共查询到20条相似文献,搜索用时 15 毫秒
1.
PLLA scaffolds were successfully fabricated using liquid–liquid phase separation with freeze extraction techniques. The effects
of different processing conditions, such as method of cooling (direct quenching and pre-quenching), freezing temperature (−80°C
and −196°C) and polymer concentration (3, 5 and 7 wt%) were investigated in relations to the scaffold morphology. SEM micrographs
of scaffolds showed interconnected porous network with pore size ranging from 20 to 60 μm. The scaffolds had porosity values
ranging from 80 to 90%. Changes to the interconnected network, porosity and pore size were observed when the method of cooling
and polymer concentration was changed. Direct quenching to −80°C gave a more porous interconnected microstructure with uniform
pore size compared to samples prepared using pre-quenching method. Larger pores were observed for samples quenched at −80°C
compared to −196°C. Scaffolds prepared using direct quenching to −196°C had higher elastic modulus and compressive stress
compared to those quenched to −80°C. The compressive elastic modulus ranged from 4 to 7 MPa and compressive stress at 10%
strain was from 0.13 to 0.18 MPa. 相似文献
2.
Doiphode ND Huang T Leu MC Rahaman MN Day DE 《Journal of materials science. Materials in medicine》2011,22(3):515-523
A solid freeform fabrication technique, freeze extrusion fabrication (FEF), was investigated for the creation of three-dimensional
bioactive glass (13–93) scaffolds with pre-designed porosity and pore architecture. An aqueous mixture of bioactive glass
particles and polymeric additives with a paste-like consistency was extruded through a narrow nozzle, and deposited layer-by-layer
in a cold environment according to a computer-aided design (CAD) file. Following sublimation of the ice in a freeze dryer,
the construct was heated according to a controlled schedule to burn out the polymeric additives (below ~500°C), and to densify
the glass phase at higher temperature (1 h at 700°C). The sintered scaffolds had a grid-like microstructure of interconnected
pores, with a porosity of ~50%, pore width of ~300 μm, and dense glass filaments (struts) with a diameter or width of ~300 μm.
The scaffolds showed an elastic response during mechanical testing in compression, with an average compressive strength of
140 MPa and an elastic modulus of 5–6 GPa, comparable to the values for human cortical bone. These bioactive glass scaffolds
created by the FEF method could have potential application in the repair of load-bearing bones. 相似文献
3.
She Z Jin C Huang Z Zhang B Feng Q Xu Y 《Journal of materials science. Materials in medicine》2008,19(12):3545-3553
Tissue engineering requires the development of three-dimensional water-stable scaffolds. In this study, silk fibroin/chitosan
(SFCS) scaffold was successfully prepared by freeze-drying method. The scaffold is water-stable, only swelling to a limited
extent depending on its composition. Fourier Transform Infrared (FTIR) spectra and X-Ray diffraction curves confirmed the
different structure of SFCS scaffolds from both chitosan and silk fibroin. The homogeneous porous structure, together with
nano-scale compatibility of the two naturally derived polymers, gives rise to the controllable mechanical properties of SFCS
scaffolds. By varying the composition, both the compressive modulus and compressive strength of SFCS scaffolds can be controlled.
The porosity of SFCS scaffolds is above 95% when the total concentration of silk fibroin and chitosan is below 6 wt%. The
pore sizes of the SFCS scaffolds range from 100 μm to 150 μm, which can be regulated by changing the total concentration.
MTT assay showed that SFCS scaffolds can promote the proliferation of HepG2 cells (human hepatoma cell line) significantly.
All these results make SFCS scaffold a suitable candidate for tissue engineering. 相似文献
4.
Jesús Román María Victoria Caba?as Juan Pe?a María Vallet-Regí 《Science and Technology of Advanced Materials》2011,12(4)
Hydrogels (gellan or agarose) reinforced with nanocrystalline carbonated hydroxyapatite (nCHA) were prepared by the GELPOR3D technique. This simple method is characterized by compositional flexibility; it does not require expensive equipment, thermal treatment, or aggressive or toxic solvents, and yields a three-dimensional (3D) network of interconnected pores 300–900 μm in size. In addition, an interconnected porosity is generated, yielding a hierarchical porous architecture from the macro to the molecular scale. This porosity depends on both the drying/preservation technology (freeze drying or oven drying at 37 ○C) and on the content and microstructure of the reinforcing ceramic. For freeze-dried samples, the porosities were approximately 30, 66 and below 3% for pore sizes of 600–900 μm, 100–200 μm and 50–100 nm, respectively. The pore structure depends much on the ceramic content, so that higher contents lead to the disappearance of the characteristic honeycomb structure observed in low-ceramic scaffolds and to a lower fraction of the 100–200-μm-sized pores. The nature of the hydrogel did not affect the pore size distribution but was crucial for the behavior of the scaffolds in a hydrated medium: gellan-containing scaffolds showed a higher swelling degree owing to the presence of more hydrophilic groups. 相似文献
5.
AbstractHydrogels (gellan or agarose) reinforced with nanocrystalline carbonated hydroxyapatite (nCHA) were prepared by the GELPOR3D technique. This simple method is characterized by compositional flexibility; it does not require expensive equipment, thermal treatment, or aggressive or toxic solvents, and yields a three-dimensional (3D) network of interconnected pores 300–900 μm in size. In addition, an interconnected porosity is generated, yielding a hierarchical porous architecture from the macro to the molecular scale. This porosity depends on both the drying/preservation technology (freeze drying or oven drying at 37 ○C) and on the content and microstructure of the reinforcing ceramic. For freeze-dried samples, the porosities were approximately 30, 66 and below 3% for pore sizes of 600–900 μm, 100–200 μm and 50–100 nm, respectively. The pore structure depends much on the ceramic content, so that higher contents lead to the disappearance of the characteristic honeycomb structure observed in low-ceramic scaffolds and to a lower fraction of the 100–200-μm-sized pores. The nature of the hydrogel did not affect the pore size distribution but was crucial for the behavior of the scaffolds in a hydrated medium: gellan-containing scaffolds showed a higher swelling degree owing to the presence of more hydrophilic groups. 相似文献
6.
Qiang Fu Mohamed N. Rahaman B. Sonny Bal Roger F. Brown 《Journal of materials science. Materials in medicine》2009,20(5):1159-1165
Previous work by the authors showed that hydroxyapatite (HA) scaffolds with different types of oriented microstructures and
a unique ‘elastic–plastic’ mechanical response could be prepared by unidirectional freezing of suspensions. The objective
of the present work was to evaluate the in vitro cellular response to these freeze-cast HA scaffolds. Unidirectional scaffolds
with approximately the same porosity (65–70%) but different pore architectures, described as ‘lamellar’ (pore width = 25 ± 5 μm)
and ‘cellular’ (pore diameter = 100 ± 10 μm), were evaluated. Whereas both groups of scaffolds showed excellent ability to
support the proliferation of MC3T3-E1 pre-osteoblastic cells on their surfaces, scaffolds with the cellular-type microstructure
showed far better ability to support cell proliferation into the pores and cell function. These results indicate that freeze-cast
HA scaffolds with the cellular-type microstructure have better potential for bone repair applications. 相似文献
7.
A new class of scaffolds with a gain size of 200 nm was prepared from wollastonite/tricalcium phosphate (WT) nanocomposite
powders (termed “nano-sintered scaffolds”) through a two-step chemical precipitation and porogen burnout techniques. For a
comparison, WT scaffolds with a grain size of 2 μm were also fabricated from submicron composite powders (termed “submicron-sintered
scaffolds”) under the same condition. The resultant scaffolds showed porosities between 50 ± 1.0% and 65 ± 1.0% with a pore
size ranging from 100 μm to 300 μm. The WT nano-sintered scaffolds exhibited compressive strength and elastic modulus values
that were about twice that of their submicron-sintered counterparts. The in vitro degradation tests demonstrated that the
degradability could be regulated by the grain size of bioceramics. The decreased specific surface area of pores in the nano-sintered
scaffolds led to their reduced degradation rate. The mechanical properties of the nano-sintered scaffolds exhibited less strength
loss during the degradation process. The WT macroporous nano-sintered scaffolds are a promising and potential candidate for
bone reconstruction applications. 相似文献
8.
Devendra Verma Kalpana S. Katti Dinesh R. Katti 《Materials science & engineering. C, Materials for biological applications》2009,29(7):2079-2084
In the current work, polyelectrolyte complex (PEC) fibrous scaffolds for tissue engineering have been synthesized and a mechanism of their formation has been investigated. The scaffolds are synthesized using polygalacturonic acid and chitosan using the freeze drying methodology. Highly interconnected pores of sizes in the range of 5–20 µm are observed in the scaffolds. The thickness of the fibers was found to be in the range of 1–2 µm. Individual fibers have a nanogranular structure as observed using AFM imaging. In these scaffolds, PEC nanoparticles assemble together at the interface of ice crystals during freeze drying process. Further investigation shows that the freezing temperature and concentration have a remarkable effect on structure of scaffolds. Biocompatibility studies show that scaffold containing chitosan, polygalacturonic acid and hydroxyapatite promotes cell adhesion and proliferation. On the other hand, cells on scaffolds fabricated without hydroxyapatite nanoparticles showed poor adhesion. 相似文献
9.
Since pore connectivity has significant effects on the biological behaviors of biomedical porous hydroxyapatite (PHA), the
preparation of PHA with interconnected pore architecture is of great practical significance. In the present study, PHA with
highly interconnected architecture was prepared via a simple burnout route with rod-like urea as the porogen. Microscopy and
porosimetry data showed that the as-prepared PHA had open and interconnected pore structure with the average fenestration
size of about 120 μm. Open pores occupied up to 98% of the total porosity. The compressive strength and modulus of the as-prepared
PHA were respectively 1.3–7.6 MPa and 4.0–10.4 GPa. 相似文献
10.
Hydroxyapatite scaffolds processed using a TBA-based freeze-gel casting/polymer sponge technique 总被引:1,自引:0,他引:1
Tae Young Yang Jung Min Lee Seog Young Yoon Hong Chae Park 《Journal of materials science. Materials in medicine》2010,21(5):1495-1502
A novel freeze-gel casting/polymer sponge technique has been introduced to fabricate porous hydroxyapatite scaffolds with controlled “designer” pore structures and improved compressive strength for bone tissue engineering applications. Tertiary-butyl alcohol (TBA) was used as a solvent in this work. The merits of each production process, freeze casting, gel casting, and polymer sponge route were characterized by the sintered microstructure and mechanical strength. A reticulated structure with large pore size of 180–360 μm, which formed on burn-out of polyurethane foam, consisted of the strut with highly interconnected, unidirectional, long pore channels (~4.5 μm in dia.) by evaporation of frozen TBA produced in freeze casting together with the dense inner walls with a few, isolated fine pores (<2 μm) by gel casting. The sintered porosity and pore size generally behaved in an opposite manner to the solid loading, i.e., a high solid loading gave low porosity and small pore size, and a thickening of the strut cross section, thus leading to higher compressive strengths. 相似文献
11.
Collins NJ Leeke GA Bridson RH Hassan F Grover LM 《Journal of materials science. Materials in medicine》2008,19(4):1497-1502
Macroporous polylactide (PLA) scaffolds were fabricated using a supercritical CO2 foaming process. The addition of silica particles to the polymer matrix resulted in a significant modification in the pore
size distribution exhibited by the scaffold. In the absence of silica, the scaffolds contained pores between 88 μm and 980 μm
in diameter as determined using X-ray computed microtomography. The addition of silica at only 2 wt% resulted in the elimination
of pores of >620 μm, with no significant influence on the total porosity of the material. This effect was attributed to the
silica nucleating the formation of gas bubbles in the polymeric material. Although the addition of further silica to the scaffold
resulted in a further reduction in modal pore diameter, when more than 20 wt% was added to the matrix little additional effect
was noted. In addition to enabling some control over pore diameter, mineral deposition was shown to occur considerably more
rapidly on the silica-modified scaffolds than on those containing no silica. 相似文献
12.
A series of poly(lactide-co-glycolide) (PLGA)/ hyaluronic acid (HA) blend with different HA composition were used to fabricate
scaffolds successfully. The pores of the three dimensional scaffold were prepared by particle leaching and freeze drying.
The pore size was about 50–200 μ m and the porosity was about 85%. The characterizations of the scaffold, such as mechanical
properties, hydrophilicity and surface morphologies were determined. Mouse 3T3 fibroblast was directly seeded on the scaffolds.
The cell adhesion efficiency, cell morphology observed by scanning electron microscopy (SEM) and the degradation behavior
of the blend scaffold were evaluated. In summary, the results show that the adhesion efficiency of cells on the PLGA/HA blend
scaffold is higher than that on the PLGA scaffold. Moreover, the incorporation of HA in PLGA not only helps to increase the
cell affinity but also tends to lead the water and nutrient into the scaffold easily. 相似文献
13.
Freeze-extraction, which involves phase separation principle, gave highly porous scaffolds without the time and energy consuming
freeze-drying process. The presented method eliminates the problem of formation of surface skin observed in freeze-drying
methods. The effects of different freezing temperature (−80 and −24°C), medium (dry ice/ethanol bath and freezer) and polymer
concentrations (1, 3, and 5 wt.%) on the scaffold properties were investigated in connection with the porous morphology and
physicomechanical characteristics of the final scaffolds. The FESEM micrographs showed porous PLLA scaffolds with ladder-like
architecture. The size of the longitudinal pores was in the range of 20–40 μm and the scaffolds had high porosity values ranging
from 90% to 98%. Variation in porosity, mechanical resistance, and degree of regularity in the spatial organization of pores
were observed when polymer concentration was changed. More open scaffold architecture with enhanced pore interconnectivity
was achieved when a dry ice/ethanol bath of −80°C was used. Polymer concentration played an important role in fabricating
highly porous scaffolds, with ladder-like architecture only appearing at polymer concentrations of above 3 wt.%. With the
freeze-extraction method used here, highly porous and interconnected poly(l-lactide) scaffolds were successfully fabricated, holding great potential for tissue engineering applications. 相似文献
14.
Li JP Li SH Van Blitterswijk CA de Groot K 《Journal of materials science. Materials in medicine》2006,17(2):179-185
A highly porous T{i}6Al4V with interconnected porous structure has been developed in our previous study. By using a so-called
“Multiple coating” technique, the porous T{i}6Al4V can be tailored to resemble cancellous bone in terms of porous structure
and mechanical properties. A thin layer of T{i}6Al4V slurry was coated on the struts of base porous T{i}6Al4V to improve the
pore structure. After two additional coating, pore sizes ranged from 100 μm to 700 μm, and the porosity was decreased from
∼90% to ∼ 75%, while the compressive strength was increased from 10.3 ± 3.3 MPa to 59.4 ± 20.3 MPa and the Young's modulus
increased from 0.8 ± 0.3 GPa to 1.8 ± 0.3 GPa. The pore size and porosity are similar to that of cancellous bone, meanwhile
the compressive strength is higher than that of cancellous bone, and the Young's modulus is between that of cancellous bone
and cortical bone. Porosity, pore size and mechanical properties can be controlled by the parameters in such multiple coating
processes. Therefore the porous T{i}6Al4V with the characteristics of cancellous bone is expected to be a promising biomaterial
for biomedical applications.
Author to whom all correspondence should be addressed. 相似文献
15.
Ribeiro CC Barrias CC Barbosa MA 《Journal of materials science. Materials in medicine》2006,17(5):455-463
In the present work, a novel route for the preparation of porous ceramic microspheres is described. Two ceramic powders, calcium-titanium-phosphate
(CTP) and hydroxyapatite (HAp), were mixed with a sodium alginate solution that enabled the preparation of spherical particles,
using the droplet extrusion method combined with ionotropic gelation in the presence of Ca2+. The spherical particles were subsequently sintered, to burn-off the polymer and obtain calcium-phosphate microspheres with
a uniform size and an interconnected porous network. CTP microspheres with diameters ranging from 513 ± 24 μm to 792 ± 35
μm and with pores of approximately 40 μm were obtained. HAp microspheres presented diameters of 429 ± 46 μm and 632 ± 40 μm
and pores of ca. 2 μm. Depending on the formulations tested, the structure of both calcium phosphates may become altered during
the sintering process, suggesting that the ratio between the ceramic phase and the polymer solution is a critical parameter.
Porous microspheres prepared using the described methodology are promising candidates as bone defect fillers and scaffolds
for bone tissue regeneration. 相似文献
16.
Hong Li Lili Yang Xieping Dong Yifei Gu Guoyu Lv Yonggang Yan 《Journal of materials science. Materials in medicine》2014,25(5):1257-1265
In this study, nano calcium deficient hydroxyapatite (n-DA)/multi-(amino acid) copolymer composite scaffolds were prepared by injection molding foaming method using calcium sulphate dihydrate as a foaming agent. The composite scaffolds showed well interconnected macropores with the pore size of ranging from 100 to 600 μm, porosity of 81 % and compressive strength of 12 MPa, and the compressive strength obviously affected by the porosity. The composite scaffolds could be slowly degraded in phosphate buffered solution (PBS), which lost its initial weight of 61 w % after immersion into PBS for 12 weeks, and the porosity significantly affected the degradability of the scaffolds. Moreover, it was found that the composite scaffolds could promote the MG-63 cells growth and proliferation, and enhance its alkaline phosphatase activity. The implantation of the scaffolds into the femoral bone of rabbits confirmed that the composite scaffolds were biocompatibitive, degradable, and osteoconductive in vivo. 相似文献
17.
Capes JS Ando HY Cameron RE 《Journal of materials science. Materials in medicine》2005,16(12):1069-1075
The design of tissue engineering scaffolds must take into account many factors including successful vascularisation and the
growth of cells. Research has looked at refining scaffold architecture to promote more directed growth of tissues through
well-defined anisotropy in the pore structure. In many cases it is also desirable to incorporate therapeutic ingredients,
such as growth factors, into the scaffold so that their release occurs as the scaffold degrades. Therefore, scaffold fabrication
techniques must be found to precisely control, not only the overall porosity of scaffolds, but also the pore size, shape and
spatial distribution.
This work describes the use of a regularly shaped porogen, sugar spheres, to manufacture polymeric scaffolds. Results show
that pre-assembling the spheres created scaffolds with a constant porosity of 60%, but with varying pores sizes from 200–800
μm, leading to a variation in the surface area and likely degradation rate of the scaffolds. Employing different polymer impregnation
techniques tailored the number of pores present with a diameter of less than 100 μm to suit different functions, and altering
the packing structure of the sugar spheres created scaffolds with novel layered porosity. Replacing sugar spheres with sugar
strands formed scaffolds with pores aligned in one direction. 相似文献
18.
S. Cardea L. Baldino P. Pisanti E. Reverchon 《Journal of materials science. Materials in medicine》2014,25(2):355-362
Various techniques have been reported in the literature for the fabrication of biodegradable scaffolds; but, it is very difficult to obtain in the same structure macro, micro and nanostructural characteristics. In this work we developed a supercritical freeze extraction process (SFEP) for the formation of poly(l-lactic acid) (PLLA) scaffolds, that combines the advantages of thermally induced phase separation with those of supercritical drying. We processed solutions in chloroform of two PLLA molecular weights and at different polymer concentrations ranging between 5 and 20 % w/w. Supercritical drying was performed at 35 °Cand pressures ranging between 100 and 250 bar. 3-D scaffolds characterized by high porosity (between 88 and 97.5 %), with coexisting micro and nanometric morphology were obtained. Structures generated were characterized by pores ranging between 10 and 30 μm and with a wrinkled nanostructure of about 200 nm, superimposed on the internal pore surface, that could be useful for biomedical applications. A solvent residue lower than 5 ppm was also measured. 相似文献
19.
A novel all-aqueous process is described to form three-dimensional porous silk fibroin (SF) scaffolds, which not only avoided
the use of organic solvents or harsh chemicals, but also can form scaffolds with various sizes and in large quantities. The
scaffolds show a rough surface on the pores and the pores are highly interconnected. The porosity of the scaffolds, which
varied between a large range (67.6~99.3%), can be controlled by the SF concentrations and the salt/fibroin ratio. The results
of measurements indicated that this novel process can improve and enforce the transformation in SF structure from a random
coil to a β-sheet. Swelling studies showed that the scaffold has excellent properties of hydrophilicity. The cell culture
experiments demonstrated that the scaffolds facilitated the human osteosarcoma cells attachment and proliferation in vitro. 相似文献
20.
Schumacher M Deisinger U Detsch R Ziegler G 《Journal of materials science. Materials in medicine》2010,21(12):3119-3127
While various materials have been developed for bone substitute and bone tissue engineering applications over the last decades,
processing techniques meeting the high demands of scaffold shaping are still under development. Individually adapted and mechanically
optimised scaffolds can be derived from calcium phosphate (CaP-) ceramics via rapid prototyping (RP). In this study, porous
ceramic scaffolds with a periodic pattern of interconnecting pores were prepared from hydroxyapatite, β-tricalcium phosphate
and biphasic calcium phosphates using a negative-mould RP technique. Moulds predetermining various pore patterns (round and
square cross section, perpendicular and 60° inclined orientation) were manufactured via a wax printer and subsequently impregnated
with CaP-ceramic slurries. Different pore patterns resulted in macroporosity values ranging from about 26.0–71.9 vol% with
pore diameters of approximately 340 μm. Compressive strength of the specimens (1.3–27.6 MPa) was found to be mainly influenced
by the phase composition as well as the macroporosity, both exceeding the influence of the pore geometry. A maximum was found
for scaffolds with 60 wt% hydroxyapatite and 26.0 vol% open porosity. It has been shown that wax ink-jet printing allows to
process CaP-ceramic into scaffolds with highly defined geometry, exhibiting strength values that can be adjusted by phase
composition and pore geometry. This strength level is within and above the range of human cancellous bone. Therefore, this
technique is well suited to manufacture scaffolds for bone tissue engineering. 相似文献