Papers by Author: Xin Long Wang

Abstract: The effect of different hydroxyapatite particles on malignant melanoma cell was evaluated in vitro. Two kinds of short-rode hydroxyapatite particles, which range from 0.4 to 1 um and 0.5 to 1.5 um, were co-cultured with human’s malignant melanoma (MM) cell line A375 for 24, 48, and 72 h. Both of these HA particles showed the same cell proliferation rate as blank control, and there was no statistically significant correlation of matrix metalloproteinases-2 (MMP-2) expression to the HA particle size. SEM images showed that the membrane of tumor cell, which co-cultured with HA particles, was shrunk. The cell superficial sentus was reduced and small size particle’ effect was more obvious. Since immunohistochemistry and SEM data are qualitative technique, further precise methods might bring more information about the effect of HA particles on tumor behaviors. But this study can provide the bio-security test of micrometer HA particles in transplantation after tumor excision.

Abstract: The study is aimed at to explore the construction of bone graft with calcium phosphate ceramics implanted in subcutaneous fat, and provide applying technique for the in vivo bone tissue engineering. Forty-eight calcium phosphate ceramics (Ca-P ceramics) columns with Φ 5×8 mm were prepared, and eight dogs were used in this experiment. Six samples were implanted in each dog. Three in dorsal muscles while the others in subcutaneous fat. The specimens were harvested at 4, 6, 12 and 24 weeks post operation, for gross observation, SPECT and histological studies. The osseous or osteoid tissue formation at different times in the two non-osseous sites was compared and the new bone grafts in subcutaneous fat and intramuscular implantations were evaluated. The results demonstrated that the bone graft could be constructed not only in muscle but also in subcutaneous fat. Compared to that in muscle, constructing bone graft in subcutaneous fat could have brighter prospect to clinical application.

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: Hydroxyapatite (HA) ceramics is one of the most widely used bone substitute in clinics. Limited information is available concerning how HA ceramics may affect osteoprotegerin (OPG) and RANKL expression. In this study, osteoblastic-like SaOS-2 cells were grown on HA ceramics sintered at different temperature for 3 and 6 days, RANKL and OPG mRNA expression were analyzed with quantitative in situ hybridization (QISH) technique. Result showed that SaOS-2 grown on HA ceramics sintered at 800°C expressed higher RANKL mRNA than on other two HA ceramics after 3 days’ culture. No significant difference in OPG expression on different surfaces was detected after 3 days and 6 days culture. This result suggests that HA sintered at low temperature tend to induce more bone remodeling after implantation.

Abstract: The mRNA expression of Cbfa1 and osteocalcin gene induced by calcium phosphate ceramics (Ca/P) were quantitative analyzed according to real-time RT-PCR method in this work. C2C12 cells were co-culture with four kinds of porous Ca/P ceramics for 2 and 5d without adding other growth factors. The four kinds of Ca/P ceramics were pure hydroxyapatite (HA) sintered at 1250°C and HA/TCP with a ratio of 60/40 sintered at 1100°C (HT1), 1200°C (HT2) and 1250°C (HT3) respectively. Real-time RT-PCR analysis found the Ca/P ceramics induced positive expression of Cbfa1 and osteocalcin in C2C12 cells, After 5 days culture, Cbfa1 and osteocalcin showed obvious higher expression compared with that in 2 days. Cbfa1 and osteocalcin expression in BCP was much higher than HA, and the expression level of osteocalcin was HT1>HT2>HT3>HA. Our results showed that Ca/P ceramics alone were sufficient to induce C2C12 cells to osteoblastic differentiation and the sinter temperature and phase composition of Ca/P ceramics could affect their osteoindctive capacity significantly.

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 aim of this study is to reveal the response of highly malignant tumor cell to different hydroxyapatite particles. Human’s highly malignant melanoma (MM) cell line A875 is exposed to two kinds of short-rod hydroxyapatite particles. After incubated with hydroxyapatite particles at different time points, the effects of MM cell morphology, proliferation and invasion are evaluated by SEM, MTT, and MMP2 protein immunohistochemistry respectively. SEM figures show that superficial sentus of MM cells reduce; more secretion is found; and smaller HA particles have more obvious effect. At the same time, no statistic difference can be found in MTT assay and MMP2 expression measurement. This study also provides useful information about biosecurity of hydroxyapatite ceramic in transplantation after highly malignant tumor excision.

Abstract: The aim of this study is to prepare nano hydroxyapatite powder. Hydroxyapatite powder was prepared via co-precipitated method with the addition of citric acid at pH 9-11 in ambient environment. The precipitates were aged for 24hs, and then milled into powder after washed and dried. The particle morphology and particle size of as prepared HA powders were characterized. The results showed that hydroxyapatite powder with width of 10-30nm and length of 30-100nm was prepared by wet co-precipitation.

Abstract: With the outstanding biocompatibility of hydroxyapatite (HA) and biodegradation of poly(D,L)lactide(PDLLA), and the expected good bio-mechanical compatibility, nano-HA / PDLLA (n-HA/PDLLA)composite has been paid great interests in hard tissue repair. One of the key factors affecting the potential of the composite is the degradation of the composite. That is what the mechanism of degradation in the composite is and if the degradation of the materials would induce the crack of the composite or a porous structure facile for tissue ingrowth would be formed. In this study, an n-HA/ PDLLA composite containing about 40% n-HA (wt%) was prepared and the degradation of the composite in bony tissue of rabbits and tissue response were studied by implanting composite rods and control HA rods into the femora of 16 New Zealand rabbits. After definite intervals, the histological analysis was completed by light microscopy and the degradation behavior was observed by scanning electron microscopy. The results suggested that a nano-HA/PDLLA composite was obtained and the materials showed good biocompatibility and osteoconductivity. The substantial degradation of the composite occurred at 8 weeks in vivo. After a longer period of implantation, the further degradation of the composite led to the formation of interconnected microporous and macroporous structure in the materials that might facilitate the tissue ingrowth in the composite.

Abstract: Microwave processing of porous hydroxyapatite ceramics was investigated in a dual frequency microwave-sintering furnace. The results revealed that microwave-sintering process could get sintered ceramics at much shorter sintering time and at lower sintering temperature than that of the conventionally heat-sintering process. Further, the microwave-sintered samples showed much smaller grain size and more uniform microstructure and reached a comparable compressive strength. The mechanism of rapid heating behavior of hydroxyapatite ceramics in microwave was also discussed. The results revealed that microwave processing was a promising method for sintering porous hydroxyapatite ceramics.