共查询到20条相似文献,搜索用时 31 毫秒
1.
Schofer MD Boudriot U Wack C Leifeld I Gräbedünkel C Dersch R Rudisile M Wendorff JH Greiner A Paletta JR Fuchs-Winkelmann S 《Journal of materials science. Materials in medicine》2009,20(3):767-774
The aim of this study was to compare biological collagen I (ColI) and synthetic poly-(l-lactide) (PLLA) nanofibers concerning their stability and ability to promote growth and osteogenic differentiation of human
mesenchymal stem cells in vitro. Matrices were seeded with human stem cells and cultivated over a period of 28 days under
growth and osteoinductive conditions and analyzed during the course. During this time the PLLA nanofibers remained stable
while the presence of cells resulted in an attenuation of the ColI nanofiber mesh. Although there was a tendency for better
growth and osteoprotegerin production of stem cells when cultured on collagen nanofibers, there was no significant difference
compared to PLLA nanofibers or controls. The gene expression of alkaline phosphate, osteocalcin and collagen I diminished
in the initial phase of cultivation independent of the polymer used. In the case of PLLA fibers, this gene expression normalized
during the course of cultivation, whereas the presence of collagen nanofibers resulted in an increased gene expression of
osteocalcin and collagen during the course of the experiment. Taken together the PLLA fibers were easier to produce, more
stable and did not compromise growth and differentiation of stem cells over the course of experiment. On the other hand, collagen
nanofibers supported the differentiation process to some extent. Nevertheless, the need for fixation as well as the missing
stability during cell culture requires further work. 相似文献
2.
Schofer MD Veltum A Theisen C Chen F Agarwal S Fuchs-Winkelmann S Paletta JR 《Journal of materials science. Materials in medicine》2011,22(7):1753-1762
Mesenchymal stem cell differentiation of osteoblasts is triggered by a series of signaling processes including integrin and
bone morphogenetic protein (BMP), which therefore act in a cooperative manner. The aim of this study was to analyze whether
these processes can be remodeled in an artificial poly-(l)-lactide acid (PLLA) based nanofiber scaffold. Matrices composed of PLLA-collagen type I or BMP-2 incorporated PLLA-collagen
type I were seeded with human mesenchymal stem cells (hMSC) and cultivated over a period of 22 days, either under growth or
osteoinductive conditions. During the course of culture, gene expression of alkaline phosphatase (ALP), osteocalcin (OC) and
collagen I (COL-I) as well as Smad5 and focal adhesion kinase (FAK), two signal transduction molecules involved in BMP-2 or
integrin signaling were analyzed. Furthermore, calcium and collagen I deposition, as well as cell densities and proliferation,
were determined using fluorescence microscopy. The incorporation of BMP-2 into PLLA-collagen type I nanofibers resulted in
a decrease in diameter as well as pore sizes of the scaffold. Mesenchymal stem cells showed better adherence and a reduced
proliferation on BMP-containing scaffolds. This was accompanied by an increase in gene expression of ALP, OC and COL-I. Furthermore
the presence of BMP-2 resulted in an upregulation of FAK, while collagen had an impact on the gene expression of Smad5. Therefore
these different strategies can be combined in order to enhance the osteoblast differentiation of hMSC on PLLA based nanofiber
scaffold. By doing this, different signal transduction pathways seem to be up regulated. 相似文献
3.
Seyedjafari E Soleimani M Ghaemi N Sarbolouki MN 《Journal of materials science. Materials in medicine》2011,22(1):165-174
A new stem cell-scaffold construct based on poly-l-lactide (PLLA) nanofibers grafted with collagen (PLLA-COL) and cord blood-derived unrestricted somatic stem cells (USSC)
were proposed to hold promising characteristics for bone tissue engineering. Fabricated nanofibers were characterized using
SEM, ATR-FTIR, tensile and contact angle measurements. The capacity of PLLA, plasma-treated PLLA (PLLA-pl) and PLLA-COL scaffolds
to support proliferation and osteogenic differentiation of USSC was evaluated using MTT assay and common osteogenic markers
such as alkaline phosphatase (ALP) activity, calcium mineral deposition and bone-related genes. All three scaffolds showed
nanofibrous and porous structure with suitable physical characteristics. Higher proliferation and viability of USSC was observed
on PLLA-COL nanofibers compared to control surfaces. In osteogenic medium, ALP activity and calcium deposition exhibited the
highest values on PLLA-COL scaffolds on days 7 and 14. These markers were also greater on PLLA and PLLA-pl compared to TCPS.
Higher levels of collagen I, osteonectin and bone morphogenetic protein-2 were detected on PLLA-COL compared to PLLA and PLLA-pl.
Runx2 and osteocalcin were also expressed continuously on all scaffolds during induction. These observations suggested the
enhanced proliferation and osteogenic differentiation of USSC on PLLA-COL nanofiber scaffolds and introduced a new combination
of stem cell-scaffold constructs with desired characteristics for application in bone tissue engineering. 相似文献
4.
Huijun Lu Zhangqi Feng Zhongze Gu Changjian Liu 《Journal of materials science. Materials in medicine》2009,20(9):1937-1944
Tissue engineering holds great promise in providing vascular grafts as substitutes for damaged small-diameter blood vessels.
Two of the key factors in vascular tissue engineering are biocompatible scaffolds that mimic the effects of extracellular
matrix and the source of seeding cells. Synthetic poly-l-lactic acid (PLLA) nanofibers has been shown to be excellent scaffolds for tissue engineering. Outgrowth endothelial cells
(OECs) isolated from human peripheral blood could also be expanded in vitro and stably maintain the differentiated phenotypes
and could be used as the seeding cells for engineering autologous vascular crafts. Here we tested the possibility of combining
these two together. We found that PLLA nanofibers are not only biocompatible with OECs originally isolated from rabbit peripheral
blood, the aligned PLLA fibers actually promoted and guided their sustained proliferation. These results suggest that aligned
PLLA could be excellent both as the scaffolds and as a promoter of cell growth during vascular tissue engineering. 相似文献
5.
Chen Y Cho MR Mak AF Li JS Wang M Sun S 《Journal of materials science. Materials in medicine》2008,19(7):2563-2567
Biomimetic apatite/collagen composite coating, previously reported particularly with regard to its fabrication, characterization and interaction with osteoblast-like cells, has been investigated in this study to understand the response of human mesenchymal stem cells (hMSC) to such surface. PLLA films and PLLA films with apatite coating were compared with PLLA films with apatite/collagen composite coating. The hMSC morphology in response to such conditions was first observed using fluorescence microscopy. To further understand such cell-material interactions at a molecular level, integrin expression, actin assembly and vinculin-positive focal adhesion plaques were examined. Our results demonstrated that spreading of stem cells on the apatite/collagen composite surface was determined best among the three types of surfaces, followed by the apatite surface and then the PLLA control. Integrin expression on the apatite/collagen surface was higher than those on the apatite surface and PLLA surface. Immunostaining for vinculin and actin suggested that the composite coating on PLLA enhanced the formation of focal adhesion. 相似文献
6.
V. U. Unnikrishnan G. U. Unnikrishnan J. N. Reddy C. T. Lim 《Journal of Materials Science》2007,42(21):8844-8852
Theoretical analysis of Poly-(l)-Lactic Acid (PLLA) nanofibers is a necessary step towards designing novel biomedical applications. This paper aims to analyze
the mechanical properties of PLLA nanofibers so that optimal scaffolds in tissue engineering applications can be developed.
We carry out analysis of PLLA nanofibers to estimate the mechanical properties from basic building blocks to the nanofibrous
structures. A single PLLA nanofiber is made up of Shish–Kebab like fibrils intertwined together and can contain both amorphous
and crystalline phases. The elastic modulus of the Lactic acid monomeric formation in the crystalline phase is derived using
second-derivative of the strain energy using molecular dynamics simulation. The mechanical property of the Shish–Kebab fibril
is derived by homogenization. The fiber modulus is then obtained using the Northolt and van der Hout’s continuous chain theory.
One of the significant contributions in this paper is the use of modified continuous chain theory, where a combined multiscale
approach is used in the estimation of the mechanical properties of PLLA nanofibers. The theoretical results correlate well
with reported experimental data. 相似文献
7.
Ulla König Anja Lode Petra B. Welzel Yuichiro Ueda Sven Knaack Anja Henß Anke Hauswald Michael Gelinsky 《Journal of materials science. Materials in medicine》2014,25(3):607-621
This study intended to evaluate a contemporary concept of scaffolding in bone tissue engineering in order to mimic functions of the extracellular matrix. The investigated approach considered the effect of the glycosaminoglycan heparin on structural and biological properties of a synthetic biomimetic bone graft material consisting of mineralized collagen. Two strategies for heparin functionalization were explored in order to receive a three-component bone substitute material. Heparin was either incorporated during matrix synthesis by mixing with collagen prior to simultaneous fibril reassembly and mineralization (in situ) or added to the matrix after fabrication (a posteriori). Both methods resulted in an incorporation of comparable amounts of heparin, though its distribution in the matrix varied as indicated by TOF-SIMS analyses, and a similar modulation of their protein binding properties. Differential scanning calorimetry revealed that the thermal stability and thereby the degree of crosslinking of the heparinized matrices was increased. However, in contrast to the a posteriori modification, the in situ integration of heparin led to considerable changes of morphology and composition of the matrix: a more open network of collagen fibers yielding a more porous surface and a reduced mineral content were observed. Cell culture experiments with human mesenchymal stem cells (hMSC) revealed a strong influence of the mode of heparin functionalization on cellular processes, as demonstrated for proliferation and osteogenic differentiation of hMSC. Our results indicate that not only heparin per se but also the way of its incorporation into a collagenous matrix determines the cell response. In conclusion, the a posteriori modification was beneficial to support adhesion, proliferation and differentiation of hMSC. 相似文献
8.
Chen Y Mak AF Wang M Li JS Wong MS 《Journal of materials science. Materials in medicine》2008,19(6):2261-2268
To investigate the methods to improve the cell–material interaction of devices or tissue engineering scaffolds made of poly(l-lactic acid) (PLLA) polymer, apatite and apatite/collagen composite coatings were formed on PLLA films within 24 h through
accelerated biomimetic processes. In vitro investigation using Saos-2 osteoblast-like cells through cell culture was conducted
to assess the biological performance of these biomimetic coatings. The cell morphology on three types of surfaces, viz., PLLA
film, PLLA film with the apatite coating, and PLLA film with the apatite/collagen composite coating, was studied using scanning
electron microscopy (SEM). Cell viability was estimated using the MTT assay. The differentiated cell function was assessed
by measuring the alkaline phosphatase (ALP) activity. The results obtained indicated that the biomimetic apatite and apatite/collagen
composite coatings could significantly enhance the proliferation and differentiation of osteoblast-like cells. The apatite/collagen
composite coating appears to be promising for the surface modification of PLLA-based devices with much improved interactions
with osteoblastic cells. 相似文献
9.
Dingying Shan Yuzhou Shi Shun Duan Yan Wei Qing Cai Xiaoping Yang 《Materials science & engineering. C, Materials for biological applications》2013,33(6):3498-3505
Magnetic poly(l-lactide) (PLLA)/Fe3O4 composite nanofibers were prepared with the purpose to develop a substrate for bone regeneration. To increase the dispersibility of Fe3O4 nanoparticles (NPs) in the PLLA matrix, a modified chemical co-precipitation method was applied to synthesize Fe3O4 NPs in the presence of PLLA. Trifluoroethanol (TFE) was used as the co-solvent for all the reagents, including Fe(II) and Fe(III) salts, sodium hydroxide, and PLLA. The co-precipitated Fe3O4 NPs were surface-coated with PLLA and demonstrated good dispersibility in a PLLA/TFE solution. The composite nanofiber electrospun from the solution displayed a homogeneous distribution of Fe3O4 NPs along the fibers using various contents of Fe3O4 NPs. X-ray diffractometer (XRD) and vibration sample magnetization (VSM) analysis confirmed that the co-precipitation process had minor adverse effects on the crystal structure and saturation magnetization (Ms) of Fe3O4 NPs. The resulting PLLA/Fe3O4 composite nanofibers showed paramagnetic properties with Ms directly related to the Fe3O4 NP concentration. The cytotoxicity of the magnetic composite nanofibers was determined using in vitro culture of osteoblasts (MC3T3-E1) in extracts and co-culture on nanofibrous matrixes. The PLLA/Fe3O4 composite nanofibers did not show significant cytotoxicity in comparison with pure PLLA nanofibers. On the contrary, they demonstrated enhanced effects on cell attachment and proliferation with Fe3O4 NP incorporation. The results suggested that this modified chemical co-precipitation method might be a universal way to produce magnetic biodegradable polyester substrates containing well-dispersed Fe3O4 NPs. This new strategy opens an opportunity to fabricate various kinds of magnetic polymeric substrates for bone tissue regeneration. 相似文献
10.
Meng Zhang Yajiang Huang Miqiu Kong Hong Zhu Guangling Chen Qi Yang 《Journal of Materials Science》2012,47(3):1339-1347
The successful development of co-continuous structure from poly(l-lactide) (PLLA) blends by melt mixing with lower PLLA content is highly desired in preparing macroporous biomaterials. However,
the low viscosity of PLLA makes it difficult to prepare co-continuous PLLA blends at low PLLA concentration. In this study,
hydrophilic silica nanoparticle is adopted to control the morphology of co-continuous polystyrene (PS)/PLLA blends. The influence
of nanoparticle concentration on the co-continuity intervals and rheological properties of PS/PLLA blends are examined. The
morphological stability of blends against melt annealing is also determined and discussed with a conceptual coarsening model
for co-continuous structure. The results demonstrate that the incorporation of silica nanoparticles into PS/PLLA blends can
be used to prepare macroporous PLLA structure with controllable pore size at lower PLLA content. 相似文献
11.
Yan Su Xiaoqiang Li Hongsheng Wang Chuanglong He Xiumei Mo 《Journal of materials science. Materials in medicine》2009,20(11):2285-2294
The aim of this study is to investigate an innovative tissue engineering scaffold with a controllable drug-releasing capability.
The hypothesis is that the nanofibers fabricated by coaxial electrospinning could encapsulate and release sustainedly Tetracycline
Hydrochloride (TCH). To testify the hypothesis, nanofibers were prepared by coaxial electrospinning from Poly(l-lactid-co-ε-caprolactone) [PLLACL]/2,2,2-Frifluoroethanol (TFE) solutions (as the shell solutions) and TCH/TFE solutions
(as the core solutions). In addition, nanofibers of PLLACL-blend-TCH were also prepared as the control by mix electrospinning.
The relationship between fibers morphologies and processed conditions in electrospinning were investigated. TCH release behaviors
from the nanofibrous mats were studied. The antibacterial properties of aforementioned nanofibers were detected by the Escherichia coli growth-inhibiting tests. The results indicated that the nanofibers prepared by coaxial-electrospinning had the desired and
controllable TCH encapsulation/release profile; thus, it could be utilized as both a drug encapsulation/release vehicle and
a tissue engineering scaffold. 相似文献
12.
Doan Van Hong Thien Ming Hua Ho Sheng Wen Hsiao Chung Hsing Li 《Journal of Materials Science》2015,50(4):1575-1585
In this study, chitosan/hydroxyapatite (CS/HA) nanofibers were prepared using a wet chemical method. First, CS nanofibers with uniform diameters were fabricated using electrospinning. Then, a wet chemical process was used to mineralize nanofiber surfaces to form a homogeneous HA deposit. Reactions with three cycles were found to optimize biomimetic properties of the HA. The mineralization process required only approximately 3 h, which corresponded to a saving of 98 % in preparation time compared with that needed by the process using a simulated body fluid (SBF). According to the attachment and spreading of UMR (rat osteosarcoma) cells on the CS/HA composite fibers, the deposited mineralization layer significantly enhanced cell affinity of the CS nanofibers and the HA created by the wet chemical method was as effective as that created by the SBF. The composite nanofibrous scaffolds produced by the wet chemical process also promoted osteogenic differentiation by inducing ossification. Thus, expressions of collagen type I, alkaline phosphatase, osteocalcin, bone sialoprotein, and osterix were all enhanced. These results demonstrated that composite electrospun fibers can be efficiently prepared using wet chemical method and the resulting nanofibrous scaffolds have considerable potential in future bone tissue engineering applications. 相似文献
13.
Lin Jia Molamma P. Prabhakaran Xiaohong Qin Seeram Ramakrishna 《Materials science & engineering. C, Materials for biological applications》2013,33(8):4640-4650
Nanotechnology has enabled the engineering of a variety of materials to meet the current challenges and requirements in vascular tissue regeneration. In our study, poly-l-lactide (PLLA) and hybrid PLLA/collagen (PLLA/Coll) nanofibers (3:1 and 1:1) with fiber diameters of 210 to 430 nm were fabricated by electrospinning. Their morphological, chemical and mechanical characterizations were carried out using scanning electron microscopy (SEM), attenuated total reflectance Fourier transform infrared (ATR-FTIR), and tensile instrument, respectively. Bone marrow derived mesenchymal stem cells (MSCs) seeded on electrospun nanofibers that are capable of differentiating into vascular cells have great potential for repair of the vascular system. We investigated the potential of MSCs for vascular cell differentiation in vitro on electrospun PLLA/Coll nanofibrous scaffolds using endothelial differentiation media. After 20 days of culture, MSC proliferation on PLLA/Coll(1:1) scaffolds was found 256% higher than the cell proliferation on PLLA scaffolds. SEM images showed that the MSC differentiated endothelial cells on PLLA/Coll scaffolds showed cobblestone morphology in comparison to the fibroblastic type of undifferentiated MSCs. The functionality of the cells in the presence of ‘endothelial induction media’, was further demonstrated from the immunocytochemical analysis, where the MSCs on PLLA/Coll (1:1) scaffolds differentiated to endothelial cells and expressed the endothelial cell specific proteins such as platelet endothelial cell adhesion molecule-1 (PECAM-1 or CD31) and Von Willebrand factor (vWF). From the results of the SEM analysis and protein expression studies, we concluded that the electrospun PLLA/Coll nanofibers could mimic the native vascular ECM environment and might be promising substrates for potential application towards vascular regeneration. 相似文献
14.
左旋聚乳酸/多壁碳纳米管/羟基磷灰石电纺丝纳米纤维的形态及生物降解性能 总被引:2,自引:0,他引:2
采用静电纺丝法制备了左旋聚乳酸/多壁碳纳米管/羟基磷灰石(PLLA/MW NT s/HA)杂化纳米纤维无纺毡,分析了MW NT s的加入对杂化纤维形态结构的影响,以及不同工艺条件下纤维的直径分布,并研究了纤维无纺毡在磷酸盐缓冲溶液(pH 7.4,37℃)中的体外降解过程。结果表明:MW NT s的加入使PLLA/HA纤维直径略有减小;PLLA/MW NT s/HA杂化纤维体系降解液的pH值下降到一定程度后,在降解后期呈缓慢上升趋势;碱性MW NT s/HA的加入抑制了PLLA降解过程中的自催化作用,减缓了PLLA的降解速度。 相似文献
15.
A novel poly(l-lactic acid) (PLLA)/tobermorite composite porous membrane for use as filter materials was synthesized by electrospinning
a mixture of tobermorite modified by poly(dialyldimethylammoniumchloride) (PDDA) and PLLA. X-ray diffraction patterns of the
sample indicated the existence of tobermorite in the sample. Scanning electron micrographs of the sample showed that the nonwoven
membrane consists of a few microscopic fibers despite the existence of tobermorite particles. This was due to repulsive force
and surface tension. However, no tobermorite particle was exposed at its fiber surface. Thermal analysis showed PLLA of the
sample pyrolyzed with two steps of weight loss (44% at around 170 °C and 34% at around 270 °C). Heat treatment of the sample
at 130 and 250 °C led to crystallization of a part of amorphous PLLA in the fiber and elimination of the remaining amorphous
PLLA, respectively. After the treatment, the membrane maintained its porous structure and was coated with tobermorite particles
at the fiber surface. 相似文献
16.
Jaclyn Lock Thanh Yen Nguyen Huinan Liu 《Journal of materials science. Materials in medicine》2012,23(10):2543-2552
Human mesenchymal stem cells (hMSCs) typically range in size from 10 to 50 μm and proteins that mediate hMSC adhesion and differentiation usually have a size of a few nanometers. Nanomaterials with a feature size smaller than 100 nm have demonstrated the unique capability of promoting osteoblast (bone forming cell) adhesion and long-term functions, leading to more effective bone tissue regeneration. For new bone deposition, MSCs have to be recruited to the injury or disease sites and then differentiate into osteoblasts. Therefore, designing novel nanomaterials that are capable of attracting MSCs and directing their differentiation is of great interest to many clinical applications. This in vitro study investigated the effects of nanophase hydroxyapatite (nano-HA), nano-HA/poly(lactide-co-glycolide) (PLGA) composites and a bone morphogenetic protein (BMP-7) derived short peptide on osteogenic differentiation of hMSCs. The short peptide was loaded by physical adsorption to nano-HA or by dispersion in nanocomposites and in PLGA to determine their effects on hMSC adhesion and differentiation. The results showed that the nano-HA/PLGA composites promoted hMSC adhesion as compared to the PLGA controls. Moreover, nano-HA/PLGA composites promoted osteogenic differentiation of hMSCs to a similar extent with or without the presence of osteogenic factors in the media. In the MSC growth media without the osteogenic factors, the nanocomposites supported greater calcium-containing bone mineral deposition by hMSC than the BMP-derived short peptide alone. The nanocomposites provided promising alternatives in controlling the adhesion and differentiation of hMSCs without osteogenic factors from the culture media, and, thus, should be further studied for clinical translation and the development of novel nanocomposite-guided stem cell therapies. 相似文献
17.
R Ravichandran JR Venugopal S Sundarrajan S Mukherjee R Sridhar S Ramakrishna 《Nanotechnology》2012,23(38):385102
Myocardial tissue lacks the ability to appreciably regenerate itself following myocardial infarction (MI) which ultimately results in heart failure. Current therapies can only retard the progression of disease and hence tissue engineering strategies are required to facilitate the engineering of a suitable biomaterial to repair MI. The aim of this study was to investigate the in?vitro properties of an injectable biomaterial for the regeneration of infarcted myocardium. Fabrication of core/shell fibers was by co-axial electrospinning, with poly(glycerol sebacate) (PGS) as core material and poly-l-lactic acid (PLLA) as shell material. The PLLA was removed by treatment of the PGS/PLLA core/shell fibers with DCM:hexane (2:1) to obtain PGS short fibers. These PGS short fibers offer the advantage of providing a minimally invasive injectable technique for the regeneration of infarcted myocardium. The scaffolds were characterized by SEM, FTIR and contact angle and cell-scaffold interactions using cardiomyocytes. The results showed that the cardiac marker proteins actinin, troponin, myosin heavy chain and connexin 43 were expressed more on short PGS fibers compared to PLLA nanofibers. We hypothesized that the injection of cells along with short PGS fibers would increase cell transplant retention and survival within the infarct, compared to the standard cell injection system. 相似文献
18.
Zeeshan Khatri Ryu Nakashima Gopiraman Mayakrishnan Ki-Hoon Lee Young-Hwan Park Kai Wei Ick-Soo Kim 《Journal of Materials Science》2013,48(10):3659-3664
Recently, attempts have been made to develop nanofiber tubes suitable for nerve regeneration made of biodegradable nanofibers. Among all polymeric nanofibers, poly(ε-caprolactone) (PCL) is distinctively known for better mechanical stability and poly(l-lactic acid) (PLLA) for relatively faster biodegradability. Our purpose of study is to investigate their blending compatibility and the ability to form nanofiber tubes via electrospinning. We electrospun the PCL–PLLA nanofiber tubular using different blend ratios of PCL–PLLA. The electrospun nanofibers were continuously deposited over high speed rotating mandrel to fabricate nanofiber tubes having inner diameter of 2 mm and the wall thickness of 55–65 μm. The diameters of nanofibers were between 715 and 860 nm. The morphologies of PCL–PLLA nanofiber tubes were examined under scanning electron microscope, and showed better structural stability and formability than the neat PLLA nanofibers. Fourier transform infrared spectroscopy study revealed that the PCL–PLLA blend nanofiber exhibited characteristic peaks of both PCL and PLLA and was composition-dependent. Raman and X-ray diffraction studies showed that the increasing PCL ratio in the PCL–PLLA blend increased crystallinity of PCL–PLLA blends. Differential scanning calorimetry revealed recrystallization peaks in PCL–PLLA blends ratios of 1:2 and 1:1. Based on characterization, the electrospun PCL–PLLA nanofiber tubes is considered to be a better candidate for further in vivo or in vitro investigation, and resolve biocompatibility issues in tissue engineering. 相似文献
19.
Evaluation of hydroxylapatite/poly(l-lactide) composites: physico-chemical properties 总被引:7,自引:0,他引:7
C. C. P. M. Verheyen C. P. A. T. Klein J. M. A. De Blieck-Hogervorst J. G. C. Wolke C. A. Van Blitterswijn K. De Groot 《Journal of materials science. Materials in medicine》1993,4(1):58-65
The aim of this in vitro study was to examine the physico-chemical behaviour of hydroxylapatite/poly(l-lactide) (HA/PLLA) composites in solution tests. The polymer PLLA, the composites 30 wt% HA/PLLA (C30) and 50 wt% HA/PLLA (C50) and a one-side HA-coated PLLA (HAcP) were evaluated. Rectangular specimens were incubated in various acellular aqueous buffer solutions [citrate, Gomori's and phosphate-buffered saline (PBS)] up to 24 weeks. Data for cumulative release of calcium, phosphate and l-lactate release in solutions containing C30 or C50 showed linear patterns. Release data for solutions containing HAcP combined with scanning micrographs, X-ray microanalysis and X-ray diffraction patterns of the specimens in time showed that the plasma-sprayed HA coating on PLLA dissolves significantly, progressively in the first weeks and almost completely within the tested period of 24 weeks in vitro. A precipitate of scaly crystallites (calcium phosphates) was observed at the HA coating-PBS interface. After 24 weeks incubation all materials were still above their initial weight, indicating that swelling still exceeded dissolution. Application of C30, C50 and HAcP as implant materials seems interesting where initial stabilization through bone bonding is needed or where the linear release of constituents is a requirement. HAcP has the advantage that the HA coating acts as a hydrolysis barrier and consequently delays the degradation of PLLA in vitro. 相似文献
20.
The enhanced thermal diffusivity and mechanical properties of poly(l-lactic acid) (PLLA) nanocomposites reported here are based on the percolation network formed when PLLA is hybridized with
short carbon fibers (CFs) and functionalized zinc oxide whiskers. The PLLA nanocomposite containing 30 wt% (≈9.5 vol%) ZnO
whiskers and 10 wt% (≈8.1 vol%) CFs had a thermal diffusivity almost as high as that of stainless steel and an insulator-level
electrical resistivity (>1010 Ωm). Modifying the surface of the ZnO whiskers by esterifying them using specific alcohols with long linear alkyl chains
improved the elastic strength and toughness of the nanocomposites significantly. These results suggest that hybridizing PLLA
with short CFs and functionalized ZnO whiskers yields nanocomposites with high thermal diffusivity as well as high electrical
resistivity and excellent mechanical properties. 相似文献