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Query: UMLS:C0432222 (SEM)
 47,337 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The degradation of P(DLAX-ran-CLY)-b-PEG-b-P(DLAX-ran-CLY)s ( P(DLAX-ran-CLY): Poly(D,L-lactide-ran-epsilon-caprolactone), PEG: Poly(ethylene glycol), X: D,L-lactyl unit fraction, Y: epsilon-caproyl unit fraction) is investigated. The fraction of DLA in the both end blocks is varied while the overall molecular weight and molecular weight of PEG are kept constant. DSC, XRD and GPC are employed to track the degradation process up to 200 days. Also the change in the surface and cross-sectional morphology is provided by SEM micro-photographs. The result of water absorption and weight loss characterization reveals that the incorporation of DLA in the polyester block could be an effective tool to facilitate degradation as well as water absorption. By tracking the change of molecular weight and polydispersity, chain scission and transport or removal of degraded product from the specimen were found to play a complex role in overall degradation.
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PMID:The effect of epsilon-caproyl/D,L-lactyl unit composition on the hydrolytic degradation of poly(D,L-lactide-ran-epsilon-caprolactone)-poly(ethylene glycol)-poly(D,L-lactide-ran-epsilon-caprolactone). 1609 97

Poly(3-hydroxybutyrate) (P3HB), its co-polymers with 3-hydroxyvalerate (HV) (PHBV8 and PHBV22), and their hydroxyapatite (HAp) containing composites (5 and 15%, w/w) were prepared by injection molding. PHBV bone plates with low valerate contents and 15% (w/w) HAp appear to have better mechanical properties than the others. Flexural strengths of 15% (w/w) HAp-loaded P3HB, PHBV8 and PHBV22 were 78.28, 63.45 and 39.38 MPa, respectively. Tensile strengths of 15% (w/w) HAp-loaded P3HB, PHBV8 and PHBV22 were 18.99, 15.44 and 11.02 MPa, respectively. For the ageing test, bone plates were incubated in phosphate-buffered saline PBS (0.1 M, pH 7.4) at 37 degrees C and at pre-determined time points they were removed and subjected to a three-point bending test. Incubation in PBS caused a sharp decrease in the mechanical properties within the first 24 h, followed either by a gradual decrease or no change for a period of about 1 month. SEM results showed that there was no significant material erosion in the 4-week incubation period. P3HB loaded with 15% HAp appeared to yield the most suitable bone plate, insofar as mechanical properties are concerned with potential for further testing in vivo.
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PMID:Hydroxyapatite reinforced poly(3-hydroxybutyrate) and poly(3-hydroxybutyrate-co-3-hydroxyvalerate) based degradable composite bone plate. 1636 34

Poly(vinylidenefluoride)-hexafluoropropylene (PVdF(HFP))-ionic liquid gel electrolytes were prepared using ionic liquids based on 1-(2-hydroxyethyl)-3-methyl imidazolium tetrafluoroborate and 1-(2-hydroxyethyl)-3-methyl imidazolium hexafluorophosphate. A conventional metathesis reaction was used to prepare these ionic liquids, which have high purity and exhibit a liquid state at room temperature. The prepared polymer-ionic liquid gel proved to be a free-standing and rubbery film in which the degree of transparency differed according to the ratio and type of ionic liquid used. TGA and FTIR analyses confirmed that the solvent, N,N-Dimethylacetamide (DMAC), used for mixing PVdF(HFP) polymer with ionic liquid was almost totally removed during the gelling and drying processes. SEM photographs were taken of the surface structure of the PVdF(HFP)-ionic liquid gel in order to evaluate the morphology of the film's surface according to the mixing ratio and the nature of the ionic liquid. The thermal behaviors of PVdF(HFP)-ionic liquid gels were observed to be similar to those of neat ionic liquids through DSC analysis, and the compatibility between the polymer and ionic liquid was investigated by XRD analysis. The ionic conductivities of all the gels were 10(-3)-10(-5) S cm(-1) in a temperature range of 20-70 degrees C.
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PMID:Characterization of PVdF(HFP) gel electrolytes based on 1-(2-Hydroxyethyl)-3-methyl imidazolium ionic liquids. 1685 1

Nanofibers have recently gained substantial interest for potential applications in tissue engineering. The objective of this study was to determine whether electrospun nanofibers accommodate the viability, growth, and differentiation of human mesenchymal stem cells (hMSCs) as well as their osteogenic (hMSC-Ob) and chondrogenic (hMSC-Ch) derivatives. Poly(d,l-lactide-co-glycolide) (PLGA) beads with a PLA:PGA ratio of 85:15 were electrospun into non-woven fibers with an average diameter of 760+/-210 nm. The average Young's modulus of electrospun PLGA nanofibers was 42+/-26 kPa, per nanoindentation with atomic force microscopy (AFM). Human MSCs were seeded 1-4 weeks at a density of 2 x 10(6)cells/mL in PLGA nanofiber sheets. After 2 week culture on PLGA nanofiber scaffold, hMSCs remained as precursors upon immunoblotting with hKL12 antibody. SEM taken up to 7 days after cell seeding revealed that hMSCs, hMSC-Ob and hMSC-Ch apparently attached to PLGA nanofibers. The overwhelming majority of hMSCs was viable and proliferating in PLGA nanofiber scaffolds up to the tested 14 days, as assayed live/dead tests, DNA assay and BrdU. In a separate experiment, hMSCs seeded in PLGA nanofiber scaffolds were differentiated into chodrogenic and osteogenic cells. Histological assays revealed that hMSCs continuously differentiated into chondrogenic cells and osteogenic cells after 2 week incubation in PLGA nanofibers. Taken together, these data represent an original investigation of continuous differentiation of hMSCs into chondrogenic and osteogenic cells in PLGA nanofiber scaffold. Consistent with previous work, these findings also suggest that nanofibers may serve as accommodative milieu for not only hMSCs, but also as a 3D carrier vehicle for lineage specific cells.
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PMID:Continuing differentiation of human mesenchymal stem cells and induced chondrogenic and osteogenic lineages in electrospun PLGA nanofiber scaffold. 1701 Apr 25

Poly(D,L-lactide-co-glycolide) (PLGA) biodegradable microspheres with gentamicin for local treatment of microbial bone infection were prepared and characterized. Gentamicin was assayed spectrophotometrically at 332 nm after derivation with the o-phthalaldehyde; biodegradable polymers studied did not interfere with this method of gentamicin analysis. PLGA microspheres were made by the double emulsion solvent evaporation method with modifications. The first W(1)/O emulsion was obtained by ultrasonication or high-speed homogenization, and a large aqueous phase W(2) (200 ml) was used. The ultrasonication method increases the microsphere percentage observed in the 20-40 microm size range and, in all cases SEM-microphotographs revealed homogeneous and spherically shaped particles with smooth surfaces. The method including ultrasonication proposed in the present work improved the encapsulation efficiency of gentamicin by nearly 100% (97.94%). Several mathematical models based on heterogeneous hydrolytic degradation were applied to evaluate their suitability in describing gentamicin released from PLGA microspheres. Two models, one of them including an autocatalytic process, were finally proposed to contribute to understand the mass transport mechanism involved in drug release from these microspheres.
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PMID:Improvement of gentamicin poly(D,L-lactic-co-glycolic acid) microspheres for treatment of osteomyelitis induced by orthopedic procedures. 1706 61

Poly(2-hydroxy-3-phenoxypropylacrylate, 4-hydroxybutyl acrylate, dibutyl maleate) membrane was synthesized by UV curing method in our laboratory for the first time. When above-mentioned monomers were in the weight ratio of 4:4:2, the membrane not only had perfect permeation property but also had excellent plasticity, so the membrane made from monomers in the ratio of 4:4:2 was chosen as an optimized membrane. The optimized membrane provided perfect linear permeation properties in clonidine transdermal drug delivery system. The permeation rate decreased in proportion to the thickness of membrane. When the concentrations of clonidine were in the range of 0.5-7.0mg/ml, the permeation rate was proportional to the square root of clonidine concentrations. The optimized membrane was characterized by FTIR, DSC and SEM.
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PMID:Poly(2-hydroxy-3-phenoxypropylacrylate, 4-hydroxybutyl acrylate, dibutyl maleate) membrane controlled clonidine zero-order release. 1719 6

Controlling cell adhesion and proliferation on synthetic polymers is key to tissue engineering scaffold development. It is accepted that surface topography influences cell response but the mechanisms behind this remain unclear. In this work, cell response is assessed to topographies larger than focal complexes (FXs) but smaller than focal adhesions (FAs). Poly(L-lactic acid) was patterned with 400- and 700-nm pillars via replication molding. Human fibroblast adhesion and proliferation were assessed. The development of focal contacts and actin microfilaments were evaluated via immunofluorescence. Cell interactions with surface topography were observed via scanning electron microscopy. Initial fibroblast adhesion (<1 day) increased with texture as 400 nm > 700 nm > smooth, but proliferation (>1 day) decreased with texture. Increased FX formation was observed on textured surfaces. However, FAs were narrower on textured surfaces compared with smooth materials and confined to interpillar regions. SEM showed that fibroblasts deformed the 400-nm pillars. It is hypothesized that surface texture mediated FX formation and increased cell adhesion, possibly via increased material surface area. Texture geometry limited maturation of FXs to FAs, decreasing proliferation. We conclude that surface texture can alter cell adhesion and proliferation and propose geometric constraint as a mechanism for this process.
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PMID:Submicron poly(L-lactic acid) pillars affect fibroblast adhesion and proliferation. 1726 38

Poly-L-lactic acid (PLLA)/hydroxyapatite (HA) hybrid membranes were fabricated via electrospinning of the PLLA/HA dispersion for use in bone tissue regeneration. The structural properties and morphologies of PLLA and PLLA/HA hybrid membrane were investigated by measuring the Brunauer-Emmett-Teller specific surface area, observations of SEM, and TEM. The dispersion and integrating of HA nanoparticles in the hybrid membrane were studied by energy dispersion X-ray analysis and FTIR. The mechanical properties of PLLA/HA membrane were also measured by tensile tests. For exploring biological behaviors of the hybrid membrane, in vitro degradation tests were carried out. The osteoblast cell (MG-63) was cultured in PLLA/HA hybrid membrane extract containing medium; the cell adhesion and growth capability were investigated by SEM observation and MTT assay. HA nanoparticles were not only dispersed in the PLLA but also reacted with the functional group of PLLA, resulting in strong surface bonding and high tensile strength of hybrid membrane. The cell adhesion and growth on the PLLA/HA hybrid membrane were far better than those on the pure PLLA membrane, which proves that the PLLA/HA hybrid membrane can be one of the promising biomaterials for bone tissue regeneration.
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PMID:Poly-L-lactic acid/hydroxyapatite hybrid membrane for bone tissue regeneration. 1729 52

(Poly)acrylonitrile/chitosan (PANCHI) composite membranes were prepared. The chitosan layer was deposited on the surface as well as on the pore walls of the base membrane. This resulted in the reduction of the pore size of the membrane and in an increase of their hydrophilicity. The pore structure of PAN and PANCHI membranes were determined by TEM and SEM analyses. It was found that the average size of the pore under a selective layer base PAN membrane is 7 microm, while the membrane coated with 0.25% chitosan shows a reduced pore size--small or equal to 5 microm and with 0.35% chitosan--about 4 microm. The amounts of the functional groups, the degree of hydrophilicity and transport characteristics of PAN/Chitosan composite membranes were determined. Urease was covalently immobilized onto all kinds of PAN/chitosan composite membranes using glutaraldehyde. Both the amount of bound protein and relative activity of immobilized urease were measured. The highest activity (94%) was measured for urease bound to PANCHI2 membranes (0.25% chitosan). The basic characteristics (pH(opt), pH(stability), T(opt), T(stability), heat inactivation and storage stability) of immobilized urease were determined. The obtained results show that the poly(acrylonitrile)chitosan composite membranes are suitable for enzyme immobilization.
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PMID:Poly(acrylonitrile)chitosan composite membranes for urease immobilization. 1732 Feb 33

The objective of this study is to construct complex of DNA and PLGA/HAp composite scaffold for bone tissue engineering. Naked DNA has low transfection efficiency so DNA loaded chitosan particles are used nowadays in gene delivery due to their high transfection efficiency, but unfortunately this is accompanied by strong immunological reaction of cells. In order to preserve the advantage of polymeric particles and reduce immunological effect at the same time, a new DNA release system is developed which makes possible sustained DNA release with negligible immunological effects. Poly (lactide-co-glycolide) (PLGA)/Hydroxylapatite (HAp) composite scaffolds with different HAp contents (0%, 5% and 10%) are fabricated by an electrospinning method and DNA is incorporated into the scaffolds in 3 ways (i.e. naked DNA, encapsulation of DNA/chitosan nanoparticles into scaffolds after fiber fabrication by dripping, and encapsulation of DNA/chitosan nanoparticles into scaffold by mixing with PLGA/HAp solution before fiber fabrication). All the scaffolds are characterized by SEM, XRD, DSC and GC-MS and the results show that the scaffolds are non-woven, nano- to micro-fibered membrane structures composed predominantly of PLGA with amorphous dispersion of HAp nanoparticles inside polymeric matrix. In vitro release tests were carried out on 9 different scaffolds to check the effects of HAp contents and the encapsulation ways of DNA on the release properties. These effects are also tested by human marrow stem cells (hMSCs) by comparing their cell attachment ability, cell viability and DNA transfection efficiency. It is demonstrated that the addition of HAp nanoparticles increased the release rate of DNA for both naked and encapsulated DNA. Cell culture experiments show that the scaffolds with encapsulated DNA/chitosan nanoparticles have higher cell attachment, higher cell viablility and desirable transfection efficiency of DNA. The observations show that DNA/chitosan nanoparticles encapsulated PLGA/HAp composite scaffold is promising for use in bone regeneration.
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PMID:Fabrication and characterization of PLGA/HAp composite scaffolds for delivery of BMP-2 plasmid DNA. 1751 77


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