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Stimulated bone growth and metal-infused skeletons: From comic books to commonplace

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Science Translational Medicine  29 Jul 2020:
Vol. 12, Issue 554, eabd3627
DOI: 10.1126/scitranslmed.abd3627

Abstract

Three-dimensional titanium surfaces patterned with nanometer-sized features demonstrate accelerated bone growth and mineralization in mice.

Arthroplasty is one of the most frequent surgeries performed today, with volumes increasing as the population ages. Current limitations of joint replacement surgery include the need for extensive rehabilitation after surgery and the possibility of revision surgery if the implant fails. Greer et al. describe a new technique to pattern three-dimensional (3D) surfaces with titanium dioxide to simulate bone growth at the artificial joint interface. This presents a practical pathway to enhance the osteogenesis of orthopedic implants, potentially decreasing healing times after surgery and extending the life of current artificial joints.

Previous experiments showed that altering the surface of titanium can stimulate bone growth, but it has been difficult to pattern non-planar surfaces with the nanometer features that are most effective in stimulating bone growth. The authors developed a method of patterning 3D titanium surfaces with titanium oxide sol-gels and then annealing these to leave ~20-nm-high pillars attached to the surface. A key feature of this method is the use of disordered pillar arrays, which have previously been shown to induce the clustering of integrins, allowing bone stem cells to anchor to the extracellular matrix and stimulating them to produce bone.

In a series of experiments, the authors characterized the nanopatterned titanium surfaces and investigated the ability of the surfaces to accelerate bone formation at the interface. Their main finding is that surfaces with disordered nanopillars increased bone tissue formation and enhanced mineralization compared to non-patterned, flat surfaces. The authors confirmed these findings in a mouse model using nanopatterned titanium implants placed subcutaneously.

This paper demonstrates how innovations in nanopatterning and fabrication can be translated into enhanced orthopedic implants. A limitation of the study is that the implants were studied in vivo in a mouse model over a relatively short period of time (28 days). Further work is required to understand the implications for implant durability and healing times after joint replacement surgery in humans. This work enables researchers to use a cost-effective, scalable method to pattern 3D surfaces with nanostructures that accelerate bone growth and mineralization for the development of more effective artificial joints.

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