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

Poly(ethylene glycol) (PEG) and sodium chloride (NaCl) are excipients used in PLGA microsphere preparation to stabilize proteins and reduce their burst release. No information is till now available in the literature on the effect due to the use of such excipients on the biopharmaceutical performance of gamma-irradiated microparticulate systems. On this purpose, different batches of microspheres containing ovalbumin (OVA) were prepared by using a PLGA 50:50 (average Mr: 13000), different amounts of PEG (Mr: 400 or 4000) and/or sodium chloride. The non-irradiated and irradiated microspheres were characterized in terms of morphology (SEM, particle size distribution), OVA and PEG content and in vitro OVA release. Radiolysis mechanisms of OVA and OVA loaded microspheres were investigated by EPR analysis. Gamma irradiation affects either microsphere morphology or the release of OVA as a function of the amount of PEG, and the use of NaCl. Irradiation significantly reduces release rate of protein from the microspheres containing 15% and 30% of PEG and from controls (microspheres without additives), while no significative effect on protein release rate is highlighted on microspheres containing lower amounts of PEG. EPR investigation shows that increasing amounts of PEG up to 30% have a perturbation effect on OVA radiolysis path.
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PMID:The effect of gamma-irradiation on PLGA/PEG microspheres containing ovalbumin. 1602 54

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

The purpose was to produce solid dispersions of a poorly water-soluble drug, Lu-X, by melt agglomeration in a laboratory scale rotary processor. The effect of binder type and method of manufacturing on the dissolution profile of Lu-X was investigated. Lactose monohydrate and Lu-X were melt agglomerated with Rylo MG12, Gelucire 50/13, PEG 3000, or poloxamer 188. Either a mixture of binder, drug, and excipient was heated to a temperature above the melting point of the binder (melt-in procedure) or a dispersion of drug in molten binder was sprayed on the heated excipient (spray-on procedure). The agglomerates were characterized by DSC, XRPD, SEM, and EDX-SEM. The study showed that the agglomerates containing solid dispersions had improved dissolution rates compared to physical mixtures and pure drug. The melt-in procedure gave a higher dissolution rate than the spray-on procedure with PEG 3000, poloxamer 188, and Gelucire 50/13, whereas the opposite was found with Rylo MG12. This was explained by differences in mechanisms of agglomerate formation and growth, which were dominated by immersion with PEG 3000, poloxamer 188, and Gelucire 50/13, and by distribution and coalescence with Rylo MG12. The spray-on procedure resulted in a higher content of Lu-X in the core of the agglomerates when immersion was the dominating mechanism, and in a higher content in the agglomerate surface when distribution was dominating. The melt-in procedure resulted generally in a homogeneous distribution of Lu-X in the agglomerates. The compounds in the agglomerates were found primarily to be crystalline, and the dissolution profiles were unchanged after 12 weeks storage at 25 degrees C at 50% RH.
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PMID:Effect of a melt agglomeration process on agglomerates containing solid dispersions. 1613 73

This paper reports the study of the complete degradation process for a series of newly synthesized multi-block poly(ester urethane)s consisting of poly[(R)-3-hydroxybutyrate] (PHB) as hard and hydrophobic block and poly(ethylene glycol) (PEG) as soft and hydrophilic segment. The initial stages of degradation of the poly(PHB/PEG urethane)s were monitored by carrying out the degradation experiments at pH 7.4 and 37 degrees C. The weight loss of the copolymer films was traced, and the degraded copolymer films were characterized by GPC, (1)H NMR, TGA, and SEM. The induction phase of the polymer degradation was characterized by a random chain scission of the ester backbone bonds of the PHB segments and an insignificant decline in the weight of the polymer films. An accelerated degradation process was carried out at pH 11.5 and 37 degrees C to investigate the long-term degradation behaviour. The characterization of the degraded polymer films was similar to that for the experiment at pH 7.4. In addition, the water-soluble degradation products were characterized by GPC, (1)H NMR, and FTIR. The main components of the water-soluble degradation products were found to be PEG blocks (monomeric up to quadmeric), 3-hydroxybutyric acid, and crotonic acid. It was found that the copolymer incorporating the highest amount of PEG degraded at the highest rate of all the copolymers studied. The complete degradation of the poly(PHB/PEG urethane)s was monitored using a combination of the physiological and accelerated hydrolytic degradation.
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PMID:The in vitro hydrolysis of poly(ester urethane)s consisting of poly[(R)-3-hydroxybutyrate] and poly(ethylene glycol). 1630 7

To investigate the effect of three kinds of polymeric scaffolds on attachment, proliferation and differentiation of bone marrow mesenchymal stem cells, the cells were different polymeric scaffolds of PLA-PEG, PLA, PLGA, respectively. The proliferation of cell was evaluated by cell count; the attachment and morphology of BMSCs were observed by SEM; and differentiation was detected by alkaline phosphatase activity, fluorescence, and RT-PCR methods. Results showed that the cells in PLGA group spread better among BMSCs adhered to the three polymeric scaffolds. The activity of ALP was detected after 3 days culture in these three groups. There were no significant differences between PLA-PEG and PLGA groups, but the activity of ALP was higher than PLA group. The gene expressions of osteocalicin and collagen I were also observed in the early culture time. Calcium nodes formation in these polymeric scaffolds were detected. BMSC spreading first, then overlapping growth and secretion of matrix around the bottom and surface of scaffolds were observed through SEM. In summary, PLA-PEG and PLGA are better polymeric scaffolds for the bone tissue engineering, compared with PLA.
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PMID:[Effect of polymeric scaffolds on attachment and growth of bone marrow mesenchymal stem cells]. 1642 95

A depot drug delivery system, fibrin encapsulated liposome-in-chitosan matrix (FLCM), has been developed to deliver a water-soluble drug which is configured by a porous chitosan matrix containing a bovine fibrin network encapsulated different surface properties of liposomes. Quinacrine (QR), a water-soluble, low-molecular weight fluorescent marker, is used as a model drug to evaluate the delivery characteristics of the system. The SEM photographs show that the fibrin network adheres to the surfaces and pores of the chitosan matrix of a FLCM system. The QR release periods of the FLCM are sustained for about four times longer than those of QR encapsulated into the liposomes. However, the QR release periods and profiles of the FLCM are influenced by the surface properties of liposomes. The release of QR from FLCM is sustained for 9 days for neutral liposomes and only 5 days for PEG modified liposomes (PEG-liposome). After crosslinking the fibrin network of the FLCM with 0.5% of glutaldehyde, the release of QR is further sustained for 17 days with good linear profiles (e.g., 13 days) and with 50% of reduced burst release compared with those of without crosslinking, indicating that the stability of the fibrin network plays an important role on QR release of the system. More interestingly, the release periods and profiles of QR of the FLCM system are highly similar to those of Tirofiban, low-molecular weight of a water-soluble clinical cardiovascular drug, although the study has been done by human platelet poor plasma instead of bovine fibrinogen as a source of fibrin network. It suggests that the QR is a suitable model for investigating the drug delivery behaviors for water-soluble, low-molecular weight drugs of the FLCM. In conclusion, with QR as a model drug, FLCM with crosslinked fibrin network can effectively sustain the release of QR for 17 days but the release profiles are influenced by the surface properties of encapsulated liposomes. This study suggests that FLCM may have the potential as a depot drug delivery system for water-soluble drugs.
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PMID:A fibrin encapsulated liposomes-in-chitosan matrix (FLCM) for delivering water-soluble drugs. Influences of the surface properties of liposomes and the crosslinked fibrin network. 1644 64

This study focused on the synthesis and characterization of poly(ethylene glycol)-poly(D,L-lactide-co-glycolide)-poly(ethylene glycol) tri-block co-polymer (PEG-PDLLG-PEG), and its modification with type-I collagen. To this aim, a PEG-PDLLG-PEG tri-block co-polymer was synthesized in two steps by reacting poly(ethylene glycol)bis(carboxymethyl)ether with thionyl chloride to obtain an acyl-halide-terminated poly(ethylene glycol) and subsequently coupling this compound to hydroxyl-terminated poly(D,L-lactide-co-glycolide) (PDLLG). The new carboxyl endgroups of PEG-PDLLG-PEG were subsequently reacted with N-hydroxysuccinimide (NHS) in the presence of the hetero-bifunctional cross-linking agent dicyclohexylcarbodiimide (DCC) in order to activate the co-polymer for coupling with collagen. PEG-PDLLG-PEG and its activated form PEG-PDLLG-NHS were characterized by Fourier transform infrared (FT-IR) and 1H-NMR spectroscopy. Molecular weights of the polymeric products were determined by SEC. Type-I collagen in phosphate buffer was reacted with PEG-PDLLG-NHS. The resultant product, PEG-PDLLG-Col, was characterized by FT-IR. This biopolymer was used for preparation of a suitable surface for cell growth experiment. To measure the degree of cell proliferation, the films prepared with PDLLG, PEG-PDLLG-NHS and PEG-PDLLG-Col were seeded with L929 mouse fibroblasts. Cell growth was followed by SEM photography and quantitated by the neutral red uptake assay. It was shown that the attachment of collagen significantly increased the number of cells on the co-polymers.
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PMID:Synthesis and characterization of poly(ethylene glycol)-poly(D,L-lactide-co-glycolide) poly(ethylene glycol) tri-block co-polymers modified with collagen: a model surface suitable for cell interaction. 1668 18

New amorphous amphiphilic triblock copolymers of poly(3-hydroxybutyrate)-poly(ethylene glycol)-poly(3-hydroxybutyrate) (PHB-PEG-PHB) were synthesized using the ring-opening copolymerization of beta-butyrolactone monomer. They were characterized by fluorescence, SEM and (1)H NMR. These triblock copolymers can form biodegradable nanoparticles with core-shell structure in aqueous solution. Comparing to the poly(ethylene oxide)-PHB-poly(ethylene oxide) (PEO-PHB-PEO) copolymers, these nanoparticles exhibited much smaller critical micelle concentrations and better drug loading properties, which indicated that the nanoparticles were very suitable for delivery carriers of hydrophobic drugs. The drug release profile monitored by fluorescence showed that the release of pyrene from the PHB-PEG-PHB nanoparticles exhibited the second-order exponential decay behavior. The initial biodegradation rate of the PHB-PEG-PHB nanoparticles was related to the enzyme amount, the initial concentrations of nanoparticle dispersions and the PHB block length. The biodegraded products detected by (1)H NMR contained 3HB monomer, dimer and minor trimer, which were safe to the body.
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PMID:Biodegradable nanoparticles of amphiphilic triblock copolymers based on poly(3-hydroxybutyrate) and poly(ethylene glycol) as drug carriers. 1674 Mar 6

Porous poly(ethylene glycol) terephthalate:poly (butylene terephthalate) (PEGT:PBT) scaffolds with high PEG molecular weight (1000 g/mole) and PEGT content (60%) were fabricated using two different processes-paraffin templating and compression molding-for cartilage engineering applications. This polymer composition has previously been shown to enable chondrocyte adhesion and maintain differentiated phenotype in 2D monolayer culture. The influence of 3D polymer scaffold processing on the formation of cartilaginous tissue was studied by seeding primary immature bovine chondrocytes within cylindrical scaffolds in mixed flask reactors for 3 days, followed by cultivation in culture plates for a total of 10 or 24 days. Tissue-polymer constructs were evaluated morphologically by SEM and histology, and quantitatively for cellularity, total collagen, and glycosaminoglycan content, all of which remained statistically equivalent for each time point tested, irrespective of fabrication method. These data demonstrate that the polymers engineered for this study were able to support chondrogenesis independent of scaffold fabrication process, with the influence of pore architecture lessened by the highly hydrated scaffold microenvironments induced by high PEG content.
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PMID:Evaluation of chondrogenesis within PEGT: PBT scaffolds with high PEG content. 1688 18

We report the encapsulation of MIN6 cells, a pancreatic beta-cell line, using thermally induced gelable materials. This strategy uses aqueous solvent and mild temperatures during encapsulation, thereby minimizing adverse effects on cell function and viability. Using a 2:1 mixture of PNIPAAm-PEG-PNIPAAm tri-block copolymer and PNIPAAm homopolymer that exhibit reversible sol-to-gel transition at approximately 30 degrees C, gels were formed that exhibit mechanical integrity, and are stable in H(2)O, PBS and complete DMEM with negligible mass loss at 37 degrees C for 60 days. MTT assays showed undetectable cytotoxicity of the polymers towards MIN6 cells. A simple microencapsulation process was developed using vertical co-extrusion and a 37 degrees C capsule collection bath containing a paraffin layer above DMEM. Spherical capsules with diameters ranging from 500 to 900 microm were formed. SEM images of freeze-dried capsules with PBS as the core solution showed homogenous gel capsule membranes. Confocal microscopy revealed that the encapsulated cells tended to form small aggregates over 5 days, and staining for live and dead cells showed high viability post-encapsulation. A static glucose challenge with day-5 cultured microencapsulated cells exhibited glucose-dependent insulin secretion comparable to controls of free MIN6 cells grown in monolayers. These results demonstrate the potential use of these thermo-responsive polymers as cell encapsulation membranes.
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PMID:Thermally induced gelable polymer networks for living cell encapsulation. 1689 33


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