Yuhui Shen

Effects of strontium in modified biomaterials

Strontium (Sr) plays a special role in bone remodelling, being associated with both the stimulation of bone formation and a reduction in bone resorption. Thus, the modification of biomaterials by partial or full substitution by Sr is expected to increase both bioactivity and biocompatibility. However, such effects have to be studied individually. Although no phase transition was found in Sr-substituted hydroxyapatite (Sr-HA), Sr-containing calcium silicate (Sr-CS) or Sr-containing borosilicate (Sr-BS), their biological performance was substantially affected by changes in the physico-chemical properties and Sr content of the materials. Three distinct outcomes were found for the presence of Sr: (1) increased HA solubility; (2) no significant effect on the degradation rate of CS; (3) apparent inhibition of the otherwise rapid degradation of BS. In each case the released Sr affected osteoblast proliferation and alkaline phosphatase activity, with clear evidence that an optimum Sr dose exists. Such chemical and biological variations must be disentangled for the behaviour to be properly understood and materials design to be advanced.

Hollow magnetic hydroxyapatite microspheres with hierarchically mesoporous microstructure for pH-responsive drug delivery

The hollow magnetic hydroxyapatite [Ca10(PO4)6(OH)2, HAp] microspheres with hierarchically mesoporous structures were hydrothermally fabricated using the similar structured CaCO3/Fe3O4 hollow microspheres as the sacrificial hard-templates. The magnetic property, in vitro biocompatibility, drug loading and release properties in different pH solutions were further investigated. The results showed that the magnetic properties for these biocompatible HAp microspheres could be well adjusted by modulation of the Fe3O4 amount, and the drug release rate increased apparently with the decrease of the pH values of the solution medium. The high drug-loading capacity and sustained drug release property suggest that the fabricated multifunctional hollow microspheres have great potential for magnetic and pH responsive drug-delivery applications.

Anthropometry of the proximal tibia of patients with knee arthritis in Shanghai.

We measured the resected bony surface of the proximal tibia from reconstructed 3D models of the 179 arthritis knees using CT data. We found that the mediolateral (ML) dimension (69.6 ± 9.2 mm) and anteroposterior (AP) dimension (46.1 ± 6.1 mm) were less than those of Westerners. It was observed the medial anteroposterior (MAP) dimension (47.1 ± 7.2 mm) was much larger and closer to middle point of ML dimension than lateral anteroposterior (LAP) dimension (42.9 ± 6.3 mm). The aspect ratio (AR) (1.5 ± 0.07) was constant in Shanghai population. Only half of the prostheses we used in clinic mostly matched the resected bony surface of Shanghai population very well in ML, AP and AR dimension.

Strontium (Sr) strengthens the silicon (Si) upon osteoblast proliferation, osteogenic differentiation and angiogenic factor expression

The control over the chemical compositions of hydroxyapatite [Ca10(PO4)6(OH)2, HAp] bioceramic materials is of great importance for their application. In the present study, the silicon (Si) substituted HAp (Si-HAp) and the Si and strontium (Sr) co-substituted HAp (Si/Sr-HAp) nanowires were synthesized via the hydrothermal transformation of calcium silicate (CS) and Sr-substituted calcium silicate (Sr-CS) powders as the precursors, respectively, in Na3PO4 aqueous solution. Then the effects of the Si substitution and Si/Sr co-substitutions on the proliferation and differentiation of osteoblast cells (MC3T3-E1) were investigated. The results revealed that the synthetic products were wire-shaped with a diameter of ∼60 nm and a length of up to several micrometers, while the Sr substitution amount of Si/Sr-HAp nanowires could be tailored by regulating the Sr substitution level. Compared with pure HAp materials, the Si substitution could enhance the osteoblast growth and differentiation. Moreover, the substitution of the materials by a second functional element of Sr ions in appropriate levels could further promote the proliferation, osteogenic differentiation and angiogenic factor expression of osteoblasts. Our study suggests that the Sr can strengthen the Si upon osteoblast proliferation, osteogenic differentiation and angiogenic factor expression, which might be used as bioactive materials for bone regeneration applications.

Strontium Incorporated Coralline Hydroxyapatite for Engineering Bone

Goniopora was hydrothermally converted to coralline hydroxyapatite (CHA) and incorporated with Sr (Sr-CHA). The pore size of Goniopora was in the range of 40–300 μm with a porosity of about 68%. Surface morphologies of the coral were modified to flake-like hydroxyapatite structures on CHA and the addition of Sr detected on Sr-CHA as confirmed by SEM and EDX. As the first report of incorporating Sr into coral, about 6%–14% Sr was detected on Sr-CHA. The compressive strengths of CHA and Sr-CHA were not compromised due to the hydrothermal treatments. Sr-CHA was studied in vitro using MC3T3-E1 cells and in vivo with an ovariectomized rat model. The proliferation of MC3T3-E1 cells was significantly promoted by Sr-CHA as compared to CHA. Moreover, higher scaffold volume retention (

Synthesis of water-dispersible silicon-containing hydroxyapatite nanoparticles with adjustable degradation rates and their applications as pH-responsive drug carriers

Silicon-containing hydroxyapatite (Si-HAp) nanoparticles with adjustable degradation rates were successfully synthesized via simple hydrothermal treatment of a precursor, calcium silicate hydrate powder, in trisodium phosphate aqueous solution. The degradation rate of the products could be facilely tailored by regulating the hydrothermal temperature, while the obtained Si-HAp nanoparticles exhibited high loading capacities toward doxorubicin (DOX) as well as sustained and pH-dependent drug release properties. HeLa cell culture results confirmed that the toxicity of DOX loaded in Si-HAp nanoparticles was more sustained than that of free DOX. Their biodegradability, good water dispersibility and drug-loading capacity, and sustained and pH-responsive drug release properties suggest that these synthetic Si-HAp nanoparticles have great potential applications as drug carriers.

Biocompatibility and bioactivity of hydroxyapatite whiskers reinforced bis-GMA based composites

Novel bioactive bis-GMA-based resin composites were successfully developed by incorporating hydroxyapatite (HA) whiskers in the polymeric matrix. The whiskers had good dispersibility and wettability with bis-GMA-based polymer, showing good bonding with the matrix, which conferred good reinforcement. The mechanical properties of the composites were significantly enhanced when compared with the particulate filler. The morphology change of HA did not cause obvious variations in the proliferation and viability of L929 cells and the apatite-forming ability of the composites in SBF. The in vitro cytotoxicity of the composites was depressed by addition of hydroxyapatite filing materials. Such a favorable response indicated an important similarity in surface chemistry of the HA filler, and HA whiskers appeared to have potential as most promising reinforcements for resin-based polymers.