Cobalt-doped Ti surface promotes immunomodulation

Acemannan coated, cobalt-doped biphasic calcium phosphate nanoparticles for immunomodulation regulated bone regeneration

Biomaterials are used as scaffolds in bone regeneration to facilitate the restoration of bone tissues. The local immune microenvironment affects bone repair but the role of immune response in biomaterial-facilitated osteogenesis has been largely overlooked and it presents a major knowledge gap in the field. Nanomaterials that can modulate M1 to M2 macrophage polarization and, thus, promote bone repair are known. This study investigates a novel approach to accelerate bone healing by using acemannan coated, cobalt-doped biphasic calcium phosphate nanoparticles to promote osteogenesis and modulate macrophage polarization to provide a prohealing microenvironment for bone regeneration. Different concentrations of cobalt were doped in biphasic calcium phosphate nanoparticles, which were further coated with acemannan polymer and characterized. The nanoparticles showed >90% cell viability and enhanced cell proliferation along with osteogenic differentiation as demonstrated by the enhanced alkaline phosphatase activity and osteogenic calcium deposition. The morphology of MC3T3-E1 cells remained unchanged even after treatment with nanoparticles. Acemannan coated nanoparticles were also able to decrease the expression of M1 markers, iNOS, and CD68 and enhance the expression of M2 markers, CD206, CD163, and Arg-1 as indicated by RT-qPCR, flow cytometry, and ICC studies. The findings show that acemannan coated nanoparticles can create a supportive immune milieu by inducing and promoting the release of osteogenic markers, and by causing a reduction in inflammatory markers, thus helping in efficient bone regeneration. As per our knowledge, this is the first study showing the combined effect of acemannan and cobalt for bone regeneration using immunomodulation. The work presents a novel approach for enhancing osteogenesis and macrophage polarization, thus, offering a potent strategy for effective bone regeneration.

Macrophages in the process of osseointegration around the implant and their regulatory strategies

PURPOSE/AIM OF THE STUDY

To summarize and discuss macrophage properties and their roles and mechanisms in the process of osseointegration in a comprehensive manner, and to provide theoretical support and research direction for future implant surface modification efforts.

MATERIALS AND METHODS

Based on relevant high-quality articles, this article reviews the role of macrophages in various stages of osseointegration and methods of implant modification.

RESULTS AND CONCLUSIONS

Macrophages not only promote osseointegration through immunomodulation, but also secrete a variety of cytokines, which play a key role in the angiogenic and osteogenic phases of osseointegration. There is no "good" or "bad" difference between the M1 and M2 phenotypes of macrophages, but their timely presence and sequential switching play a crucial role in implant osseointegration. In the implant surface modification strategy, the induction of sequential activation of the M1 and M2 phenotypes of macrophages is a brighter prospect for implant surface modification than inducing the polarization of macrophages to the M1 or M2 phenotypes individually, which is a promising pathway to enhance the effect of osseointegration and increase the success rate of implant surgery.

Li-Doped Ti Surface for the Improvement of Osteointegration

Aseptic loosening is the main factor that leads to the failure of orthopedic implants. Enhancing the early osteointegration of a bone implant can lower the risk of aseptic loosening. Here, a Li-doped surface was constructed on a Ti surface via plasma electrolytic oxidation (PEO) to improve osteointegration. The prepared Li-doped PEO coating showed a porous morphology and the sustained release of Li ions. In vitro results of rat bone marrow mesenchymal stem cell (rBMSC) culture studies suggested that the Li-doped Ti surface significantly favored cell adhesion. Moreover, it was found that the Li-doped surface enhanced alkaline phosphatase activity and extracellular matrix mineralization of rBMSCs. In addition, the surface improved the expression of osteogenesis-related genes. Furthermore, a bone implantation model indicated that the Li-doped Ti surface showed improved osteointegration. The incorporation of Li into a Ti surface is a promising method for orthopedic applications.