied to titanium alloy (Ti6Al4V) samples with different surface finishing of the implant material (polished, hydroxyapatite and corundum blasted). The samples were submersed into either double-distilled water, human serum, or cell culture medium. Subsequently, the Cu concentration in the supernatant was measured using atomic absorption spectrometry. The test fluid as well as the surface roughness can alter the Cu release significantly, whereby the highest Cu release was determined for samples with corundum-blasted surfaces stored in cell medium.