Implant osseointegration and the role of microroughness and nanostructures: lessons for spine implants

The response of macrophages and their osteogenic potential modulated by micro/nano-structured Ti surfaces

Current understanding on the interactions between micro/nano-structured Ti surfaces and macrophages is still limited. In this work, TiO₂ nano-structures were introduced onto acid-etched Ti surfaces by alkali-heat treatment, ion exchange and subsequent heat treatment. By adjusting the concentration of NaOH during alkali-heat treatment, nano-flakes, nano-flakes mixed with nano-wires or nano-wires could formed on acid-etched Ti surfaces. The micro- and micro/nano-structured Ti surfaces possessed similar surface chemical and phase compositions. In vitro results indicate that the morphology of macrophages was highly dependent on the morphological features of nano-structures. Nano-flakes and nano-wires were favorable to induce the formation of lamellipodia and filopodia, respectively. Compared to micro-structured Ti surface, micro/nano-structured Ti surfaces polarized macrophages to their M2 phenotype and enhanced the gene expressions of osteogenic growth factors in macrophages. The M2 polarized macrophages promoted the maturation of osteoblasts. Compared to that with nano-flakes or nano-wires, the surface with mixed features of nano-flakes and nano-wires exhibited stronger anti-inflammatory and osteo-immunomodulatory effects. The findings presented in the current work suggest that introducing micro/nano-topographies onto Ti-based implant surfaces is a promising strategy to modulate the inflammatory response and mediate osteogenesis.

An In Vitro Evaluation of the Hierarchical Micro/Nanoporous Structure of a Ti3Zr2Sn3Mo25Nb Alloy after Surface Dealloying

A process to dealloy a Ti-3Zr-2Sn-3Mo-25Nb (TLM) titanium alloy to create a porous surface structure has been reported in this paper aiming to enhance the bioactivity of the alloy. A simple nanoporous topography on the surface was produced through dealloying the as-solution treated TLM alloy. In contrast, dealloying the as-cold rolled alloy created a hierarchical micro/nanoporous topography. SEM and XPS were performed to characterize the topography and element chemistry of both porous structures. The roughness, hydrophilicity, protein adsorption, cell adhesion, proliferation, and osteogenic differentiation were tested. The elements of Zr, Mo, Sn, and Nb were depleted at the nanoporous TLM surface with a diameter of 15.6 ± 2.3 nm. Dissolving the microscale α phase from the alloy surface contributed to the formation of the microscale grooves on the surface. The simple nanoporous topographical surface exhibited hydrophilicity and higher protein adsorption ability, which facilitated the early adhesion of osteoblasts compared with the hierarchical micro/nanoporous surface. On the other hand, the hierarchical micro/nanoporous surface improved cell proliferation and differentiation and still retained the contact guidance function, which implied good bonding for osseointegration. This research revealed the effect of phase composition on the surface morphology of dealloying titanium alloy and the synergistic effect of micron and nanometer topography on the function of osteoblasts. This paper therefore provides insights into the surface topological design of titanium-based biomaterials with improved biocompatibility.

Influences of niobium pentoxide on roughness, hydrophilicity, surface energy and protein absorption, and cellular responses to PEEK based composites for orthopedic applications

To improve the bio-performances of polyetheretherketone (PEEK) for orthopedic applications, submicro-particles of niobium pentoxide (Nb2O5) were synthesized using a sol-gel method, and PEEK/Nb2O5 composites (PNC) with a Nb2O5 content of 25v% (PNC25) and 50v% (PNC50) were fabricated by utilizing a process of pressing-sintering. The results showed that the Nb2O5 particles were not only dispersed in the composites but also exposed on the surface of the composites, which formed submicro-structural surfaces. In addition, the hydrophilicity, surface energy, surface roughness and absorption of proteins of the composites were improved with increasing Nb2O5 content. Moreover, the release of Nb ions with the highest concentration of 5.01 × 10-6 mol L-1 from the composite into the medium displayed no adverse effects on cell proliferation and morphology, indicating no cytotoxicity. Furthermore, compared with PEEK, the composites, especially PNC50, obviously stimulated adhesion and proliferation as well as osteogenic differentiation of bone mesenchymal stem cells of rats. The results suggested that the incorporation of Nb2O5 submicro-particles into PEEK produced novel bioactive composites with improved surface properties, which played important roles in regulating cell behaviors. In conclusion, the composites, especially PNC50 with good cytocompatibility and promotion of cellular responses, exhibited great potential as implantable materials for bone repair.

In-Vivo response to a novel pillared surface morphology for osseointegration in an ovine model

Primary stability and secondary fixation of orthopedic implants to bony tissues are important for healing and long-term functionality. Load sharing and stress transfer are key requirements of an effective implant/tissue interface. This paper presents a novel, macro-scale osseointegration surface morphology which addresses the implant/tissue interface from both the biologic as well as biomechanical perspective. The surface morphology is a controlled, engineered, open topography manifested as discrete pillars projecting from the implant enabling continuous bone ingrowth. The pillared surface is distinct from other porous surfaces and can be differentiated by the localization of the implant material into discrete pillars enabling a continuous mass of bone to freely and easily interdigitate into the pillared structure. Traditional porous structures distribute the implant material throughout the surface forcing the bone to grow in a discontinuous manner. Creating an open and continuous space or "open porosity" in and around the pillar structure allows the bone to easily interdigitate with the implant surface without encumberment from a continuous porous structure. An in-vivo study, using an established ovine model, was undertaken examining the effects of pillar morphology on bone ingrowth and mechanical performance. Cortical and cancellous sites were evaluated utilizing histology, histomophometry, and mechanical pushout, at 4 and 12 weeks. Robust bone ingrowth occurred for all morphologies as was noted in review of the study results. An increase in volume and maturity of bone was noted between the intermediated and final time points. Histomophometry demonstrated over 40% and 80% new bone occupied the available "ingrowth" area at 12 weeks for cancellous and cortical sites (respectively). Histologic review showed little fibrous tissue ingrowth at the interface with no adverse cellular reactions. Testing of cortical samples demonstrated a significant increase in pushout load between the 4 and 12 week timepoints and a 4-8 fold increase in pushout load as compared to the grit blast control. These results demonstrated the effectiveness of the novel interface for orthopedic applications in an in-vivo ovine model.

Molecular Mechanisms of Topography Sensing by Osteoblasts: An Update

Bone is a specialized tissue formed by different cell types and a multiscale, complex mineralized matrix. The architecture and the surface chemistry of this microenvironment can be factors of considerable influence on cell biology, and can affect cell proliferation, commitment to differentiation, gene expression, matrix production and/or composition. It has been shown that osteoblasts encounter natural motifs in vivo, with various topographies (shapes, sizes, organization), and that cell cultures on flat surfaces do not reflect the total potential of the tissue. Therefore, studies investigating the role of topographies on cell behavior are important in order to better understand the interaction between cells and surfaces, to improve osseointegration processes in vivo between tissues and biomaterials, and to find a better topographic surface to enhance bone repair. In this review, we evaluate the main available data about surface topographies, techniques for topographies’ production, mechanical signal transduction from surfaces to cells and the impact of cell–surface interactions on osteoblasts or preosteoblasts’ behavior.

Cell Behavior of Primary Fibroblasts and Osteoblasts on Plasma-Treated Fluorinated Polymer Coated with Honeycomb Polystyrene

The development of new biocompatible polymer substrates is still of interest to many research teams. We aimed to combine a plasma treatment of fluorinated ethylene propylene (FEP) substrate with a technique of improved phase separation. Plasma exposure served for substrate activation and modification of surface properties, such as roughness, chemistry, and wettability. The treated FEP substrate was applied for the growth of a honeycomb-like pattern from polystyrene solution. The properties of the pattern strongly depended on the primary plasma exposure of the FEP substrate. The physico-chemical properties such as changes of the surface chemistry, wettability, and morphology of the prepared pattern were determined. The cell response of primary fibroblasts and osteoblasts was studied on a honeycomb pattern. The prepared honeycomb-like pattern from polystyrene showed an increase in cell viability and a positive effect on cell adhesion and proliferation for both primary fibroblasts and osteoblasts.

Efficacy of strontium supplementation on implant osseointegration under osteoporotic conditions: A systematic review

STATEMENT OF PROBLEM

Strontium has been validated for potent bone-seeking and antiosteoporotic properties and elicits a potentially beneficial impact on implant osseointegration in patients with osteoporosis. However, the efficacy of strontium supplementation on improving new bone formation and implant osseointegration in the presence of osteoporotic bone is still unclear.

PURPOSE

The purpose of this systematic review was to comprehensively assess the efficacy of strontium supplementation, encompassing oral intake and local delivery of strontium, on implant osseointegration in patients with osteoporosis.

MATERIAL AND METHODS

Searches on electronic databases (MEDLINE or PubMed, Web of Science, EBSCO, Embase, and Clinicaltrials.gov) and manual searches were conducted to identify relevant preclinical animal trials up to June 2020. The primary outcomes were the percentage of bone-implant contact and bone area; the secondary outcomes were quantitative parameters of biomechanical tests and microcomputed tomography (μCT).

RESULTS

Fourteen preclinical trials (1 rabbit, 1 sheep, and 12 rat), with a total of 404 ovariectomized animals and 798 implants, were eligible for analysis. The results revealed a significant 17.1% increase in bone-implant contact and 13.5% increase in bone area, favoring strontium supplementation despite considerable heterogeneity. Subgroup analyses of both bone-implant contact and bone area exhibited similar outcomes with low to moderate heterogeneity. Results of biomechanical and μCT tests showed that strontium-enriched implantation tended to optimize the mechanical strength and microarchitecture of newly formed bone despite moderate to generally high heterogeneity.

CONCLUSIONS

Based on the available preclinical evidence, strontium supplementation, including local and systemic delivery, showed promising results for enhancing implant osseointegration in the presence of osteoporosis during 4 to 12 weeks of healing. Future well-designed standardized studies are necessary to validate the efficacy and safety of strontium supplementation and to establish a standard methodology for incorporating Sr into implant surfaces in a clinical setting.

RNA-seq reveals correlations between cytoskeleton-related genes and the osteogenic activity of mesenchymal stem cells on strontium loaded titania nanotube arrays

Strontium loaded titania nanotube arrays (NTSr), as well as titania nanotube arrays (NT), have been regarded as effective coatings to promote bone regeneration on titanium implants, but an understanding of the full extent of early processes affected by such surface modifications is absent. To address this limitation, we performed RNA sequencing (RNA-seq) of Sprague-Dawley rat bone marrow mesenchymal stem cells (rBMMSCs) cultured on unmodified titanium sheets (Con), NT and NTSr specimens. By pairwise comparisons we found that NT and NTSr shared a majority of differentially expressed genes. The Gene Ontology (GO) analysis revealed that NT and NTSr up-regulated a bunch of genes that are annotated to the cytoskeleton. The results were supported by immunofluorescent, transmission electron microscopy (TEM) and western blotting assays. By inhibiting the cytoskeleton through pharmacological agents, the activities of alkaline phosphatase (ALP) on NT and NTSr were also suppressed. Informed by these results, we concluded that NT and NTSr specimens reorganized the cytoskeleton of cultured cells that may play a crucial role in osteogenic lineage commitment.

Atomic Layer Deposition of Bioactive TiO2 Thin Films on Polyetheretherketone for Orthopedic Implants

TiO₂ thin films were deposited on the orthopedic implant material polyetheretherketone (PEEK) by plasma enhanced atomic layer deposition (PEALD) and characterized for their ability to enhance the osseointegrative properties. PEALD was chosen for film deposition to circumvent drawbacks present in line-of-sight deposition techniques, which require technically complex setups for a homogeneous coating thickness. Film conformality was analyzed on silicon 3D test structures and PEEK with micron-scale surface roughness. Wettability and surface energy were determined through contact angle measurements; film roughness and crystallinity were determined by atomic force microscopy and X-ray diffraction, respectively. Adhesion properties of TiO₂ on PEEK were determined with tensile strength tests. Cell tests were performed with the mouse mesenchymal tumor stem cell line ST-2. TiO₂-coated PEEK disks were used as substrates for cell proliferation tests and long-term differentiation tests. After 28 days of cultivation, a mineralized bone matrix was observed. Furthermore, the collagen I and osteocalcin content were determined. The results reveal that the osteogenic properties of the TiO₂ thin film are comparable to those of hydroxyapatite, and thus bioactive properties of PEEK implants are improved by TiO₂ thin films deposited with PEALD.

Nanotubular Oxide Layer Formed on Helix Surfaces of Dental Screw Implants

Surface modification is used to extend the life of implants. To increase the corrosion resistance and improve the biocompatibility of metal implant materials, oxidation of the Ti-13Nb-13Zr titanium alloy was used. The samples used for the research had the shape of a helix with a metric thread, with their geometry imitating a dental implant. The oxide layer was produced by a standard electrochemical method in an environment of 1M H3PO4 + 0.3% HF for 20 min, at a constant voltage of 30 V. The oxidized samples were analyzed with a scanning electron microscope. Nanotubular oxide layers with internal diameters of 30–80 nm were found. An analysis of the surface topography was performed using an optical microscope, and the Sa parameter was determined for the top of the helix and for the bottom, where a significant difference in value was observed. The presence of the modification layer, visible at the bottom of the helix, was confirmed by analyzing the sample cross-sections using computed tomography. Corrosion tests performed in the artificial saliva solution demonstrated higher corrosion current and less noble corrosion potential due to incomplete surface coverage and pitting. Necessary improved oxidation parameters will be applied in future work.

Synergistic antibacterial activity of physical-chemical multi-mechanism by TiO2 nanorod arrays for safe biofilm eradication on implant

Treatment of implant-associated infection is becoming more challenging, especially when bacterial biofilms form on the surface of the implants. Developing multi-mechanism antibacterial methods to combat bacterial biofilm infections by the synergistic effects are superior to those based on single modality due to avoiding the adverse effects arising from the latter. In this work, TiO2 nanorod arrays in combination with irradiation with 808 near-infrared (NIR) light are proven to eradicate single specie biofilms by combining photothermal therapy, photodynamic therapy, and physical killing of bacteria. The TiO2 nanorod arrays possess efficient photothermal conversion ability and produce a small amount of reactive oxygen species (ROS). Physiologically, the combined actions of hyperthermia, ROS, and puncturing by nanorods give rise to excellent antibacterial properties on titanium requiring irradiation for only 15 min as demonstrated by our experiments conducted in vitro and in vivo. More importantly, bone biofilm infection is successfully treated efficiently by the synergistic antibacterial effects and at the same time, the TiO2 nanorod arrays improve the new bone formation around implants. In this protocol, besides the biocompatible TiO2 nanorod arrays, an extra photosensitizer is not needed and no other ions would be released. Our findings reveal a rapid bacteria-killing method based on the multiple synergetic antibacterial modalities with high biosafety that can be implemented in vivo and obviate the need for a second operation. The concept and antibacterial system described here have large clinical potential in orthopedic and dental applications.

Near-infrared light II - assisted rapid biofilm elimination platform for bone implants at mild temperature

Light-triggered therapy is a prospective method to combat implant-associated infection but near-infrared I (NIR-I) light has insufficient penetrating ability in tissues and local hyperthermia induced by the photothermal treatment may destroy surrounding healthy tissues. Herein, a near-infrared II (NIR-II) phototherapy system composed of upconversion elements doped titanium dioxide nanorods (TiO₂ NRs)/curcumin (Cur)/hyaluronic acid (HA)/bone morphogenetic protein-2 (BMP-2) is designed for biomedical titanium and demonstrated to overcome the above hurdles simultaneously. Incorporation of F, Yb, and Ho not only improves the photocatalytic ability, but also renders the implants with the upconversion capability, so that the NRs can generate enough reactive oxygen species (ROS) when irradiated by the NIR-II laser. Furthermore, the combined actions of quorum sensing inhibitors, ROS, and physical puncture by NRs eliminate Staphylococcus aureus biofilms on titanium rapidly at a mild temperature of 45 °C by only requiring irradiation with the 1060 nm laser for only 15 min in vitro and in vivo. The presence of Cur mitigates the immune response and BMP-2 improves osteogenic differentiation, thus accelerating new bone formation. This low-temperature NIR-II light-triggered antibacterial platform has large potential in combating deep-tissue infection in clinical applications.

Hydrophilic titanium surface modulates early stages of osseointegration in osteoporosis

OBJECTIVE

Using a mouse osteoporotic model, this study aimed to determine the influence of hydrophilic titanium surfaces on gene expression and bone formation during the osseointegration process.

BACKGROUND

Based on the previous evidence, it is plausible to assume that osteoporotic bone has a different potential of bone healing. Therefore, implant surface modification study that aims at enhancing bone formation to further improve short- and long-term clinical outcomes in osteoporosis is necessary.

MATERIAL AND METHODS

Fifty female, 3-month-old mice were included in this study. Osteoporosis was induced by ovariectomy (OVX, test group) in 25 mice. The further 25 mice had ovaries exposed but not removed (SHAM, control group). Seven weeks following the ovariectomy procedures, one customized implant (0.7 × 8 mm) of each surface was placed in each femur for both groups. Implants had either a hydrophobic surface (SAE) or a hydrophilic treatment surface (SAE-HD). Calcium (Ca) and phosphorus (P) content was measured by energy-dispersive X-ray spectroscopy (EDS) after 7 days. The femurs were analyzed for bone-to-implant contact (BIC) and bone volume fraction (BV) by nano-computed tomography (nano-CT) after 14 and 28 days. Same specimens were further submitted to histological analysis. Additionally, after 3 and 7 days, implants were removed and cells were collected around the implant to access gene expression profile of key osteogenic (Runx2, Alp, Sp7, Bsp, Sost, Ocn) and inflammatory genes (IL-1β, IL-10, Tnf-α, and Nos2) by qRT-PCR assay. Statistical analysis was performed by ANOVA and paired t test with significance at P < .05.

RESULTS

The amount of Ca and P deposited on the surface due to the mineralization process was higher for SAE-HD compared to SAE on the intra-group analysis. Nano-CT and histology revealed more BV and BIC for SAE-HD in SHAM and OVX groups compared to SAE. Analysis in OVX group showed that most genes (ie, ALP, Runx2) involved in the bone morphogenetic protein (BMP) signaling were significantly activated in the hydrophilic treatment.

CONCLUSION

Both surfaces were able to modulate bone responses toward osteoblast differentiation. SAE-HD presented a faster response in terms of bone formation and osteogenic gene expression compared to SAE. Hydrophilic surface in situations of osteoporosis seems to provide additional benefits in the early stages of osseointegration.

Complete Osseointegration of a Retrieved 3-D Printed Porous Titanium Cervical Cage

Introduction: Porous 3D-printed titanium has only recently been introduced for spinal applications. Evidence around its use is currently limited to animal studies and only few human case series. This study describes the histological findings of a retrieved EIT cervical cage, explanted 2 years after insertion.

Materials and Methods: The patient underwent a double level C4/C5 & C5/C6 anterior cervical decompression using EIT cervical cages without an anterior plate. Two years later the C6/7 level degenerated and began to cause myelopathic symptoms. In order to address the kyphotic imbalance of the cervical spine and fix the C6/7 level, the surgeon decided to remove the C5/6 cervical cage and bridge the fusion from C4 to C7 inclusive. The retrieved cage was histologically evaluated for bone ingrowth and signs of inflammation.

Results: MRI demonstrated spinal canal stenosis at C6/C7. Plain radiographs confirmed well-integrated cervical cages at 2 years postoperative. The peroperative surgical need to use a chisel to remove the implant at C5/C6 reconfirmed the solid fusion of the segment. Macroscopically white tissue, indicative of bone, was present at both superior and inferior surfaces of the explanted specimen. Histological evaluation revealed complete osseointegration of the 5 mm high EIT Cellular Titanium^® cervical cage, displaying mature lamellar bone in combination with bone marrow throughout the cage. Furthermore, a pattern of trabecular bone apposition (without fibrous tissue interface) and physiological remodeling activity was observed directly on the cellular titanium scaffold.

Conclusion: This histological retrieval study of a radiologically fused cervical EIT cage clearly demonstrates complete osseointegration within a 2-year time frame. The scaffold exhibits a bone in growth pattern and maturation of bone tissue similar of what has been demonstrated in animal studies evaluating similar porous titanium implants. The complete osseointegration throughout the cage indicates physiological loading conditions even in the central part of the cage. This pattern suggests the absence, or at least the minimization, of stress-shielding in this type of porous titanium cage.

Cell and Tissue Response to Polyethylene Terephthalate Mesh Containing Bone Allograft in Vitro and in Vivo

BACKGROUND

Extended polyethylene terephthalate mesh (PET, Dacron) can provide containment of compressed particulate allograft and autograft. This study assessed if PET mesh would interfere with osteoprogenitor cell migration from vertebral plates through particulate graft, and its effect on osteoblast differentiation or the quality of bone forming within fusing vertebra during vertebral interbody fusion.

METHODS

The impact of PET mesh on the biological response of normal human osteoblasts (NHOst cells) and bone marrow stromal cells (MSCs) to particulate bone graft was examined in vitro. Cells were cultured on rat bone particles +/- mesh; proliferation and osteoblast differentiation were assessed. The interface between the vertebral endplate, PET mesh, and newly formed bone within consolidated allograft contained by mesh was examined in a sheep model via microradiographs, histology, and mechanical testing.

RESULTS

Growth on bone particles stimulated proliferation and early differentiation of NHOst cells and MSCs, but delayed terminal differentiation. This was not negatively impacted by mesh. New bone formation in vivo was not prevented by use of a PET mesh graft containment device. Fusion was improved in sites containing allograft/demineralized bone matrix (DBM) versus autograft and was further enhanced when stabilized using pedicle screws. Only sites treated with allograft/DBM+screws exhibited greater percent bone ingrowth versus discectomy or autograft. These results were mirrored biomechanically.

CONCLUSIONS

PET mesh does not negatively impact cell attachment to particulate bone graft, proliferation, or initial osteoblast differentiation. The results demonstrated that bone growth occurs from vertebral endplates into graft material within the PET mesh. This was enhanced by stabilization with pedicle screws leading to greater bone ingrowth and biomechanical stability across the fusion site.

CLINICAL RELEVANCE

The use of extended PET mesh allows containment of bone graft material during vertebral interbody fusion without inhibiting migration of osteoprogenitor cells from vertebral end plates in order to achieve fusion.

LEVEL OF EVIDENCE

5.

Cell Type-Specific Adhesion and Migration on Laser-Structured Opaque Surfaces

Cytocompatibility is essential for implant approval. However, initial in vitro screenings mainly include the quantity of adherent immortalized cells and cytotoxicity. Other vital parameters, such as cell migration and an in-depth understanding of the interaction between native tissue cells and implant surfaces, are rarely considered. We investigated different laser-fabricated spike structures using primary and immortalized cell lines of fibroblasts and osteoblasts and included quantification of the cell area, aspect ratio, and focal adhesions. Furthermore, we examined the three-dimensional cell interactions with spike topographies and developed a tailored migration assay for long-term monitoring on opaque materials. While fibroblasts and osteoblasts on small spikes retained their normal morphology, cells on medium and large spikes sank into the structures, affecting the composition of the cytoskeleton and thereby changing cell shape. Up to 14 days, migration appeared stronger on small spikes, probably as a consequence of adequate focal adhesion formation and an intact cytoskeleton, whereas human primary cells revealed differences in comparison to immortalized cell lines. The use of primary cells, analysis of the cell-implant structure interaction as well as cell migration might strengthen the evaluation of cytocompatibility and thereby improve the validity regarding the putative in vivo performance of implant material.

PLIF surgery with titanium-coated PEEK or uncoated PEEK cages: a prospective randomised clinical and radiological study

PURPOSE

This study aimed to compare clinical results and fusion rates of uncoated polyetheretherketone (PEEK) cages with titanium-coated PEEK cages in posterior lumbar interbody fusion (PLIF) surgery.

METHODS

A prospective randomised study including 60 patients with one- or two-segment lumbar degenerative diseases. Patients received either titanium-coated PEEK cages (group A) or uncoated PEEK cages (group B). Fusion rates were evaluated on plain X-rays and CT scans after 6 and 12 months. Clinical follow-up (visual analogue scale, VAS; Oswestry Disability Index score, ODI; EQ-5D) was performed for 24 months.

RESULTS

Fifty-five patients (92%) (36 female, 19 male) had a complete follow-up. There were no statistically significant differences in demographic, peri- or intraoperative data between groups A and B. ODI, VAS and EQ-5D improved significantly (p < 0.001) after surgery without statistically significant differences between the two groups. Overall, 65 operated segments could be evaluated for fusion (group A: 29 segments, group B: 36 segments, p = 0.6). Osseous integration of the cage surface improved significantly (p < 0.001) in both groups between 6 and 12 months after surgery. At 12-month follow-up, neither radiolucency nor signs of instability or dislocation were noted. Fusion was present in CT scans as follows: (a) bone growth through cage pores (A: 100%, B: 100%); (b) bone growth outside the cages (A: 48%, B: 61%; p = 0.3).

CONCLUSIONS

PEEK and titanium-coated PEEK cages for PLIF produce equally favourable clinical and radiological results up to 24 months post-surgery. The fusion rate was not different.

Additively Manufactured Tantalum Implants for Repairing Bone Defects: A Systematic Review

Tantalum has unique advantages as a biomaterial for repairing bone defects due to its outstanding bioactivity, excellent corrosion resistance, and mechanical properties. Ideal implants for bone repair should be of good biocompatibility and bioactivity, as well as ability to simulate the microstructure and mechanical environment of human bone tissues. Additive manufacturing can facilitate freedom of design for the macrostructure/microstructure of bone implants with controlled mechanical properties; thus, this method has great potential. Additively manufactured tantalum implants provide a novel alternative for bone repair and are gaining increasing attention. This systematic review aims to comprehensively summarize the subsistent evidence from physicochemical, cellular, animal, and clinical studies on additively manufactured tantalum implants in repairing bone defects, for the first time. This work may provide researchers an essential grasp on the advances of additively manufactured tantalum implants. Impact statement Tantalum has unique advantages as a biomaterial. Additive manufacturing facilitates design freedom and additively manufactured tantalum is a novel alternative for bone repair. Studies on additively manufactured tantalum progress greatly, while no review summarizing the progresses was published.

Biomimetic cues from poly(lactic-co-glycolic acid)/hydroxyapatite nano-fibrous scaffolds drive osteogenic commitment in human mesenchymal stem cells in the absence of osteogenic factor supplements

Mimicking the complex hierarchical architecture of the 'osteon', the functional unit of cortical bone, from the bottom-up offers the possibility of generating mature bone tissue in tissue engineered bone substitutes. In this work, a modular 'bottom-up' approach has been developed to assemble bone niche-mimicking nanocomposite scaffolds composed of aligned electrospun nanofibers of poly(lactic-co-glycolic acid) (PLGA) encapsulating aligned rod-shape nano-sized hydroxyapatite (nHA). By encoding axial orientation of the nHA within these aligned nanocomposite fibers, significant improvements in mechanical properties, surface roughness, hydrophilicity and in vitro simulated body fluid (SBF) mineral deposition were achieved. Moreover, these hierarchical scaffolds induced robust formation of bone hydroxyapatite and osteoblastic maturation of human bone marrow-derived mesenchymal stem cells (hBMSCs) in growth media that was absent of any soluble osteogenic differentiation factors. The results of this investigation confirm that these tailored, aligned nanocomposite fibers, in the absence of media-bone inductive factors, offer the requisite biophysical and biochemical cues to hBMSCs to promote and support their differentiation into mature osteoblast cells and form early bone-like tissue in vitro.

The influence of macro-textural designs over implant surface on bone on-growth: A computational mechanobiology based study

The longerterm secondary stability of an uncemented implant depends primarily on the quality and extent of bone in-growth or on-growth at the bone-implant interface. Investigations are warranted to predict the influences of implant macro-textures on bone on-growth pattern. Mechanoregulatory tissue differentiation algorithms can predict such patterns effectively. There is, however, a dearth of volumetric in silico study to assess the influence of macro-textures on bone growth. The present study investigated the influence of macro-textural grooves/ribs on changes in tissue formation at the bone-implant interface by carrying out a 3D finite element (FE) analysis. Three distinct macro-textures, loosely based on commercially viable hip stem models, were comparatively assessed for varying levels of interfacial micromotion. The study predicted elevated fibrogenesis and chondrogenesis, followed by a suppressed osteogenesis for higher levels of micromotion (60 μm and 100 μm), resulting in weak bone-implant interface strength. However, small judicious modifications in implant surface texture may enhance bone growth to a considerable extent. The numerical scheme can further be used as a template for more rigorous parametric and multi-scale studies.

Titanium Scaffolds by Direct Ink Writing: Fabrication and Functionalization to Guide Osteoblast Behavior

Titanium (Ti) and Ti alloys have been used for decades for bone prostheses due to its mechanical reliability and good biocompatibility. However, the high stiffness of Ti implants and the lack of bioactivity are pending issues that should be improved to minimize implant failure. The stress shielding effect, a result of the stiffness mismatch between titanium and bone, can be reduced by introducing a tailored structural porosity in the implant. In this work, porous titanium structures were produced by direct ink writing (DIW), using a new Ti ink formulation containing a thermosensitive hydrogel. A thermal treatment was optimized to ensure the complete elimination of the binder before the sintering process, in order to avoid contamination of the titanium structures. The samples were sintered in argon atmosphere at 1200 °C, 1300 °C or 1400 °C, resulting in total porosities ranging between 72.3% and 77.7%. A correlation was found between the total porosity and the elastic modulus of the scaffolds. The stiffness and yield strength were similar to those of cancellous bone. The functionalization of the scaffold surface with a cell adhesion fibronectin recombinant fragment resulted in enhanced adhesion and spreading of osteoblastic-like cells, together with increased alkaline phosphatase expression and mineralization.

Low cycles pulsed chemical vapor deposition of polycrystalline anatase TiO2

In this work, an atomic layer deposition (ALD) system is used to identify deposition conditions resulting in anisotropic growth and the formation of highly defined polycrystalline anatase titanium dioxide. FESEM, Raman Spectroscopy, and XRD were extensively used to characterize the deposited titania. The ALD parameter refinement resulted in the attainment of a polycrystalline anatase phase titania in as low as 30 cycles, although the final parameter resulted in a pulsed-chemical vapor deposition (pulsed-CVD). This work suggests that the anatase crystal phase’s development is more dependent on deposition process parameters such as precursor pulse, waiting time, and vacuum times than on the number of cycles. Moreover, the developed pulsed-CVD procedure to deposit anatase titania was capable of coating rough aluminum and titanium substrates with polycrystalline anatase titania, highly increasing the potential to be used in other biomedical implants made of different metals such as stainless steel or in other applications such as dielectrics

Fabrication of ultrahigh-molecular-weight polyethylene porous implant for bone application

Porous implants play a crucial role in allowing ingrowth of host connective tissue and thereby help in keeping the implant in its place. With the aim of mimicking the microstructure of natural extracellular matrix, ultrahigh-molecular-weight polyethylene (UHMWPE) porous samples with a desirable pore size distribution were developed by combining thermally induced phase separation and salt leaching techniques. The porous UHMWPE samples consisted of a nanofibrous UHMWPE matrix with a fibre diameter smaller than 500 nm, highly interconnected, with a controllable pore diameter from nanoscale to 300 µm. Moreover, a porous UHMWPE sample was also developed as a continuous and homogeneous coating onto the UHMWPE dense sample. The dense/porous UHMWPE sample supported human foetal osteoblast 1.19 cell line proliferation and differentiation, indicating the potential of porous UHMWPE with a desirable pore size distribution for bone application. An osseointegration model in the sheep revealed substantial bone formation within the pore layer at 12 weeks via SEM evaluation. Ingrown bone was more closely opposed to the pore wall when compared to the dense UHMWPE control. These results indicate that dense/porous UHMWPE could provide improved osseointegration while maintaining the structural integrity necessary for load-bearing orthopaedic application.

Investigation of Biomechanical Characteristics of Orthopedic Implants for Tibial Plateau Fractures by Means of Deep Learning and Support Vector Machine Classification

An experimental comparative study of the biomechanical behavior of commonly used orthopedic implants for tibial plateau fractures was carried out. An artificial bone model Synbone1110 was used and a Schatzker V type tibial plateau fracture was created in vitro, then stabilized with three different implant types, classic L plate, Locking Plate System (PLS), and Hybrid External Fixator (HEF). The stiffness of the bone—implant assembly was assessed by means of mechanical testing using an automated testing machine. It was found that the classic L plate type internal implant has a significantly higher value of deformation then the other two implant types. In case of the other implant types, PLS had a better performance than HEF at low and medium values of the applied force. At high values of the applied forces, the difference between deformation values of the two types became gradually smaller. An Artificial Neural Network model was developed to predict the implant deformation as a function of the applied force and implant device type. To establish if a clear-cut distinction exists between mechanical performance of PLS and HEF, a Support Vector Machine classifier was employed. At high values of the applied force, the Support Vector Machine (SVM) classifier predicts that no statistically significant difference exists between the performance of PLS and HEF.

In vitro and in vivo study on the osseointegration of BCP-coated versus uncoated nondegradable thermoplastic polyurethane focal knee resurfacing implants

Focal knee resurfacing implants (FKRIs) are intended to treat cartilage defects in middle-aged patients. Most FKRIs are metal-based, which hampers follow-up of the joint using magnetic resonance imaging and potentially leads to damage of the opposing cartilage. The purpose of this study was to develop a nondegradable thermoplastic polyurethane (TPU) FKRI and investigate its osseointegration. Different surface roughness modifications and biphasic calcium phosphate (BCP) coating densities were first tested in vitro on TPU discs. The in vivo osseointegration of BCP-coated TPU implants was subsequently compared to uncoated TPU implants and the titanium bottom layer of metal control implants in a caprine model. Implants were implanted bilaterally in stifle joints and animals were followed for 12 weeks, after which the bone-to-implant contact area (BIC) was assessed. Additionally, 18F-sodium-fluoride (18F-NaF) positron emission tomography PET/CT-scans were obtained at 3 and 12 weeks to visualize the bone metabolism over time. The BIC was significantly higher for the BCP-coated TPU implants compared to the uncoated TPU implants (p = .03), and did not significantly differ from titanium (p = .68). Similar 18F-NaF tracer uptake patterns were observed between 3 and 12 weeks for the BCP-coated TPU and titanium implants, but not for the uncoated implants. TPU FKRIs with surface modifications could provide the answer to the drawbacks of metal FKRIs.

A Magnetic Iron Oxide/Polydopamine Coating Can Improve Osteogenesis of 3D-Printed Porous Titanium Scaffolds with a Static Magnetic Field by Upregulating the TGFβ-Smads Pathway

3D-printed porous titanium-aluminum-vanadium (Ti6Al4V, pTi) scaffolds offer surgeons a good option for the reconstruction of large bone defects, especially at the load-bearing sites. However, poor osteogenesis limits its application in clinic. In this study, a new magnetic coating is successfully fabricated by codepositing of Fe₃ O₄ nanoparticles and polydopamine (PDA) on the surface of 3D-printed pTi scaffolds, which enhances cell attachment, proliferation, and osteogenic differentiation of hBMSCs in vitro and new bone formation of rabbit femoral bone defects in vivo with/without a static magnetic field (SMF). Furthermore, through proteomic analysis, the enhanced osteogenic effect of the magnetic Fe₃ O₄ /PDA coating with the SMF is found to be related to upregulate the TGFβ-Smads signaling pathway. Therefore, this work provides a simple protocol to improve the osteogenesis of 3D-printed porous pTi scaffolds, which will help their application in clinic.

Hollow cathode plasma nitriding of medical grade Ti6Al4V: A comprehensive study

Ti6Al4V used in biomedical applications still has several surface-related problems, such as poor bone compatibility and low wear resistance. In this work, the formation of a protective layer of titanium nitride obtained by plasma treatment in hollow cathode was studied, and the best experimental conditions were verified by a statistical factorial design of experiments. The samples were characterized in terms of their physical and chemical properties, correlating the effects of time (min) and temperature (°C). An achieved ideal condition was further analysed in terms of in vitro cytotoxicity, micro-abrasion, and electrochemical properties. The carried-out assessment has shown that nitrided condition has an improvement in wettability, microhardness, along with TixNy formation and roughness increment, when compared to pristine condition.

Single-cell adhesion of human osteoblasts on plasma-conditioned titanium implant surfaces in vitro

OBJECTIVES

This study aimed to demonstrate the effect of treating titanium-implant surfaces with plasma from two different sources on wettability and initial single-cell adhesion of human osteoblasts and to investigate whether aging affects treatment outcomes.

METHODS

Titanium disks with sandblasted and acid-etched (SLA) surfaces were treated with atmospheric pressure plasma (APP) and low-pressure plasma (LPP). For wetting behavior of the specimens after plasma treatment, the water contact angle was measured. The single-cell detachment force and amount of work of detachment of human osteoblasts were determined with single-cell force spectroscopy (SCFS). To evaluate the aging effect in APP-treated specimens, SCFS was conducted 10 and 60 min after treatment.

RESULTS

Significantly higher hydrophilicity was observed in the APP and LPP treatment groups than in the control group, but no significant difference was observed between the APP and LPP groups. No significant difference in cell-detachment force or work of detachment was observed, and there were no significant differences according to the conditioning mechanisms and storage time.

SIGNIFICANCE

Conditioning of the titanium surfaces with APP or LPP was not a significant influencing factor in the initial adhesion of the osteoblasts.

Integrated analysis of lncRNA-mRNA networks associated with an SLA titanium surface reveals the potential role of HIF1A-AS1 in bone remodeling

Microstructured titanium surface implants, such as typical sandblasted and acid-etched (SLA) titanium implants, are widely used to promote bone apposition in prosthetic treatment by dental implants following tooth loss. Although there are multiple factors associated with the superior osseointegration of an SLA titanium surface, the molecular mechanisms of long noncoding RNAs (lncRNAs) are still unclear. In this study, we characterized smooth (SMO) and SLA surfaces, and compared the osteoinduction of these surfaces using human bone marrow-derived mesenchymal stem cells (hBMSCs) in vitro and implants in a rat model in vivo. Then, we used microarrays and bioinformatics analysis to investigate the differential expression profiles of mRNAs and lncRNAs on SMO and SLA titanium surfaces. An lncRNA–mRNA network was constructed, which showed an interaction between lncRNA HIF1A antisense RNA 1 (HIF1A-AS1) and vascular endothelial growth factor. We further found that knockdown of HIF1A-AS1 significantly decreased osteogenic differentiation of hBMSCs. This study screened SLA-induced lncRNAs using a systemic strategy and showed that lncRNA HIF1A-AS1 plays a role in promotion of new bone formation in the peri-implant area, providing a novel insight for future surface modifications of implants.

Long non-coding RNA HIF1A-AS1 plays a role in SLA titanium surface-induced osteogenic differentiation of hBMSCs by regulating p38 MAPK.

Regulation of mesenchymal stem cell differentiation on microstructured titanium surfaces by semaphorin 3A

Peri-implant bone formation depends on the ability of mesenchymal stem cells (MSCs) to colonize implant surfaces and differentiate into osteoblasts, but the precise mechanisms controlling this process remain unclear. In vitro, MSCs undergo osteoblastic differentiation on microstructured titanium (Ti) surfaces in the absence of exogenous media supplements and produce factors that promote osteogenesis while regulating osteoclast activity, including semaphorins. The goal of this study was to evaluate the role of semaphorin 3A (Sema3A) on surface-mediated osteoblastic differentiation and determine the hierarchy of this signaling cascade. Human MSCs were cultured on 15 mm grade 2 smooth (pretreatment, PT), hydrophobic-microrough (sand blasted/acid etched, SLA), hydrophilic-microrough Ti (mSLA) (Institut Straumann AG, Basel, Switzerland), or tissue culture polystyrene (TCPS). Expression of SEMA3A family proteins increased after 7 days of culture, and the increased expression in response to microstructured Ti was dependent on recognition of the surface by integrin α2β1. Exogenous Sema3A increased differentiation whereas differentiation was decreased in cells treated with a Sema3A antibody. Furthermore, Sema3A influenced the production of osteoprotegerin and osteopontin suggesting it as an important local regulator of bone remodeling. Inhibition of Wnt3A and Wnt5A revealed that activation of Sema3A occurs downstream of Wnt5A and may facilitate the translocation of β-catenin bypassing the canonical Wnt3A initiating signal associated with osteoblastic differentiation. Furthermore, chemical inhibition of calmodulin (CaM), Ca²⁺/calmodulin-dependent protein kinase (CaMKII), phospholipase A₂ (PLA2), protein kinase C (PKC), and BMP receptors suggest that Sema3A could serve as a feedback mechanism for both Wnt5A and BMP2. Here, we show novel roles for Sema3A family proteins in the surface-dependent modulation of MSCs as well as important interactions with pathways known to be associated with osteoblastic differentiation. Moreover, their effects on bone remodeling markers have significant implications for peri-implant bone remodeling and downstream modulation of osteoclastic activity. These results suggest that Sema3A aids in peri-implant bone formation through regulation on multiple stages of osseointegration, making it a potential target to promote osseointegration in patients with compromised bone remodeling.

Titanium implant surface properties enhance osseointegration in ovariectomy induced osteoporotic rats without pharmacologic intervention

OBJECTIVES

This study determined whether implant surfaces that promote osseointegration in normal rats can promote osseointegration in osteoporotic rats without pharmacologic intervention.

MATERIALS AND METHODS

Virgin female 8-month-old CD Sprague Dawley rats (N = 25) were ovariectomized. At 6 weeks, microstructured/non-nanostructured/hydrophobic, microstructured/nanostructured/hydrophobic, or microstructured/nanostructured/hydrophilic Ti implants (Ø2.5 × 3.5 mm; Institut Straumann AG, Basel, Switzerland) were placed in the distal metaphysis of each femur. At 28 days, bone quality and implant osseointegration were assessed using microCT, histomorphometrics, and removal torque values (RTVs). Calvarial osteoblasts were isolated and cultured for 7 days on Ø15 mm Ti disks processed to exhibit similar surface characteristics as the implants used for the in vivo studies. The phenotype was assessed by measuring the production of osteocalcin, osteoprotegerin, osteopontin, BMP2, VEGF, and RANKL.

RESULTS

Microstructured/nanostructured/hydrophilic implants promoted increased bone-to-implant contact and RTVs in vivo and increased osteoblastic marker production in vitro compared to microstructured/non-nanostructured/hydrophobic and microstructured/nanostructured/hydrophobic implants, suggesting that osseointegration occurs in osteoporotic animals, and implant surface properties improve its rate.

CONCLUSIONS

Although all modified implants were able to osseointegrate in rats with OVX-induced osteoporosis without pharmacologic intervention, the degree of osseointegration was greater around microstructured/nanostructured/hydrophilic implant surfaces. These results suggest that when appropriate microstructure is present, hydrophilicity has a greater influence on Ti implant osseointegration compared to nanostructures. Moreover, modified implant surfaces can exert their control over the altered bone turnover observed in osteoporotic patients to stimulate functional osseointegration. These results provide critical insight for developing implants with improved osseointegration in patients with metabolic disorders of bone remodeling.

Nanoporosity Stimulates Cell Spreading and Focal Adhesion Formation in Cells with Mutated Paxillin

We have evaluated the response to nanotopography of CHO-K1 cells that express wild-type paxillin or paxillin with mutations at serine 273 that inhibit phosphorylation. Cells were grown on nanoporous and polished titanium surfaces. With all cell types, immunofluorescence showed that adhesion and spreading were minimally affected on the treated surface and that the actin filaments were more abundant and well-aligned. Scanning electron microscopy revealed changes in cell shape and abundant filopodia with lateral nanoprotrusions in response to nanoporosity. Gene expression of proteins associated with cellular adhesion and protrusions was significantly increased on the nanoporous surface regardless of the cell type. In particular, α-actinin, Rac1, Cdc42, and ITGα1 were upregulated in S273 cells with alanine substitutions, whereas FAK, Pxn, and Src were downregulated, leading to improved focal adhesion formation. These findings suggest that the surface nanoporosity can "compensate for" the genetic mutations that affect the biomechanical relationship of cells to surfaces.

Ti-5Al-5Mo-5V-3Cr bone implants with dual-scale topography: a promising alternative to Ti-6Al-4V

Modifications to the compositional, topographical and morphological aspects of bone implants can lead to improved osseointegration, thus increasing the success of bone implant procedures. This study investigates the creation of dual-scale topography on Ti-5Al-5Mo-5V-3Cr (Ti5553), an alloy not presently used in the biomedical field, and compares it to Ti-6Al-4V (Ti64), the most used Ti alloy for bone implants. Dual-scale surface topography was obtained by combining selective laser melting (SLM) and electrochemical anodization, which resulted in micro- and nanoscale surface features, respectively. Ti5553 and Ti64 samples were manufactured by SLM and showed comparable surface topography. Subsequent electrochemical anodization succeeded in forming titania nanotubes (TNTs) on both alloys, with larger nanotubes obtained with Ti5553 at all investigated anodization voltages. At an anodization voltage of 40 V, a minimum time of 20 min was necessary to have nanotube formation on the surface of either alloy, while only nanopores were evident for shorter times. Seeded Saos-2 cells showed ideal interactions with surface-modified structures, with filopodia extending to both surface microparticles characteristic of SLM and to the interior of TNTs. Attractiveness of Ti5553 lies in its lower elastic modulus (E = 72 GPa) compared to Ti64, which should mitigate stress-shielding phenomena in vivo. This, combined with the analogous results obtained in terms of dual-scale surface topography and cell-substrate interaction, could indicate Ti5553 as a promising alternative to the widely-employed Ti64 for bone implant device manufacturing.

Polarization of Macrophages, Cellular Adhesion, and Spreading on Bacterially Contaminated Gold Nanoparticle-Coatings in Vitro

Biomaterial-associated infections often arise from contaminating bacteria adhering to an implant surface that are introduced during surgical implantation and not effectively eradicated by antibiotic treatment. Whether or not infection develops from contaminating bacteria depends on an interplay between bacteria contaminating the biomaterial surface and tissue cells trying to integrate the surface with the aid of immune cells. The biomaterial surface plays a crucial role in defining the outcome of this race for the surface. Tissue integration is considered the best protection of a biomaterial implant against infectious bacteria. This paper aims to determine whether and how macrophages aid osteoblasts and human mesenchymal stem cells to adhere and spread over gold nanoparticle (GNP)-coatings with different hydrophilicity and roughness in the absence or presence of contaminating, adhering bacteria. All GNP-coatings had identical chemical surface composition, and water contact angles decreased with increasing roughness. Upon increasing the roughness of the GNP-coatings, the presence of contaminating Staphylococcus epidermidis in biculture with cells gradually decreased surface coverage by adhering and spreading cells, as in the absence of staphylococci. More virulent Staphylococcus aureus fully impeded cellular adhesion and spreading on smooth gold- or GNP-coatings, while Escherichia coli allowed minor cellular interaction. Murine macrophages in monoculture tended toward their pro-inflammatory "fighting" M1-phenotype on all coatings to combat the biomaterial, but in bicultures with contaminating, adhering bacteria, macrophages demonstrated Ym1 expression, indicative of polarization toward their anti-inflammatory "fix-and-repair" M2-phenotype. Damage repair of cells by macrophages improved cellular interactions on intermediately hydrophilic/rough (water contact angle 30 deg/surface roughness 118 nm) GNP-coatings in the presence of contaminating, adhering Gram-positive staphylococci but provided little aid in the presence of Gram-negative E. coli. Thus, the merits on GNP-coatings to influence the race for the surface and prevent biomaterial-associated infection critically depend on their hydrophilicity/roughness and the bacterial strain involved in contaminating the biomaterial surface.

Optimized Nanointerface Engineering of Micro/Nanostructured Titanium Implants to Enhance Cell-Nanotopography Interactions and Osseointegration

The success of orthopedic implants requires rapid and complete osseointegration which relies on an implant surface with optimal features. To enhance cellular function in response to the implant surface, micro- and nanoscale topography have been suggested as essential. The aim of this study was to identify an optimized Ti nanostructure and to introduce it onto a titanium plasma-sprayed titanium implant (denoted NTPS-Ti) to confer enhanced immunomodulatory properties for optimal osseointegration. To this end, three types of titania nanostructures, namely, nanowires, nanonests, and nanoflakes, were achieved on hydrothermally prepared Ti substrates. The nanowire surface modulated protein conformation and directed integrin binding and specificity in such a way as to augment the osteogenic differentiation of bone marrow-derived mesenchymal stem cells (BMSCs) and induce a desirable osteoimmune response of RAW264.7 macrophages. In a coculture system, BMSCs on the optimized micro/nanosurface exerted enhanced effects on nonactivated or lipopolysaccharide-stimulated macrophages, causing them to adopt a less inflammatory macrophage profile. The enhanced immunomodulatory properties of BMSCs grown on NTPS-Ti depended on a ROCK-medicated cyclooxygenase-2 (COX2) pathway to increase prostaglandin E2 (PGE2) production, as evidenced by decreased production of PGE2 and concurrent inhibition of immunomodulatory properties after treatment with ROCK or COX2 inhibitors. In vivo evaluation showed that the NTPS-Ti implant resulted in enhanced osseointegration compared with the TPS-Ti and Ti implants. The results obtained in our study may provide a prospective approach for enhancing osseointegration and supporting the application of micro/nanostructured Ti implants.

RGD-functionalized supported lipid bilayers modulate pre-osteoblast adherence and promote osteogenic differentiation

Biomaterial integration into bone requires optimal surface conditions to promote osteoprogenitor behavior, which is affected by integrin-binding via arginine-glycine-aspartate (RGD). RGD-functionalized supported lipid bilayers (SLBs) might be interesting as biomaterial coating in bone regeneration, because they allow integration of proteins, for example, growth factors, cytokines, and/or antibacterial agents. Since it is unknown whether and how they affect osteoprogenitor adhesion and differentiation, the aim was to investigate adhesion, focal adhesion formation, morphology, proliferation, and osteogenic potential of pre-osteoblasts cultured on RGD-functionalized SLBs compared to unfunctionalized SLBs and poly-l-lysine (PLL). After 17 hr, pre-osteoblast density on SLBs without or with RGD was similar, but lower than on PLL. Cell surface area, elongation, and number and size of phospho-paxillin clusters were also similar. Cells on SLBs without or with RGD were smaller, more elongated, and had less and smaller phospho-paxillin clusters than on PLL. OPN expression was increased on SLBs with RGD compared to PLL. Moreover, after 1 week, COL1a1 expression was increased on SLBs without or with RGD. In conclusion, pre-osteoblast adhesion and enhanced differentiation were realized for the first time on RGD-functionalized SLBs, pointing to a new horizon in the management of bone regeneration using biomaterials. Together with SLBs nonfouling nature and the possibility of adjusting SLB fluidity and peptide content make SLBs highly promising as substrate to develop innovative biomimetic coatings for biomaterials in bone regeneration.

Dual light-induced in situ antibacterial activities of biocompatibleTiO2/MoS2/PDA/RGD nanorod arrays on titanium

Prevention of bacterial infection and promotion of osseointegration are two important issues for titanium (Ti) implants in medical research.

Surface sulfonation and nitrification enhance the biological activity and osteogenesis of polyetheretherketone by forming an irregular nano-porous monolayer

Polyether-ether-ketone (PEEK) is becoming a popular component of clinical spinal and orthopedic applications, but its practical use suffers from several limitations. In this study, irregular nano-porous monolayer with differently functional groups was formed on the surface of PEEK through sulfonation and nitrification. The surface characteristics were detected by field-emission scanning electron microscopy, atomic force microscopy, energy-dispersive X-ray spectrometry, water contact angle measurements and Fourier transform infrared spectroscopy. In vitro cellular behaviors were evaluated by cell adhesion, morphological changes, proliferation, alkalinity, phosphatase activity, real-time RT-PCR and western blot analyses. In vivo osseointegration was examined through micro-CT and histological assessments. Our results reveal that the irregular nano-porous of PEEK affect the biological properties. High-temperature hydrothermal NP treatment induced early osteogenic differentiation and early osteogenesis. Modification by sulfonation and nitrification can broaden the use of PEEK in orthopedic and dental applications. This study provides a theoretical basis for the wider clinical application of PEEK. a To obtain a uniform porous structure, PEEK samples were treated by concentrated sulfuric acid and fuming nitric acid (82-80%) with magnetic stirring sequentially. b Effects of nanopores on biological behavior of bMSCS.

Designing laser-modified surface structures on titanium alloy custom medical implants using a hybrid manufacturing technology

The hybrid technology combines an efficient material-removal process and implant surface treatment by the laser reducing time of manufacture process compared to currently used machining technologies. It also permits precise structuring of the implant material surface. Six structures of the Ti6Al4V ELI surface were designed and studied how the structure topography prepared with the hybrid technology affected the Escherichia coli adhesion to the surface and viability, as well as the growth, adhesion, and viability of human osteogenic Saos-2 cells cultured on the investigated surfaces. Results have confirmed that the microtopography of medical titanium alloy plays a beneficial role in bacterial adhesion and viability (number of bacteria found on reference surface: [5.9 ± 0.44] × 10⁶  CFU/ml, sample no. 3: [8.8 ± 0.93] × 10⁴  CFU/ml, and sample no. 5: [1.2 ± 0.23] × 10⁷  CFU/ml; CFU - Colony Forming Unit). All tested structured surfaces enabled good cell attachment and proliferation of Saos-2 cells (viability of Saos-2 cells [% of control] for reference surface: 81.93%; sample no. 3: 75% and sample no. 5: 100%). Transcriptome analysis of genes commonly expressed in the process of osseointegration demonstrated that the use of hybrid technology allows designing structures that enhance osseointegration but it should be coupled with other methods of preventing bacterial growth, or with a different strategy to limit microbial colonization with the satisfactory osseointegration potential.

Promoting osteoblasts responses in vitro and improving osteointegration in vivo through bioactive coating of nanosilicon nitride on polyetheretherketone

Objective

To enhance the bioactivity of polyetheretherketone (PEEK) while maintain its mechanical strengths.

Methods

Suspension coating and melt bonding.

Results

Silicon nitride (Si₃N₄, SN) coating lead to higher surface roughness, hydrophilicity and protein absorption; SN coating could slowly release Si ion into simulated body fluid (SBF), which caused weak alkaline of micro-environment owing to the slight dissolution of SN; SN coating resulted in the improvements of adhesion, proliferation, differentiation and gene expressions of MC3T3-E1 cells in vitro; SN coating of PEEK with bioactive SN coating (CSNPK) obviously promoted bone regeneration and osseointegration in vivo.

Conclusions

CSNPK with SN coating as bone implant might be a promising candidate for orthopedic implants.

The Translational Potential of this Article

The silicon nitride-coated polyetheretherketone (CSNPK) prepared in this article could induce MC3T3-E1 cells adhesion, proliferation and differentiation in vitro; it could also induce bone regeneration in bone defect in vivo, which indicate its good cytocompatibility and biocompatibility. If the raw materials are medical grade, and preparation process as well as production process of this article are further improved, it will have great translational potential.

Tuning the surface immunomodulatory functions of polyetheretherketone for enhanced osseointegration

The adverse macrophage-mediated immune response elicited by the surface of polyetheretherketone (PEEK) is responsible for the formation of fibrous encapsulation and resulting inferior osseointegration of PEEK implants in the dental and orthopedic fields. Therefore, endowing the PEEK surface with immunomodulatory ability is an appealing strategy to enhance implant-bone integration. Herein, a reliable and cost-effective method to construct adherent films with tunable nanoporous structures on PEEK is described. The functionalized surface not only suppresses the acute inflammatory response of macrophages, but also provides a favorable milieu for osteogenic differentiation of human bone marrow mesenchymal stem cells (hBMSCs). Whole genome expression analysis reveals that the suppression effect arises from synergistic inhibition of focal adhesion, Toll-like receptor, and NOD-like receptor signaling pathways, as well as the attenuating loop through the JAK-STAT and TNF signaling pathways in macrophages. Further in vivo studies confirm that the functionalized surface induces less fibrous capsule formation and an improved bone regeneration. The nanoporous films fabricated on PEEK harmonize the early macrophage-mediated inflammatory response and subsequent hBMSCs-centered osteogenic functions consequently yielding superior osseointegration.

Comprehensive In Vitro Testing of Calcium Phosphate-Based Bioceramics with Orthopedic and Dentistry Applications

Recently, a large spectrum of biomaterials emerged, with emphasis on various pure, blended, or doped calcium phosphates (CaPs). Although basic cytocompatibility testing protocols are referred by International Organization for Standardization (ISO) 10993 (parts 1-22), rigorous in vitro testing using cutting-edge technologies should be carried out in order to fully understand the behavior of various biomaterials (whether in bulk or low-dimensional object form) and to better gauge their outcome when implanted. In this review, current molecular techniques are assessed for the in-depth characterization of angiogenic potential, osteogenic capability, and the modulation of oxidative stress and inflammation properties of CaPs and their cation- and/or anion-substituted derivatives. Using such techniques, mechanisms of action of these compounds can be deciphered, highlighting the signaling pathway activation, cross-talk, and modulation by microRNA expression, which in turn can safely pave the road toward a better filtering of the truly functional, application-ready innovative therapeutic bioceramic-based solutions.