The Role of Magnesium Ion Substituted Biphasic Calcium Phosphate Spherical Micro-Scaffolds in Osteogenic Differentiation of Human Adipose Tissue-Derived Mesenchymal Stem Cells.

This study was investigated the role of magnesium (Mg2+) ion substituted biphasic calcium phosphate (Mg-BCP) spherical micro-scaffolds in osteogenic differentiation of human adipose tissue-derived mesenchymal stem cells (hAT-MSCs). Mg-BCP micro-scaffolds with spherical morphology were successfully prepared using in situ co-precipitation and spray drying atomization process. The in vitro cell proliferation and differentiation of hAT-MSCs were determined up to day 14. After in vitro biological tests, Mg-BCP micro-scaffolds with hAT-MSCs showed more enhanced osteogenicity than pure hAT-MSCs as control group by unique biodegradation of TCP phase and influence of substituted Mg2+ ion in biphasic nanostructure. Therefore, these results suggest that Mg-BCP micro-scaffolds promote osteogenic differentiation of hAT-MSCs.

Long and short range order structural analysis of In-situ formed biphasic calcium phosphates.

BACKGROUND: Biphasic calcium phosphates (BCP) have attracted considerable attention as a bone graft substitute. In this study, BCP were prepared by aqueous co-precipitation and calcination method. The crystal phases of in-situ formed BCP consisting of hydroxyapatite (HAp) and ß-tricalcium phosphate (ß-TCP) were controlled by the degree of calcium deficiency of precursors. The long and short range order structures of biphasic mixtures was investigated using Rietveld refinement technique and high resolution Raman spectroscopy. The refined structural parameters of in-situ formed BCP confirmed that all the investigated structures have crystallized in the corresponding hexagonal (space group P63/m) and rhombohedral (space group R3c) structures. RESULTS: The crystal phases, Ca/P molar ratio, and lattice parameters of in-situ formed BCP consisting of HAp and ß-TCP were controlled by the degree of calcium deficiency of calcium phosphate precursors. The significant short range order structural change of BCP was determined by Raman analysis. CONCLUSIONS: The long and short range order structural changes of in-situ formed BCP might be due to the coexistence of ß-TCP and HAp crystal phases.

In vivo evaluation of porous hydroxyapatite/chitosan-alginate composite scaffolds for bone tissue engineering.

Porous hydroxyapatite (HAp)/chitosan-alginate composite scaffolds were prepared through in situ co-precipitation and freeze-drying for bone tissue engineering. The composite scaffolds were highly porous and interconnected with a pore size of around 50-220 µm at low concentrations of HAp. As the HAp content increased, the porosity of the scaffolds decreased from 84.98 to 74.54%. An MTT assay indicates that the obtained scaffolds have no cytotoxic effects on MG-63 cells, and that they have good biocompatibility. An implantation experiment in mouse skulls revealed that the composite scaffold provides a strong positive effect on bone formation in vivo in mice. Furthermore, that HAp/chitosan-alginate composite scaffold has been shown to be more effective for new bone generation than chitosan-alginate scaffold.

Morphologies of nano-sized apatite formed on titanium substrate by biomimetic process.

The apatite was formed on the titanium plates with NaOH and heat treatments by biomimetic process. The influence of titanium surface microstructure on the apatite formation onto titanium substrate in SBF solution was investigated. After biomimetic process, nano-sized apatite layers were found on the Ti plates with NaOH and heat treatments. However, the morphologies of formed apatite on substrate had different shapes such as coated, load-like, and linked. The morphology of apatite formed by biomimetic process would be affected by alkaline treatment, and substrate morphology and phase.

Hydroxyapatite scaffolds processed using a TBA-based freeze-gel casting/polymer sponge technique.

A novel freeze-gel casting/polymer sponge technique has been introduced to fabricate porous hydroxyapatite scaffolds with controlled "designer" pore structures and improved compressive strength for bone tissue engineering applications. Tertiary-butyl alcohol (TBA) was used as a solvent in this work. The merits of each production process, freeze casting, gel casting, and polymer sponge route were characterized by the sintered microstructure and mechanical strength. A reticulated structure with large pore size of 180-360 microm, which formed on burn-out of polyurethane foam, consisted of the strut with highly interconnected, unidirectional, long pore channels (approximately 4.5 microm in dia.) by evaporation of frozen TBA produced in freeze casting together with the dense inner walls with a few, isolated fine pores (<2 microm) by gel casting. The sintered porosity and pore size generally behaved in an opposite manner to the solid loading, i.e., a high solid loading gave low porosity and small pore size, and a thickening of the strut cross section, thus leading to higher compressive strengths.

Biomimetic whisker-shaped apatite coating of titanium powder.

Biomimetic apatite coatings on chemically modified titanium powder have been processed and the resulting coating layers evaluated in terms of morphology, composition and structure, using TF-XRD, XPS, SEM, TEM and FTIR analysis. After 7 days immersion in a simulated body fluid (SBF), nanometer-sized fine precipitates with an amorphous whisker-like phase and a Ca/P atomic ratio of 1.94 were obtained on the external surface of the titanium particles. When the immersion time in SBF was extended to 16 days, the coating layer consisted of the whisker-like nanostructured crystals of carbonated hydroxyapatite with a atomic ratio of 3; in such a case, a double coating layer was developed. The double layer could be divided into two regions and could be clearly distinguished: an inner dense region (approximately 200 nm in thickness) which may include hard agglomerated crystals and an outer less dense region (> 500 nm in thickness) in which crystals are loosely distributed.