Apatite Coatings Research Articles

Raman study of apatite coating, obtained by detonation spraying of the precursor salts on the titanium substrates

The results of the Raman study of the apatite coatings, obtained by detonation spraying of the precursor salts on the titanium substrates are presented. The mixture of Ca(OH)2 and (NH4)2HPO4 salts at the molar ratio 5:3 was used as precursors. A detailed analysis of the most intense Raman band showed hydroxyapatite formation with a dominant contribution of the amorphous phase. The post-deposition thermal annealing at 640 °C for 30 min in the Ar atmosphere leads to the transformation of the amorphous hydroxylapatite into the crystalline one.

Synthetic or Natural (Bio-Based) Hydroxyapatite? A Systematic Comparison between Biomimetic Nanostructured Coatings Produced by Ionized Jet Deposition.

Calcium phosphate (CaP)-based materials are largely explored in orthopedics, to increase osseointegration of the prostheses and specifically in spine surgery, to permit better fusion. To address these aims, nanostructured biogenic apatite coatings are emerging, since they better mimic the characteristics of the host tissue, thus potentially being better candidates compared to their synthetic counterpart. Here, we compare hydroxyapatite (HA) nanostructured coatings, obtained by ionized jet deposition, starting from synthetic and natural sources. The starting materials and the corresponding films are characterized and compared from a compositional and morphological point of view, then their stability is studied after post-treatment annealing. Although all the films are formed by globular aggregates and show morphological features at different scales (from nano to micro), significant differences are found in composition between the synthetic and naturally derived HA in terms of magnesium and sodium content, carbonate substitution and Ca/P ratio, while differences between the coatings obtained by the different natural HA sources are minor. In addition, the shape of the aggregates is also target-dependent. All coatings have a good stability after over 14 days of immersion in medium, with natural apatite coatings showing a better behavior, as no cracking and detachments are observed during immersion. Based on these results, both synthetic and naturally derived apatitic materials appear promising for applications in spine surgery, with coatings from natural sources possessing physiochemical properties more similar to the mineral phase of the human bone tissue.

Fluoride-Incorporated Apatite Coating on Collagen Sponge as a Carrier for Basic Fibroblast Growth Factor.

Coating layers consisting of a crystalline apatite matrix with immobilized basic fibroblast growth factor (bFGF) can release bFGF, thereby enhancing bone regeneration depending on their bFGF content. We hypothesized that the incorporation of fluoride ions into apatite crystals would enable the tailored release of bFGF from the coating layer depending on the layer's fluoride content. In the present study, coating layers consisting of fluoride-incorporated apatite (FAp) crystals with immobilized bFGF were coated on a porous collagen sponge by a precursor-assisted biomimetic process using supersaturated calcium phosphate solutions with various fluoride concentrations. The fluoride content in the coating layer increased with the increasing fluoride concentration of the supersaturated solution. The increased fluoride content in the coating layer reduced its solubility and suppressed the burst release of bFGF from the coated sponge into a physiological salt solution. The bFGF release was caused by the partial dissolution of the coating layer and, thus, accompanied by the fluoride release. The concentrations of released bFGF and fluoride were controlled within the estimated effective ranges in enhancing bone regeneration. These findings provide useful design guidelines for the construction of a mineralized, bFGF-releasing collagen scaffold that would be beneficial for bone tissue engineering, although further in vitro and in vivo studies are warranted.

Carbonate content control in carbonate apatite coatings of biodegradable magnesium

Carbonate apatite (CAp) coating has been developed as a bioabsorbable corrosion-control coating for biodegradable Mg alloys. Carbonate content in the CAp coatings can be utilized to control the bioabsorbability and corrosion rate of CAp-coated Mg alloys. In this study, the carbonate content in the CAp coatings of pure Mg was varied by NaHCO3 concentration of the coating solution from 0.25 to 1.0 mol/L, and hydroxyapatite (HAp) was formed without NaHCO3. The CAp and HAp coatings were characterized using X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). The carbonate content in the apatite coatings formed with 0, 0.25, 0.5 and 1.0 mol/L NaHCO3 was determined to be 2, 12, 15 and 18 wt%, respectively, from the apatite 002 plane XRD peak position using the existing conversion constant as well as from the coating composition obtained by the XPS analysis. The values of carbonate content obtained by each method were in good accordance, indicating that the carbonate content can be determined simply by XRD measurements. Two types of carbonate group were present in the CAp coatings, CO32− and HCO3-, and the relative content of HCO3- to CO32− increased with an increase in the carbonate content.

Evaluation of the effect of surface modification of Ti64 and 316 L by addition of calcium phosphate through electrical discharge machining process

In this investigation, the EDM process was applied to modify the surfaces of Ti-6Al-4 V alloy and AISI 316 L steel by the formation of hydroxyapatite coatings with the objective of providing a favorable environment for osseointegration of implants. The EDM process has the advantage of simultaneously machining and increasing surface roughness increasing surface contact area with bone tissue and implant anchorage. The hydroxyapatite coatings were formed during EDM currents of 30 A and 40 A with calcium phosphate additions. The coatings were analyzed in terms of hardness, roughness, surface profile, wear and tribological characteristics (pin on disk) and were characterized SEM/EDS and XRD. It was possible to show that on all processed surfaces the development of apatite coatings was achieved. Coating thickness and hardness were approximately 120 µm, 700HV and 12 µm, 300HV for the Ti-alloy and stainless steel, respectively. On both substrates, a significant increase in surface roughness was observed after EDM. The pin on disk tests revealed that the coefficient of friction varied from 0.54 to 0.80, and superior wear resistance of the coating formed on the AISI 316 L steel.

Stabilization of Apatite Coatings on PPENK Surfaces by Mechanical Interlocking to Promote Bioactivity and Osseointegration In Vivo.

Apatite coatings with high stability can effectively improve the surface bioactivity and osteogenic activity of implant materials. In clinical practice, the ability of apatite coatings to bond with the substrate is critical to the effect of implants. Here, we propose a strategy to construct a three-dimensional (3D) nanoporous structure on the surface of a poly(phthalazinone ether nitrile ketone) (PPENK) substrate and introduce a polydopamine (PDA) coating with grafted phosphonate groups to enhance the overall deposition of a bone-like apatite coating in the 3D nanoporous structure during mineralization. This method leads to a mechanical interlocking between the apatite coating and the substrate, which increases the stability of the apatite coating. The apatite coating confers a better bioactive surface to PPENK and also promotes osteogenic differentiation and adhesion of MC3T3-E1 osteoblasts in vitro. The samples are then implanted into rat femurs to characterize in vivo osseointegration. Micro-CT data and histological staining of tissue sections reveal that PPENK with a stable apatite coating induces less fibrous capsule formation and no inflammatory response and promotes osteogenic differentiation and bone-bonding strength. This enhances the long-term use of PPENK implant materials and shows great potential for clinical application as orthopedic implants.

Fluoridated Apatite Coating on Human Dentin via Laser-Assisted Pseudo-Biomineralization with the Aid of a Light-Absorbing Molecule.

A simple, area-specific coating technique for fluoridated apatite (FAp) on teeth would be useful in dental applications. Recently, we achieved area-specific FAp coating on a human dentin substrate within 30 min by a laser-assisted biomimetic (LAB) process; pulsed Nd:YAG laser irradiation in a fluoride-containing supersaturated calcium phosphate solution (FCP solution). The LAB-processed, FAp-coated dentin substrate exhibited antibacterial activity against a major oral bacterium, Streptococcus mutans. In the present study, we refined the LAB process with a combination of a dental diode laser and a clinically approved light-absorbing molecule, indocyanine green (ICG). A micron-thick FAp layer was successfully formed on the dentin surface within only 3 min by the refined LAB process, i.e., dental diode laser irradiation in the FCP solution following ICG treatment. The ICG layer precoated on the dentin substrate played a crucial role in inducing rapid pseudo-biomineralization (FAp layer formation) on the dentin surface by absorbing laser light at the solid-liquid interface. In the refined LAB process, the precoated ICG layer was eliminated and replaced with the newly formed FAp layer composed of vertically oriented pillar-like nanocrystals. Cross-sectional ultrastructural analysis revealed a smooth interface between the FAp layer and the dentin substrate. The refined LAB process has potential as a tool for the tooth surface functionalization and hence, is worth further process refinement and in vitro and in vivo studies.

Structural, chemical and osteogenic properties of GNS reinforced fluorine-doped strontiumapatite coatings on AZ31 Mg alloys for potential biomedical applications

Different ion-doped composite coatings, especially graphene and fluorine-substituted apatite coatings, are intensely interested in surface modifications of different metallic implants for medical applications due to their excellent biological and chemical properties. However, their use in clinical applications in metallic implant materials is limited due to unsuitable biomechanical properties, low corrosion resistance, insufficient osteoinductivity, and bioactivity capacities. In this study, Graphene Nanosheet (GNS) and F-substituted SrAp (SrFAp/GNS) composite coatings were deposited on AZ31 magnesium substrate by hydrothermal method, and the effects of different GNS additives on SrFAp composite were reported for the first time. Morphological investigations showed crystals of SrFAp structures of GNS to grow in a needle-like structure and transform into a bone-like nano-needle structure. In addition, these structures began to transform into a more porous leaf form in the simulated body fluid. GNS layers also improved the surface properties and cell adhesion ability by developing a porous and rough coating morphology. With the GNS additive, the wettability properties of the composite coating were also significantly increased. In addition, the corrosion resistance of the examined coatings was significantly improved with the increasing GNS ratio. Co-doping of F and GNS in SrFAp/GNS coatings also improves the cytocompatibility of the SrAp construct. SrFAp/GNS composites significantly promote cell adhesion and proliferation and do not show any adverse toxic behavior. Therefore, SrFAp/GNS coated AZ31 Mg alloys, with their combination of high cytocompatibility, good mechanical properties, and superior corrosion resistance compared to Mg alloys, have shown promising results for clinical implant applications.

Accelerated biomimetic nanosized apatite coatings deposition on alkali treated titanium

Accelerated biomimetic nanosized apatite coatings deposition on alkali treated titanium

Physicochemical, osteogenic and antimicrobial properties of graphene oxide reinforced silver/strontium-doped hydroxyapatite on titanium for potential orthopedic applications

Variety of ion-doped apatite coatings, especially strontium substituted hydroxyapatite (SrHA), have attracted eventful attention for medical metal surface modifications due to their excellent cytocompatibility and organizational affinity. However, they are still not commercially used in clinics because of their inappropriate biomechanical properties, and lack of osteoinductivity and antibacterial capabilities. Here, silver (Ag) doped SrHA (SrAgHA)/graphene oxide (GO) composite coatings were fabricated on titanium (Ti) substrate via electrodeposition (ED) and this combination has been reported for the first time. Morphological observations revealed that GO facilitated HA pricker-like crystals to grow in longitudinal directions, changing into a bone-like microneedles structure. SrAgHA/GO showed good mechanical properties to ensure mechanical strength required for the bone repair coating. The roughness of samples decreased from 120 ± 19 μm for the SrAgHA/GO coated Ti to 527 ± 66 μm for HA coated Ti. Although the introduction of GO makes the composite coating have a significant decreased roughness, it has no effect on the hydrophilicity of the composite coating, which is almost superpotropic. Ion release evaluation demonstrated that the presence of GO slowed the release rate of Sr and Ag, which was beneficial to reduce the cytotoxicity accompanying high concentration of Ag release. Simultaneously, GO increased the surface hydrophilicity and mechanical strength of the SrAgHA/GO. In addition, the corrosion rates of investigated coatings increased in the following order: SrAgHA/GO<SrHA/GO<SrAgHA<HA<Ti. SrAgHA/GO coatings demonstrated an effective antibacterial effect against common bacteria in clinical. The co-doping of Sr and GO in SrAgHA/GO coatings can effectively mitigate the cytotoxicity of Ag and promote the cytocompatibility of HA. The SrAgHA/GO coating did not exhibit any cytotoxicity, which can greatly promote adhesion, extension, proliferation and early differentiation of osteoblasts. Therefore, high cytocompatibility, excellent antimicrobial activity, and good mechanical properties of the SrAgHA/GO-coated Ti samples combined with its exceptional corrosion resistance performance displayed the beautiful prospect of the SrAgHA/GO-coated Ti for applications in hard tissue implant.

Fabrication of bioactive poly(ether ether ketone) by laser melt infiltration of poly(ether ether ketone) inside the strontium apatite coatings

A versatile method to immobilize apatite nanoparticles onto PEEK substrate by using CO2 laser was demonstrated. Various strontium apatites were synthesized and dispersed in ethanol at a low concentration of citric acid. This dispersion of strontium apatites was coated on the surface of the PEEK substrate. The apatite-coated PEEK substrate was subsequently irradiated by CO2 laser with repeated multiple scanning mode. The surface temperature was monitored in real time and controlled at approximately the melting point of PEEK. The thermally fixed apatite coatings were unified with the PEEK substrate and unable to separate off. Dissolution of apatite layer in dilute acid solution revealed highly rugged surface morphologies of the PEEK substrate hidden inside the apatite coatings. From these observations we concluded that the heat-fixed apatite layer consisted of nanocomposite of apatite and PEEK. We propose a possible mechanism for the laser bonding processes of this apatite coating, that is, when the coating surface is irradiated by a CO2 laser with rapid periodic scanning mode, this irradiation initiates periodic temperature change with thermal expansion of the air on top of the apatite layer and may induce a photoacoustic effect on them, which may generate pressure waves to hold down the apatite matrix to the PEEK substrate. The heat on the apatite matrix also initiates melting of the adjacent PEEK surface and the melted PEEK polymer intrudes into the voids of the apatite matrix by capillary forces to produce nanocomposite of them. This surface-selective formation of PEEK/apatite nanocomposites on the PEEK substrate may be seen as an alternative method to the conventional surface coatings or various PEEK composite materials.The bioactivity of the apatite-coated PEEK substrate was affirmed through biomimetic deposition of calcium phosphate from simulated body fluid and dissolution behaviors of the apatite coatings in water was also evaluated.

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.

Phosphonate-Functionalized Poly(phthalazinone ether ketones) Induce the Formation of Apatite Coatings for Enhanced Biocompatibility and Osteogenic Activity

Poly(phthalazinone ether ketone) (PPEK), a poly(aryl ether ketone) (PAEK), has good thermal stability, nitrogen-containing functional groups, and bone-like mechanical properties. However, its surface biological inertness limits its application in biomedical applications. This paper presents the synthesis of PPEK modified with quantitative introduction of phosphonate groups (PPPEK) by a simple wet chemical modification method. The biomineralization process is regulated by the number of phosphonate groups, and a coating similar to bone apatite is deposited on the surface of PPEK substrates, thus greatly improving the biocompatibility of the material surface. The chemical structures of PPPEK are confirmed by 1H NMR and FTIR. Microstructural and compositional studies performed by SEM, TEM, XPS, and XRD reveal that apatite coating is significantly enhanced with the increase in the phosphonate groups on the PPEK substrate. In addition, cell culture studies show that apatite coating induced by PPPEK promoted cell viability, cell adhesion, and osteogenesis of MC3T3-E1 cells.

Short- and long-term corrosion behavior of carbonate apatite-coated Mg-4mass% Y-3mass% RE alloy in cell culture medium

Osteoclast responsive carbonate apatite (CAp) coatings with different carbonate content rates and non-bioabsorbable hydroxyapatite (HAp) coating were formed on Mg-4mass% Y-3mass% rare earth (WE43) alloy. Electrochemical impedance spectroscopy measurement in a cell culture medium was performed for 6 h and 10 weeks, and the corrosion morphology was observed using a scanning electron microscope. Coating layer resistance of the CAp-coated specimens for 6 h was 104 Ωcm2 which was higher than 2 × 103 Ωcm2 of the HAp-coated specimen. Mean polarization resistance for the initial 4 weeks for the former was 4 × 104–7.5 × 104 Ωcm2 which was higher than 2 × 104 Ωcm2 of the latter.

3D printed concentrated alginate/GelMA hollow-fibers-packed scaffolds with nano apatite coatings for bone tissue engineering

Three-dimensional grafts/scaffolds with hierarchically biomimetic features from nano to macro scale and high porosity are required for bone tissue engineering. In this study, biomimetic organic/inorganic composite scaffolds with high porosity (78.7 ± 3.2%) and features from nano (nano apatite coatings) to macro (macro pores and hollow channels) scale were fabricated based on highly concentrated alginate/GelMA bioinks via co-axial 3D printing and in situ mineralization under mild conditions. Nano apatites were coated on both inner and outer surfaces of the hollow fiber scaffolds, homogeneously. Proteins were directly loaded in the bioinks achieving sustained release from the scaffolds over 28 days. The in vitro cell experiments showed that the scaffolds with good biocompatibility could support cells adhesion and proliferation. The nano apatite coatings presented remarkable osteogenic capability. The in vivo study indicated that the hollow fiber scaffolds with biomimetic nano apatite coatings showed the capability to enhance bone formation after 12 weeks of implantation. In conclusion, the prepared biomimetic organic/inorganic scaffolds with homogeneous nano apatite coatings and hollow channels structures might be potential candidates for bone tissue engineering.

Surface functionalization of selective electron beam melting pure tantalum by micro-arc oxidation

Selective electron beam melting (SEBM) technology provides great flexibility for tantalum (Ta) application in the next generation of personalized biomedicine. This article aims to prepare bone-like apatite coatings on the SEBM pure Ta surfaces by Micro-arc oxidation (MAO) and systematically investigate the detailed morphologies, coating thickness and corrosion resistance of as-built samples and MAO coatings. Results show that the hierarchical structures of Ta oxide coatings with thickness of 3–5 μm are successively prepared by MAO with constant current mode on the surfaces of SEBM pure Ta. Bioactive Ca, P-contained amorphous coatings are uniformly dispersed in the hierarchical porous structure and are tightly connected with substrate. The passive current of SEBM pure Ta is decreased significantly by two orders of magnitude after MAO treatment in 3.5 wt% NaCl solution. The MAO coatings can provide positive protective effects for SEBM pure Ta and exhibit great potential for active and further promote biomedical application of SEBM pure Ta.

Apatite Formation Induced by Chitosan/Gelatin Hydrogel Coating Anchored on Poly(aryl ether nitrile ketone) Substrates to Promote Osteoblastic Differentiation.

Bone-like apatite is a promising coating of poly(ether ether ketone) (PEEK) for bone implantation. Poly(aryl ether nitrile ketone) containing phthalazinone moiety (PPENK) is a novel alternative for its easy synthesis. Here, chitosan/gelatin hybrid hydrogel coating is applied to induce the formation of apatite on the surface of PPENK substrate through biomineralization to improve its biocompatibility and osteogenic property. PPENK possessing allyl groups (PPENK-d) are synthesized and spin-coated on PPENK substrate to impart reactive groups. The hydrogel coating is prepared by the ultraviolet crosslinking of gelatin methacrylate (GelMA) and chitosan methacrylate (CSMA) on PPENK substrate. PPENK-d, GelMA, and CSMA are characterized by 1 H-NMR to confirm the designed structures. The presence of chitosan increases the chelation of calcium ions and thus induces the nucleation of apatite. The microstructural and compositional results reveal that the chitosan-containing hydrogel coating induced apatite coating yields a higher apatite quantity compared to the gelatin hydrogel coating. The apatite coatings on PPENK substrate promote the cytocompatibility and osteogenesis of MC3T3-E1 preosteoblasts in vitro.

Enhanced Corrosion Resistance and In Vitro Biocompatibility of Mg-Zn Alloys by Carbonate Apatite Coating.

B-type carbonate apatite (CAp) coatings were formed on as-cast and T4-treated Mg-xZn (x = 1, 5, and 7 wt %) alloys containing various sized Zn-rich second phase to improve the corrosion resistance and biocompatibility. The CAp coating grew uniformly on the alloys with a thickness of 1.1-1.3 μm and did not show cracks or pores on 30 μm-sized second-phase particles. The CAp coating retarded corrosion of Mg-Zn substrates for the first 3-5 days in Hanks' solution. Polarization resistance of the CAp-coated alloys was 10-90 and 1-70 times higher than the uncoated and hydroxyapatite (HAp)-coated alloys, respectively. The corrosion rate of CAp-coated alloys was greatly affected by the substrate alloys once the coatings were partly broken. The CAp-coated alloys showed 40-60 and 25-45% lower 14-day average corrosion rates than the uncoated and HAp-coated alloys, respectively, in the immersion test. The CAp coating significantly enhanced the viability of osteoblastic MC3T3-E1 cells on the Mg-Zn alloys for 72 h compared to the uncoated and HAp-coated alloys. The cell densities on CAp-coated alloys were similar for 72 h regardless of substrate alloys. Therefore, the CAp coating can be a superior coating candidate for corrosion-control and biocompatibility improvement for biodegradable Mg alloys.

Nanostructure and biomimetics orchestrate mesenchymal stromal cell differentiation: An in vitro bioactivity study on new coatings for orthopedic applications

The choice of the appropriate material having suitable compositional and morphological surface characteristics, is a crucial step in the development of orthopedic implants. The purpose of this paper is to elucidate, on this regard, the influence of two important hits, i.e., biogenic apatite with bone-like composition and nanostructured morphology, providing the evidence of the efficacy of nanostructured biogenic apatite coatings in favoring adhesion, growth, proliferation, and in vitro osteogenic differentiation of human mesenchymal stromal cells (hMSCs) isolated from the bone marrow. The specific features of this coating in terms of topographical and biochemical cues, obtained by Ionized Jet Deposition, are perceived by hMSCs, as suggested by changes in different morphologic parameters as Aspect Ratio or Elongation index, suggesting the impact exerted by the nanostructure on early adhesion events, cytoskeleton organization, and cells fate. In addition, the nanostructured CaP coating sustained the metabolic activity of the cells and facilitated the osteogenic differentiation of MSC by supporting the osteogenesis-related gene expression.These findings support the use of a combined approach between technological advancement and instructive surfaces, both from the topographical and the biochemical point of view, in order to manufacture smart biomaterials able to respond to different needs of the orthopedic practice.

In vitro osteogenesis of rat bone marrow mesenchymal cells on PEEK disks with heat-fixed apatite by CO2 laser bonding

BackgroundPolyether-ether-ketone (PEEK) is increasingly being used for spinal applications. However, because of its biologically inactive nature, there are risks of false joint loosening and sinking. PEEK materials are coated with apatite to enhance the osteoconductive properties. In this study, we aimed to evaluate whether strontium apatite stimulate osteogenesis on the surface of PEEK by using the CO2 laser technique.MethodsWe prepared non-coated disks, laser-exposed disks without apatite, and four types of apatite-coated by laser PEEK disks (hydroxyapatite (HAP), strontium hydroxyapatite (SrHAP), silicate-substituted strontium apatite (SrSiP), and silicate-zinc-substituted strontium apatite (SrZnSiP)). A part of the study objective was testing various types of apatite coatings. Bone marrow mesenchymal cells (BMSCs) of rats were seeded at a density of 2 × 104/cm2 onto each apatite-coated, non-coated, and laser-irradiated PEEK disks. The disks were then placed in osteogenic medium, and alkaline phosphatase (ALP) staining and Alizarin red staining of BMSCs grown on PEEK disks were performed after 14 days of culture. The concentrations of osteocalcin (OC) and calcium in the culture medium were measured on days 8 and 14 of cell culture. Furthermore, mRNA expression of osteocalcin, ALP, runt-related transcription factor 2 (Runx2), collagen type 1a1 (Col1a1), and collagen type 4a1 (Col4a1) was evaluated by qPCR.ResultsThe staining for ALP and Alizarin red S was more strongly positive on the apatite-coated PEEK disks compared to that on non-coated or laser-exposed without coating PEEK disks. The concentration of osteocalcin secreted into the medium was also significantly higher in case of the SrHAP, SrSiP, and SrZnSiP disks than that in the case of the non-coated on day14. The calcium concentration in the PEEK disk was significantly lower in all apatite-coated disks than that in the pure PEEK disks on day 14. In qPCR, OC and ALP mRNA expression was significantly higher in the SrZnSiP disks than that in the pure PEEK disks.ConclusionsOur findings demonstrate that laser bonding of apatite—along with trace elements—on the PEEK disk surfaces might provide the material with surface property that enable better osteogenesis.