共查询到20条相似文献,搜索用时 10 毫秒
1.
Oliveira JT Crawford A Mundy JM Moreira AR Gomes ME Hatton PV Reis RL 《Journal of materials science. Materials in medicine》2007,18(2):295-302
In the present work we originally tested the suitability of corn starch-polycaprolactone (SPCL) scaffolds for pursuing a cartilage
tissue engineering approach. Bovine articular chondrocytes were seeded on SPCL scaffolds under dynamic conditions using spinner
flasks (total of 4 scaffolds per spinner flask using cell suspensions of 0.5 × 106 cells/ml) and cultured under orbital agitation for a total of 6 weeks. Poly(glycolic acid) (PGA) non-woven scaffolds and
bovine native articular cartilage were used as standard controls for the conducted experiments. PGA is a kind of standard
in tissue engineering approaches and it was used as a control in that sense. The tissue engineered constructs were characterized
at different time periods by scanning electron microscopy (SEM), hematoxylin-eosin (H&E) and toluidine blue stainings, immunolocalisation
of collagen types I and II, and dimethylmethylene blue (DMB) assay for glycosaminoglycans (GAG) quantification assay. SEM
results for SPCL constructs showed that the chondrocytes presented normal morphological features, with extensive cells presence
at the surface of the support structures, and penetrating the scaffolds pores. These observations were further corroborated
by H&E staining. Toluidine blue and immunohistochemistry exhibited extracellular matrix deposition throughout the 3D structure.
Glycosaminoglycans, and collagen types I and II were detected. However, stronger staining for collagen type II was observed
when compared to collagen type I. The PGA constructs presented similar features to SPCL at the end of the 6 weeks. PGA constructs
exhibited higher amounts of matrix glycosaminoglycans when compared to the SPCL scaffolds. However, we also observed a lack
of tissue in the central area of the PGA scaffolds. Reasons for these occurrences may include inefficient cells penetration,
necrosis due to high cell densities, or necrosis related with acidic by-products degradation. Such situation was not detected
in the SPCL scaffolds, indicating the much better biocompatibility of the starch based scaffolds. 相似文献
2.
S. Zeytin B. A. Konduk M. Ipek C. Bindal A. H. Ucisik 《Materials science & engineering. C, Materials for biological applications》2002,20(1-2):219-222
In this study, we investigated stress relaxation behavior of the human articular cartilage on femoral head. Articular cartilage is a white dense connective tissue that covers the bone ends within diarthrodial joints and works as a weight-transmitting and energy-absorbing material. Human articular cartilage on femoral head was used as test material. Relaxation tests were carried out by using the indentation technique via Instron Universal Testing Machine. Test materials were investigated in an isotonic salt solution at 37 °C. To keep the temperature constant, two vessels being in each other were utilized. Thus, hot water was circulated in the outer vessel and isotonic salt solution was kept in the inner vessel. Experimental results showed that there is a remarkable difference between normal and degenerated cartilage for the same age and sex. It was observed that the relaxation percent of normal cartilage as a function of relaxation time is much higher than that of degenerated cartilage. 相似文献
3.
Feng Li Yonglin Su Jianping Wang Gang Wu Chengtao Wang 《Journal of materials science. Materials in medicine》2010,21(1):147-154
Many biomaterials are being developed to be used for cartilage substitution and hemiarthroplasty implants. The lubrication
property is a key feature of the artificial cartilage. The frictional behavior of human articular cartilage, stainless steel
and polyvinyl alcohol (PVA) hydrogel were investigated under cartilage-on-PVA hydrogel contact, cartilage-on-cartilage contact
and cartilage-on-stainless steel contact using pin-on-plate method. Tests under static load, cyclic load and 1 min load change
were used to evaluate friction variations in reciprocating motion. The results showed that the lubrication property of cartilage-on-PVA
hydrogel contact and cartilage-on-stainless steel contact were restored in both 1 min load change and cyclic load tests. The
friction coefficient of PVA hydrogel decreased from 0.178 to 0.076 in 60 min, which was almost one-third of the value under
static load in continuous sliding tests. In each test, the friction coefficient of cartilage-on-cartilage contact maintained
far lower value than other contacts. It is indicated that a key feature of artificial cartilage is the biphasic lubrication
properties. 相似文献
4.
Chun-Hsien Wu Chih-Sheng Ko Jia-Wen Huang Hsin-Jie Huang I-Ming Chu 《Journal of materials science. Materials in medicine》2010,21(2):725-729
Cartilage extracellular matrix (ECM) is composed primarily of type II collagen (COL II) and large, networks of proteoglycans
(PGs) that contain glycosaminoglycans such as hyaluronic acid (HA) and chondroitin sulfate (CS). Since cartilage shows little
tendency for self-repair, injuries are kept unhealed for years and can eventually lead to further degeneration. During the
past decades, many investigations have pursued techniques to stimulate articular cartilage repair or regeneration. The current
study assessed the effects of exogenous glycosaminoglycans (GAGs) including CS-A, CS-B, CS-C, heparan sulfate and HA, administration
on human chondrocytes in terms of proliferation and matrix synthesis, while the cells were seeded and grown on the genipin-crosslinked
collagen type II (COL II) scaffold. DNA content was measured by Hoechst dye intercalation, matrix deposition was evaluated
by DMMB dye. Expression of collagen II and aggrecan mRNAs was assessed by RT-PCR, followed by gel electrophoresis. In a 28-day
in vitro culture, administration of 5 μg/ml CS-A, 50 μg/ml CS-B, 50 μg/ml CS-C, 5 μg/ml HS, and 500 kDa HA led to significant
increase in biosynthesis rate of PGs. Gene expression of aggrecan and collagen II were upregulated by CS-A, CS-C and HA. These
results showed considerable relevance of GAGs to the issue of in vitro/ex vivo neo-cartilage synthesis for tissue engineering
and regenerative medical applications. 相似文献
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7.
Costa Martínez E Escobar Ivirico JL Muñoz Criado I Gómez Ribelles JL Monleón Pradas M Salmerón Sánchez M 《Journal of materials science. Materials in medicine》2007,18(8):1627-1632
Human articular chondrocytes were cultured in vitro on poly(L-lactic) acid, PLLA, substrates. Influence of the surface topography on cell morphology was found. Different surface microtopographies
were obtained on PLLA by crystallizing at 120 °C after nucleation treatments that include isothermal stages at temperatures
just below (55 °C) and just above (75 °C) the glass transition temperature (T
g
= 65 °C). Isothermal crystallization from the melt gave rise to big spherulites (approx. 50 μm diameter) with approx. 1 μm
depth. Crystallization after nucleation treatments results in smaller (approx. 5 μm)—difficult to distinguish—spherulites.
Cell viability was excellent and not affected by the surface roughness. Cell population on the nucleated samples resembles
the result of culture on the reference tissue culture polystyrene (TCPS). However, cells cultured on big spherulites (PLLA
isothermally crystallized without nucleation treatment) show a peculiar morphology, with a more isolated disposition and growth
oriented in a characteristic direction. 相似文献
8.
Li-Lan Gao Chun-Qiu ZhangLi-Min Dong Yun-Wei Jia 《Materials science & engineering. C, Materials for biological applications》2012,32(2):119-125
An optimized digital image correlation (DIC) technique was applied to investigate the depth-dependent nonlinear viscoelastic properties of articular cartilage and simultaneously the biphasic nonlinear viscoelastic relaxation model of cartilage was proposed and validated. The stress relaxation tests were performed with different strain levels and it is found that the initial stress and relaxed stress at any time increase with increasing strain levels. The depth-dependent strain of cartilage was obtained by analyzing the images acquired using the optimized DIC technique and moreover the inhomogeneous relaxation modulus distributions within the tissues were determined at different relaxation time points under strain of 11.35, 19.35 and 30% respectively. The strain rate dependent nonlinear stress and strain curves were obtained for articular cartilage through uniaxial compression tests. It is noted that the Young's modulus exhibits a slight increase near the cartilage surface, and then increases fast with depth and both the magnitude and the variation of the Young's modulus are affected by increasing strain rates. A biphasic nonlinear viscoelastic relaxation model was proposed to predict the depth-dependent relaxation behavior of cartilage under unconfined compression and the results show that there are good agreements between the experimental data and predictions. 相似文献
9.
10.
纳米级铁酸盐粉体材料合成的进展 总被引:25,自引:0,他引:25
本文综述了具有尖晶石结构的纳有铁酸盐(MFe2O4,M=Mn,Zn,Co,Ni,Cu等)的合成方法,其中包括:共沉淀法,水热法,溶胶-凝胶法,微乳液法,冲击波法以及本文作者最近发展的共沉淀催化相转化法等。这些方法合成的铁酸盐的粒径一般小于100nm,是当今合成的纳米级铁酸盐粉体的有效方法。 相似文献
11.
J. Antons M. G. M. Marascio J. Nohava R. Martin L. A. Applegate P. E. Bourban D. P. Pioletti 《Journal of materials science. Materials in medicine》2018,29(5):57
Emerging 3D printing technology permits innovative approaches to manufacture cartilage scaffolds associated with layer-by-layer mechanical property adaptation. However, information about gradients of mechanical properties in human articular cartilage is limited. In this study, we quantified a zone-dependent change of local elastic modulus of human femoral condyle cartilage by using an instrumented indentation technique. From the cartilage superficial zone towards the calcified layer, a gradient of elastic modulus values between 0.020?±?0.003?MPa and 6.44?±?1.02?MPa was measured. To validate the tissue quality, the histological tissue composition was visualized by glycosaminoglycan and collagen staining. This work aims to introduce a new protocol to investigate the zone-dependent mechanical properties of graded structures, such as human articular cartilage. From this knowledge, better cartilage repair strategies could be tailored in the future. 相似文献
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13.
Amanda J. Keown James J.-W. Lee Mark B. Bush 《Journal of materials science. Materials in medicine》2012,23(12):2847-2856
Despite the durability of human teeth, which are able to withstand repeated loading while maintaining form and function, they are still susceptible to fracture. We focus here on longitudinal fracture in molar teeth??channel-like cracks that run along the enamel sidewall of the tooth between the gum line (cemento-enamel junction??CEJ) and the occlusal surface. Such fractures can often be painful and necessitate costly restorative work. The following study describes fracture experiments made on molar teeth of humans in which the molars are placed under axial compressive load using a hard indenting plate in order to induce longitudinal cracks in the enamel. Observed damage modes include fractures originating in the occlusal region (??radial-median cracks??) and fractures emanating from the margin of the enamel in the region of the CEJ (??margin cracks??), as well as ??spalling?? of enamel (the linking of longitudinal cracks). The loading conditions that govern fracture behavior in enamel are reported and observations made of the evolution of fracture as the load is increased. Relatively low loads were required to induce observable crack initiation??approximately 100?N for radial-median cracks and 200?N for margin cracks??both of which are less than the reported maximum biting force on a single molar tooth of several hundred Newtons. Unstable crack growth was observed to take place soon after and occurred at loads lower than those calculated by the current fracture models. Multiple cracks were observed on a single cusp, their interactions influencing crack growth behavior. The majority of the teeth tested in this study were noted to exhibit margin cracks prior to compression testing, which were apparently formed during the functional lifetime of the tooth. Such teeth were still able to withstand additional loading prior to catastrophic fracture, highlighting the remarkable damage containment capabilities of the natural tooth structure. 相似文献
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15.
This contribution first presents a fatigue model to elaborate fatigue behavior of materials subjected to thermal mechanical effect. To calibrate the presented model, a valid experiment is then conducted on cement asphalt mortar. The model can be further extended to other materials and valid experimental data from literature is utilized for verification. Results suggested the model is sufficient to describe thermo-mechanical fatigue behavior of cement-based materials, under the condition that no phase or morphological change occurred in the fatigue temperature range. Finally, the developed model is applied to predict fatigue life of one current track. 相似文献
16.
Omar Mertins Maria I.Z. Lionzo Yasmine M.S. Micheletto Adriana R. Pohlmann Nádya Pesce da Silveira 《Materials science & engineering. C, Materials for biological applications》2009,29(2):463-469
Two distinct supramolecular self assemblies of phosphatidylcholine and chitosan, namely liposomes and their precursory organogel, have been investigated by means of SAXS, Light Scattering and Polarized Optical Microscopy. The main goal was the evaluation of the chitosan effect on the self assemblies phase transition behavior upon heating. A distinct smectic organization was observed for the organogel prepared in the presence of chitosan, if compared to that prepared only with phosphatidylcholine. In addition, the phosphatidylcholine–chitosan organogel showed unchanged optical properties upon heating and after 24 h, indicating increased stability when compared to the organogel prepared without chitosan. For the liposomes containing chitosan, the thermotropic behavior features a lamellar pattern that is preserved under heating, until at least 81 °C. A phase transition temperature has been determined around 64 °C, which was clearly higher than that observed for liposomes prepared without chitosan. The bilayer repeat distance typical of the liposomes increases slowly by increasing the temperature and stacking fluctuations of the bilayers are delayed due to enhancement of the membrane rigidity. 相似文献
17.
K. C. Aw N. Tjitra Salim Hui Peng Lijuan Zhang J. Travas-Sejdic W. Gao 《Journal of Materials Science: Materials in Electronics》2008,19(10):996-999
Polyaniline (PANI) nanotubes configured as a field effect transistor (FET) exhibits a p–n junction diode behavior. The forward-bias
current can be modulated by a gate voltage; turning on at negative gate voltage and turning off at positive gate voltage.
An energy band diagram model has been proposed to explain the rectifying effect of the PANI nanotubes FET (PNT-FET). All the
four different forward bias conduction mechanisms of a typical p–n junction diode can be identified for this PNT-FET using
a semi-log graph to confirm this resemblance. 相似文献
18.
A devitrification procedure by annealing was applied to a multicomponent Fe-based metallic glass in order to obtain nanocrystalline materials. Phase composition and phase morphology were strongly dependent on the annealing conditions. An elevated temperature mechanical behavior of nanostructures was evaluated by tensile testing. A strong effect of phase morphology on the mechanical response of the material was revealed. A most attractive combination of strength and plasticity was observed in the nanostructure with approximately equal grain sizes of crystallized phases. 相似文献
19.
The surface effect from surface stress and surface elasticity on the elastic behavior of nanowires in static bending is incorporated into Euler-Bernoulli beam theory via the Young-Laplace equation. Explicit solutions are presented to study the dependence of the surface effect on the overall Young's modulus of nanowires for three different boundary conditions: cantilever, simply supported, and fixed-fixed. The solutions indicate that the cantilever nanowires behave as softer materials when deflected while the other structures behave like stiffer materials as the nanowire cross-sectional size decreases for positive surface stresses. These solutions agree with size dependent nanowire overall Young's moduli observed from static bending tests by other researchers. This study also discusses possible reasons for variations of nanowire overall Young's moduli observed. 相似文献
20.
Viscoelastic behavior of nano-hydroxyapatite reinforced poly(vinyl alcohol) gel biocomposites as an articular cartilage 总被引:1,自引:0,他引:1
Nanohydroxyapatite reinforced poly(vinyl alcohol) gel (nano-HA/PVA gel) composites has been proposed as an articular cartilage
repair biomaterial. In this paper, nano-HA/PVA gel composites were prepared by in situ synthesis nano-HA particles in PVA
solution and accompanied with freeze/thaw method. The influence of nano-HA content, PVA concentration, test frequency and
freeze/thaw cycle times on the viscoelastic behavior of nano-HA/PVA gel composites were evaluated using dynamic mechanical
thermal analysis (DMTA). The results showed that both storage modulus and loss modulus firstly increased and then presented
decreasing trend with the rise of nano-HA content. Their maximum values were obtained while nano-HA content was 6%. Furthermore,
the G′ and G″ of the composites improve with the increase of PVA concentrations and freeze/thaw cycle times. This effect was more distinct
at low freeze/thaw cycles. The phase angle (tan δ) of the pure PVA gel is larger than that of the nano-HA/PVA composites at
the test frequency spectra, but all the phase angle values of the tested composites were close to that of nature bone. 相似文献