Evaluation of bone matrix and demineralized bone matrix incorporated PLGA matrices for bone repair

The aim of this study was to evaluate the composite matrices prepared using Poly(lactic-co-glycolic acid)- PLGA (85:15) by incorporating human bone matrix (BM) powder or demineralized bone matrix (DBM) powder with the weight ratio of polymer: BM or DBM (75:25) to apply for bone repair. Murine Bone Marrow Stromal Cell (BMSC) attachment was studied with different time points at 30 min, 1 h, 2 h, 4 h, and 6 h for BM/PLGA, DBM/PLGA and PLGA control matrices. All types of matrices were linearly increased the BMSC attachment with the increase of time. Significantly higher number of BMSCs was attached to the both BM/PLGA and DBM/PLGA matrices after 2 h compared to the controls. If BM or DBM is incorporated into biodegradable PLGA matrices and cultured with BMSCs, those composite matrices could be potentially used for bone tissue engineering applications. In addition, particle migration and handling difficulties in DBM powder in clinical applications eliminate using a PLGA matrix. Furthermore, we have observed that DBM/PLGA matrices were structurally stronger compared to the BM/PLGA or control PLGA matrices when they exposed to physiological environment for 72 days.     

Use of an osteoinductive biomaterial as a bone morphogenetic protein carrier

A porous calcium phosphate ceramic, which induced bone formation in soft tissues of dogs, was termed as osteoinductive biomaterial and studied as a carrier of bone morphogenetic protein (rhBMP-2). Cylinder implants (ø 4×5 mm) impregnated with 0, 1, 10 and 40 g rhBMP-2 were implanted in dorsal muscles of rabbits for five weeks. Histological observation and histomorphometric analysis were performed on thin un-decalcified sections. No bone formation was detected in the implants without rhBMP-2, while mature lamellar bone was found inside the implants with 1 g rhBMP-2, both on the outer surface and inside the implants with 10 g and 40 g rhBMP-2. Little difference in formed bone was found between 1 g and 10 g rhBMP-2, but no difference was found between 10 g and 40 g rhBMP-2. A significant difference in bone marrow formation was found among 1, 10 and 40 g rhBMP-2. The more rhBMP-2, the more bone marrow formed. The present results indicate that osteoinductive biomaterial is a good carrier of BMP and high dose of BMP is not necessary for bone formation in clinic. © 2001 Kluwer Academic Publishers     

Restoration of mandibular bone defects with demineralized bone matrix combined with three-dimensional cultured bone marrow-derived mesenchymal stem cells in minipig models

Mandibular defects, caused by congenital, pathological or iatrogenic insults, can significantly affect patient quality of life. The reconstruction of mandible has recently gained the interest of clinical and tissue engineering researchers. The purpose of this study was to evaluate the effectiveness of three-dimensional (3-D) cultured autologous grafts prepared using bone marrow-derived mesenchymal stem cells (BMSCs) combined with demineralized bone matrix (DBM) scaffolds for the restoration of mandibular defects. Cylindrical defects were created in the mandibular body of minipigs and filled with 3D-cultured BMSCs/DBM autografts, 2D-cultured BMSCs/DBM autografts, DBM material (without cells), or were left unfilled (blank). Using computed tomographic (CT) imaging and histological staining, we found that treatment of mandibular defects using 3-D cultured BMSCs/DBM autografts offered improvements in bone formation over both 2-D cultured autografts and cell-free DBM scaffolds. We found increased osteoid formation in 3D and 2D cultures, with more osteogenic cells present in the 3D constructs. We suggest that 3-D cultured homograft BMSCs combined with DBM scaffolds represents a new strategy for bone reconstruction, with potential future clinical applicability.     

Loading of VEGF to the heparin cross-linked demineralized bone matrix improves vascularization of the scaffold

Deficient vascularization is one of the prominent shortcomings of porous tissue-engineering scaffolds, which results in insufficient oxygen and nutrients transportation. Here, heparin cross-linked demineralized bone matrices (HC-DBM) pre-loaded with vascular endothelial growth factor (VEGF) were designed to promote cells and new microvessels invasion into the matrices. After being chemical crosslinked with heparin by N-hydroxysuccinimide and N-(3-di-methylaminopropyl)-N’-ethylcarbodiimide, the scaffold could bind more VEGF than the non-crosslinked one and achieve localized and sustained delivery. The biological activity of VEGF binding on heparinized collagen was demonstrated by promoting endothelial cells proliferation. Evaluation of the angiogenic potential of heparinized DBM loaded with VEGF was further investigated by subcutaneous implantation. Improved angiogenesis of heparinized DBM loaded with VEGF was observed from haematoxylin-eosin staining and immunohistochemistry examination. The results demonstrated that heparin cross-linked DBM binding VEGF could be a useful strategy to stimulate cells and blood vessels invasion into the scaffolds.     

Enhanced micro-vibration sensitive high-damping capacity and mechanical strength achieved in Al matrix composites reinforced with garnet-like lithium electrolyte

A novel micro-vibration sensitive-type high-damping Al matrix composites reinforced with Li_7-xLa₃Zr_2-xNb _x O₁₂ (LLZNO, x = 0.25) was designed and prepared using an advanced spark plasma sintering (SPS) technique. The damping capacity and mechanical properties of LLZNO/Al composites (LLZNO content: 0-40 wt.%) were found to be greatly improved by the LLZNO addition. The maximum damping capacity and the ultimate tensile strength (UTS) of LLZNO/Al composite can be respectively up to 0.033 and 101.2 MPa in the case of 20 wt.% LLZNO addition. The enhancement of damping and mechanical properties of the composites was ascribed to the intrinsic high-damping capacity and strengthening effects of hard LLZNO particulate. This investigation provides a new insight to sensitively suppress micro-vibration of payloads in the aerospace environment.     

Enhanced TOF-SIMS imaging of a micropatterned protein by stable isotope protein labeling

Patterning of biomolecules on surfaces is an increasingly important technological goal. Because the fabrication of biomolecule arrays often involves stepwise, spatially resolved derivatization of surfaces, spectroscopic imaging of these arrays is important in their fabrication and optimization. Although imaging time-of-flight secondary ion mass spectrometry (TOF-SIMS) is a powerful method for spatially resolved surface analysis, TOF-SIMS images of micropatterned proteins on organic substrates can be difficult to acquire, because of the lack of high intensity, protein-specific molecular ions that are essential for imaging under static conditions. In contrast, low-mass ions are of suitable intensity for imaging, but can originate from different chemical species on the surface. A potential solution to this problem is to utilize stable isotope labeled proteins, an approach that has heretofore not been explored in TOF-SIMS imaging of micropatterned proteins and peptides. To investigate the feasibility of stable isotope enhanced TOF-SIMS imaging of proteins, we synthesized 15N-labeled streptavidin by labeling of the protein during expression from a recombinant gene. The spatial distribution of streptavidin bound to biotin micropatterns, fabricated on a polymer and on a self-assembled monolayer on gold, was imaged by TOF-SIMS. Imaging of high-intensity, low-m/z secondary ions (e.g., C15N-) unique to streptavidin enabled unambiguous spatial mapping of the micropatterned protein with a lateral resolution of a few micrometers. TOF-SIMS imaging of micropatterned 15N-labeled streptavidin also illustrated the exquisite sensitivity of TOF-SIMS to low fractional coverage of protein (5 A effective thickness) in the background regions of the protein micropattern.     

Bioglass as a carrier for reindeer bone protein extract in the healing of rat femur defect

Bioactive glasses have been developed as scaffolds for bone tissue engineering but combination with reindeer bone protein extract has not been evaluated. We investigated the effects of bone protein extract implants (5–40 mg dosages) with bioglass (BG) carrier on the healing of rat femur defects. Bioglass implants and untreated defects served as controls. All doses of extract increased bone formation compared with the control groups, and bone union was enhanced with doses of 10 mg or more. In comparison with untreated defect, mean cross-sectional bone area at the defect site was greater when implants with BG + 15 mg of extract or bioglass alone were used, bone density at the defect site was higher in all bioglass groups with and without bone extract, and the BG + 15 mg extract dosage marginally increased bone torsional stiffness in mechanical testing. Bioglass performed well as a carrier candidate for reindeer bone protein extract.     

Enhanced water-solubility of Licorice extract microparticle prepared by antisolvent precipitation process

In this study, Licorice extract (LE) microparticles were successfully prepared using antisolvent precipitation process. Ethyl acetate and dimethyl sulfoxide, were used as the antisolvent and solvent, respectively. By means of orthogonal experimental design, the influences of several process parameters on the mean particle size (MPS) were investigated. The concentration range of the LE solution, the volume ratio of solvent to antisolvent, dripping speed, and temperature were 4.3–34.5 mg/mL, 1:1–1:12, 1–10 mL/min, and 20–35 °C, respectively. Based on the above orthogonal experiments, the optimum antisolvent precipitation process conditions were found to be: temperature 20 °C, concentration of the LE solution 17.2 mg/mL, volume ratio of solvent to antisolvent 1:4, dripping speed 10 mL/min. The LE microparticles were characterized by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform-infrared (FT-IR) spectroscopy, thermal gravimetric analysis (TG), differential scanning calorimetry (DSC), HPLC analysis and dissolution test. And the morphology, crystalline state and chemical structure, drug purity, dissolution rate and bioavailability of LE microparticles were investigated. Under optimum antisolvent precipitation process conditions, the MPS of LE microparticles reached to 85.3 nm, and with uniform distribution. And the LE microparticles had the same chemical structure as the unprocessed drug, but the crystallinity was reduced, purity was increased. Furthermore, the water solubility increased from 4.82 mg/mL to 16.10 mg/mL, and bioavailability is increased by 64.36%.     

Enhanced damping capacity of ferromagnetic Fe-Ga alloys by introducing structural defects

The irreversible motion of magnetic domain walls in ferromagnets can dissipate a large portion of the elastic energy,and the associated damping capacity is proportional to the magnetostriction constant.In contrast,here we found that the damping capacity of the large magnetostriction Fe-Ga alloys can be enhanced by 2-3 times through introducing structural defects including interfacial dislocations and stacking faults,despite that these defects deteriorate the magnetostriction.These structural defects were introduced by aging the BCC(body-centered-cubic)solution-treated precursor,for which the formation of mechanically harder FCT(face-centered-tetragonal)and/or FCC(face-centered-cubic)phases can result in high-density partial dislocations at the semi-coherent phase interfaces and quasi-periodically stacked nano-layer substructure inside the FCC variants.The structural defects act as extra damping sources besides the magnetic domain walls because the structural accommodation of the semi-coherent phase interfaces between BCC and FCT/FCC nanoprecipitates with different elastic moduli and the nano-layer substructure towards long-range ordered periodical stacking can dissipate a large portion of mechanical energy.These findings suggest that introducing structural defects provides fresh freedom to design high damping ferromagnetic materials.     

Preparation and evaluation of osteoinductive porous biphasic calcium phosphate granules obtained from eggshell for bone tissue engineering

The synthetic bone graft substitutes currently used clinically are osteoconductive but not osteoinductive; their low success rate is thus their biggest disadvantage. The use of biomass raw materials for synthesizing calcium phosphate has gradually attracted increased research attention. In this study, hydroxyapatite powder was prepared through liquid-phase precipitation from eggshell, and porous biphasic calcium phosphate granules (EBGs) were then obtained using a pore former and sintering procedure. The EBGs were discovered to have high biocompatibility and no cytotoxicity. The results of animal experiments showed that the area of new bone growth was high, numerous Haversian canals could be observed, and almost all EBGs were surrounded by new bone tissue, which proved that the EBGs had excellent osteoinductivity. By contrast, numerous fat cells were found in the femoral defect area when a commercial bone graft was employed. Various biological inorganic ions (Mg, Sr, Na, and Fe) originally in the eggshell raw materials were incorporated into the EBGs, and the EBGs exhibited excellent osteogenic abilities. The developed approach provides an economical and feasible solution for the treatment of bone defects.     

Enhanced repair of a critical-sized segmental bone defect in rabbit femur by surface microstructured porous titanium

Repair of load-bearing bone defects remains a challenge in the field of orthopaedic surgery. In the current study, a surface microstructured porous titanium (STPT) successively treated with H₂O₂/TaCl₅ solution and simulated body fluid was used to repair the critical-sized segmental bone defects in rabbit femur, and non-treated porous titanium (NTPT) and porous biphasic calcium phosphate ceramics (PBCP) were used as control, respectively. A 15 mm long implant was positioned in the femoral defect and stabilized by a plate and screws fixation. After implantation into the body for 1, 3 and 6 months, X-ray observation confirmed that porous titanium groups (NTPT and STPT) provided better mechanical support than PBCP group at the early stage. However, there was no obvious difference in the formed bony callus between PBCP and STPT groups in the later stage, and they both showed better shape of bony callus than NTPT group. Micro-CT and histomorphometric analysis for the samples of 6-month implantation demonstrated that more new bone formed in the inner pores of PBCP and STPT groups than that in NTPT group. Moreover, the biomechanical tests revealed that STPT group could bear larger compressive load than NTPT and PBCP groups, almost reaching the level of the normal rabbit femur. STPT exhibited the enhanced repairing effect on the critical-sized segmental bone defect in rabbit femur, meaning that it could be an ideal material for the repair of large bone defect in load-bearing site.     

6061铝颗粒层增强7075铝基复合材料的微观结构及阻尼性能

采用热轧法制备出具有颗粒层状结构的6061p/7075铝基复合材料以改善7075铝合金的阻尼性能。通过OM、SEM、EDS和XRD分析6061p/7075层状铝基复合材料的微观组织,分别采用万能力学试验机和动态热机械分析仪分析其力学性能和阻尼行为。研究表明,6061铝颗粒层存在大量的颗粒间界面和微小孔隙,6061铝颗粒层与7075铝基体之间界面结合良好,没有发生界面反应;6061p/7075层状铝基复合材料最大抗拉强度为370.5 MPa,比7075铝基体提高了30%;6061p/7075层状铝基复合材料和基体材料的内耗值分别随着温度和应变量的升高而增大,复合材料的阻尼性能明显优于7075铝基体,在360℃时,复合材料的内耗值高达0.117,比7075铝基体提高了149%;6061p/7075层状铝基复合材料和基体材料的储能模量分别随着温度和应变量的升高而降低,在30℃时,复合材料的储能模量为38601 MPa,比7075铝基体高16%。      

In-capillary protein enrichment and removal of nonbuffering salts using capillary electrophoresis with discontinuous buffers

Salt is abundant in biological samples and can cause problems in capillary electrophoresis (CE) due to excessive Joule heating and electrodispersion. Desalting with solid phase minibeds is currently most compatible with the small sample volumes of CE. They are however difficult to prepare and suffer from poor bed-to-bed reproducibility. Alternatively, enrichment of proteins and peptides was developed using CE, by trapping them at their isoelectric points with a discontinuous buffer of mismatched pH. Ionic salts, such as sodium chloride, do not possess isoelectric points and therefore are not retained by the discontinuous buffer. In this work, the removal of ionic salt during protein enrichment using CE with discontinuous buffers was investigated. Nonbuffering ions were found to electromigrate through the pH junction without disrupting the enrichment process and were eventually removed from the capillary. Mass spectral data obtained from the enriched and desalted sample confirmed a significant signal enhancement. Finally, a strong acid was introduced to remove the pH junction and thus facilitated a subsequent capillary zone electrophoresis separation. An integrated procedure of enrichment, desalting, and separation was demonstrated on a mixture of three protein standards.     

Enhanced tensile properties of aluminium matrix composites reinforced with graphene encapsulated SiC nanoparticles

Due to a high propensity of nano-particles to agglomerate, making aluminium matrix composites with a uniform dispersion of the nano-particles using liquid routes is an exceptionally difficult task. In this study, an innovative approach was utilised to prevent agglomeration of nano-particle by encapsulating SiC nano-particles using graphene sheets during ball milling. Subsequently, the milled mixture was incorporated into A356 molten alloy using non-contact ultrasonic vibration method. Two different shapes for graphene sheets were characterised using HRTEM, including onion-like shells encapsulating SiC particles and disk-shaped graphene nanosheets. This resulted in 45% and 84% improvement in yield strength and tensile ductility, respectively. The former was ascribed to the Orowan strengthening mechanism, while the latter is due primarily to the fiber pull-out mechanism, brought about by the alteration of the solidification mechanism from particle pushing to particle engulfment during solidification as a consequence of high thermal conductive graphene sheets encapsulating SiC particles.     

Regeneration of critical bone defects with anionic collagen matrix as scaffolds

The aim of this study was to make a histomorphometric evaluation of the osteogenic potential of anionic collagen matrix as scaffolds; either crosslinked in glutaraldehyde or not cross-linked and, implanted in critical bone defects in rat calvaria. Seventy-two rats were randomly distributed in three groups: anionic collagen scaffolds treated for 24 h of selective hydrolysis (ACSH); anionic collagen scaffolds treated for 24 h of selective hydrolysis and 5 min of crosslinking in glutaraldehyde 0.05 % (ACSHGA); empty bone defect (Control), evaluated at the biological points of 15, 45, 90 and 120 days. The results showed that the biomaterials implanted were biocompatible and showed a high osteogenic potential. These biomaterials presented a speed of biodegradation compatible with bone neoformation, which was shown to be associated with angiogenesis inside the scaffolds at all biological points. The percentage of mineralization of ACSH (87 %) differed statistically from that found in ACSHGA (66 %). It was concluded that the regeneration of critical bone defect was more evident in anionic collagen without crosslinking (ACSH).     

Enhanced and tunable fluorescent quantum dots within a single crystal of protein

The design and synthesis of bio-nano hybrid materials can not only provide new materials with novel properties, but also advance our fundamental understanding of interactions between biomolecules and their abiotic counterparts. Here, we report a new approach to achieving such a goal by growing CdS quantum dots （QDs） within single crystals of lysozyme protein. This bio-nano hybrid emitted much stronger red fluorescence than its counterpart without the crystal, and such fluorescence properties could be either enhanced or suppressed by the addition of Ag（I） or Hg（II）, respectively. The three-dimensional incorporation of CdS QDs within the lysozyme crystals was revealed by scanning transmission electron microscopy with electron tomography. More importantl~ since our approach did not disrupt the crystalline nature of the lysozyme crystals, the metal and protein interactions were able to be studied by X-ray crystallography, thus providing insight into the role of Cd（II） in the CdS QDs formation.     

Enhanced strength and excellent transport properties of a superaligned carbon nanotubes reinforced copper matrix laminar composite

Superaligned carbon nanotube (SACNT) reinforced copper matrix laminar composites have been fabricated by means of the traditional copper sulfate electroplating process. The mechanical properties and transport properties of the Cu/SACNT composites with different SACNT content have been studied systematically, and the experimental results show that the as-prepared composites possess a better comprehensive performance than pure copper. The simple rule of mixtures (ROM) has been used to estimate the potential maximum properties of the Cu/SACNT composites. The Cu/SACNT composite is considered to be a promising material for electronics and communications applications.     

Printable and flexible macroporous organosilica film with high protein adsorption capacity

An approach for creating a flexible and macroporous silsesquioxane film using phase separation method is described. The porous film was prepared by a simple coating method where sol-gel solution containing polyacrylic acid (PAA) and 1,6-bis(trimethoxysilyl)hexane in water was applied on boehmite silica coated polymethylmethacrylate (PMMA) film. After drying, the water soluble PAA template was removed by washing the film with water revealing the porous film. With certain ratios of PAA and water, fully co-continuous pore system with open surface was obtained. Porous films with 3-4 μm thickness were found to be highly flexible. The biocompatibility of the porous film was tested by immobilizing a high affinity biotin-binding chimeric avidin (ChiAVD(I117Y)) into the porous matrix The porous film was found to adsorb higher amounts of functional chimeric avidin compared to the pure PMMA film or a boehmite silica coated PMMA film.