Papers by Author: Ji Yong Chen

Abstract: Porous alpha- tricalcium phosphate (α-TCP) was implanted in rabbit and dog models to investigate its induction of calcium phosphate (Ca-P) formation. The morphology and structure of the formed Ca-Ps were examined using scanning electron microscopy (SEM) and transmission electron microscopy (TEM), respectively. The results showed an animal-dependent behavior of in vivo Ca-P formation. There were flake-like octacalcium phosphate (OCP) precipitates in the rabbit but rod-like hydroxyapatite (HA) precipitates in the dog model. In addition, high-resolution TEM (HRTEM) image revealed that there was OCP structure in certain portions of the rod-like HA precipitates in the dog model. And the orientation relation of OCP/HA was deduced as OCP (010)//HA (0 10) and OCP (001)//HA (00 1) . This implied that the in vivo HA was formed via OCP precursor phase.

Abstract: The initial interactions of plasma-sprayed HA coating surface with osteoblasts was investigated. Two kind of post-treatment methods were been used for HA coating: (1) Heated in air at 650oC for 30 min, (2) Heated in water vapor at 125oC, 0.15Mpa for 6 hours. The third passage rabbit osteoblasts were cultured on the HA coating plates for 24 h. The results showed: The lower dissolution rate and more surface hydroxyl groups (OH-1) group in the HA coating resulted in greater numbers of adhered osteoblasts and higher cell activity, The post-water vapor treated HA coating have better biological behavior in vitro.

Abstract: A composite hydrogel with interpenetrating network structure was prepared via in-situ synthesis of calcium phosphates during the physical-chemical crosslinking of poly(vinyl alcohol) (PVA) and poly(acrylic acid) (PAA). The hydrogel water content was tested. Fourier transform infrared absorption spectrum (FT-IR), X-ray diffraction and scanning electron microscopy were employed to evaluate the characteristics of the composite hydrogel. The results showed that the composite hydrogel had high water content and that the inorganic phase was poorly crystalline calcium phosphates. FT-IR confirmed that the interpenetrating network structure was formed between PVA and PAA. The chemical interactions between inorganic and organic phases were further investigated and discussed. The composite hydrogel with an interpenetrating network achieved using the present novel method could be a promising material for tissue engineering.

Abstract: Calcium phosphate cement (CPC) has many advantages and is frequently used as a carrier of antibiotic and bone growth factors. Salmon calcitonin(S-CT) is effective in treating osteoporosis. Due to its potential of promoting bone cell proliferation, S-CT was combined with injectable CPC to accelerate the restoring of the bone defect induced by osteoporosis and the composite can be used in minimal invasive surgery. Uniform design was used to optimize the prescription, and the effects of pore-maker and S-CT on the characters of CPC were studied. The in vitro releasing of S-CT from the optimum CPC in deionized water, SBF and rabbit serum was studied with HPLC, respectively. The results showed that the contents of HA and citric acid-NaHCO3 affect the physical characters of CPC sharply, but S-CT has little effect on it. The releasing of S-CT in three different medium follow Hugichi equation, but the speed is slower in rabbit serum than in deionized water and SBF. S-CT carried porous injectable CPC composite possesses the basic performance for clinical needs, and it is promising to be used in osteoporosis induced bone defect and accelerate bone repair.

Abstract: The bioactivity of a composite of titania and hydroxyapatite was studied in vitro in this paper. After the titania ceramics was added 10% HA, it could induce apatite formation in simulated body fluid in 2d, while the pure titania ceramics could not induced apatite formation even after 14d. After the composite of titania and HA was subjected to alkali-heat treatment, it has a faster speed for apatite formation in SBF than the composite without treatment. When the osteoblast was cultured on the materials, the amount of osteoblasts attaching on the composite was more than that on the pure titania ceramics. It has the most osteoblasts cells on the composite subjected to alkali-heat treatment. These results showed that the composite of titania and HA is a bioactive materials, while the alkali-heat treatment could improved the bioactivity of this composite.

Abstract: Bonelike apatite coating on metal implants is an effective method to enhance bioactive properties of the metal surface. In the present study, the effectiveness of cathode deposition (CD) coating methods was investigated. And biomimetic deposition (BD) was also investigated as the parallel. The revised simulated body fluid (R-SBF) was chosen as an electrolyte and simulated body fluid. Both deposition methods could produce bonelike apatite coating on rough surfaces of the titanium. The uniformity of the CD coatings were better than the BD coatings’. And CD method was less sensitive to the condition of the titanium plate surfaces and much faster in the coating deposition. The spectra of FTIR showed that the characteristic peaks of CO3 2- apeared on the surface of ceramics, combined with spectra of XRD and SEM, it was concluded that a sertain thickness of bonelike apatite coating could be formed on the acided treatment (AT) titanium plate surfaces by CD method.

Abstract: The electrochemical cathode bioactivating titanium with additive of citrate was reported. After the treatment, there was a uniform dense layer with very tiny granules on the surface of the titanium, this layer was composed of amorphous calcium phosphate-citrate (ACP-CIT) with a thickness of about 150nm. After immersion in saturated calcium phosphate solution, the morphology at different time points of the early stage was quite different. The changes of morphology showed that the citrate in amorphous calcium phosphate modulated the crystal growth.

Abstract: In vitro method has often been used in the biodegradation/bioactivity evaluation of bioactive ceramics for its convenience and saving in time and outlay. The simulated body fluid (SBF) suggested by Kokubo was a good simulation of the osteoproduction environment in osseous tissue and has been proved to be a good method to study the bioactivity of biomaterials and the mechanism of bone bonding. But SBF is not a suitable method to research the osteoinduction of biomaterials. The results from SBF were not consistent with that from in vivo in muscle. The local ion concentration is the key factors to affect the nucleation and growth of apatite. In muscle the effect of body fluid flowing on local ion concentration cannot be ignored. A dynamic SBF suggested by these authors of this paper not only simulated the ion concentration of body fluid, but also simulated the effect of body fluid flowing on the local ion concentration near the surface or in biomaterials in muscle. The results from the dynamic SBF were in good agreement with that of the implantation experiments in muscle. The results from dynamic SBF showed that apatite only formed on the walls of macropores of the porous CaP, no apatite formed on the surface of both dense and porous CaP. The new bone only formed on the walls of macropores of porous CaP implanted in muscles, no apatite or osseous tissue could be found on the surfaces of both porous and dense CaP. The dynamic SBF preferably simulated the osteoinduction environment in non-osseous tissue and can be used in osteoinductivity evaluation of bioceramics.

Abstract: Studying on the interaction between proteins and calcium phosphate implants is one of the basic subjects in biomaterials science and engineering. In this work, zeta potentials and contact angles of hydroxyapatite (HA) and biphasic calcium phosphate (BCP) ceramics were measured, and the adsorption behaviors of bovine serum albumin (BSA) on the surfaces were investigated. The adsorption isotherms of BSA on both ceramics follow the Langmuir type, however, BCP shows higher BSA adsorption ability. The differences of contact angles and zeta potentials in HA and BCP are the key factors to determine their ability to bind BSA molecules.

Abstract: A kind of medical collagen was prepared by hydrogel formation method. Chemical and physical properties were investigated by FTIR, amino acid analysis, SDS-PAGE, carbohydrate content analysis, heavy metal content analysis. Degradation experiments in vivo and subsequent histological investigations were carried out to evaluate the biological performance. The results suggested that the collagen achieved is promising in tissue engineering scaffold materials for a long-term (more than 12 weeks) implantation application.