Bare Polyetheretherketone Research Articles

Mechanical and tribological assessment of PEEK and PEEK based polymer composites for artificial hip joints

Abstract Human hip failure remains a significant issue, and constructing artificial joints is imperative for affected individuals. This study examined the mechanical and wear behavior of polyether ether ketone (PEEK) polymers, including bare PEEK (BP), HA (Hydroxyapatite)-infused PEEK (HA-PEEK), and GO (Graphene oxide)-infused HA-PEEK (GO-HA-PEEK). The samples were prepared using compression molding, and wear characteristics were evaluated using a linear reciprocating tribo-tester against a stainless-steel counterface under a load 50 N, frequency 5 Hz, stroke length 20 mm, and time 30 min. The 10 % w/w HA inclusions slightly elevate the PEEK’s tensile strength from 29.85 ± 1.11 MPa (BP) to 34.23 ± 1.09 MPa, and the 0.5 % w/w GO with 10 % w/w HA encapsulations have significantly improved tensile properties (65.10 ± 1.12 MPa), which is 2.2 fold higher than the BP. However, the attained impact properties fall below the satisfactory level. Coefficient of friction and wear rate are significantly reduced. The wear rate reduced from 3.39 × 10−6 mm3 N−1 m−1 (BP) to 2.54 × 10−6 mm3 N−1 m−1 on HA-PEEK, and more than two times reduction (1.69 × 10−6 mm3 N−1 m−1) with 0.5 % w/w GO incorporating HA-PEEK. The results show that the reinforcements significantly reduced wear and improved the mechanical strength of PEEK polymers. Unlike BP and HA with lowered impact resistance, GO integrated HA-PEEK exhibited outstanding mechanical and wear performance. Therefore, HA and GO-infused PEEKs are suitable alternatives for hip repair applications.

Enhanced biocompatibility and osteogenic ability on amino-modified polyetheretherketone

Polyetheretherketone (PEEK) is a potential implant material for dental application due to its excellent mechanical properties and low elasticity modulus. However, its biological inertia results in weak osseointegration between implants and bone tissue, which limited its clinical application. In this study, amino groups were covalently grafted on the PEEK surface using a simple facile self-assembly method to address its poor osteogenic ability. The surface characterization, cell adhesion, proliferation and osteogenic differentiation of MC3T3-E1 cells on bare PEEK and amino-modified PEEK (PEEK-APTES) were studied. After grafting amino groups onto the PEEK, the surface morphology changed, the contact angle decreased significantly. The PEEK-APTES showed boosted cell adhesion, proliferation, alkaline phosphate (ALP) activity, extracellular matrix (ECM) mineralization, and expression of osteogenic genes in MC3T3-E1 cells. These findings suggested that amino modification significantly improved the biocompatibility and osteogenic ability of PEEK in vitro.

Tuning the tribological performance of plasma-treated hybrid layers of PEEK-GO-DLC

Graphene and graphene oxide (GO)-based coatings are of great interest due to their mechanical, electrical and/or thermal performance that add functionalities to materials employed in many industrial and biomedical applications. Hybrid diamond-like carbon (DLC)/GO coatings on poly ether etherketone (PEEK) devices, e.g. orthopaedic implants, can add multiple functionalities, such as an enhanced bioactivity. In this work, we describe the mechanical stability and tribological behaviour of such coating, comparing it to a DLC-coated bare PEEK. The GO functionalisation of PEEK is realised from a water solution, whereas the DLC coatings are obtained through plasma-enhanced chemical vapour deposition, using various combinations of different precursor gases. We employ atomic force microscopy to investigate the morphology and interfacial adhesion characteristics of the materials. Then, the scratch coefficient of friction of the samples is measured under both constant-load and progressive-load conditions, also in combination with acoustic emission signals. We identify the most effective and promising plasma treatments to ensure stable coating, and discuss the effect of the presence of an intermediate GO layer.

Fabrication and in vitro study of 3D novel porous hydroxyapatite/polyether ether ketone surface nanocomposite.

The unique characteristics of polyether ether ketone (PEEK) including low elastic modulus, high mechanical strength, and biocompatibility have made it an attractive alternative for the metallic biomaterials. However, its bioinert property is always the main concern, which could lead to poor osseointegration and subsequent clinical failure of the implant. Changing the surface structure to porous structure and mixing it with bioactive hydroxyapatite (HA) are the common methods, which could be used to enhance the properties of the PEEK-based implants. In this study, friction stir processing was utilized for the fabrication of porous HA/PEEK surface nanocomposite. Scanning electron microscopic image of the nanocomposite surface showed nano-scale roughness of the porous structure. Water contact angle test confirmed the increase in the wettability of the treated specimens. In vitro bioactivity test via simulated body fluid solution, initial cell adhesion, cell proliferation, and cell differentiation assay also confirmed the enhancement in bioactivity of the treated surface in comparison to the bare PEEK. This surface modification method requires no special equipment and would not damage the heat-sensitive PEEK substrate due to the low temperature used during the fabrication process.

Enhancing the mechanical properties of SCF/PEEK composites in FDM via process-parameter optimization

Short-carbon-fiber (SCF)–reinforced poly-ether-ether-ketone (PEEK) is a promising polymer composite material with good biocompatibility, a high strength-to-weight ratio, and low friction properties. In artificial-bone fabrication and other applications with more flexible fabrication demands, fused-deposition modeling (FDM) technology enables the rapid and low-cost fabrication of SCF/PEEK parts with sophisticated structures. Owing to the high viscosity of melting PEEK composites, great challenges, associated with the poor internal interface, need to be overcome before enhanced mechanical properties can be obtained. In this study, key processing parameters and various SCF amounts were studied to investigate their effects on the mechanical properties of PEEK composites. It was revealed that the existence of voids and gaps between the SCF and PEEK led to a decrease in the strength of the composite systems. The FDM processing parameters were tuned to eliminate these defects in the PEEK composites. The tensile strength of the 2% SCF/PEEK sample reached 96.4 MPa, which is comparable to that of PEEK parts prepared by injection molding. Meanwhile, its elastic modulus reached 2.6 GPa, which is 169% higher than that of the bare PEEK sample.

Bioactive amorphous magnesium phosphate-polyetheretherketone composite filaments for 3D printing

ObjectiveThe aim of this study was to develop bioactive and osseointegrable polyetheretherketone (PEEK)-based composite filaments melt-blended with novel amorphous magnesium phosphate (AMP) particles for 3D printing of dental and orthopedic implants. Materials and methodsA series of materials and biological analyses of AMP-PEEK were performed. Thermal stability, thermogravimetric and differential scanning calorimetry curves of as-synthesized AMP were measured. Complex viscosity, elastic modulus and viscous modulus were determined using a rotational rheometer. In vitro bioactivity was analyzed using SBF immersion method. SEM, EDS and XRD were used to study the apatite-forming ability of the AMP-PEEK filaments. Mouse pre-osteoblasts (MC3T3-E1) were cultured and analyzed for cell viability, proliferation and gene expression. For in vivo analyses, bare PEEK was used as the control and 15AMP-PEEK was chosen based on its in vitro cell-related results. After 4 or 12 weeks, animals were euthanized, and the femurs were collected for micro-computed tomography (μ-CT) and histology. ResultsThe collected findings confirmed the homogeneous dispersion of AMP particles within the PEEK matrix with no phase degradation. Rheological studies demonstrated that AMP-PEEK composites are good candidates for 3D printing by exhibiting high zero-shear and low infinite-shear viscosities. In vitro results revealed enhanced bioactivity and superior pre-osteoblast cell function in the case of AMP-PEEK composites as compared to bare PEEK. In vivo analyses further corroborated the enhanced osseointegration capacity for AMP-PEEK implants. SignificanceCollectively, the present investigation demonstrated that AMP-PEEK composite filaments can serve as feedstock for 3D printing of orthopedic and dental implants due to enhanced bioactivity and osseointegration capacity.

NaOH-etched/boron-doped nanohydroxyapatite-coated PEEK implants enhance the proliferation and differentiation of osteogenic cells

The aim of the present study is to eliminate the bioinertness of polyetheretherketone (PEEK) material and to increase its osteogenic activity by applying a number of surface modifications in order to discover the most effective method. First, the surface of the bare PEEK (B-PEEK) was mechanically modified by sandblasting (S-PEEK). As a second method, physical modification was provided by etching of B-PEEK in 10 M sodium hydroxide (NaOH) solution at 60 °C for 48 h (N-PEEK). Following the sandblasting, S-PEEK samples were also etched with NaOH to obtain SN-PEEK samples. In order to increase osteogenic activity of the mechanically and/or physically modified PEEK samples, they were coated with boron-doped nanohydroxyapatite (B-nHAp) in the presence of microwave energy. Thus, B-PEEK/B-nHAp, S-PEEK/B-nHAp, N-PEEK/B-nHAp and SN-PEEK/B-nHAp samples were obtained. While water contact angles and surface roughness of the B-PEEK samples increased after modification, hydrophilicity increased with B-nHAp coating. Cell culture results demonstrated that high proliferation and differentiation capacities of MC3T3-E1 cells were obtained on the B-nHAP-coated surfaces compared to uncoated specimens. However, channeled texture of both the N-PEEK and N-PEEK/B-nHAp samples enhanced Col1a1 mRNA expression and collagen secretion in addition to increased alkaline phosphatase (ALP) activity when compared to other groups. As a result, it was determined that the bioactivity increased on the modified PEEK surfaces, but the most effective osteogenic activity was provided with B-nHAp coatings. The synergetic effect of NaOH etching and B-nHAp coatings might be used as a promising surface modification method to use PEEK material in orthopedic and dental applications with increased osteogenic activity.

Triple-functional polyetheretherketone surface with enhanced bacteriostasis and anti-inflammatory and osseointegrative properties for implant application

Polyetheretherketone (PEEK) is considered a potential orthopedic/dental material because of its excellent mechanical and chemical properties (e.g., similar elastic modulus to that of human bone). However, the poor bacteriostasis and anti-inflammatory and osseointegrative properties of bioinert PEEK impede its clinical application. We previously developed a facile and versatile surface modification method using dexamethasone plus minocycline-loaded liposomes (Dex/Mino liposomes) bonded by a mussel-inspired polydopamine coating, which effectively modulated cell inflammatory response and discouraged bacterial colonization in vitro. Herein, we report the application of this multifunctional surface modification method to improve bioinert PEEK, aimed at further studying the in vitro osteogenesis and in vivo properties of Dex/Mino liposome-modified PEEK to prevent bacterial contamination, attenuate the inflammatory response, and enhance ossification for physiologic osseointegration. Our study established that the Dex/Mino liposome-modified PEEK surface presented favorable stability and cytocompatibility. Compared with bare PEEK, improved osteogenic differentiation of human mesenchymal stem cells under both osteoinductive and osteoconductive conditions was found on the functionalized surface due to the liposomal Dex releasing. In vivo bacteriostasis assay confirmed that Mino released from the functionalized surface provided an effective antibacterial effect. Moreover, the subcutaneous foreign body reaction and beagle femur implantation models corroborated the enhanced anti-inflammatory and osteointegrative properties of the functionalized PEEK. Our findings indicate that the developed Dex/Mino liposome-modified PEEK with enhanced antibacterial, anti-inflammatory, and osseointegrative capacity has great potential as an orthopedic/dental implant material for clinical application.

An etched polyether ether ketone tube covered with immobilized graphene oxide for online solid phase microextraction of quaternary alkaloids prior to their quantitation by HPLC-MS/MS

Polyether ether ketone (PEEK) is an ideal substrate for in tube solid-phase microextraction (SPME) because it overcomes the shortcomings of conventional silica fibers in terms of fragility and poor flexibility. Commonly used bare PEEK tubes suffer from difficult modification with selective sorbents and low inner surface areas. This problem was solved by etching with concentrated sulfuric acid, which dissolves the amorphous regions of the PEEK surface and yields a rough inner surface with plenty of microscopically small holes. The etched tube was then stepwise functionalized with polydopamine and graphene oxide which was in-situ immobilized. The modified tube displays excellent efficiency for the extraction of positively charged quaternary alkaloids by a mixed-mode extraction. Enrichment factors from 221 to 275 can be obtained for the extraction of the alkaloids jatrorrhizine, palmatine and berberine. The alkaloiods were then quantified by online SPME-HPLC-MS/MS detection. The method has detection limits of 0.1 pg mL−1, good linearity, and good intra-day reproducibility (≤ 2.4%). It was applied to the analysis of the three alkaloids in Cortex Phellodendri herb and rat plasma after oral administration.

Study on the AFM Force Curve Common Errors and Their Effects on the Calculated Nanomechanical Properties of Materials

The atomic force microscope (AFM) force curve has been widely used for determining the mechanical properties of materials due to its high resolution, whereby very low (piconewton) forces and distances as small as nanometers can be measured. However, sometimes the resultant force curve obtained from AFM is slightly different from those obtained from a more typical nanoindentation force curve due to the AFM piezo’s hysteresis. In this study the nanomechanical properties of either a sulfonated polyether ether ketone (SPEEK) treated layer or bare polyether ether ketone (PEEK) were evaluated via AFM nanoindentation and a nanomechanical test system to probe the possible error of the calculated nanomechanical properties due to the AFM piezo’s hysteresis. The results showed that AFM piezo’s hysteresis caused the error in the calculated nanomechanical properties of the materials.

Enhancement of bioactivity on medical polymer surface using high power impulse magnetron sputtered titanium dioxide film.

This study utilizes a novel technique, high power impulse magnetron sputtering (HIPIMS), which provides a higher ionization rate and ion bombardment energy than direct current magnetron sputtering (DCMS), to deposit high osteoblast compatible titanium dioxide (TiO2) coatings with anatase (A-TiO2) and rutile (R-TiO2) phases onto the biomedical polyetheretherketone (PEEK) polymer substrates at low temperature. The adhesions of TiO2 coatings that were fabricated using HIPIMS and DCMS were compared. The in vitro biocompatibility of these coatings was confirmed. The results reveal that HIPIMS can be used to prepare crystallinic columnar A-TiO2 and R-TiO2 coatings on PEEK substrate if the ratio of oxygen to argon is properly controlled. According to a tape adhesion test, the HIPIMS-TiO2 coatings had an adhesion grade of 5B even after they were immersed in simulated body fluid (SBF) environments for 28days. Scratch tests proved that HIPIMS-TiO2 coatings undergo cohesive failure. These results demonstrate that the adhesive force between HIPIMS-TiO2 coating/PEEK is stronger than that between DCMS-TiO2 coating/PEEK. After a long period (28days) of immersion in SBF, a bone-like crystallinic hydroxyapatite layer with a corresponding Ca/P stoichiometry was formed on both HIPIMS-TiO2. The osteoblast compatibility of HIPIMS-TiO2 exceeded that of the bare PEEK substrate. It is also noticeable that the R-TiO2 performed better in vitro than the A-TiO2 due to the formation of many negatively charged hydroxyl groups (-OH(-)) groups on R-TiO2 (110) surface. In summary, the HIPIMS-TiO2 coatings satisfied the requirements for osseointegration, suggesting the possibility of using HIPIMS to modify the PEEK surface with TiO2 for spinal implants.

In vitro evaluation of bioactivity of chemically deposited hydroxyapatite on polyether ether ketone.

Polyether ether ketone (PEEK) is considered the best alternative material for titanium for spinal fusion cage implants due to its low elasticity modulus and radiolucent property. The main problem of PEEK is its bioinert properties. Coating with hydroxyapatite (HA) showed very good improvement in bioactivity of the PEEK implants. However the existing methods for deposition of HA have some disadvantages and damage the PEEK substrate. In our previous study a new method for deposition of HA on PEEK was presented. In this study cell proliferation of mesenchymal stem cell and apatite formation in simulated body fluid (SBF) tests were conducted to probe the effect of this new method in improvement of the bioactivity of PEEK. The mesenchymal stem cell proliferation result showed better cells proliferation on the treated layer in comparison with untreated PEEK. The apatite formation results showed the growth of the HA on the treated PEEK but there was not any sight of the growth of HA on the untreated PEEK even after 2 weeks. The results showed the new method of the HA deposition improved the bioactivity of the treated PEEK in comparison with the bare PEEK.

In Vivo Osseointegration Performance of Titanium Dioxide Coating Modified Polyetheretherketone Using Arc Ion Plating for Spinal Implant Application.

Polyetheretherketone (PEEK), which has biomechanical performance similar to that of human cancellous bone, is used widely as a spinal implant material. However, its bioinertness and hydrophobic surface properties result in poor osseointegration. This study applies a novel modification method, arc ion plating (AIP), that produces a highly osteoblast compatible titanium dioxide (TiO2) coatings on a PEEK substrate. This PEEK with TiO2 coating (TiO2/PEEK) was implanted into the femurs of New Zealand white male rabbits to evaluate its in vivo performance by the push-out test and histological observation. Analytical results show that AIP can prepare TiO2 coatings on bullet-shaped PEEK substrates as implant materials. After prolonged implantation in rabbits, no signs of inflammation existed. Newly regenerated bone formed more prominently with the TiO2/PEEK implant by histological observation. The shear strength of the bone/implant interface increases as implantation period increases. Most importantly, bone bonding performance of the TiO2/PEEK implant was superior to that of bare PEEK. The rutile-TiO2 coatings achieved better osseointegration than the anatase-TiO2 coatings. Therefore, AIP-TiO2 can serve as a novel surface modification method on PEEK for spinal interbody fusion cages.

Polyetheretherketone/nano-fluorohydroxyapatite composite with antimicrobial activity and osseointegration properties

Lack of antibacterial activity and binding ability to natural bone tissue has significantly limited polyetheretherketone (PEEK) for many challenging dental implant applications. Here, we have developed a polyetheretherketone/nano-fluorohydroxyapatite (PEEK/nano-FHA) biocomposite with enhanced antibacterial activity and osseointegration through blending method. Smooth and rough surfaces of PEEK/nano-FHA biocomposites were also prepared. Our results showed that in vitro initial cell adhesion and proliferation on the nano-FHA reinforced PEEK composite were improved. In addition, higher alkaline phosphatase activity and cell mineralization were also detected in cells cultured on PEEK/nano-FHA biocomposites, especially for rough PEEK/nano-FHA surfaces. More importantly, the as-prepared PEEK/nano-FHA biocomposite could effectively prevent the proliferation and biofilm formation of bacterial. For in vivo test, the newly formed bone volume of PEEK/nano-FHA group was higher than that of bare PEEK group based on 3D microcomputed tomography and 2D histomorphometric analysis. These reports demonstrate that the developed PEEK/nano-FHA biocomposite has increased biocompatibility and antibacterial activity in vitro, and promoted osseointegration in vivo, which suggests that it holds potential to be applied as dental implant material in dental tissue engineering applications.

Creation of nanoporous TiO2surface onto polyetheretherketone for effective immobilization and delivery of bone morphogenetic protein

This study evaluated the utility of the creation of a nanoporous TiO2 surface to enhance the in vitro biocompatibility and in vivo osseoconductivity of polyetheretherketone (PEEK) implants by providing favorable sites for the effective immobilization of bone morphogenetic protein-2 (BMP-2). A uniform nanoporous TiO2 layer with a pore diameter of ∼70 nm was successfully created by anodizing a Ti film, which had been deposited onto a PEEK substrate via electron beam (e-beam) evaporation technique. This nanoporous, hydrophilic TiO2 surface enabled the efficient immobilization of BMP-2, resulting in a remarkable enhancement in in vitro biocompatibility that was assessed in terms of cell attachment, proliferation, and differentiation. The in vivo animal tests also confirmed that the nanoporous TiO2 surface immobilized with BMP-2 could significantly enhance the osseoconductivity of PEEK implants. The BMP-immobilized PEEK implant with the nanoporous TiO2 surface showed much higher bone-to-implant contact (BIC) ratio (60%) than the bare PEEK (30%), PEEK with the nanoporous TiO2 surface (50%) and even BMP-immobilized PEEK without the nanoporous TiO2 surface (32%).

Improved osteoblast compatibility of medical‐grade polyetheretherketone using arc ionplated rutile/anatase titanium dioxide films for spinal implants

Titanium dioxide (TiO(2)), known to exhibit good biocompatibility, is applied in this study as a thin film formed onto polyetheretherketone (PEEK) substrate, which has been widely used in spinal interbody fusion cages. For successful deposition, an arc ionplating (AIP) technique was applied to deposit TiO(2) at low deposition temperature without damaging PEEK substrate, while providing satisfactory film adhesion. This study systematically investigates the effects of TiO(2) thin film phase composition and surface characteristics, controlled by using different target current and substrate bias, on osteoblast compatibility. Experimental results showed that anatase phase (A-TiO(2)) and/or rutile phase (R-TiO(2) ) TiO(2) coatings, respectively, can be prepared in appropriate deposition conditions. Overall, the TiO(2)-coated PEEK presented better osteoblast compatibility than the bare PEEK material in terms of cell adhesion, cell proliferation, and cell differentiation abilities, as well as osteogenesis performance (as determined by levels of osteopontin, osteocalcin, and calcium content). Surface roughness and hydrophilicity of the AIP-TiO(2) films were found to be responsible for significant osteoblast cell growth. It is also noticeable that the R-TiO(2) exhibited better osteoblast compatibility than the A-TiO(2) due to the presence of negatively charged hydroxyl groups on R-TiO(2) (110) surface in nature.

Low-temperature deposition of anatase TiO 2 on medical grade polyetheretherketone to assist osseous integration

A thin film Titanium dioxide (TiO 2) was deposited onto Polyetheretherketone (PEEK) substrate at low deposition temperature via using an arc ion plating (AIP) technique. The microstructure, mechanical properties and osteoblast compatibility of the TiO 2-deposited PEEK are investigated to evaluate the feasibility of using this technique for faster osseous integration on spinal interbody fusion cages. The results showed that the deposited TiO 2 possesses a dense columnar structure with major anatase and minor rutile crystal phase. The highest rank (5B) in an adhesion tape test, a critical load of 14.5 N and cohesive failure mode in the scratch test all proved the strong adhesion of the coating. High corrosion potential with very low corrosion current was detected both in 3.5 wt.% NaCl electrolyte and simulated body fluid (SBF), indicating the electro-chemical inertness of the TiO 2 coating. The TiO 2-coated specimens presented better osteoblast cell adhesion compatibility than the bare PEEK material in terms of cell proliferation and alkaline phosphatase (ALP) activity in an osteoblast culture.