Coatings For Orthopedic Implants Research Articles

The effect of CNTs/PEEK coating thickness on the friction and wear behavior of porous Ti‐30Ta alloys for biomaterial implants

AbstractElectrophoretic deposition was used to deposit carbon nanotube/polyether ether ketone (CNTs/PEEK) composite coatings onto porous titanium‐tantalum (Ti‐30Ta) substrates at different PEEK concentrations (4.5, 6.0, and 7.5 mg/mL). Coatings were analyzed for thickness, porosity, surface roughness, microhardness and bonding strength, with higher PEEK concentrations producing thicker and more uniform coatings. However, optimal coating thickness showed highest bonding strength; lower and higher thickness led to decreased bonding strength. The tribological properties of the CNTs/PEEK coated Ti‐30Ta samples of different thicknesses (50, 70, and 100 μm) were evaluated using ball‐on‐flat linear reciprocating sliding tests under dry and wet conditions using simulated body fluid (SBF) as a lubricant. The CNTs/PEEK coatings provided excellent tribological protection under dry friction, with thicker coatings having lower friction and negligible wear. However, under wet sliding, the coating's wear rate increased significantly due to softening of the rubbing surface caused by SBF lubrication that increase transfer film onto the counter body surface. Coating with optimal thickness of 74 μm demonstrated the lowest friction and wear under SBF lubrication due to its highest hardness and bonding strength. This study highlights the importance of controlling coating thickness in determining the performance of the CNTs/PEEK coatings for orthopedic implants.

Improved biocompatibility and antibacterial property of zinc alloy fabricated with γ-polyglutamic acid-g-dopamine/copper coatings for orthopedic implants

Zinc-lithium (Zn-Li) alloys have attracted considerable attention as potential biodegradable orthopedic implant materials. However, the biocompatibility and antibacterial property need further improvement to meet the clinical requirements. In this study, poly(γ-glutamic acid)-g-dopamine/copper (γ-PGA-g-DA/Cu) hybrid coatings were fabricated on a Zn alloy to improve its biocompatibility and antibacterial performance. Corrosion analysis in simulated body fluid indicated that the γ-PGA-g-DA/Cu coatings afforded tunable degradation rates of Zn alloys. The cytotoxicity evaluation revealed that the presence of copper ions in the coatings could reduce the cytotoxicity problem caused by zinc ions and enhance the biocompatibility of Zn alloy. In vitro antibacterial tests exhibited that the antibacterial activity of Zn alloy enhanced due to the γ-PGA-g-DA/Cu coatings and the antibacterial performance of γ-PGA-g-DA/Cu coated samples increased with increasing copper content of the coatings. In summary, γ-PGA-g-DA/Cu coatings provide a feasible strategy to design Zn alloy implant materials with improved functional performance.

Cold Spraying of Thick Biomimetic and Stoichiometric Apatite Coatings for Orthopaedic Implants

Ceramic coatings have a long history in the orthopaedic field, with plasma sprayed coatings of hydroxyapatite as leading standard in the manufacturing process; however, these coatings can contain secondary phases resulting from the decomposition of hydroxyapatite at high temperatures, which limit the lifetime of implants and their osseointegration. This work aims to produce coatings that can maximize bone osseointegration of metallic implants. In order to preserve the raw characteristics of hydroxyapatite powders that are thermally unstable, coatings were deposited by cold spray onto Ti6Al4V alloy substrates. In contrast with other thermal spray technologies, this process presents the advantage of spraying particles through a supersonic gas jet at a low temperature. On top of hydroxyapatite, carbonated nanocrystalline apatite was synthesized and sprayed. This biomimetic apatite is similar to bone minerals due to the presence of carbonates and its poor crystallinity. FTIR and XRD analyses proved that the biomimetic characteristics and the non-stoichiometric of the apatite were preserved in the cold spray coatings. The cold spray process did not affect the chemistry of the raw material. The adhesion of the coatings as well as their thicknesses were evaluated, showing values comparable to conventional process. Cold spraying appears as a promising method to preserve the characteristics of calcium phosphate ceramics and to produce coatings that offer potentially improved osseointegration.

Antibacterial Effects of Sodium Borate and Calcium Borate Based Polymeric Coatings for Orthopedic Implants.

IntroductionImplants used in orthopedic surgery can be colonized by bacteria that form biofilm layers complicating treatment. We aimed to determine titanium implants' antibacterial and biofilm-degrading properties when coated with sodium borate (NaB) and calcium borate (CaB) minerals.MethodsWe analyzed twenty-four different implants. Three implants were not coated, three were coated with only a carrier polymer (alginate), and eighteen were coated with either CaB or NaB at different concentrations. The implants were incubated with Staphylococcus aureus, and then the bacterial colonies were enumerated.ResultsThe highest microbial load was observed on the implant coated with alginate (1000 colony-forming units [CFU]/mL). The implant without coating contained a microbial load of 420 CFU/mL. The microbial loads of the implants coated with 0.75 mg/mL CaB or 0.25, 0.5, and 0.75 mg/mL NaB (100, 200, 0, and 0 CFU/mL, respectively) were lower than that of the implant without coating. No biofilm formation was observed on implant surfaces coated with 0.5 mg/mL NaB, 0.75 mg/mL NaB, or 0.75 mg/mL CaB; biofilm formation was observed on the implant without coating and alginate-coated implants surfaces.ConclusionAt high concentrations, borate minerals (NaB and CaB) have a potent antibacterial effect on colonization and biofilm formation on the implant surface. These elements may be used in implant coating in the future because of their potential antibacterial effects.

Preparation and morphological investigation on bioactive ion-modified carbonated hydroxyapatite-biopolymer composite ceramics as coatings for orthopaedic implants

Bioactive ions (Mg, Sr, Zn) doped carbonated hydroxyapatite powders (dHAp) and pure carbonated hydroxyapatite (HAp) powders were prepared by wet chemical precipitation method. The bioactive ions were incorporated into the HAp matrix by co-precipitation from solution containing the appropriate amount of chloride salt of different ions. The morphology of pure HAp was mainly needle-like in nanometre size and the particles were disordered showing quasi-amorphous structure. The ion doping changed the morphology of particles, the dHAp particles had distorted spheroid shapes. Owing to the ion addition, the crystallinity of particles decreased. Particle aggregations can also be observed in both types of samples. HAp and dHAp loaded biopolymer polyvinylpyrrolidone (PVP) composite materials have also been developed by novel electrospinning technique. It has been shown that both the HAp and dHAp particles can be successfully incorporated into the PVP fibre web matrix and simultaneously the bioceramic powders were attached to the surface of polymer fibres. The surface of fibres was not fully covered with the particles. The ceramic powder addition to the polymer solution caused the polymer fibres to become more entangled and the diameters of fibres varied over a wider range compared to the base polymer fibres without bioceramic powder addition.

The application of ceragenins to orthopedic surgery and medicine.

Osteomyelitis and infections associated with orthopedic implants represent a significant burden of disease worldwide. Ceragenins (CSAs) are a relatively new class of small-molecule antimicrobials that target a broad range of Gram-positive and Gram-negative bacteria as well as fungi, viruses, and parasites. This review sets the context of the need for new antimicrobial strategies by cataloging the common pathogens associated with orthopedic infection and highlighting the increasing challenges of managing antibiotic-resistant bacterial strains. It then comparatively describes the antimicrobial properties of CSAs with a focus on the CSA-13 family. More recently developed members of this family such as CSA-90 and CSA-131 may have a particular advantage in an orthopedic setting as they possess secondary pro-osteogenic properties. In this context, we consider several new preclinical studies that demonstrate the utility of CSAs in orthopedic models. Emerging evidence suggests that CSAs are effective against antibiotic-resistant Staphylococcus aureus strains and can prevent the formation of biofilms. There remains considerable scope for developing CSA-based treatments, either as coatings for orthopedic implants or as local or systemic antibiotics to prevent bone infection.

Erratum to: Irradiation with visible light enhances the antibacterial toxicity of silver nanoparticles produced by laser ablation

The rise of antibiotic-resistant bacteria is a rapidly growing global health concern. According to the Center for Disease Control, approximately 2 million illnesses and 23,000 deaths per year occur in the USA due to antibiotic resistance. In recent years, there has been a surge in the use of metal nanoparticles as coatings for orthopedic implants, wound dressings, and food packaging, due to their antimicrobial properties. In this report, we demonstrate that the antibacterial efficacy of silver nanoparticles (AgNPs) is enhanced with exposure to light from the visible spectrum. We find that the increased toxicity is due to augmented silver ion release and bacterial uptake. Interestingly, silver ion toxicity does not appear to depend on the formation of reactive oxygen species. Our findings provide a novel paradigm for using light to regulate the toxicity of AgNPs which may have a significant impact in the development of new antimicrobial therapeutics.

Progress on Biomedical Ceramic Coatings Prepared by Thermal Spraying

Biomedical ceramic coatings on metallic substrates deposited via thermal spraying have attracted extensive attentions in the field of orthopedic implants due to their excellent mechanical strengths and biological properties.The studies on biomedical coatings for orthopedic implants are overviewed,and improvements of thermal sprayed hydroxyapatite coatings are summarized.Newly developed bioactive calcium silicate coatings are reviewed as well.

Novel sphene coatings on Ti–6Al–4V for orthopedic implants using sol–gel method

Hydroxyapatite (HAp) is commonly used to coat titanium alloys (Ti–6Al–4V) for orthopedic implants. However, their poor adhesion strength and insufficient long-term stability limit their application. Novel sphene (CaTiSiO 5) ceramics possess excellent chemical stability and cytocompatibility. The aim of this study is to use the novel sphene ceramics as coatings for Ti–6Al–4V. The sol–gel method was used to produce the coatings and the thermal properties, phase composition, microstructure, thickness, surface roughness and adhesion strength of sphene coatings were analyzed by differential thermal analysis–thermal gravity (DTA–TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), atom force microscopy (AFM) and scratch test, respectively. DTA analysis confirmed that the temperature of the sphene phase formation is 875 °C and XRD analysis indicated pure sphene coatings were obtained. A uniform structure of the sphene coating was found across the Ti–6Al–4V surface, with a thickness and surface roughness of the coating of about 0.5–1 μm and 0.38 μm, respectively. Sphene-coated Ti–6Al–4V possessed a significantly improved adhesion strength compared to that for HAp coating and their chemical stability was evaluated by testing the profile element distribution and the dissolution kinetics of calcium (Ca) ions after soaking the sphene-coated Ti–6Al–4V in Tris–HCl solution. Sphene coatings had a significantly improved chemical stability compared to the HAp coatings. A layer of apatite formed on the sphene-coated Ti–6Al–4V after they were soaked in simulated body fluids (SBF). Our results indicate that sol–gel coating of novel sphene onto Ti–6Al–4V possessed improved adhesion strength and chemical stability, compared to HAp-coated Ti–6Al–4V prepared under the same conditions, suggesting their potential application as coatings for orthopedic implants.

Nitric oxide-releasing sol?gels as antibacterial coatings for orthopedic implants

Nitric oxide-releasing sol?gels as antibacterial coatings for orthopedic implants

Bioactive, Bone-like Coatings for Orthopedic Implants Produced by Biomimetic Techniques

Bioactive, Bone-like Coatings for Orthopedic Implants Produced by Biomimetic Techniques

Layered, adhesively bonded hydroxyapatite coatings for orthopaedic implants

A method of producing layered, adhesively bonded hydroxyapatite coatings is described. The coatings have a flexible polymeric interlayer which can improve load transfer from the implant to the bone, and a hydroxyapatite-rich surface which can provide mechanical interlocking with the bone. The coatings have been characterized using a number of methods including optical and electron microscopy, mechanical testing and finite element analysis. Some ways in which the coatings could be used to produce orthopaedic implants with improved mechanical and biological compatibility are discussed.

Mechanical failure of hydroxyapatite- and polysulfone-coated titanium rods in a weight-bearing canine model

Three types of material that have shown potential as coatings for orthopaedic implants were studied. Using a weight-bearing canine model, Ti-6A1-4V femoral intramedullary rods coated with (1) sintered titanium beads, (2) plasma-sprayed hydroxyapatite, and (3) silyl coupled polysulfone beads were evaluated for mechanical strength and bone ingrowth. The model was designed to secure optimal prosthetic stability by obtaining maximal bony ingrowth during an initial non-weight-bearing phase, then stressing the implant during a full-weight-bearing phase. None of the rods coated with titanium beads failed. All 17 polysulfone-coated rods failed, 13 of them at the interface between the polysulfone coating and the titanium core. Of 18 rods coated with hydroxyapatite, 15 suffered implant breakdown at the interface between the hydroxyapatite coating and the titanium core. This may be due to dissolution of the plasma-sprayed hydroxyapatite in vivo. Testing of retrieved specimens from both hydroxyapatite- and polysulfone-coated implants showed that the shear strength at the coating-rod interface had decreased to less than 40% of the shear strength at manufacture. Despite mechanical failure, histologic study showed extensive bone ingrowth or apposition onto both the polysulfone and hydroxyapatite coatings.