Papers by Author: Chun Lin Deng

Abstract: Porous HA/TCP bioceramics were immersed in pure bovine serum to observe the growth and formation of apatite. HRTEM, FTIR, and SEM coupled with EDS were used for the characterization of immersed samples. SEM results showed that some beamed crystals formed on the surface of ceramics granules, and with postponement of immersion time, crystals extended and became bigger, strap-like crystals became sheet-like crystals. HRTEM observations indicated that new-formed crystals developed along axes direction according to parallel layers. IR spectrum showed CO3 2- characteristic peaks existed besides O-P-O and OH- characteristic peaks. EDS results showed that calcium and phosphor ratio was 1.95 (mol ratio). The results indicated that bovine serums were advantaged to bone-like apatite formation.

Abstract: Dense HA/TCP bioceramics were immersed in pure bovine serum, rabbit serum and dog serum to observe apatite formation. Deposited crystals were examined using SEM. Results showed that some needle-like crystals formed on surface of sterilized HA/TCP, and needle crystals developed into sheet crystals and stick crystals after ceramics were immersed in bovine serum and rabbit serum respectively. The growth of crystals was maybe affected by the content of calcium, various kinds of albumen and alkaline phosphatase in different serums and the different pH of serum.

Abstract: Porous tricalcium phosphate ceramics were immersed in static and dynamic revised simulated body fluid (RSBF) at 37°C. Morphology, composition and phase of precipitates on TCP were identified by SEM, FTIR and TEM methods. FTIR and TEM results indicated the deposits on the inner pore walls of TCP were OCP, and SEM results implied that the deposited way of precipitates in static system was different from that in dynamic system.

Abstract: Porous HA/TCP bioceramics were immersed in pure dog serum to observe apatite formation. Deposited crystals were examined using SEM. Results showed that beamed sheet-like crystals formed on the surface of ceramics granules, and after postponement immersion time, crystals extended and became bigger. EDS and IR results suggested formed crystals were defect-calcium type carbonated hydroxyapatite. HRTEM photograph suggested formation process of new-formed crystals from non-crystal to crystal in serum. Directional organisms acted maybe as a template in process of crystals formation, so new crystals developed along certain direction.

Abstract: The PCL plates hydrolyzed by NaOH aqueous solutions and carboxylate groups were introduced onto the surfaces of specimen. Specimens were treated by CaCl2 and K2HPO4⋅3H2O under the normal-pressure condition and low-pressure of 103 Pa condition for 30min separately. Dense and uniform bone-like layers could be formed on the surface of specimens after mineralizing for less than 24h in simulated body fluids (SBF). The low-pressure condition could accelerate the formation of apatite layer.

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: The purpose of this study was to evaluate the response of osteoblasts to calcium phosphate with different surface modification, and to evaluate the osteoinductive capabilities of these biomaterials. 60HA/40α-TCP ceramics sintered at 1250oC was applied in this study. A ceramic cylinder with F5mm×8mm and slice with F10mm×1mm were prepared respectively. One third of the ceramics was used to form bone-like apatite (BLA), and the surface of another one third was modified with collagen. Osteoblasts (1×106/ml) were co-cultured with the three kinds of thin slices for 12h, 24h and 48h. SEM observation was applied to evaluate whether the surface modification and BLA formation could affect the attachment and proliferation of osteoblast in vitro. The three kinds of cylinder samples were implanted in dog muscle to evaluate their differences in osteoinduction. Cells grew in multi-layers and attached to the surface and proliferated well in the collagen and HA/TCP group. In the untreated and BLA precipitated groups, cells did not attach to the surface well. Osteoinduction was good in the BLA precipitated group and the amount of bone formed was higher; in the untreated group and collagen-treated group, no bone formation was observed in the tested period. This result indicated that the scaffold used in cell-materials composites in vitro and that in osteoinductive material based tissue engineering in vivo was not same.

Abstract: A revised dynamic immersion device was designed, and the effects of flowing speed of SBF in inner pores of ceramics on the formation of apatite in the pores were investigated in this study. The results showed some crystals were overlaid on the walls of inner pores. The crystal shape changed with flow rate of RSBF. When flow rates of RSBF were 2 ml/min, some stamen-like crystals formed on the inner walls of ceramics. In the ceramics in RSBF with flow rate of 5ml/min, besides more stamen -like crystals, a thin layer of fine deposits was overlaid on the walls of inner holes and the surface of the stamen -like crystals. But when the flow rate was 8 ml/min, only a thick layer of fine deposits on the walls of inner pores could be found. Energy dispersive spectroscopy (EDS) and Fourier Transform Infrared spectroscopy (FTIR) results revealed the deposits obtained in this study are carbonate hydroxyapatite (CHA).

Abstract: Dense hydroxyapatite (HA) and hydroxyapatite/tricalcium (HA/TCP) were immersed in Fast calcified solution (FCS) at 37°C in constant temperature culture box for 7 days. It was observed that the phase components of dense ceramics affected the composition, crystallinity and phase components of formed apatites on the surface of ceramics. It is a mixture of hydroxyapatite with a strong preferential crystallographic direction of 002 and octacalcium phosphate (OCP) on the surface of HA/TCP ceramics, whereas only an HA phase was detected on the surface of HA ceramics.

Abstract: The purpose of this study was to evaluate the response of osteoblasts to the calcium phosphate with different surface modification, and to evaluate the osteoinductive capabilities of these biomaterials. 60HA/40α-TCP ceramics sintered at 1250oC was applied in this study. The ceramic cylinder with F5mm×8mm and slice with F10mm×1mm were prepared respectively. One thirds of the ceramics were formed bone-like apatite (BLA), and the surface of another one thirds was modified with collagen. Osteoblasts (1×106/ml) were co-cultured with the three kinds of thin slices for 12h, 24h and 48h. SEM observation was applied to evaluate if the surface modification and BLA formation could affect the attachment and proliferation of osteoblast in vitro. The three kinds of cylinder samples were implanted in dog muscle to evaluate their differences in osteoinduction. Cells grew in multi-layers and well attached to the surface and proliferated well in the group of collagen and HA/TCP. In untreated and BLA precipitated group, cells did not attach to the surface well. Osteoinduction was good in BLA precipitated group and the amount of bone formed was higher; in untreated group and collagen-treated group, no bone formation was observed in the tested period. This result indicated that the scaffold used in cell-materials composites in vitro and that in osteoinductive material based tissue engineering in vivo was not same.