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It is difficult for the articular cartilage to self-heal any damage it may incur due to its lack of nerves and blood vessels. Development in stem cell technology provides new prospects for articular cartilage regeneration. Currently, stem cells from different sources and their diverse applications have demonstrated different degrees of therapeutic effect and potential in articular cartilage repair. However, stem cells are highly sensitive to their microenvironment. Therefore, more and more researchers are focusing their attention on regulating stem cells and thus accelerating cartilage regeneration through the biomimetic microenvironment constructed by biologically functional scaffolds. We reviewed in this paper the sources of the stem cells used for cartilage repair, the application method of these stem cells, as well as the therapeutic effect, mechanism and limitations in the application of stem cells synergizing with the biomimetic microenvironment in promoting articular cartilage repair and regeneration. We hoped to provide suggestions for practical clinical research in the design and improvement of biofunctional cartilage repair scaffolds that synergize with stem cells.

The Z-Axis tipper electromagnetic (ZTEM) technique is based on a frequency-domain airborne electromagnetic system that measures the natural magnetic field. A survey area was divided into several blocks by using the Maxwell’s equations, and the magnetic components at the center of each edge of the grid cell are evaluated by applying the staggered-grid finite-difference method. The tipper and its divergence are derived to complete the 3D ZTEM forward modeling algorithm. A synthetic model is then used to compare the responses with those of 2D finite-element forward modeling to verify the accuracy of the algorithm. ZTEM offers high horizontal resolution to both simple and complex distributions of conductivity. This work is the theoretical foundation for the interpretation of ZTEM data and the study of 3D ZTEM inversion.

The present study aimed to investigate the association between the expression of pituitary tumor-transforming 2 (PTTG2), and cell proliferation, invasion and apoptosis in glioblastoma. The U251 human glioblastoma cell line was transfected with the pcDNA-PTTG2 and small interfering (si)RNA-PTTG2 plasmids using Lipofectamine 2000. The expression of PTTG2 in U251 glioblastoma cells was determined using reverse transcription-quantitative polymerase chain reaction (RT-qPCR) and western blot analysis. The association between PTTG2 expression, and cell proliferation, invasion and apoptosis in vitro were investigated using an MTT assay, Matrigel Transwell assay and flow cytometry combined with Annexin V/propidium iodide staining, respectively. RT-qPCR and western blot analysis demonstrated that PTTG2 mRNA and protein expression were significantly overexpressed and significantly suppressed following transfection with pcDNA-PTTG2 and short interfering RNA (siRNA)-PTTG2 plasmids, respectively (P

Transcription factors encoded by HOX genes are vital in the determination of cell fate and identity during embryonic development. In certain malignancies, HOX genes also behave as oncogenes. The present study demonstrated suppression of the invasive tendency of glioblastoma multiforme U-118 and U-138 cells by the introduction of the antisense fragments of HOXA6 and B13 genes using electroporation. The invasion index indicated 79 and 72% reductions in the invasive ability of antisense HOXA6 and B13, respectively. No significant differences in the invasive index of the parental and mock cells of each HOX gene were observed (invasive index, 0.75-0.91; P=0.05). A reduction in invasion tendency was also observed following betulinic acid (BA) treatment: The results from the matrigel assay analysis clearly demonstrated a significant inhibition in the invasive behaviour of U-118 and U-138 cell lines from day 15 following BA treatment, with a maximum effect on day 30. The invasion index demonstrated 62 and 65% reductions in invasion ability in the U-118 and U-138 cell lines, respectively. The suppression of HOXC6 and B13 expression by the introduction of the corresponding antisense fragments in addition to BA reduced invasion tendency in U-118 and U-138 cell lines. The mechanism underlying the association between the HOX gene and invasive behavior in glioma cells is yet to be understood. However, the anti-invasive behavior of BA may aid understanding of the mechanism in future studies.

Mutations in leucine-rich repeat kinase 2 (LRRK2) are the most common cause of Parkinson's disease (PD). LRRK2 contains a Ras of complex proteins (ROC) domain that may acts as a GTPase to regulate its protein kinase activity. Here, we performed 10 ns molecular dynamics simulations on LRRK2 Apo, complex with GDP and mutations (R1441C, R1441G and R1441H). Our results strongly suggest that the formations of helix in L1 and its pliable plays a major role in the LRRK2 functions.

In geophysics exploration, using gradient tensor instead of the full magnetic field gradient has many advantages, which magnetic gradient tensor data to better describe small anomalies. However, the measurement of magnetic gradiometer contains a very complex motion noise, separating the motion noise from the signal component is a large challenge. In this paper, we show the expression for the magnetic gradient tensor, and then through model tests proved the Kalman filter good filtering effect.

Mechanical strength and biocompatibility are issues of most concern for scaffolds in cartilage tissue engineering. Collagen modification is always used to strengthen scaffolds. There are mainly two ways for collagen modification: inclusion of reinforcing phase to form composites and chemical cross-linking. To explore an alternative approach, the collagen hydrogel modified by a reinforcement phase was compared with cross-linking. Collagen-alginate hydrogel (CAH) and collagen hydrogel cross-linked by genipin (CGH), which were different in modification methods, were chosen candidates. A comprehensive study was carried out on mechanical, structural and biological properties including swelling ratio measurement, in vitro degradation, AFM, mechanical test, thermogravimetric analysis, and in vitro cartilage tissue engineering. The results showed that mechanical strength of collagen was more enhanced for CGH than CAH, as evidenced by analysis of swelling ratio, in vitro degradation, AFM, mechanical test and thermostability. MTT and histological results showed that CGH was superior to CAH with less cytotoxicity and more chondrocytes distributed as well as more aggrecan secreted. With the increase in culture time, the cytotoxicity of cross-linker may be alleviated. CGH may provide a more favorable biomimetic environment for cartilage growth. All these indicated that selecting a cross-linker with a minimal cytotoxicity could be more promising for collagen modification, with improvements observed in both physical and biological properties. For reinforcement, it was required that the incorporated component should be equipped with better or equivalent properties compared with collagen. This study provided important implications to engineering collagen-based hydrogels for cartilage graft applications.

Bone tissue engineering (BTE) is approached via implantation of autogenous mesenchymal stem cells (MSCs), marrow cells, or platelet-rich plasma, etc. To the contrary, gene therapy combining with the bone marrow (BM) has not been often reported. This study was performed to investigate whether a modified BTE method, that is, the BM and a recombinant human bone morphogenetic protein-2 adenovirus (Ad.hBMP-2) gene administering in hydroxyapatite/β-tricalcium phosphate (HA/β-TCP) ceramics could accelerate the healing of segmental defects in the rabbit radius. In our study, ceramics were immersed in the adenovirus overnight, and half an hour before surgery, autologous BM aspirates were thoroughly mixed with the ceramics; at the same time, a 15-mm radius defect was introduced in the bilateral forelimbs of all animals, after that, this defect was filled with the following: (1) Ad.hBMP-2 + HA/β-TCP + autologous BM (group 1); (2) HA/β-TCP + Ad.hBMP-2 (group 2); (3) HA/β-TCP alone (group 3); (4) an empty defect as a control (group 4). Histological observation and μ-CT analyses were performed on the specimens at weeks 2, 4, 8, and 12, respectively. In group 1, new bone was observed at week 4 and BM appeared at week 12, in groups 2 and 3, new bone was observed at week 8 and it was more mature at week 12, in contrast, the defect was not bridged in group 4 at week 12. The new bone area percentage in group 1 was significantly higher than that in groups 2 and 3. Our study indicated that BM combined with hBMP-2 adenovirus and porous ceramics could significantly increase the amount of newly formed bone. And this modified BTE method thus might have potentials in future clinical application.

In the present study, three types of tetracalcium phosphate (TTCP) were prepared by solid-solid reaction or co-precipitation method and by different cooling modes. The effect of TTCP on the performance of calcium phosphate cement (CPC) was investigated. The result showed that the characteristic of TTCP varied with preparation method and played an important role in CPC performance. A solid-solid reacted TTCP yielded smaller particle size and resulted in bad workability and mechanical strength of CPC. The fast cooling of sintering TTCP by liquid nitrogen could avoid the decomposition of TTCP and make pure TTCP. TTCP prepared by wet-precipitation could improve performance of CPC and was promising to optimization of CPC.

Collagen has been widely used in biomedical field, such as scaffolds for tissue engineering. However, the rapidly biodegradation and weak mechanical strength of collagen limited its application. In this study, an insoluble collagen extracted from cattle hide was designed as scaffold to act as a three-dimensional substrate for tissue engineering. The received insoluble collagen sponge was analyzed by scanning electron microscopy, infrared spectroscopy, mechanical testing and thermogravimetric-differential thermal analysis. In addition, the degradation was performed in vitro using collagenase. The results showed that the insoluble collagen had the same triple helical domain as acid-soluble collagen, while the compression strength was greatly improved and the degradation rate was reduced. The insoluble collagen sponge with good stability should be promising in tissue engineering scaffold applications.

With good biocompatibility, collagen is often used in cartilage tissue engineering. Collagen/alginate composite was hoped to improve the poor mechanical property of pure collagen but the biocompatibity was decreased. In this study, hydroxyapatite (HA) particles were used to get collagen/alginate/HA (CAHA) composite film to enhance the bioactivity properties. The bioactivity of the composite was investigated by in vitro co-culture with chondrocytes. During the 6-day cell culture in vitro, the composite showed a significant improvement in promoting proliferation and maintaining morphology/phenotype of the chondrocytes over collagen/alginate composite by MTT, SEM, fluorescent and immunohistochemical assays. Cytocompatibility and cytoviablility of CAHA even come up to that of collagen film alone. The results indicated that the composite film may provide an appropriate environment for the proliferation and maintaining the morphology and phenotype of chondrocytes and have a potential clinical application in the cartilage tissue engineering field.

PcrA helicase, a member of the superfamily 1, is an essential enzyme in many bacteria. The first crystal structures of helicases were obtained with PcrA. Based on structural and biochemical studies, it was proposed and then generally believed that PcrA is a monomeric helicase that unwinds DNA by an inchworm mechanism. But a functional state of PcrA from unwinding kinetics studies has been lacking. In this work, we studied the kinetic mechanism of PcrA-catalysed DNA unwinding with fluorometric stopped-flow method under both single- and multiple-turnover conditions. It was found that the PcrA-catalysed DNA unwinding depended strongly on the PcrA concentration as well as on the 3'-ssDNA tail length of the substrate, indicating that an oligomerization was indispensable for efficient unwinding. Study of the effect of ATP concentration on the unwinding rate gave a Hill coefficient of approximately 2, suggesting strongly that PcrA functions as a dimer. It was further determined that PcrA unwound DNA with a step size of 4 bp and a rate of approximately 9 steps per second. Surprisingly, it was observed that PcrA unwound 12-bp duplex substrates much less efficiently than 16-bp ones, highlighting the importance of protein-DNA duplex interaction in the helicase activity. From the present studies, it is concluded that PcrA is a dimeric helicase with a low processivity in vitro. Implications of the experimental results for the DNA unwinding mechanism of PcrA are discussed.

The rubber accelerator, 2-mercaptobenzothiazole (MBT), is known to cause allergic contact dermatitis (ACD), but the mechanism is unknown. The role of the thiol group in MBT's allergenicity was investigated in the present study. Guinea pigs were sensitized to MBT using a modified guinea pig maximization test (GPMT) and reactivity was assessed toward 2-mercaptobenzothiazole disulfide (MBTS), 2-hydroxybenzothiazole (HBT; thiol-substituted), 2-(methylthio)benzothiazole (MTBT; thiol-blocked), and benzothiazole (BT; thiol-lacking). MBT and MBTS, but not BT, HBT, or MTBT, elicited ACD in MBT-sensitized animals, demonstrating that the thiol group is critical to MBT's allergenicity. In addition, both MBT and MBTS were shown to inhibit both glutathione reductase and thioredoxin reductase, and thus contribute to the stability of MBT-protein mixed disulfides. It is concluded that the probable haptenation mechanism of MBT is through initial oxidation to MBTS with subsequent reduction to form mixed disulfides with proteins.

It is well known that the cellular responses are related with both physical and chemical characteristics of substrate, including surface topography. In the present study，the effect of surface topography of hydroxyapatite (HA) on rat bone marrow cell (rBMCs) response was investigated. HA disc-shaped pellets with various topography were manufactured by single-axis pressing methods. The rBMCs responses on materials including cell morphology and proliferation were evaluated by SEM and MTT methods respectively, and the differentiation potential was assessed by total protein content and alkaline phosphatase (ALP) activity testing. The results showed that the cell porliferation was higher on HA surfaces with macropore structure, while ALP activity was lower. No significant difference in the cellular responses on the pore distribution and orietation was observed. However, the pore structure had a potential to guide cell orientation by gathering the cells inside the pores rather than on the ridges. Since ALP served as an indicator of early osteoblast differentiation, in this study its higher expression on HA surface with micropores suggested that surface microtopograhy exhibited an important effect on early osteoblast differentiation process.

Bloom syndrome (BS) is an autosomal recessive disorder characterized by genomic instability and the early development of many types of cancer. Missense mutations have been identified in the BLM gene (encoding a RecQ helicase) in affected individuals, but the molecular mechanism and the structural basis of the effects of these mutations remain to be elucidated. We analysed five disease-causing missense mutations that are localized in the BLM helicase core region: Q672R, I841T, C878R, G891E and C901Y. The disease-causing mutants had low ATPase and helicase activities but their ATP binding abilities were normal, except for Q672, whose ATP binding activity was lower than that of the intact BLM helicase. Mutants C878R, mapping near motif IV, and G891E and C901Y, mapping in motif IV, displayed severe DNA-binding defects. We used molecular modelling to analyse these mutations. Our work provides insights into the molecular basis of BLM pathology, and reveals structural elements implicated in coupling DNA binding to ATP hydrolysis and DNA unwinding. Our findings will help to explain the mechanism underlying BLM catalysis and interpreting new BLM causing mutations identified in the future.

L9 (34) orthogonal array design was employed to optimize experimental conditions for the preparation of the composite using in situ synthesis method and to analyze the relationships between experimental parameters and mechanical property of the composites. Bending strength of the composite was considered as a target property of the composites. Hydroxyapatite content in the composite, synthesis temperature and pH were chosen as main parameters. As a result of this study, bending strength of the composite appeared in peak with the increase of the hydroxyapatite content of the composites and synthesis pH, while with the increase of temperature, bending strength decreased. Optimum experimental conditions for the synthesis of the composites with higher bending strength were determined. The bending strength of the composites was 90 MPa at the optimal synthesis conditions.

Stress concentration is one of the main mechanical problems leading to the failure of clinical application for osteointegrated implant of percutaneous osteointegrated prosthesis, which is especially marked for higher amputated leg prosthesis. Traditionally design was composed of only the distal part. To improve the biomechanical safety, a new design with the lag part similar to the lag screw was introduced. Based on CT scan data, relatively accurate model of femur for finite element analysis (FEA) were obtained. The FEA results with the new implant demonstrated that compared to traditional design, the declination of bone stress peak ranged from 15.68% to 28.67%, perpendicular deformation from 34.73% to 72.16%, and maximal stress of implant from 14.51% to 23.36% with the increasing of loads from 3750N to 2000N. So the new design of osteointegrated implant would be more secure mechanically, in the case of higher amputated leg attachment.

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.

Linear and Star-shaped PCL-b-PEG copolymers were synthesized through a two step process, including the first step to synthesize the star-shaped PCL through ring-opening polymerization of Γ-caprolactone initiated from multi-functional alcohol under the existence of tin(II) ethylhexanoate [Sn(Oct)2] catalyst, and the following step to couple the obtained star-shaped PCL with PEG segments using bi-functional linker. The structure of the polymers was confirmed by IR, NMR, GPC, et al. The aggregation behaviors of the star-shape copolymers were compared with that of the linear block copolymer with corresponding molecular weight of each arm, and the influences of structure factors were discussed.

As a natural biomaterial, collagen especially pepsin-solubilized collagen (type I) has been used widely in biomedical fields due to its excellent biocompatibility. In this preliminary study, we investigate the effect of some inorganic ions which are frequently utilized in the preparation of collagen on the morphology and crystallinity of fibrils. The scanning electron microscope and x-ray diffraction were applied to analyze the morphology and the crystallization of the reconstituted collagen fibrils, respectively. Although further studies are needed, these initial results indicate that by controlling the self-assembly conditions of collagen molecules, we may achieve the desired properties of fibrillar collagen products.

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.

The bioactivities of titanium oxide film on titanium surface received from different chemical treatment methods were studied in SBF in vitro and mechanically and histologically investigated in vivo. Three groups of titanium specimens were prepared: untreated titanium(S), acid-alkali treated titanium (H), and acid-alkali and heat-treated titanium(X). The oxide film of X surface resulted in more apatite formation and significantly higher strength of the interface between the samples and bone than those of the other titanium groups. The surface of the acid-alkali treated titanium and that further treated by heat treatment had higher bioactivity and stronger bone-bonding ability.

Zirconia toughened alumina (ZTA) nano-ceramic composite has excellent mechanical properties. Preparation of ZTA was conducted in the present study with an attempt to use as dental ceramics. On the basis of the study on the effect of the die pressing forces on the density and Vickers hardness of the sintered ZTA, additive aids TiO2, MgO, SiO2 and CaO were introduced in order to reduce the sintering temperature of ZTA nano-ceramic composite with good densification. Scanning electron microscopy was employed to evaluate the microstructural morphology. Phase composition was confirmed by using X-ray diffraction. Thermal analysis was further used to study the structural change. The results indicated that the ZTA product sintered at 1450°C had dense and uniform microstructure due to the combinative effect of additive aids, including the formation of an intermediate compound. This study suggested that such ZTA nano-ceramics had potential applications as dental prosthetic materials.

The achievement of biological sealing is determined by the quality of the skin attachment on the surface of the percutaneous implant in the area where the implant penetrates the skin. It has been known that certain surface features of the implants can significantly influence the interactions between cells and substrate. In this study, titanium plates were bioactivated through anode-oxidization firstly, and then cultured with human epithelium cells for 72h. Untreated Ti plates were used as control. After the samples were dehydrated, the morphology of the cultured epithelium cells was tested with Scanning electron microscopy (SEM). The surfaces of control group did not enhance epithelium cell attachment and growth, while the bioactivated microporous surface of anode-oxidized group would be beneficial to induce the formation of the pseudopod of epithelium cell, and then interlock the human epithelium cells through the pseudopod, which imply that the surface modification method of anode oxidization may be one of the most effective methods to resolve the biological sealing.

Nano-titania ceramics is a potential biomaterial for orthopaedic application. In our previous studies, a bioactive nano-titania ceramics was prepared by using alkali-heat treatment. In this paper, hydroxyapatite was used as a grain growth inhibitor additive to get nano-titania ceramics with different grain size, and the effect of grain size on the bioactivity was studied in vitro.

This study was carried out to investigate the effect of acid-alkali treatment and alkaliheat treatment on the push-out strength and tissue response of the porous titanium in vivo. Porous titanium with different treatment was implanted in dog bony site for 2 months and 5 months and the push-out strength was tested. At 2 months, the mean push-out strengths of the acid-alkali treated and alkali-heat treated porous titanium were 11.3 and 15 MPa, respectively. At 5 months, the values reached 29.8 and 35 MPa, respectively. Histological observation showed a close contact between implants and bone, and more bone tissue filled inside the pores of porous titanium increasing with implantation time. The results indicated higher bonding strength between bone and porous titanium in alkali-heat treated samples. Therefore, alkali-heat treatment can provide porous titanium implants with better fixation as a bone substitute for clinical use under load-bearing conditions.

After the Tantalum metal was subjected to the anodic oxidation at suitable voltage in 2M H2SO4 solution, tantalum oxide with rhombic or amorphous structure formed on the metal surface. The Oxide showed apatite formation ability in simulative body fluid at 6d. It meant the anodic oxidation treatment ia an effective method to accelerate the bioactivity of tantalum metal.

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.

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.

Circumambient tissues infection is a common complication of implanted percutaneous and permucosal devices (PDs). In order to counter the infection, the titanium abutment surface of PDs was modified to achieve antibacterial and antiadhesive activities. Titanium discs were immersed into hydroxyapatite (HA) sol containing different mass fraction silver and thermally treated to get modified discs. The modified discs become more smoother and get crystal HA coatings containing silver. Silver ion release test demonstrate the release rate is very slow and the coating is a reservoir of silver. The antibacterial and antiadhesive effects of modified discs on Staphylococcus aureus and Porphyromonas gingivalis were evaluated. Modified titanium discs with silver significantly inhibited the growth of these two bacteria compared with both the polished titanium discs control and modified titanium discs without silver. And titanium discs modified with more silver have higher antibacterial activity and less bacteria adhesion in this study. These findings indicate that titanium surface modified with the HA sol-gel containing silver could achieve antibacterial and antiadhesive activities, and the abutments of PDs are promising to be modified by this method.

In order to prepare nano-hydroxyapatite/poly(lactide) (n-HA/PLA) composite with good interfacial interaction, some groups which could bind with Ca ions in HA crystals need to be introduced onto PLA surface. Poly(α-methacrylic acid) (PMAA) was grafted on the PLA surfaces via photooxidization and subsequent UV induced polymerization. Suspension of PMAA-PLA microparticles with an average size as 133.1nm was prepared with solvent evaporation technique. Then utilizing the action of template manipulating of PMAA-PLA microparticles, n-HA/PLA composite were synthesized. Zeta potentials measurement and SEM indicated that there were good interfacial interactions between two phases of n-HA/PLA composite. The results of cell viability confirmed that n-HA/PLA composite possessed good cytocompatibility, so the n-HA/PLA composite scaffold obtained by electrospun technology might be used as bone tissue engineering scaffold.

Poly(vinyl alcohol) (PVA) was introduced during in situ synthesis of hydroxyapatite (HA) in neutral collagen (COL) solution and final PVA-COL-HA nanohybrids were achieved via sequential steps including gelation by fibrillogenesis, freezing-thawing physical crosslinking, removal of unreacted residues and dehydration. This method is expected to endow the pure PVA with good bioactivity and meanwhile the presence of elastic PVA would improve the properties of COL-HA composites. The phase, microstructure and possible molecular interactions of the achieved PVA-COL-HA nanohybrids were analyzed by using X-ray diffraction, Fourier transform infra-red spectroscopy and scanning electron microscopy. The results indicate that the inorganic phase is poorly crystallized apatite with a nanometer size due to the confinement of organic macromolecules which forms a network structure.

In order to develop a bone-filling material with osteoinductive potential, a composite micorspheres of collagen molecules and biphasic calcium phosphate (BCP) was prepared by utilizing emulsion polymerization and the intrinsic self-assembly of collagen. The prepared microspheres were analyzed by granularity test, scanning electron microscopy (SEM), infrared spectra (IR) and enzymatic digestion experiment. The results showed that the collagen matrix of fibrils was reconstituted in the droplets, and the native triple-helix structure of collagen was still maintained. The study provides an effective way to prepare microspheres of collagen and BCP composite.

The purpose of this study was to evaluate biocompatibility of a new injectable root canal sealer. The cytotoxicity of zinc oxide-eugenol cements, CCQ and the new injectable root canal sealer were assessed by the MTT assays. These materials were filled into the root canals of the dog. One month later, the dog was sacrificed and the X-ray photos were taken. The histological response was observed through the microscope. The results show the new injectable root canal sealer showed better biocompatibility than the other two materials.

Collagenous molecule was successfully immobilized to hydroxyapatite (HA) surface through a molecular bridge (2-Hydroxyethyl acrylate, HEMA) that was grafted to the surface with covalent bond by gamma irradiation. Hydroxyapatite modified by atelocollagen had been characterized by several surface sensitive techniques, such as FT-IR, SEM, XPS. The investigations showed that the collagen, a bioactive macromolecule, was immobilized on the HA surface through covalent bond.

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.

Protein adsorption is driven by various interactions. The contribution of surface charge to bovine serum albumin (BSA) adsorption on hydroxyapatite (HA) ceramic was investigated by adjusting the liquid environment in which the solid particles dispersed. Zeta potentials of HA and the adsorption of BSA on the surface were tested as a function of pH, ionic strength, Ca2+ and PO4 3- concentrations in the aqueous solutions, and the results showed that both of them were greatly affected by those experimental variations. Besides, the amount of adsorbed BSA was related to the variation of zeta potential of HA, as could be well understood in terms of electrostatic interactions.

Collagen (Col) and chitosan (Chi) are both natural polymers and have received extensive investigation in recent years in the field of tissue engineering, but there are few reports on the introduction of hydroxyapatite (HA) into the Col-Ch system. In this study, based on the miscibility of these two polymers under proper condition, hydroxyapatite (HA) was synthesis in the Col-Chi system by in-situ co-precipitate method to give rise to a novel nanocomposite. The structural characterization of such Col-Ch-HA nano-materials was carried out by using FT-IR, XRD, SEM and TGA analyses with main components and Col-Chi samples used for comparison. It was found that there exist interactions between Col and Chi molecules. The nucleation and growth of inorganic phase occurs in the Col-Chi system and final products are uniform dispersion of nano-sized HA in the Col-Chi network without obvious phase separation. This novel nanocomposite would be a promising material for bone tissue engineering.

Synthesis of hydroxyapatite (HA) in organic solutions has received extensive attention in recent years with an attempt to obtain HA of a nanometer level. In this preliminary study, we demonstrated that organic-HA nanocomposites could also be achieved with one step method via in situ mineralization and subsequent crosslinking of organic species. This design was realized through in situ synthesis of hydroxyapatite in poly(vinyl alcohol) and acrylic acid aqueous solution as an organic template. The aforementioned organic-inorganic nanocomposites were analyzed by using X-ray diffraction, Fourier-transform infrared spectroscopy, scanning electrical microscopy, thermal analysis. The comparative structural measurements were also conducted with the synthesized HA with absence of the organic template. The results indicated that the existence of organic species effectively inhibits the growth of calcium phosphate and that relatively pure HA can be obtained in sintered composite products. The present study provides a direct and versatile route for fabrication of nanocomposite biomaterials.

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.

Hydroxyapatite/collagen composites were prepared in-situ synthesis. The composites were finally achieved by dehydration including air-drying and freeze-drying methods. FTIR, XPS and DSC were employed to investigate the composites dehydrated by two methods. The air-dried composites had better mechanical properties than those of the composites dried by freeze drying. Air-drying of the composite induced more bond formation and crosslink between collagen fibers and HA crystals compared with freeze-drying of the composite, as indicated by the shifting of amide A and I bands to the lower wavenumber and by the changes in the binding energy of O1s, Ca2p, and P2p, leading to the increase of the peak temperature of the composites. Collagen crosslink and bond formation in the air-dried composites were key factors to increase the bending strength of the composites. The results of this study confirm that in situ synthesis and air-dry method are effective ways to obtain nanoHA/COL composites with high mechanical properties.

The purpose of this study was to explore the feasibility of repairing massive bone defect with in vivo tissue engineering(TE) bone, and to provide experimental evidence for the application of in vivo TE bone into clinic in the future. Six calcium phosphate ceramics (Ca-P ceramics) columns were prepared, and then immersed in dynamic revised simulated body fluid (RSBF). 72 hours later, the bone-like apatite was formed on the surface and pore walls of ceramics. Three dogs were used in this study. Two ceramic columns were implanted bilaterally in the femoral muscles of each dog to construct living bone graft of in vivo TE bone. 6 weeks after implantation, they were transplanted to the box-like bone defects sites created in bilateral mandible of the same animals. The dogs were sacrificed at 8, 12 week after operation respectively. Samples were harvested for gross observation, X-ray examination, tetracycline fluorescence labeling, SPECT and histological observation. These results demonstrated that as a living bone graft, in vivo TE bone participated in the bone metabolism of host, and integrated with the host bone. It is feasible to reconstruct box-like bone defect of mandible with the in vivo TE bone.

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.

In this study, bovine serum albumin protein (BSA) was introduced to investigate the co-precipitation process of calcium phosphate and BSA on bioactivated Ti. Commercially pure titanium were bioactivated firstly, and then immersed in a highly supersaturated stable calcium phosphate (Ca-P) solution at three different conditions. The samples designated as Ti-C, Ti-C-CB, and Ti-C-B for control. The samples were evaluated by SEM with EDX, XRD and XPS. The co-precipitation of BSA protein and Ca-P influenced the morphology of the crystals of Ti-C-CB significantly. In terms of the immersion in the Ca-P solution containing BSA, the co-precipitation of Ca-P with BSA on the surface of Ti-C-CB was a chemical process rather than simple physical adsorption, which was most possibly achieved by the linkage of –COO− groups to Ca-P. Such coprecipitated interaction led to the formation of a tight, dense and uniform Ca-P coating.

In this study, three kinds of photo-reactive polymers, namely positively charged azidophenyl-derived polyallylamine (AzPhPAAm), negatively charged azidophenyl-derived poly(acrylic acid) (AzPhPAAc) and neutral azidophenyl-derived poly(ethylene glycol) (AzPhPEG), were synthesized by introduction of photo-reactive group (-N3) into polyallylamine, poly(acrylic acid) and poly(ethylene glycol), respectively. The structure of the azidophenyl-derived polymers was confirmed by 1H-NMR measurement. All of the photo-reactive polymers can be pattern-grafted on the surface of cells culture plate, which was confirmed by the optical microscopy observation. The contact angle decreased after surface modification by the photo-reactive polymers. Human mesenchymal stem cells (MSC) cultured on the modified surfaces showed different morphology. The cells adhered and spread more on the PAAm- and PAAc-grafted surfaces than on the PEG-grafted surface. The pellets formed on PAAm- and PEG-grafted surfaces in condrogenic differentiation medium were positively stained by safranin O/ fast green. But the pellet formed on PAAc-grafted surface did not show obviously positive staining for safranin O/ fast green. These results indicate that the PAAm- and PEG-grafted surfaces promoted chondrogenic differentiation of MSC.

This study investigated the utility of genetically modified cell line for fast and non-destructive cytotoxicity evaluation of biomaterials. The EGFP(enhanced green fluorescence protein)-expressing plasmid pcDNA-EGFP was constructed, and electroporated into ROS 17/28 osteoblastic cells to generate an EGFP-labeled stable cell line, ROS-EGFP. This genetically modified cell line provided two unique opportunities to qualitative and semi-quantitative evaluation of cell growth on biomaterials without destruction of samples. Firstly, utilizing the fluorescence of EGFP expressed in the cells, the viability state of cells on biomaterials was evaluated using a fluorescent light microscope. Secondly, the proliferation of cells on biomaterials, which was identified by MTT assay，was demonstrated according to the microscopically counted fluorescent cell numbers. From the results, it could be concluded that the ROS-EGFP cell line was an effective tool to trace the fate of cells on biomaterials and to evaluate the biocompatibility of biomaterials to cell growth in vitro.

The purpose of this study was to develop a feasible approach for repairing periodontal bone defects with the in vivo tissue engineering bone incorporated with bioabsorbable PLA membrane and to provide evidences for the clinical application. Osteoinductive HA/β-TCP sintered at 1100°C were implanted in the femur medial muscles in the hind legs of three dogs. Four weeks after implantation, the in vivo tissue engineering (TE) bone was explanted. Meanwhile, artificial periodontal bone defects of 8mm×6mm were performed on the buccal side of 4th premolar and 1st molar of mandible bilaterally, with the exposure of dental roots. The defects were treated as follows: (1) in vivo TE bone and PLA membrane; (2) HA/β-TCP ceramics and PLA membrane; (3) PLA membrane only; (4) empty control. At the 2, 4, 8 weeks post-transplantation, the dogs were sacrificed. The specimen were harvested and evaluated by gross inspection, dental radiography, SPECT (99mTC-MDP) and histological observation by MPIA2500. The results showed that more mature osseointegration was found in the group 1. We presumed that the in vivo TE bone graft could enhance the reparation of periodontal bone defects.