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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Hexakis[p-(hydroxylmethyl)phenoxy]cyclotriphosphazene was synthesized by the reaction of hexachlorocyclotriphosphazene with the sodium salt of 4-hydroxybenzaldehyde and subsequent reduction of aldehyde groups to alcohol groups by using sodium borohydride. This compound was employed in initiating the ring-opening polymerization of epsilon-caprolactone and L-lactide to produce star-shaped poly(L-lactide) (PLA), poly(epsilon-caprolactone) (PCL), and their block copolymer with cyclophosphazene cores. 1H NMR and GPC analysis showed narrow-distributed star-shaped polyesters were successfully synthesized with high yields.
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PMID:Synthesis of the star-shaped copolymer of epsilon-caprolactone and L-lactide from a cyclotriphosphazene core. 1460 71

To evaluate the predominant mechanism of chondrogenic cell [mesenchymal stem cells (MSCs) and chondrocytes] adhesion under serum free conditions, we measured the surface roughness and wettability of poly(lactic acid:polyglycolic acid=75:25) (PLGA), poly(lactic acid) (PLA), and poly(-epsilon-caprolactone) (PCL)-coated glass plates. Also to evaluate the biological reactions involved in cell-polymer interactions, integrin beta1, one of the cell adhesion molecules, was blocked with monoclonal antibody. In cell attachment test, MSCs and chondrocytes adhesion to synthetic polymers in 1h were very low and ranged from 2.8% to 8.0%. In present study, the correlation between attachment rate and surface roughness, contact angle, or integrin beta1 blocking on PLGA, PLA and PCL-coated plates could not be proved. However, we found that L-arginine-coated PLA highly increased the attachment rates of MSCs (30.2%) and of chondrocytes (26%), whereas integrin beta1 blocking significantly decreased these attachment rates to 5.6% and 7.4%, respectively, suggesting that increased cell adhesion to L-arginine-coated plates is mediated by integrin beta1. In this study, we showed that polymer characteristics such as roughness and wettability did not play an important role in cell adhesion under serum free conditions, because there was no significant difference according to polymer characteristics, whereas biological interactions mediated by integrin beta1 were critical during the early period of cell adhesion. The results suggest that L-arginine could be useful for facilitating early cell adhesion to synthetic polymers in cartilage tissue engineering.
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PMID:Importance of integrin beta1-mediated cell adhesion on biodegradable polymers under serum depletion in mesenchymal stem cells and chondrocytes. 1473 54

Nanospheres (NS) formulated using biodegradable and biocompatible polymers, poly(D,L-lactide-co-glycolide) (PLGA), poly(D,L-lactide) (PLA) and poly(epsilon-caprolactone) (PCL), loaded with the pure anti-estrogen RU 58668 (RU), a promising estrogen-dependent anticancer agent, have been prepared. They all possess a small size compatible with an intratumoral extravasation behavior and their pegylation reduce significantly their zeta potential. Characterization by freeze fracture electron microscopy have shown that NS are spheric particles with a size ranging between 30 and 50nm and a tendency to agglomerate which is reduced by polyethylene glycol (PEG) grafting. PEG-grafted NS are all non-toxic as revealed by cell viability assay. A specific cellular model has been used to evaluate not only the release extent of the drug but also its biological activity. All formulations tested showed that they release slowly RU as measured by the delayed ability of RU to inhibit estrogen-induced transcription in human breast cancer cells and that they possess only a small amount of surface adsorbed RU.
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PMID:Pure antiestrogen RU 58668-loaded nanospheres: morphology, cell activity and toxicity studies. 1475 10

Controlled release polymer vesicles are prepared using hydrolysable diblock copolymers of polyethyleneglycol-poly-l-lactic acid (PEG-PLA) or polyethyleneglycol-polycaprolactone (PEG-PCL). Encapsulation studies with a common anti-cancer agent, doxorubicin, show loading comparable to liposomes. Rates of encapsulant release from the hydrolysable vesicles are accelerated with an increased proportion of PEG but are delayed with a more hydrophobic chain chemistry (i.e. PCL). Rates of release also rise linearly with the molar ratio of degradable copolymer blended into membranes of a non-degradable, PEG-based block copolymer (PEG-polybutadiene (PBD)). With all compositions, in both 100 nm and giant vesicles, the average release time (from hours to days) reflects a highly quantized process in which any given vesicle is either intact and retains its encapsulant, or is porated and slowly disintegrates. Poration occurs as the hydrophobic PLA or PCL block is hydrolytically scissioned, progressively generating an increasing number of pore-preferring copolymers in the membrane. Kinetics of this evolving detergent mechanism overlay the phase behavior of amphiphiles with transitions from membranes to micelles allowing controlled release.
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PMID:Self-porating polymersomes of PEG-PLA and PEG-PCL: hydrolysis-triggered controlled release vesicles. 1506 28

The aim of this work was to encapsulate superoxide dismutase (SOD) into biodegradable microparticles by spray-drying technique. The nature of the organic solvent to dissolve the polymer, the method of incorporation of the drug in the organic phase (with or without a surfactant, namely sucrose ester of HLB = 6), the surfactant/polymer ratio, and the nature of the biodegradable polyesters were investigated as formulation variables. The polyesters investigated as matrix were poly(epsilon-caprolactone) (PCL), poly(d, l, lactide-co-glycolide) (PLG-RG756), and poly(d, l-lactide) (PLA-R207) of respective molecular weight 78.2 kDa, 84.8 kDa, and 199.8 kDa. At surfactant/polymer ratio of 1/10, the SOD-retained enzymatic activities were higher (> 95%) for PLG-RG756 and PLA-R207 but relatively lower for the PCL (approximately 85%) probably due to the PCL relatively higher hydrophobicity. The obtained microparticles exhibited average volume mean diameter of 4-10 microm, the smaller for PCL and the larger for PLG-RG756 polymeric matrix. The in vitro release profile showed that SOD was completely (100%) released from PLA-R207 in 48 hr and from PLG-RG756 and PCL within 72 hr. These results showed that spray-drying with incorporation of surfactant such as sucrose ester may efficiently encapsulate SOD into biodegradable microparticles. Such formulations may improve the bioavailability of SOD and similar biopharmaceuticals.
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PMID:Microencapsulation of superoxide dismutase into biodegradable microparticles by spray-drying. 1520 40

Biodegradable polymers such as poly(lactide) (PLA) and poly(epsilon-caprolactone) (PCL) are increasingly used in biomedical applications as temporary implants. However, melt processing of these materials in particular of PLA is difficult due to the temperature sensitivity. Within this study, PLA and PCL were injection molded conventionally and by using the process shear controled orientation in injection molding (SCORIM) in order to investigate the effect of processing parameters on the physical properties of the moldings. Therefore, flexural testing, differential scanning calorimetry (DSC), wide-angle X-ray diffraction (WAXD), molecular weight (MW) and orientation measurements were performed. PLA showed high sensitivity to melt temperature. In the case of amorphous poly(DL-lactide), the molecular weight and subsequently the ductility is substantially reduced by processing at higher melt temperatures. In the case of crystallizable poly(L-lactide), higher melt temperatures and shear induced by the SCORIM process resulted in enhanced crystallinity, which compromised the mechanical properties. Generally, SCORIM processing improved the mechanical properties, in particular the ductility, by orientating the molecular structure. PCL was shown to be less sensitive to shear and temperature than PLA. Stress at yield and stiffness are more improved by SCORIM processing. However, the processing temperature in combination with the grade used proved to be influential for the mechanical properties of resulting moldings.
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PMID:Non-conventional injection molding of poly(lactide) and poly(epsilon-caprolactone) intended for orthopedic applications. 1533 53

In this study, porous polymer (PLA/PCL) membrane was first treated with ethanol to become hydrophilic, and then immersed into DMEM with 50% fetal bovine serum to enhance the affinity to cells. MSCs cultured in osteogenic medium were loaded into the membrane at density of 5 x 10(6)/cm2 for 7 days, and scanning electrical microscope was used to observe the growth of the MSCs. The growth of MSCs inside the constructs was functionally well, and the cells proliferated with the time of culture. We concluded from current study that the membrane had satisfactory biocompatibility and the constructs could be used to guided bone regeneration.
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PMID:[Construction of guided bone regeneration membrane by tissue engineering in vitro]. 1535 36

For use in micro-patterned scaffolds in tissue engineering, novel diacrylated triblock macromers (PLA-b-PCL-b-PLA, PGA-b-PCL-b-PGA and PCL-b-PEO-b-PCL) were synthesized and characterized by Fourier transform infrared spectroscopy (FTIR), nuclear magnetic resonance spectroscopy (NMR) and gel permeation chromatography (GPC). All diacrylated polymers were designed as triblock copolymers and involved biodegradable blocks of relatively non-polar epsilon-caprolactone (CL) and polar monomers such as glycolide (GA), lactide (LA) or ethylene oxide (EO). All triblock polymers were prepared in molecular weights of a few kilo daltons via the anionic ring-opening polymerization (ROP) of the corresponding lactide, glycolide or caprolactone using stannous octoate [Sn(Oct)(2)] as catalyst. The polymers had low polydispersity indices, ranging from 1.23 to 1.56. Biodegradable polymeric networks were prepared with conversions of 72-84% via photopolymerization of the triblock diacrylated polymers with 2,2-dimethoxy-2-phenylacetophenone (DMPA) as photoinitiator. PLA-b-PCL-b-PLA copolymers crumbled easily and were not suitable for micro-patterning. PGA-b-PCL-b-PGA copolymers had higher water contact angles than PCL-b-PEO-b-PCL and were also cytocompatible with Fibroblasts 3T3.
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PMID:Novel photopolymerizable biodegradable triblock polymers for tissue engineering scaffolds: synthesis and characterization. 1546 60

A highly sensitive analytical method for evaluation of poly(L-lactide) (PLA), poly(epsilon-caprolactone) (PCL), poly(beta-hydroxybutyrate) (PHB), and poly(butylene succinate) (PBS) degradability was developed using coated cellulose paper, prepared by penetration and adhesion of these plastics into/onto the cellulose paper. Enzymatic degradability of the obtained plastic coated papers was evaluated using various commercial proteases and lipases. PLA coated paper was highly susceptible to subtilisin and mammalian enzymes, alpha-chymotrypsin, elastase and trypsin. To our knowledge, this is the first report on the degradation of PLA coated paper using subtilisin and mammalian enzymes. Almost all lipase preparations degraded PCL and PHB coated papers but not PBS coated paper. The biodegradability of plastic coated paper was greater than that of plastic powder. The penetration of plastic into cellulose paper by coating improved the plastic degradability, and can be regulated easily.
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PMID:A new method for the evaluation of biodegradable plastic using coated cellulose paper. 1546 96

A series of poly(epsilon-caprolactone)/poly(L-lactic acid) (PCL/PLA) biodegradable poly(ester-urethane)s, was synthesized and characterized. The first step of the synthesis consisted of the ring opening polymerization of L-lactide, initiated by the hydroxyl terminal groups of the PCL chain, followed by the chain extension of these PLA-PCL-PLA triblocks, using hexamethylene diisocyanate (HDI). The trimers comprised PCL2000 flexible segments, while the length of each PLA block covered the 550-6000 molecular weight range. The morphology of the copolymers gradually changed, as the length of the PLA blocks increased. The multiblock copolymers produced displayed enhanced mechanical properties, with ultimate tensile strength values around 32 MPa, Young's modulus as low as 30 MPa and elongation at break values well above 600%. The longer the PLA block, the slower the in vitro degradation of the material, with all copolymers degrading faster than the respective homopolymers.
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PMID:Designing biodegradable multiblock PCL/PLA thermoplastic elastomers. 1558 32


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