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1.
Tissue engineering for articular cartilage repair has shown success in ensuring the integration of neocartilage with surrounding natural tissue, but the rapid restoration of biomechanical functions remains a significant challenge. The poly(vinyl alcohol) (PVA) hydrogel is regarded as a potential articular cartilage replacement for its fair mechanical strength, whereas its lack of bioactivity limits its utility. To obtain a scaffold possessing expected bioactivity and initial mechanical properties, we herein report a novel salt‐leaching technique to fabricate a porous PVA hydrogel simultaneously embedded with poly(lactic‐co‐glycolic acid) (PLGA) microspheres. Through the investigation of environmental scanning electron microscopy, we found that the porous PVA/PLGA scaffold was successfully manufactured. The compression and creep properties were also comprehensively studied before and after cell culturing. The relationship between the compressive modulus and strain ratio of the porous PVA/PLGA scaffold showed significant nonlinear behavior. The elastic compressive modulus was influenced a little by the porogen content, whereas it went higher with a higher PLGA microsphere content. The cell‐cultured scaffolds presented higher compressive moduli than the initial ones. The creep resistance of the cell‐cultured scaffolds was much better than that of the initial ones. In all, this new scaffold is a promising material for articular cartilage repair. © 2013 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014 , 131, 40311.  相似文献   

2.
A fibrous scaffold is required to provide three‐dimensional (3D) cell growth microenvironments and appropriate synergistic cell guidance cues. In this study, porous scaffolds with different mass ratio of poly(lactic acid) to poly(3‐hydroxybutyrate‐co‐4‐hydroxybutyrate) (P(3HB‐co‐4HB)) for tissue engineering were prepared by a modified particle leaching method. The effect of the addition of P(3HB‐co‐4HB) on microstructural morphology, compression property, swelling behavior, and enzymatic degradation of hybrid scaffolds was systematically investigated. The results indicated that this method was simple but efficient to prepare highly interconnected biomimetic 3D hybrid scaffolds (PP50/50 and PP33/67) with fibrous pore walls. The cytocompatibility of hybrid scaffolds was evaluated by in vitro culture of mesenchymal stem cells. The cell‐cultured hybrid scaffolds presented a complete 3D porous structure, thus allowing cell proliferation on the surface and infiltration into the inner part of scaffolds. The obtained hybrid scaffolds with pore size ranging from 200 to 450 µm, over 90% porosity, adjustable biodegradability, and water‐uptake capability will be promising for cartilage tissue engineering applications. POLYM. ENG. SCI., 54:2902–2910, 2014. © 2014 Society of Plastics Engineers  相似文献   

3.
Poly(lactide‐co‐glycolide) (PLGA) nanoparticles (NPs) represent a promising tool for effective delivery of biomacromolecules, thanks to their biodegradability and biocompatibility properties. PLGA NPs are often synthesized by the emulsion‐solvent evaporation method and poly(vinyl alcohol) (PVA) represents one of the most commonly used surfactants. Although PVA‐mediated synthesis of PLGA NPs is effective in tailoring NP size and stability, the resulting negative surface charge can prevent both endosomal escape and biomacromolecule release in cell cytosol. To overcome this limit, a novel amino‐modified PVA (amino‐PVA) surfactant with a cationic charge was synthesized and its potential for the formulation of PLGA NPs was investigated. In either single (oil‐in‐water) or double (water‐in‐oil‐in‐water) emulsion synthesis, different mixtures of PVA and amino‐PVA were studied, by monitoring their effects on NP size and surface charge. Optimized properties were obtained with a combination of 0.975% (w/v) of PVA with 0.025% (w/v) of amino‐PVA. This formulation was further investigated for degradation properties and cytocompatibility. High stability and low cytotoxicity make the system promising for the encapsulation and release of hydrophilic drugs and biomacromolecules. © 2016 Society of Chemical Industry  相似文献   

4.
Polyblend fibrous scaffolds in mass ratios of 100/0, 90/10, 80/20, and 70/30 from poly(L ‐lactide) (PLLA) and poly(?‐caprolactone) (PCL) for cartilage tissue engineering were prepared in three steps: gelation, solvent exchanging, and freeze‐drying. Effects of the blend ratio, the exchange medium, and the operating temperature on the morphology of scaffolds were investigated by SEM. PLLA/PCL scaffolds presented an ultrafine fibrous network with the addition of a “small block” structure. Smooth and regular fibrous networks were formed when ethanol was used as the exchange medium. Properties of the scaffolds, such as thermal and mechanical properties, were also studied. The results suggested that the compressive modulus declined as PCL amount increased. The incorporation of PCL effectively contributed to reduce the rigidity of PLLA. Bovine chondrocytes were seeded onto PLLA/PCL scaffold. Cells attached onto the fibrous network and their morphology was satisfactory. This polyblend fibrous scaffold will be a potential scaffold for cartilage tissue engineering. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 91: 1676–1684, 2004  相似文献   

5.
Biopolymers are gaining increasing interest because of decline of mineral oil reserves, increasing waste problem, and increasing consciousness of society for environmental problems. However, competitiveness of biopolymers compared with conventional plastics is still limited due to partly insufficient properties and high prices. This study investigates the influence of blending of poly(hydroxybutyrate‐co‐hydroxyvalerate) (PHBV) with poly(butylene adipate‐co‐terephthalate) (PBAT) as well as the influence of addition of functionalized montmorillonite (OMMT) to the blends on morphology and thermal behavior. Dispersion state and morphology of the nanocomposites are studied by X‐ray diffraction as well as scanning electron microscopy. Thermal stability is studied by thermogravimetric analysis and crystallization behavior is studied by differential scanning calorimetry and polarized optical microscopy. With respect to the morphology for the blends it can be seen that the immiscible biopolymers PHBV and PBAT are distributed in interlocking zones. There is a good dispersion and homogeneous distribution of OMMT within the biopolymer blends. The addition of 50% or more PBAT to PHBV as well as the insertion of OMMT enhances thermal stability of PHBV. In the blends, the addition of PBAT retards crystallization of PHBV. The OMMT acts as nucleating agent leading in total to more but less perfect crystals in the blends, and the crystallization slows further due to constraint in the movement of polymer chains. These results contribute to the understanding of the structure–properties relationship of bionanocomposite materials for packaging applications. POLYM. COMPOS., 36:2051–2058, 2015. © 2014 Society of Plastics Engineer  相似文献   

6.
The viscoelasticity of poly(trimethylene terephthalate)/maleinized poly(octene‐ethylene) copolymer/organomontmorillonite (OMMT) nanocomposites were investigated at both liquid and glassy states by using the rotational rheometer and dynamic mechanical analysis, respectively. The viscoelasticity results suggest that OMMT has many important influences on the structure, modulus, toughness, and cold‐crystallization of the nanocomposites. The OMMT has a strip‐like sheet morphology in the polymer matrix and when OMMT content increases to 4 wt%, the physical network‐like structure begins to form in the nanocomposites. The pseudoplasticity of the melts is increased by OMMT. In addition, the complex viscosity, storage modulus, and viscous behavior of the melts are increased with increasing OMMT content. The creep resistance of the nanocomposites is improved by OMMT, and it plays an important role on reinforcing the melts. The stress relaxation of the melts suggests that the nanofillers can not only enhance the interfacial interactions of the nanocomposites but also inhibit the recovery of the polymer chain segments. At glassy state, the nanocomposites' storage modulus increases with increasing OMMT content. As glass transition occurs, the loss factor and loss modulus suggest that OMMT toughens the polymer matrix. At rubber‐elastic state, OMMT depresses the cold‐crystallization of the polymer matrix due to its limitation effect on the motion of molecular chains. POLYM. COMPOS., 2012. © 2012 Society of Plastics Engineers  相似文献   

7.
High‐molecular‐weight atactic poly(vinyl alcohol) (a‐PVA) gels loaded with (R,S)‐2‐(3‐benzoylphenyl)propionic acid (ketoprofen) were prepared from 5, 6, 7, and 8 g/dL solutions of a‐PVA with a number‐average degree of polymerization of 4000 in an ethylene glycol/water mixture with an aging method to identify the effect of the initial polymer concentration on the swelling behavior, morphology, and thermal properties of a‐PVA gels. Then, the release behavior of ketoprofen from a‐PVA gels was investigated. As the polymer concentration decreased, the ability for network formation decreased, and the degree of swelling of the a‐PVA gels increased. In addition, the enthalpy increased with an increase in the a‐PVA concentration, but the melting temperatures of the gels prepared at different initial polymer concentrations were the same; this indicated that tighter gel networks would be formed by a higher polymer chain density. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci 2007  相似文献   

8.
Organo‐modified montmorillonites and poly(p‐dioxanone) (PPDO) diol prepolymers were used to prepare Poly(p‐dioxanone)‐PU/organic montmorillonite (PPDO‐PU/OMMT) nanocomposites by chain‐extending reaction. The crystallization behavior and spherulitic morphology of PPDO‐PU/OMMT nanocomposites were investigated by WXRD, differential scanning calorimetry, and polarized optical microscopy. The results show that the regularity of the chain structure plays a dominant role during the crystallization process rather than that of OMMT content and its dispersion status in PPDO matrix. With similar molecular weight and same OMMT content, PPDO‐PU/OMMT nanocomposite, which derived from lower molecular weight PPDO prepolymer, exhibits lower crystallization rate, melting point, and crystallinity. The influence of the clay content on the crystallization behavior highly depends on its dispersing state. The nucleating effect of OMMT can be only observed at high loading percentage. For the nanocomposites with low clay loading percentage, the retarding effect of exfoliated platelets on the chain‐ordering into crystal lamellae became the key factor. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013  相似文献   

9.
In this study, poly(ethylene terephthalate)/organo‐montmorillonite (PET/OMMT) nanocomposites were melt‐compounded using twin screw extruder followed by injection molding. Maleic anhydride grafted styrene‐ethylene/butylene‐styrene (SEBS‐g‐MAH) was used to improve the impact properties of the PET/OMMT nanocomposites. The notched and un‐notched impact strength of PET/OMMT nanocomposites increased at about 2.5 times and 5.5 times by the addition of 5 wt % of SEBS‐g‐MAH. Atomic force microscopy (AFM) scans were taken from the polished surface of both PET/OMMT and SEBS‐g‐MAH toughened PET/OMMT nanocomposites. The addition of SEBS‐g‐MAH altered the phase structure and clay dispersion in PET matrix. It was found that some of the OMMT silicate layers were encapsulated by SEBS‐g‐MAH. Further, the addition of SEBS‐g‐MAH decreased the degree of crystallinity of the PET/OMMT nanocomposites. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

10.
Ultrafine fibrous webs of poly(lactide‐co‐glycolic acid) (PLGA) containing the bactericidal antibiotic drug rifampin were prepared by electrospinning, and their properties were investigated for wound‐dressing applications. Because PLGA is a biodegradable and biocompatible polymer, it is one of the best materials for the preparation of wound‐dressing substrates. Through this investigation of PLGA/rifampin electrospun webs, we found that the in vitro degradation reached approximately 60% in 10 days, and the drug release from the webs showed a fast and constant profile suitable for wound‐dressing applications. Also, we observed that both the web‐degradation rate and the drug‐release rate increased as the drug concentration in the PLGA/rifampin electrospun webs and the content level of glycolide units in the PLGA polymer matrix increased. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

11.
Star‐shaped and linear block thermoplastic poly(styrene‐b‐butadiene) copolymer (SBS)/organophilic montmorillonite clays (OMMT) were prepared by a solution approach. The intercalation spacing in the nanocomposites and the degree of dispersion of nanocomposites were investigated by X‐ray diffraction (XRD) and transmission electron microscopy (TEM), respectively. The mechanical properties, dynamic mechanical properties, and thermal stability of these nanocomposites were determined. Results showed that SBS chains were well intercalated into the clay galleries and an intercalated nanocomposite was obtained. The mechanical strength of nanocomposites with the star‐shaped SBS/OMMT were significantly increased. The addition of OMMT also gave an increase of the elongation, the dynamic storage modulus, the dynamic loss modulus, and the thermal stability of nanocomposites. The increase of the elongation of nanocomposites indicates that SBS has retained good elasticity. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 92: 3430–3434, 2004  相似文献   

12.
Electrospun fibers of poly(vinyl alcohol) (PVA) and PVA/poly(4‐styrenesulfonic acid) (PSSA) were obtained. By varying PVA to PSSA weight ratios, various fiber sizes and shapes were observed. The fiber diameters ranged from 176 to 766 nm, and the largest fibers were obtained from 15 wt % aqueous PVA solution. The effect of solution viscosity on fiber morphology was discussed. The presence of PSSA in electrospun fibers was confirmed by Fourier Transform Infrared spectroscopy. The PVA fibers were thermally stable up to 250°C, and the PVA/PSSA fibers were stable up to approximately 150°C. The water stability of the fibers was improved by heat‐treatment at 120°C. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012  相似文献   

13.
A novel reactive phosphorus–nitrogen‐containing monomer, N‐(2‐(5,5‐dimethyl‐1,3,2‐dioxaphosphinyl‐2‐ylamino)ethyl)‐acrylamide (DPEAA), was synthesize and characterized. Flame retardant poly(methyl methacrylate)/organic‐modified montmorillonite (PMMA‐DPEAA/OMMT) nanocomposites were prepared by in situ polymerization by incorporating methyl methacrylate, DPEAA, and OMMT. The results from X‐ray diffraction and transmission electron microscopy (TEM) showed that exfoliated PMMA‐DPEAA/OMMT nanocomposites were formed. Thermal stability and flammability properties were investigated by thermogravimetric analysis, cone calorimeter, and limiting oxygen index (LOI) tests. The synergistic effect of DPEAA and montmorillonite improved thermal stability and reduced significantly the flammability [including peak heat release rates (PHRR), total heat release, average mass loss rate, etc.]. The PHRR of PMMA‐DPEAA/OMMT was reduced by about 40% compared with pure PMMA. The LOI value of PMMA‐DPEAA/OMMT reached 27.3%. The morphology and composition of residues generated after cone calorimeter tests were investigated by scanning electronic microscopy (SEM), TEM, and energy dispersive X‐ray (EDX). The SEM and TEM images showed that a compact, dense, and uniform intumescent char was formed for PMMA‐DPEAA/OMMT nanocomposites after combustion. The results of EDX confirmed that the carbon content of the char for PMMA‐DPEAA/OMMT nanocomposites increased obviously by the synergistic effect of DPEAA and montmorillonite. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

14.
Poly(lactic acid)/poly(ε‐caprolactone)/organically modified montmorillonite (PLA/PCL/OMMT) nanocomposites were melt‐processed in a twin‐screw extruder under high shear conditions. As a result of the processing conditions employed, the OMMT layers located in the less compatible PCL phase in all the ternary nanocomposites. The morphology of the PLA/PCL blend evolved from “sea‐island” to co‐continuous upon the addition of OMMT. Both the X‐ray diffraction (XRD) and viscoelastic characterization suggested similar OMMT dispersion in the reference PLA binary and in the PLA/PCL ternary nanocomposites, regardless of its location in the PLA and PCL phase, respectively. The reinforcing effect of the organoclay was also similar. The addition of OMMT to the PLA/PCL blend fully compensated the loss in stiffness and oxygen barrier performance produced by PCL in PLA; the nanocomposite with 3% OMMT showed the same modulus and permeability values as those of pure PLA. Moreover, the ductile behavior (elongation at break > 80%) of the PLA/PCL blend remained constant even in the nanocomposite containing 5% OMMT. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43815.  相似文献   

15.
The isothermal crystallization behavior of poly(L ‐lactic acid)/organo‐montmorillonite nanocomposites (PLLA/OMMT) with different content of OMMT, using a kind of twice‐functionalized organoclay (TFC), prepared by melt intercalation process has been investigated by optical depolarizer. In isothermal crystallization from melt, the induction periods (ti) and half times for overall PLLA crystallization (100°C ≤ Tc ≤ 120°C) were affected by the temperature and the content of TFC in nanocomposites. The kinetic of isothermal crystallization of PLLA/TFC nanocomposites was studied by Avrami theory. Also, polarized optical photomicrographs supplied a direct way to know the role of TFC in PLLA isothermal crystallization process. Wide angle X‐ray diffraction (WAXD) patterns showed the nanostructure of PLLA/TFC material, and the PLLA crystalline integrality was changed as the presence of TFC. Adding TFC led to the decrease of equilibrium melting point of nanocomposites, indicating that the layered structure of clay restricted the full formation of crystalline structure of polymer. The specific interaction between PLLA and TFC was characterized by the Flory‐Huggins interaction parameter (B), which was determined by the equilibrium melting point depression of nanocomposites. The final values of B showed that PLLA was more compatible with TFC than normal OMMT. POLYM. COMPOS., 2009. © 2008 Society of Plastics Engineers  相似文献   

16.
Electrospinning is an effective technology for the fabrication of ultrafine fibers, which can be the basic component of a tissue engineering scaffold. In tissue engineering, because cells seeded on fibrous scaffolds with varying fiber diameters and morphologies exhibit different responses, it is critical to control these characteristics of electrospun fibers. The diameter and morphology of electrospun fibers can be influenced by many processing parameters (e.g., electrospinning voltage, needle inner diameter, solution feeding rate, rotational speed of the fiber‐collecting cylinder, and working distance) and solution properties (polymer solution concentration and conductivity). In this study, a factorial design approach was used to systematically investigate the degree of influence of each of these parameters on fiber diameter, degree of fiber alignment, and their possible synergetic effects, using a natural biodegradable polymer, poly(hydroxybutyrate‐co‐hydroxyvalerate), for the electrospinning experiments. It was found that the solution concentration invoked the highest main effect on fiber diameter, whereas both rotational speed of the fiber‐collecting cylinder and addition of a conductivity‐enhancing salt could significantly affect the degree of fiber alignment. By carefully controlling the electrospinning parameters and solution properties, fibrous scaffolds of desired characteristics could be made to meet the requirements of different tissue engineering applications. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

17.
Surface modification of montomorillonite for improvement in d‐spacing was done by column chromatography with quaternary long chain ammonium salt having cation exchange capacity of 110 meq/100 g. Organically modified montomorillonite (OMMT)/poly(vinyl chloride) (PVC) nanocomposites were prepared through direct melt compounding on a conventional twin screw extruder. Because of improved d‐spacing of OMMT, the polymer chains get exfoliated in between the plates of clay and dispersed uniformly. The mechanical properties of the nanocomposites were found to be appreciable at 12 wt % loading of OMMT. Moreover, rheological data, such as torque, fusion time, viscosity, and shear rate were also recorded on Brabender Plasticorder. The improvement in mechanical properties with increase in amount of OMMT loading is evidenced from reduction in shear viscosity and torque. Also nanoclay is acting as a lubricating agent with packing effect, which reduces the torque with decrease in viscosity along with increment in elongation at break. Because of soft nature of OMMT and improvement in d‐spacing the processing of PVC becomes easier, and hence, OMMT is playing a dual role as a (i) good processing aid and (ii) filler. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2011  相似文献   

18.
Poly(vinyl chloride) (PVC)/organophilic‐montmorillonite (OMMT) nanocomposites were prepared by direct melt intercalation. PVC/compatibilizer ((vinyl acetate) copolymer (VAc))/OMMT nanocomposites were also prepared by melt intercalation by a masterbatch process. The effect of OMMT content on the nanostructures and properties of nanocomposites was studied. The nanostructures were studied by wide angle X‐ray diffraction (WAXD) and transmission electron microscopy (TEM). The linear viscoelastic properties and dynamic mechanical properties of PVC/OMMT nanocomposites were also investigated by an advanced rheometric expansion system (ARES) rheometer. The results showed that partially exfoliated and partially intercalated structures coexisted in the PVC/OMMT and PVC/VAc/OMMT nanocomposites. The mechanical properties test results indicated that the notched Charpy impact strengths of nanocomposites were improved compared to that of pristine PVC and had a maximum value at 1 phr OMMT loadings. The compatibilizer could further improve the impact strengths. But the existence of OMMT decreased the thermal stability of PVC/OMMT and PVC/VAc/OMMT nanocomposites. The linear viscoelastic properties test results indicated the dependence of G′ and G″ on ω shows nonterminal behaviors, and they had better processibility compared with pristine PVC. However, the glass transition temperatures of PVC/OMMT nanocomposites almost had little change compared to that of pristine PVC. POLYM. COMPOS., 27:55–64, 2006. © 2005 Society of Plastics Engineers  相似文献   

19.
In this study, amphiphilic poly(ε‐caprolactone)–pluronic–poly(ε‐caprolactone) (PCL–pluronic–PCL, PCFC) copolymers were synthesized by ring‐opening copolymerization and then reacted with isophorone diisocyanate to form polyurethane (PU) copolymers. The molecular weight of the PU copolymers was measured by gel permeation chromatography, and the chemical structure was analyzed by 1H‐nuclear magnetic resonance and Fourier transform infrared spectra. Then, the PU copolymers were processed into fibrous scaffolds by the electrospinning technology. The morphology, surface wettability, mechanical strength, and cytotoxicity of the obtained PU fibrous mats were investigated by scanning electron microscopy, water contact angle analysis, tensile test, and MTT analysis. The results show that the molecular weights of PCFC and PU copolymers significantly affected the physicochemical properties of electrospun PU nanofibers. Moreover, their good in vitro biocompatibility showed that the as‐prepared PU nanofibers have great potential for applications in tissue engineering. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016 , 133, 43643.  相似文献   

20.
Organoclay reinforced poly(lactic acid) (PLA)/poly(vinyl alcohol) (PVA) blend based porous nanocomposite scaffolds are prepared by microcompounding/injection molding and subsequent polymer (PVA)/particle (NaCl) leaching method. The objective of the study is to investigate the effect of clay content on the properties of scaffolds for tissue engineering. It is revealed from X‐ray diffraction and TEM studies that incorporation of PVA to PLA matrix as a polymeric porogen enhance the state of dispersion of clay particles resulting in an exfoliated structure. The porosities of all the scaffolds are higher than 70% and the pores are well‐interconnected as observed by SEM. The addition of clay to the scaffolds improves the compressive modulus. Differential scanning calorimeter analysis shows that Tg of neat‐PLA is shifted to lower values when it is compounded with PVA. As a result, it is demonstrated that the method applied in this work can be a good candidate for production of polymeric scaffolds for tissue engineering applications. POLYM. COMPOS., 2010. © 2009 Society of Plastics Engineers  相似文献   

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