Qianli Huang

A dual-layer macro/mesoporous structured TiO 2 surface improves the initial adhesion of osteoblast-like cells

A dual-layer TiO2 surface with hierarchical macro and mesoporous structure was prepared by a combinational approach of micro-arc oxidation followed by evaporation-induced self-assembly of nano-crystallites. The mesoporous layer contains pores with an average size of <10nm and consists of anatase TiO2 nanocrystallites. The dual-layer hierarchical macro/mesoporous structured TiO2 surface improves the hydrophilicity and fibronectin adsorption ability in comparison with the sole macroporous or smooth TiO2 surface. With the formation of an additional mesoporous layer on macroporous TiO2 surface, the attached number of human osteogenic sarcoma cells (SaOS-2) increases in the initial incubation of 4h but it does not show significant difference after 24h compared to that attached on the macroporous or smooth surfaces. Whereas, it was noticed that SaOS-2 cells have larger spread area and more stress fibers on the macro/mesoporous structured surface than those on the other surfaces. To understand the intracellular mechanism of the initial cell adhesion on the macro/mesoporous surface, the Rho/ROCK pathway was investigated to reveal the topography-induced biological functions by introducing the ROCK inhibitor Y-27632 during cell culture. In the presence of Y-27632, cells on the macroporous surface and macro/mesoporous surface both show stellate appearance, with poor assembly stress fibers and long cell membrane protrusions. Cells on the smooth surface have larger spread areas compared to the former two surfaces. And the attached cells significantly reduced but there are no differences among the three surfaces. It reveals that the ROCK inhibitor invalidates the promotion of initial cell adhesion on the macro/mesoporous structure. This study may shed light on the mechanism behind the enhancement effect of macro/mesoporous structure for initial cell adhesion.

The effect of hydroxyapatite nanoparticles on adipogenic differentiation of human mesenchymal stem cells: EFFECT OF nHA ON ADIPOGENIC DIFFERENTIATION OF hMSCs

Due to its excellent biocompatibility, nanosized hydroxyapatite (nHA) has drawn much attention for various applications in biomedical fields. There are growing concerns about its biosecurity; however, little is known about its effects on adipogenesis. In the present study, nHA with three different sizes were synthesized, and the in vitro effects of nHA on cell proliferation and adipogenic differentiation of human mesenchymal stem cells (hMSCs) were investigated. The results clearly show that nHA does not affect the cell viability, the lipids droplets formation, triglyceride (TG) synthesis, and the expression of adipogenic marker genes/proteins of hMSCs at concentrations lower than 50 μg/mL. It is concluded that the adipogenic differentiation potential of hMSCs is not affected by nHA at noncytotoxic concentrations. These will provide a reference for the applications of nHA in biomedical fields.

Effects of the hierarchical macro/mesoporous structure on the osteoblast-like cell response: EFFECTS OF THE HIERARCHICAL MACRO/MESOPOROUS STRUCTURE

To improve the success of medical devices, implants with strong surface bioactivity are urgently required. Coatings with a macroporous structure produced by micro-arc oxidation possess advantages, such as strong adhesion to substrate and excellent resistance to wear and corrosion. Mesoporous structures contain pores with sizes of 2-50 nm, which can endow the biomaterials with the ability to enhance osteogenesis and to be loaded with diverse drugs. Thus, in this study, we aimed to evaluate the effects of both macroporous and mesoporous structures using a hierarchical macro/mesoporous structure to modify the titanium implant surface. The behaviors of SaOS-2 human osteosarcoma cells on the macro/mesoporous structure, including initial adhesion, proliferation, alkaline phosphatase (ALP) activity, and collagen secretion, were investigated. Cells that attached on the macro/mesoporous surface showed the highest cell numbers and greatest spreading area after incubation for 1, 2, and 4 h compared with the polished smooth substrate and macroporous surface in the presence of fetal bovine serum (FBS). However, in the absence of FBS, cell adhesion on the polished substrate, macroporous structure, and macro/mesoporous structure did not differ significantly. Cell proliferation on the macroporous and macro/mesoporous surfaces increased compared with that on the smooth substrate surface. Furthermore, ALP activity and collagen secretion were enhanced on the macro/mesoporous structure. Our findings provided important insights into the cellular responses to macro/mesoporous structures in the field of implant surface modification.

Reduced inflammatory response by incorporating magnesium into porous TiO2 coating on titanium substrate

The implant materials with proper anti-inflammatory and osteogenic properties may be promising for orthopedic applications. The inflammatory response induced by biomaterials has been regarded as one of the critical factors in determining in vivo fate of implants. Therefore, a novel bone biomaterial should have inflammation regulatory effects instead of being completely bio-inert. In the present work, the inflammation regulatory effects of exogenous magnesium (Mg) ions were investigated. Under the stimulation of lipopolysaccharide (LPS), macrophages exposed to Mg2+ exhibited down-regulated gene expressions of M1 markers (CD86, CD11c and inducible nitric oxide synthase (iNOS)) and pro-inflammatory cytokines (tumor necrosis factor-α (TNF-α), interleukin-6 (IL-6) and IL-1β), up-regulated gene expression of M2 marker CD163 and decreased TNF-α release, indicating that Mg2+ could switch macrophages from M1 to M2 phenotype. Thereafter, micro-arc oxidation (MAO) technique was employed to fabricate Mg-containing ceramic coatings on titanium substrates. Macrophages grown on Mg-containing surface were switched from M1 to M2 phenotype with the stimulation of LPS, evidenced by suppressed gene expressions of M1 markers (CD86, CD11c and iNOS) and pro-inflammatory cytokines (TNF-α and IL-1β), promoted gene expression of M2 marker CD163 and decreased TNF-α release. Moreover, gene expressions of bone morphogenetic protein-2 (BMP-2), BMP-6 and vascular endothelial growth factor (VEGF) were up-regulated on Mg incorporated MAO surface without LPS stimulation. Together, Mg could be used as an anti-inflammatory agent for suppressing inflammation and mediating osteogenesis. The integration of Mg in biomaterials could endow bone biomaterials with anti-inflammatory property.

The Cu-containing TiO2 coatings with modulatory effects on macrophage polarization and bactericidal capacity prepared by micro-arc oxidation on titanium substrates

The implant materials with both osteogenic and anti-bacterial properties are promising for orthopedic and dental applications. Moreover, the inflammatory response induced by biomaterials has been recently recognized as one of the critical factors in determining implantation fate. A new generation of implant materials should have modulatory effects on the local inflammatory environment such that it favors osteogenesis and osteointegration instead of being bio-inert. In this study, the micro-arc oxidation (MAO) technique was employed to fabricate Cu-containing ceramic coatings on titanium substrates. The macrophages cultured on Cu-containing MAO-fabricated surfaces were polarized to M1 phenotype, evidenced by the high expression levels of inducible nitric oxide synthase (iNOS), low expression levels of arginase1 (Arg1), enhanced pro-inflammatory cytokine interleukin-6 (IL-6) release and inhibited IL-4 and IL-10 (anti-inflammatory cytokines) release. The MAO-treated surface incorporated with larger amounts of Cu (referred as Cu(h)-MAO) could modulate a favorable inflammatory microenvironment for osteoblast-like cell differentiation. Moreover, the macrophages cultured on Cu(h)-MAO surface exhibited enhanced bacteria uptake and killing rate, indicating that the Cu(h)-MAO surface promoted the bactericidal capacity of macrophages. Together, Cu could be used as a promising modulatory agent for macrophage functions. The integration of Cu in biomaterials could lead to enhanced macrophage-mediated osteogenesis and bactericidal capacity.

The immunomodulatory effects of Zn-incorporated micro/nanostructured coating in inducing osteogenesis

Abstract Micro/nanostructured TiO2/ZnO coating has been shown to possess multiple functions, including antibacterial activity and bioactivity. Osteoblast-like SaOS-2 cells were employed for evaluating the in vitro osteogenic capacity of this coating and positive results were obtained. However, traditional principles of osseointegration focus only on the osteogenic differentiation alone. The effects of immunomodulation on the osteogenic activity have been largely ignored. In this study, the inflammatory responses of macrophages on the micro/nanostructured TiO2/ZnO coating were investigated. The extract media of macrophage cell line RAW264.7 cultured on the TiO2/ZnO coating were collected as indirect co-culture conditioned media. The osteogenic activity of SaOS-2 cells in the conditioned media was investigated. Adhesion, ALP activity and extracellular mineralization of cells grown in the conditioned media extracted from the micro/nanostructured TiO2/ZnO coating were found to be enhanced, compared to those grown in the conditioned media extracted from the macroporous TiO2 coating. The immune microenvironment produced by the micro/nanostructured TiO2/ZnO coating showed excellent capacity to promote osteogenesis, indicating that this coating could be a promising candidate for implant surface modification in orthopaedic and dental applications. Furthermore, this work could help us understand the interplay between the host immune system and the osteoimmunomodulatory properties of the biomaterials, and optimize the design for coating biomaterials.