Baoe Li

Influences of ionic dissolution products of dicalcium silicate coating on osteoblastic proliferation, differentiation and gene expression

This work aims to explore the influence of the ionic products of dicalcium silicate coating on osteoblastic proliferation and differentiation, as well as on the expression of BMP2 and its signal transducers Smad1, 6 and 7 in MG-63 osteoblast-like cells. Plasma-sprayed dicalcium silicate coatings were soaked in DMEM to obtain culture media containing the ionic dissolution products of dicalcium silicate coating (Ca2SiO4-DMEM). MG63 osteoblast-like cells were cultured in Ca2SiO4-DMEM (experimental group) for 3-12 days, while those cultured in normal DMEM served as control (control group). MTT assay was used to evaluate cell viability and proliferation. Alkaline phosphatase activity (ALP), osteocalcin (OC) and type I collagen (COLI) were investigated as differentiation markers. Gene expression of BMP2 and Smad1, 6, 7 was also detected. BMP2 protein was examined by ELISA assay. Alizarin Red-S (AR-S) assay was used to detect mineralization. The results demonstrated that Si concentration in Ca2SiO4-DMEM is markedly higher than that in normal DMEM. Compared to the control group, MG63 cells of the experimental group exhibited upregulated proliferation on day 3, and markedly upregulated gene expression of the differentiation markers, especially on days 9 and 12 for OC and on days 3, 6 and 9 for ALP. Gene expression of BMP2 and Smad1, as well as BMP2 protein secreted into culture media, was also upregulated in the experimental group, while gene expression of Smad6 and 7 was not influenced. AR-S assay indicated a higher calcium mineral content deposition in cells of the experimental group. In conclusion, the ionic products of plasma-sprayed dicalcium silicate coating are beneficial to the proliferation and differentiation of MG63 osteoblast-like cells.

Bioactive calcium silicate ceramics and coatings.

CaO-SiO2 based ceramics have been regarded as potential candidates for artificial bone due to their excellent bone bioactivity and biocompatibility. However, they cannot be used as implants under a heavy load because of their poor mechanical properties, in particular low fracture toughness. Plasma spraying CaO-SiO2 based ceramic coatings onto titanium alloys can expand their application to the hard tissue replacement under a heavy load. Plasma sprayed wollastonite, dicalcium silicate and diopside coatings have excellent bone bioactivity and high bonding strength to titanium alloys. It is possible that these plasma sprayed CaO-SiO2 based ceramic coatings will be applied in clinic after they are widely and systematically researched.

UV-irradiation-induced bioactivity on TiO2 coatings with nanostructural surface

Titania (TiO2) coatings with nanostructural surface prepared using plasma spraying technology were irradiated by ultraviolet light in simulated body fluids to improve their bioactivity. The in vitro bioactivity of the coatings was evaluated by investigating the formation of apatite on their surfaces in simulated body fluids. Bone-like apatite was observed to precipitate on the UV-irradiated TiO2 coating with nanostructural surface after it was immersed in simulated body fluid for a certain period, but not on the as-sprayed and UV-irradiated TiO2 coatings without nanostructural surface. The results indicate that the nano-TiO2 surface can be activated by UV-irradiation to induce its bioactivity. The ability of apatite formation on the nano-TiO2 surface was improved with the increase of UV-irradiation time. The in vivo results reveal that the as-prepared TiO2 coating with nanostructural surface cannot induce the formation of new bones during the implantation period, but the UV-irradiated TiO2 coating with nanostructural surface could do so during an implantation time longer than 2 months. Our results indicate that the osseointegration ability of the plasma-sprayed TiO2 coating with nanostructural surface can be improved by UV irradiation.

Biological and antibacterial properties of plasma sprayed wollastonite/silver coatings.

In this work, plasma sprayed wollastonite/silver coatings were prepared to obtain an implant material having excellent bioactivity, cytocompatibility as well as antibacterial property. The surface characteristics of wollastonite/silver coating were investigated by scanning electron microscopy, energy dispersive spectrometer, atomic absorbance spectroscope and x-ray diffraction. The bioactivity was examined by simulated body fluid soaking test. The antibacterial activity against Escherichia coli was examined by bacterial counting method. And the cytocompatibility and in vitro osteotoxicity was evaluated by alamarBlue Assay using MG-63 osteoblasts. The results showed that silver existed in the wollastonite coating homogeneously as silver oxide and metal silver, which ensured a sustained release of silver for 28 days in deionized water. The loaded silver showed strong inhibition against the growth of Escherichia coli, however exhibited no osteotoxicity. Although the wollastonite/silver coating can not induce apatite formation as quickly as the wollastonite coating did in simulated body fluid, it still exhibited good bioactivity. Therefore, the plasma sprayed wollastonite/silver coating is a promising implant material to be applied in surgery, reducing postoperative infections.

Grafting Collagen on the Plasma Sprayed Titania Coating Treated by Sodium Hydroxide

In this work, collagen type I was covalently grafted on the surface of plasma sprayed titania coatings to improve their biocompatibility. The plasma sprayed titania coatings were pretreated by sodium hydroxide to induce the formation of hydroxyl groups which can covalently graft collagen, rendering the collagen having good stability. The dependence of collagen grafting on the sodium hydroxide treatment conditions (concentration, time and temperature) was investigated by measuring the amount of collagen grafted on the titania surface. The biocompatibility of the titania coatings with grafted collagen was evaluated by in vitro cell culture. The results showed that the amount of collagen grafted on the titania coatings increased with the concentration of the sodium hydroxide and the treating temperature, while that on the coating is slightly dependent on the treatment time in sodium hydroxide. In vitro cell culture test proved the positive effects of collagen on the biocompatibility of the plasma sprayed titania coating.

Chemical Treatment for Inducing Bioactivity of TiO2 Coating

In this work, nano-TiO2 powders were deposited onto Ti-6Al-4V substrates to produce coating using plasma spraying. The TiO2 coatings were respectively by acid, alkali and heat treatment to produce the bioactive surface. The bioactivity of TiO2 coating was examined by simulated body fluids test. The results obtained indicated apatite was formed on the surfaces of nano-TiO2 coatings treated by H2SO4, HCl and HF solutions, while it could not be formed on the surface of the nano-TiO2 coating treated by NaOH solution at low concentration. After alkali attack and heat treatment at 600°C, the bioactivity of nano-TiO2 coating disappeared.