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

A new plasticizer for poly(L-lactide) (PLA)-poly(propylene glycol) (PPG) is proposed. The advantage of using PPG is that it does not crystallize, has low glass transition temperature, and is miscible with PLA. PLA was plasticized with PPGs with nominal Mw of 425 and 1000 g/mol. Poly(ethylene glycol) (PEG), long known as a plasticizer for PLA, with nominal Mw of 600 g/mol, was also used to plasticize PLA for comparison. The thermal and tensile properties of PLA and PLA with 5-12.5 wt % of the plasticizers were studied. In blends of PLA with PPGs the glass transition temperature was lower than that of neat PLA. Both PPGs enhanced the crystallizability of PLA albeit less than PEG. All of the plasticizers increased also the ability of PLA to plastic deformation which was reflected in a decrease of yield stress and in an increase of elongation at break. The effect was enhanced by the higher PPG content and also by lower molecular weight of PPG. A phase separation occurred only in the blend containing 12.5 wt % of PPG with higher molecular weight. The evidences of crazing were found in deformed samples of PLA with low plasticizer content, whereas the samples with higher content of plasticizers crystallized due to deformation.
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PMID:Plasticization of poly(L-lactide) with poly(propylene glycol). 1682 79

Camptothecin (CPT)-loaded nanoparticles were prepared using poly(dl-lactic acid) (PLA) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymer (PEG-PPG-PEG), and examined for particle characteristics, in vitro release, pharmacokinetics and efficacy. The preparative condition, in which the ratio of PLA/PEG-PPG-PEG/CPT was 35/35/4 (w/w/w) and organic solvent (dichloromethane) was evaporated from the emulsion at 18 degrees C, gave the nanoparticles with the diameter of approximately 230nm, fairly high drug content (ca. 1.6% (w/w)) and stable entrapment of the drug, which were used for in vivo studies. After i.v. administration to normal rats, the nanoparticles showed slightly smaller AUC but much larger MRT as compared with CPT solution, and delivered the drug greatly to the surrounding tissues, in particular to the liver. When antitumor effect was examined by i.v. administration to mice bearing sarcoma 180 (S-180) solid tumor, the nanoparticles showed a significant suppression of tumor growth without body weight loss, and their effect was better than that of CPT solution. The PLA/PEG-PPG-PEG nanoparticles were considered potentially useful to enhance the efficacy of CPT, to which the high drug retention in the body and gradual drug release appeared to be importantly related.
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PMID:Preparation and antitumor characteristics of PLA/(PEG-PPG-PEG) nanoparticles loaded with camptothecin. 1733 72

Poly(DL-lactic acid) (PLA)/poly(ethylene glycol)-block-poly (propylene glycol)-block-poly(ethylene glycol) copolymer (PEG-PPG-PEG) nanoparticles loaded with camptothecin (CPT), called CPT-NP, were prepared and examined for particle size change and drug release in phosphate-buffered saline, pH 7.4, (PBS), and drug biodistribution profiles in mice bearing sarcoma 180 solid tumor. CPT-NP kept an almost constant mean size and exhibited an initial rapid release of approximately 20%, following by very slow release. As compared with CPT solution, CPT-NP showed higher tissue accumulation and better tumor localization, which were considered essentially associated with the better efficacy of CPT-NP reported in the previous study.
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PMID:Particle characteristics and biodistribution of camptothecin-loaded PLA/(PEG-PPG-PEG) nanoparticles. 1819 17

Multiblock poly(ether ester urethane)s comprising of poly(lactic acid) (PLA), poly(ethylene glycol) (PEG), and poly(propylene glycol) (PPG) segments were synthesized, and their aqueous solutions exhibited thermogelling behavior at critical gelation concentrations (CGC) ranging from 7 to 9 wt%. The chemical structures and molecular characteristics of the copolymers were studied by GPC, 1H NMR, 13C NMR and FTIR. The thermal stability of the poly(PEG/PPG/PLA urethane)s was studied by thermogravimetry analysis (TGA), and the PLA contents were calculated based on the thermal degradation profile. The results were in good agreement with those obtained from the 1H NMR measurements. The critical micellization concentration (CMC) of these water-soluble poly(ether ester urethane)s was determined at different temperatures using a dye solubilization method. The thermodynamic parameters for micelle formation were calculated, indicating that the process is largely entropy-driven. Interestingly, it appears that there exists a requirement for the system to possess a minimum gain in entropy before the thermogelling effect can be observed. Dilute copolymer solutions showed a lower critical solution temperature (LCST) behavior similar to pNIPAM dissolved in aqueous solutions. The thermogels hydrolytically degraded to polymer fragments corresponding to the constituent segment blocks within 3 months.
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PMID:Biodegradable thermogelling poly(ester urethane)s consisting of poly(lactic acid)--thermodynamics of micellization and hydrolytic degradation. 1827 2

In this study a new branched methacrylated poly(propylene glycol-co-lactic acid) (PPG-PLA-IEM) and methacrylated cellulose acetate butyrate resin (CAB-IEM) were synthesized. Hydrogels with various amounts of PPG-PLA-IEM and CAB-IEM (25, 50 and 75 wt% IEM modified) were prepared by photopolymerization. Collagen tethered PEG-monoacrylate (PEGMA-collagen) was prepared and introduced as a bioactive moiety to modify the hydrogel in order to enhance cell affinity. In vitro attachment and growth of 3T3 mouse fibroblasts and human umbilical vein endothelial cells (HUVEC) on the hydrogels with and without collagen were also investigated. It was observed that, the collagen improves the cell adhesion onto the hydrogel surface. With the increasing amount of collagen, cell viability increased by 28% for ECV304 (P < 0.05) and 30% for 3T3 (P < 0.05).
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PMID:Preparation of collagen modified photopolymers: a new type of biodegradable gel for cell growth. 1993 89

Surface modification of poly(dl-lactic acid) (PLA) scaffolds has been performed using a biofunctional small peptide composed of collagen-like repetitive sequence and laminin-derived sequence (AG73-G(3)-(PPG)(5)) via hydrophobic interaction. The results of surface analysis suggest that AG73-G(3)-(PPG)(5) can be stably adsorbed onto PLA films via hydrophobic interaction at the (PPG)(5) region, and form an extracellular matrix-like layer composed of both structural and biosignalling sequences. In addition, neurite outgrowth of PC12 cells was observed on the AG73-G(3)-(PPG)(5)-adsorbed PLA film. These results indicate that AG73-G(3)-(PPG)(5) very effectively enhances neurite outgrowth activity on PLA films. The hydrophobic adsorption of collagen-like peptide bound to biosignalling molecules may be widely applied as a surface modifier of PLA films for tissue engineering.
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PMID:Stable modification of poly(lactic acid) surface with neurite outgrowth-promoting peptides via hydrophobic collagen-like sequence. 1996 10

Dexamethasone (Dex)-loaded implants were prepared by poly(d,l-lactic acid) (PLA) and poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymer (PEG-PPG-PEG, Pluronic F68) using hot-melt extrusion method. The purpose of this research was to develop a hot-melt extruded implant PLA/F68/Dex for controlling release of Dex at the implant site. Drug loading and encapsulation efficiency were determined by UV spectrophotometer analysis. The maximum value of the drug loading and encapsulation efficiency for the implants was up to 48.9% and 97.9%, respectively. Differential scanning calorimetry was used to evaluate stability and interaction between the implant and drug. We had studied the water uptake of PLA/F68 implants kept constant at about 12% due to the water was absorbed to a large extent. Dex release profile in vitro was studied, and the results showed that the maximum value of the release rate was approximately 20%. The degradation behavior was confirmed by mass loss and scanning electron microscopy. In addition, the in vivo biocompatibility study indicated that the implants had no negative influence as a foreign material in the body response.
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PMID:PLA/F68/dexamethasone implants prepared by hot-melt extrusion for controlled release of anti-inflammatory drug to implantable medical devices: I. Preparation, characterization and hydrolytic degradation study. 2317 16

In this study, 5-FU, a potent anticancer drug, is planned to be delivered via a new and promising drug delivery system, nanoparticles formed with hydrophobic core polymer and triblock copolymers; Poly(DL-lactic acid), Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymer (PLA/PEG-PPG-PEG) and Poly(D,L-lactide-co-glycolide)/Poly(ethylene glycol)-block-poly(propylene glycol)-block-poly(ethylene glycol) copolymer (PLGA/PEG-PPG-PEG) nanoparticles. Particle size range of nanoparticles was found to be between 145 and 198 nm, which would promote the passive targeting of the nanoparticles to tumor cells based on the enhanced permeability and retention (EPR) effect. SEM images revealed all nanoparticles formulations to be spherical and without pores. Zeta potential, yield value and encapsulation efficiencies of 5-FU-loaded nanoparticles were within the range of -11.1 and -13.7 mV, 72.7-87.7% and 83.6-93.9%, respectively. Cumulative release of 5-FU was observed between 90% and 94.4% in all nanoparticle formulations by the end of 72 h, and fitness of release profiles to Higuchi model indicated matrix-controlled diffusion of the 5-FU from polymeric nanoparticles. Cell viability values of the cells treated with 5-FU-loaded nanoparticles were obtained as low as 47% and 52% with tetrazolium dye assay, suggesting that delivery of 5-FU via amphiphilic triblock copolymer nanoparticles would be a promising delivery system because of the EPR effect.
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PMID:5-Fluorouracil-loaded PLA/PLGA PEG-PPG-PEG polymeric nanoparticles: formulation, in vitro characterization and cell culture studies. 2359 73

Hot-melt extrusion (HME) plays an important role in preparing implants as local drug delivery systems in pharmaceutical fields. Here, a new PLA/PEG-PPG-PEG/Dexamethasone (PLA/F68/Dex) implant prepared by HME has been developed. Importantly, the implant was successfully achieved to control release of immunosuppressive drug to an implanted device. In particular, this implant has not been reported previously in pharmaceutical fields. FTIR and XRD were adopted to investigate the properties of the samples. The in vivo release study showed that the maximum value of Dex release from the implants was approximately 50% at 1 month. The in vivo degradation behavior was determined by UV spectrophotometer and scanning electron microscopy studies, and the weight loss rate of the implants were up to 25% at 1 month. Furthermore, complete blood count (CBC) test, serum chemistry and major organs were performed, and there is no significant lesion and side effects observed in these results. Therefore, the results elucidated that the new PLA/F68/Dex implant prepared by HME could deliver an immunosuppressive drug to control the inflammatory reaction at the implant site.
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PMID:PLA/PEG-PPG-PEG/dexamethasone implant prepared by hot-melt extrusion for controlled release of immunosuppressive drug to implantable medical devices, Part 2: in vivo evaluation. 2374 20