CaP-coated Zn-Mn-Li alloys regulate osseointegration via influencing macrophage polarization in the osteogenic environment

Immune response is an important factor in determining the fate of bone replacement materials, in which macrophages play an important role. It is a new idea to design biomaterials with immunomodulatory function to reduce inflammation and promote bone integration by regulating macrophages polarization. In this work, the immunomodulatory properties of CaP Zn-Mn-Li alloys and the specific mechanism of action were investigated. We found that the CaP Zn0.8Mn0.1Li alloy promoted the polarization of macrophages toward M2 and reduced inflammation, which could effectively upregulate osteogenesis-related factors and promote new bone formation, indicating the important role of macrophages polarization in biomaterial induction of osteogenesis. In vivo studies further demonstrated that CaP Zn0.8Mn0.1Li alloy could stimulate osteogenesis better than other Zn-Mn-Li alloys implantations by regulating macrophages polarization and reducing inflammation. In addition, transcriptome results showed that CaP Zn0.8Mn0.1Li played an important regulatory role in the life process of macrophages, activating Toll-like receptor signaling pathway, which participated in the activation and attenuation of inflammation, and accelerated bone integration. Thus, by preparing CaP coatings on the surface of Zn-Mn-Li alloys and combining the bioactive ingredient with controlled release, the biomaterial will be imbibed with beneficial immunomodulatory properties that promote bone integration.

Effect of working gas on physicochemical and biological properties of CaP coatings deposited by RFMS

Thin calcium phosphate (CaP) coatings were deposited on titanium substrates by radio frequency magnetron sputtering of hydroxyapatite target in the neon (Ne), argon (Ar), krypton (Kr) and xenon (Xe). The influence of the working gas (Ne, Ar, Kr and Xe) on the wettability, biodegradation in the RPMI 1640 synthetic culture medium of the CaP coatings. This paper is the first comprehensive study of working gas effect on properties of the CaP coatings. There was an increase in the polar component of surface free energy (SFE) and a decrease in the dispersion component of SFE with an increase of the atomic mass of the working gas. All CaP coatings had a pronounced protective effect up to 2 times reducing the number of dead cells in culture compared to the Ti control. The most soluble CaP coatings formed in the atmosphere of Xe stimulated the hAMMSCs division, which led to an increase in the total number of cells (208% of the initial culture). Samples with CaP coatings formed in an inert gases atmosphere increased gene expression (ALPL, BMP6, BMP2) in vitro. The most biocompatible coatings were coatings formed in the atmosphere of Xe and Ar.