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Nanopatterned Titanium Implants Accelerate Bone Formation In Vivo.

ABSTRACT: Accelerated de novo formation of bone is a highly desirable aim of implants targeting musculoskeletal injuries. To date, this has primarily been addressed by biologic factors. However, there is an unmet need for robust, highly reproducible yet economic alternative strategies that strongly induce an osteogenic cell response. Here, we present a surface engineering method of translating bioactive nanopatterns from polymeric in vitro studies to clinically relevant material for orthopedics: three-dimensional, large area metal. We use a titanium-based sol-gel whereby metal implants can be engineered to induce osteoinduction both in vitro and in vivo. We show that controlled disordered nanotopographies presented as pillars with 15-25 nm height and 100 nm diameter on titanium dioxide effectively induce osteogenesis when seeded with STRO-1-enriched human skeletal stem cells in vivo subcutaneous implantation in mice. After 28 days, samples were retrieved, which showed a 20-fold increase in osteogenic gene induction of nanopatterned substrates, indicating that the sol-gel nanopatterning method offers a promising route for translation to future clinical orthopedic implants.

SUBMITTER: Greer AIM

PROVIDER: S-EPMC7467557 | biostudies-literature | 2020 Jul

REPOSITORIES: biostudies-literature

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Nanopatterned Titanium Implants Accelerate Bone Formation In Vivo.

Greer Andrew I M AIM Goriainov Vitali V Kanczler Janos J Black Cameron R M CRM Turner Lesley-Anne LA Meek Robert M D RMD Burgess Karl K MacLaren Ian I Dalby Matthew J MJ Oreffo Richard O C ROC Gadegaard Nikolaj N

ACS applied materials & interfaces 20200717 30

Accelerated de novo formation of bone is a highly desirable aim of implants targeting musculoskeletal injuries. To date, this has primarily been addressed by biologic factors. However, there is an unmet need for robust, highly reproducible yet economic alternative strategies that strongly induce an osteogenic cell response. Here, we present a surface engineering method of translating bioactive nanopatterns from polymeric in vitro studies to clinically relevant material for orthopedics: three-dim ...[more]

PMID: 32633478

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Project description:Orthopedic implant failure due to aseptic loosening and mechanical instability remains a major problem in total joint replacement. Improving osseointegration at the bone-implant interface may reduce micromotion and loosening. Bone sialoprotein (BSP) has been shown to enhance bone formation when coated onto titanium femoral implants and in rat calvarial defect models. However, the most appropriate method of BSP coating, the necessary level of BSP coating, and the effect of BSP coating on cell behavior remain largely unknown. In this study, BSP was covalently coupled to titanium surfaces via an aminosilane linker (APTES), and its properties were compared to BSP applied to titanium via physisorption and untreated titanium. Cell functions were examined using primary human osteoblasts (hOBs) and L929 mouse fibroblasts. Gene expression of specific bone turnover markers at the RNA level was detected at different intervals. Cell adhesion to titanium surfaces treated with BSP via physisorption was not significantly different from that of untreated titanium at any time point, whereas BSP application via covalent coupling caused reduced cell adhesion during the first few hours in culture. Cell migration was increased on titanium disks that were treated with higher concentrations of BSP solution, independent of the coating method. During the early phases of hOB proliferation, a suppressive effect of BSP was observed independent of its concentration, particularly when BSP was applied to the titanium surface via physisorption. Although alkaline phosphatase activity was reduced in the BSP-coated titanium groups after 4 days in culture, increased calcium deposition was observed after 21 days. In particular, the gene expression level of RUNX2 was upregulated by BSP. The increase in calcium deposition and the stimulation of cell differentiation induced by BSP highlight its potential as a surface modifier that could enhance the osseointegration of orthopedic implants. Both physisorption and covalent coupling of BSP are similarly effective, feasible methods, although a higher BSP concentration is recommended.

Project description:Multiple surface treatment methods for titanium alloy prostheses, widely used in orthopedics, are available; however, these can affect bone integration and regeneration efficiency. In this study, through cell and animal experiments, we devised seven bone implant categories of Ti6Al4V based on surface preparation and post-processing technology (polishing, grit-blasting, fine titanium spraying, coarse titanium spraying, electron beam melting [EBM] printing, selective laser melting [SLM] printing, and post-processed SLM printing) and imaged each microscopic surface structure with a scanning electron microscope (SEM). Mechanical testing revealed excessive post-processing damaged the mechanical properties of the implants. In vitro, human bone marrow mesenchymal stem cells (hBMSCs) were cultured with implants, and the morphology of the cells adhering to the implant surface was observed using SEM and confocal laser scanning microscopy. Cell Counting Kit-8 (CCK-8) semi-quantitatively determined cell activity, indirectly reflecting the proliferation of hBMSCs. Alizarin red and alkaline phosphatase experiments assessed osteogenic differentiation. In vivo, experiments utilized the New Zealand rabbit femoral condyle bone defect model to assess bone regeneration and integration using micro-computed tomography, Van Giesen staining, and Masson staining. We found that 3D-printed implants with regular pore structures were more conducive to hBMSC osteogenic differentiation, while the presence of metal powder on NPT-SLM-printed implants hindered such differentiation. The post-treatment SLM scaffold surface may have some residual semi-melted powder; however, these powder residues have no significant effect on cell activity and differentiation. Surface treatment (grit-blasting and titanium spraying) of planar structures can enhance hBMSC adhesion but does not necessarily promote their differentiation. The framework structure of 3D printing may affect the osteogenic differentiation of hBMSCs, and for SLM-printed implants, excessive pursuit of a "powderless" state will damage the mechanical properties of the implant.

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Nanopatterned Titanium Implants Accelerate Bone Formation In Vivo.

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Nanopatterned Titanium Implants Accelerate Bone Formation In Vivo.

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