Setting property and compressive strength of nHA/α-CSH combined bone grafts / 医用生物力学

Objective To develop a new type of combined bone grafts mainly including nanometer hydroxyapatite (n-HA) and α-calcium sulphate hemihydrate (α-CSH), and investigate its setting property and compressive strength. Methods The setting time and compressive strength of nHA/α-CSH combined bone grafts with different liquid-to-solid (L/S) ratio or calcium sulphate dehydrate (CSD) amount were measured and observed by the X-ray diffraction (XRD) and the scanning electron microscope (SEM). Results The setting time of combined bone grafts was increased along with the increase of L/S ratio or nHA amount, and reduced with the increase of CSD amount. The setting time of the compound with 20% of nHA, 80% of α-CSH was (169±36) min, while that of the compound with 5% of nHA, 20% of CSD, 75% of α-CSH was (6±1.1) min. The compressive strength of combined bone grafts reduced along with the increase of nHA amount. The average compressive strength of pure α-CSH was (12.3±2.4) MPa, while that of the compound with 20% of nHA, 80% of CSH was (4.8±0.6) MPa. The XRD results showed that no other materials were produced except that α-CSH was transformed to CSD during the setting process. The SEM results indicated that nHA was filled in the crystal structure of the CSD, presenting two-phase structure. Conclusions The setting time and compressive strength of nHA/α-CSH combined bone grafts can be adjusted by the different proportion of nHA, CSD amount and L/S ratio, which provides an appropriate condition for clinical application.

A surface-modified biodegradable urethral scaffold seeded with urethral epithelial cells / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Efficient cell adhesion and proliferation is a central issue in cell-based tissue engineering, which offers great promise for repair of urethral defects or strictures. This study evaluated the adhesion and growth of rabbit uroepithelium on a surface-modified three-dimensional poly-L-lactic acid (PLLA) scaffold.</p><p><b>METHODS</b>Urethral mucosa were harvested from male New Zealand rabbits and the urothelium were dissociated and then cultured. Immunocytochemistry on cultured uroepithelium for pancytokeratin and uroplakin II and TE-7 confirmed pure populations. After in vitro proliferation, cells were seeded onto a surface-modified urethral scaffold with non-knitted filaments. The morphology and viability of the cells were examined by immunohistochemical and fluorescence staining. Inverted and scanning microscopes were used to document cell growth and adhesion.</p><p><b>RESULTS</b>Three to five days after primary culture, the uroepithelial cells gradually became confluent, assuming a cobblestone pattern. The filaments of the urethral scaffold had excellent biocompatibility and allowed growth of the uroepithelium, without affecting viability. The uroepithelial cells adhered to and grew well on the scaffold. After 3 - 7 days, the cells grew vigorously and meshes of the scaffold were full of uroepitheliums.</p><p><b>CONCLUSIONS</b>The surface-modified urethral scaffold with non-knitted filaments allows the growth of uroepithelium and can serve as a carrier for the tissue engineering of urethra.</p>

Effects of TCP/HA-coating titanium on the adhesion behavior of human gingival fibroblasts / 中华口腔医学杂志

<p><b>OBJECTIVE</b>To investigate effects of hydroxyapatite (HA) and porous tricalcium phosphate/hydroxyapatite (TCP/HA)-coating titanium on the adhesion behavior of human gingival fibroblasts (HGFs).</p><p><b>METHODS</b>Coatings of HA and duplex phases TCP/HA on titanium (Ti) were formed by ion beam assisted deposition (IBAD) method. Attachment, spreading, extracellular matrix (ECM) production, and focal adhesion plaque formation of HGFs were investigated on commercially pure (CP) titanium, HA-coated CP titanium and porous TCP/HA-coated CP titanium. After incubation of HGFs on these substrates, the number of attached cell, the area of cell spreading, immunostained ECM including fibronectin (FN) and type I collage, and vinculin (presenting the formation of focal adhesion plaque) were quantified by morphometric analysis using immunofluorescence microscope.</p><p><b>RESULTS</b>TCP/HA and HA coatings exhibited that the attached cell number and cell spreading area were greater than those of CP titanium (P < 0.05), and the formation of focal adhesion plaque was earlier than that of uncoated substrate (P < 0.05). The number of attached cell and the formation of type I collagen on TCP/HA were more than those on Ti and HA. After 24-hour incubation on TCP/HA surface, the number of attached cell was 198.1 +/- 27.7 and the fluorescent intensity of type I collagen was 154.10 +/- 31.56. While under the same condition, the corresponding numbers for the CP titanium were 125.1 +/- 29.9 and 132.63 +/- 35.26. The differences between the two groups were significant (P < 0.05).</p><p><b>CONCLUSIONS</b>In this study, the porous TCP/HA coating significantly facilitated the adherence of human gingival fibroblasts to Ti surface and could improve the biocompatibility of titanium.</p>

Effect of nano-hydroxyapatite/collagen composite and bone morphogenetic protein-2 on lumbar intertransverse fusion in rabbits / 中华创伤杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the effect of nano-hydroxyapatite/collagen (nHA/collagen) composite as a graft extender and enhancer when combined with recombinant human bone morphogenetic protein-2 (rhBMP-2) on lumbar intertransverse fusion in rabbits.</p><p><b>METHODS</b>Sixty-four adult female New Zealand white rabbits, aged 1 year and weighing 3.5-4.5 kg, underwent similar posterolateral intertransverse process arthrodesis and were randomly divided into 4 groups based on different grafts: autogenous cancellous bone alone (ACB group), nHA/collagen alone (HAC group), half autogenous cancellous bone and half nHA/collagen (ACB+HAC group) and nHA/collagen combined with rhBMP-2 (HAC+BMP group). The fusion masses were analyzed by manual palpation, radiography, biomechanical testing and histological examination.</p><p><b>RESULTS</b>Fusion was observed in 4 cases in the 6th week and in 5 cases in the 10th week after surgery in ACB group. No case showed fusion in HAC group. In ACB+HAC group, there was fusion in 3 cases in the 6th week and in 4 cases in the 10th week after surgery. In HAC+BMP group, fusion in 1 case was found in the 4th week, in 5 cases in the 6th week and in 6 cases in the 10th week after surgery. It suggested that ACB, ACB+HAC and HAC+BMP groups showed similar fusion ratio and mechanical strength in the 6th and 10th week after surgery. According to the microstructure analysis of the samples, nHA/collagen had no negative effect when implanted together with ilium autograft. In HAC+BMP group, new bone-like tissue was observed in the 2nd week postoperatively, and nearly all of the implanted composites were replaced by mature bone matrix and new bones in 10th week postoperatively.</p><p><b>CONCLUSIONS</b>The nHA/collagen, especially combined with rhBMP-2, is a promising bone substitute, for it has quick biodegradation, fine bone-bending ability, and high osteoconductivity on posterolateral spinal fusion in rabbits.</p>

Mineralized collagen based composite for bone tissue engineering / 中国医学科学院学报

<p><b>OBJECTIVE</b>To construct a mineralized collagen based composite by biomimetic synthesis for bone tissue engineering.</p><p><b>METHODS</b>Using the molecular collagen as the template, the calcium phosphate is deposited on it to produce a mineralized collagen based composite, then is combined with minute amount of poly lactic acid (PLA), the three-dimensional scaffold composite is prepared by liquid phase separation. Using osteoblast culture technique, the biocompatibility of this biomaterial in vitro is detected by x-ray diffraction, SEM, TEM, fluoroscopy and CLSM.</p><p><b>RESULTS</b>Both degree and the size of crystals in the composite are low, which are similar to that of nature bone. It possesses porous structure and the porosity of the composite is high. The typical fibrillar microstructure is self-assembled of the collagen and the nano-crystal hydroxyapatite (HA) in the composite, moreover, the x-ray diffraction graphic of HA crystal shows the [002]-oriented.</p><p><b>CONCLUSIONS</b>The biomimetic three-dimensional composite can serve as one of the optimal scaffold material for bone tissue engineering both on structure and on property.</p>

Nano-hydroxyapatite/collagen composite for bone repair / 中国医学科学院学报

<p><b>OBJECTIVE</b>To develop nano-hydroxyapatite/collagen (NHAC) composite and test its ability in bone repairing.</p><p><b>METHODS</b>NHAC composite was developed by biomimetic method.</p><p><b>RESULTS</b>The composite showed some features of natural bone in both composition and microstructure. The minerals could contribute to 50% by weight of the composites in sheet form. The inorganic phase in the composite was carbonate-substituted hydroxyapatite (HA) with low crystallinity and nanometer size. HA precipitates were uniformly distributed on the type I collagen matrix without preferential orientation. The composite exhibited an isotropic mechanical behavior. However, the resistance of the composite to localized pressure could reach the lower limit of that of femur compacta. The tissue response to the NHAC composite implanted in marrow cavity was investigated. Knoop micro-hardness test was performed to compare the mechanical behavior of the composite and bone. At the interface of the implant and marrow tissue, solution-mediated dissolution and macrophage-mediated resorption led to the degradation of the composite, followed by interfacial bone formation by osteoblasts. The process of implant degradation and bone substitution was reminiscent of bone remodeling.</p><p><b>CONCLUSION</b>The composite can be incorporated into bone metabolism instead of being a permanent implant.</p>