Additive manufacturing and performance of bioceramic scaffolds with different hollow strut geometries.

Additively manufactured hollow-strut bioceramic scaffolds present a promising strategy towards enhanced performance in patient-tailored bone tissue engineering. The channels in such scaffolds offer pathways for nutrient and cell transport and facilitate effective osseointegration and vascularization. In this study, we report an approach for the slurry based additive manufacturing of modified diopside bioceramics that enables the production of hollow-strut scaffolds with diverse cross-sectional forms, distinguished by different configurations of channel and strut geometries. The prepared scaffolds exhibit levels of porosity and mechanical strength that are well suited for osteoporotic bone repair. Mechanical characterization in orthogonal orientations revealed that a square outer cross-section for hollow struts in woodpile scaffolds gives rise to levels of compressive strength that are higher than those of conventional solid cylindrical strut scaffolds despite a significantly lower density. Finite element analysis confirms that this improved strength arises from lower stress concentration in such geometries. It was shown that hollow struts in bioceramic scaffolds dramatically increase cell attachment and proliferation, potentially promoting new bone tissue formation within the scaffold channel. This work provides an easily controlled method for the extrusion-based 3D printing of hollow strut scaffolds. We show here how the production of hollow struts with controllable geometry can serve to enhance both the functional and mechanical performance of porous structures, with particular relevance for bone tissue engineering scaffolds.

Bioadaptive nanorod array topography of hydroxyapatite and TiO2 on Ti substrate to preosteoblast cell behaviors.

Bioadaptive nanostructure coatings of hydroxyapatite (HAP) and TiO2 on titanium (Ti) implants are essential for biomaterial-tissue osteointegration. However, there is no specific report, so far, that focuses on the different influences of the two bioadaptive coatings on preosteoblast behaviors. Herein, adhesion, proliferation, and osteogenic potential of preosteoblast on HAP and TiO2 coatings with nanorod array topography were studied. XRD, TEM, and SAED analysis indicated that rod-like HAP nanoarray and anatase TiO2 nanoarray coatings were fabricated successfully, and there was insignificant difference in roughness and fibronectin adsorption of the two coatings. Adhesion and proliferation of MC3T3-E1 cells on the two coatings were of no significant difference, besides a larger projected area of the cells on HAP coating. MC3T3-E1 cells cultured on the HAP coating displayed significantly higher expression of runt-related transcription factor-2 (Runx2), osteocalcin (OCN) and collagen type-1 (Col I) after culture for 21 days compared with those on TiO2 coating, except alkaline phosphatase (ALP). This study provides beneficial suggestion for intelligent selection of biocoatings.

Tuning inflammation response via adjusting microstructure of hydroxyapatite and biomolecules modification.

Excellent biocompatibility and inflammatory regulation ability are essential to bone repair materials. Herein, Rod-like HAP with a diameter of 0.1 µm and Flake-like HAP with a width of 0.5-1 µm were synthesized by hydrothermal method, and then combined with two kinds of biomolecules, Icariin and Kaempferol. Two kinds of HAPs have similar crystal structure, but different zeta potentials and specific surface area. Rod-like HAP possesses stronger loading capacity and internalization efficiency than Flake-like one. in vitro inflammation assay reveals that HAP particles up-regulate the expression of IL-1ß, TNF-α, IL-6, IL-10, IFN-γ and IL-2 cytokines. HAP particles loaded with Icariin or Kaempferol biomolecules up-regulate anti-inflammatory cytokines and down-regulate the expression of inflammatory cytokines.

Fabrication of two distinct hydroxyapatite coatings and their effects on MC3T3-E1 cell behavior.

How the surface topography of hydroxyapatite (HAP) coatings remodels hard tissue is of utmost importance and a contributing factor to ambiguity regarding this subject. Here, HAP coatings with different topographies of a rod-like nanoarray with c-axis orientation and a flake-like micro-flower array with a(b)-axis orientation on a Ti substrate were synthesized via hydrothermal-electrodeposition by controlling the concentration of electrolytes. XRD, TEM and SAED analyses indicated that the rod-like HAP nanoarray was predominant with an orientation of (001), while the HAP micro-flower samples were based on an orientation of (100). Compared to the flake-like HAP, the rod-like nanoarray HAP possessed better hydrophilic properties and lower roughness, which not only enhanced adsorption of specific fibronectin proteins but also promoted the spreading and growth of MC3T3-E1 cells. Runx2, alkaline phosphatase, collagen and osteocalcin were also analyzed by RT-PCR on the two distinctive HAP-coated samples. MC3T3-E1 cells on the rod-like nanoarray coating had higher osteo-related gene expression. This finding suggested that the ordered assembly structure of the HAP might cause topography-dependent coordination with biomolecules for enhancing osteoblast-like cell proliferation and osteogenic differentiation. This study provided an understanding of the surface's features for biomaterials to ensure better bioactivity.