Papers by Author: Xing Dong Zhang

Abstract: Biological sealing is a key factor for successful development of percutaneous device (PD). A new device with arc-perforated flange as subcutaneous part and groove-shaped percutaneous part, was intended to improve integration of soft tissue and implant. Material and surface properties are known to have great impact on tissue-implant integration. To understand how a material and its surface property can influence tissue reaction, and to find the appropriate material for PD fabrication, five different kinds of materials were prepared for in vivo animal tests with corresponding histological evaluation. Results revealed that a more stable junction was formed between the soft tissue and HA coated titanium implant than other combinations.

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: This study was to develop an injectable biocompatible and porous calcium phosphate collagen composite cement scaffold by in situ setting. TTCP was prepared as main material of the CPC powder, and the collagen solution was added into the phosphoric acid directly to form the liquid phase. The injectable time (tI), setting time (tS) and setting temperature (TS), along with the PH value were recorded during the setting process. The compressive strength, morphology and porosity were tested. With the increase of collagen, this novel CPC get a tI of 5mins to 8mins, tS of 20mins to 30mins, compressive strength from 1.5MPa to 4MPa, and the porosity from 40% to 60%. This study gave a possibility to form a porous scaffold of collagen/CPC composite with the nature of injectability and setting in situ.

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: The purpose of this study was to develop a feasible technique for bone reparation and further explore the possible applications of Ca-P ceramics in segmental load-bearing bone reparation. HA/TCP ceramics sintered at 1250oC were fabricated into tube-like columns of Φ15mm×30mm with a central canal of Φ4mm. Bone-like apatite was precipitated on the ceramics before implantation. 12 male dogs were used in this study, and a 30mm long segmental bone defect was made in the middle of one femur of each dog. Supported by the fixation of net-cage-structured TC4, the osteoinductive Ca-P ceramic cylinder was used to repair the segmental defect in dog femur. Stress was analyzed by ANSYS. The morphology recovery, function restoration, gait analyses and bone regeneration were evaluated. After implantation at 2, 4 and 8 months, the specimens were harvested respectively. The specimens were evaluated with morphological observation and mechanical testing. Stress analysis showed that the thickness of TC4 net cage was 0.3mm. The morphology recovery of the experimental animal was good and function was restored after 2 months gradually. Aided by stress analysis and by optimizing the design and fixation of implants, Ca-P materials with excellent osteoinductivity could be applied in repairing segmental bone defects.

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.