Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UNIPROT:P00750 (PLA)
 16,800 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The use of natural pigments such as lobster carotenoids in fish feed formulations offers advantages over the use of the synthetic alternatives. Microencapsulation of the pigments, with or without the addition of antioxidants to the formulation, may be of benefit in terms of stabilizing pigment colour. In the present study, lobster carotenoids were extracted from lobster shell into petroleum ether and microencapsulated by phase separation and salt coacervation within (poly vinyl alcohol) and poly(vinyl alcohol)/poly(D,L-lactic acid) membranes. Spherical microcapsules, with smooth, thin and resilient membranes were obtained with mean diameters ranging from 50 to 150 microns, depending on the membrane material, and source of pigment. The microcapsules were pink-orange in colour, and colour stability was followed spectrophotometrically. Enhanced stability was observed in both membrane materials, in comparison to the non-encapsulated control. Rates of discoloration were determined under a variety of storage conditions, including the absence of light, reduced temperatures and under nitrogen atmosphere. The best stability of lobster carotenoids was observed under a nitrogen atmosphere within PVA/PLA membranes, representing an 11-fold enhancement of pigment stability in comparison to the controls. Under ambient conditions, the enhancement in pigment stability was approximately 6-fold. The optimum concentration of PVA during microencapsulation was 3-4%, and the microencapsulated pigments appeared most stable under acidic conditions. The rate of discoloration appeared independent of pigment concentration.
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PMID:Microencapsulation of lobster carotenoids within poly(vinyl alcohol) and poly(D,L-lactic acid) membranes. 854 93

The design of biodegradable microparticle drug delivery systems with precisely tailored surface properties requires surface analytical methods that can relate polymer chemistry and fabrication parameters to the final surface chemistry of the microparticles. We demonstrate using X-ray photoelectron spectroscopy (XPS) that it is possible to identify significant variations in the surface chemistry of microparticles composed of poly(lactic acid) (PLA), poly(lactide-co-glycolide) (PLGA), or block copolymers of PLA or PLGA with poly(ethylene glycol) (PEG). These variations are related to the mechanism by which the microparticle/water interface is stabilized. This, in turn, is controlled by the interfacial surface tensions of the polymers within aqueous environments. For PEG containing block copolymers, adsorption of a surfactant, poly(vinyl alcohol) (PVA), from the aqueous medium onto the polymer is reduced compared with the PLA and PLGA polymers. This reduction is achieved because the PEG segments, within the copolymer structure, stabilize the polymer/water interface. Estimates of the relative amounts of lactide, lactide-co-glycolide, vinyl alcohol, and ethylene glycol monomer units at the microparticle surfaces are presented based on curve-fitting analysis of the XPS data.
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PMID:The Adsorption of Poly(vinyl alcohol) to Biodegradable Microparticles Studied by X-Ray Photoelectron Spectroscopy (XPS) 902 8

The development of injectable microspheres for sustained drug delivery to the arterial wall is a major challenge. We demonstrated the possibility of entrapping an antiproliferative agent, taxol, in poly(ethylene glycol) (PEG)-coated biodegradable poly(lactic acid) (PLA) microspheres with a mean diameter of 2-6 microm. A solution of taxol and PLA dissolved in an acetone/dichloromethane mixture was poured into an aqueous solution of PEG [or poly(vinyl alcohol) (PVA] with stirring with a high-speed homogenizer for the formation of microspheres. Taxol recovery in PLA-PEG microspheres was higher (61.2 +/- 2.3%) than with PVA-based (41.6 +/- 1.8%) preparations. An analysis by diffuse reflectance infrared Fourier transform spectroscopy revealed that PEG was incorporated well on the PLA microsphere surface. Scanning electron microscopy revealed that the PEG-coated PLA microspheres were spherical in shape and had a smooth surface texture like those of PVA-based preparations. The amount of drug release was much higher initially (25-30%); this was followed by a constant slow-release profile for a 30-day period of study. This PEG-coated PLA microsphere formulation may have potential for the targeted delivery of antiproliferative agents to treat restenosis.
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PMID:Controlled delivery of taxol from poly(ethylene glycol)-coated poly(lactic acid) microspheres. 1142 3

The purpose of the present work was to produce and characterize poly(lactic acid)-poly(ethylene glycol) (PLA-PEG) nanoparticles (size lower than 300 nm) containing a high loading of plasmid DNA in a free form or co-encapsulated with either poly(vinyl alcohol) (PVA) or poly(vinylpyrrolidone) (PVP). The plasmid alone or with PVA or PVP was encapsulated by two different techniques: an optimized w/o/w emulsion-solvent evaporation technique as well as by a new w/o emulsion-solvent diffusion technique. Particle size, zeta potential, plasmid DNA loading and in vitro release were determined for the three plasmid-loaded formulations. The influence of the initial plasmid loadings (5, 10, 20 microg plasmid DNA/mg PLA-PEG) on those parameters was also investigated. The plasmid loaded into the nanoparticles and released in vitro was quantified by fluorimetry and the different molecular forms were identified by gel electrophoresis. PLA-PEG nanoparticles containing plasmid DNA in a free form or co-encapsulated with PVA or PVP were obtained in the range size of 150-300 nm and with a negative zeta potential, both parameters being affected by the preparation technique. Encapsulation efficiencies were high irrespective of the presence of PVA or PVP (60-90%) and were slightly affected by the preparation technique and by the initial loading. The final plasmid DNA loading in the nanoparticles was up to 10-12 microg plasmid DNA/mg polymer. Plasmid DNA release kinetics varied depending on the plasmid incorporation technique: nanoparticles prepared by the w/o diffusion technique released their content rapidly whereas those obtained by the w/o/w showed an initial burst followed by a slow release for at least 28 days. No significant influence of the plasmid DNA loading and of the co-encapsulation of PVP or PVA on the in vitro release rate was observed. In all cases the conversion of the supercoiled form to the open circular and linear forms was detected. In conclusion, plasmid DNA can be very efficiently encapsulated, either in a free form or in combination with PVP and PVA, into PLA-PEG nanoparticles. Additionally, depending on the processing conditions, these nanoparticles release plasmid DNA either very rapidly or in a controlled manner.
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PMID:Poly(lactic acid)-poly(ethylene glycol) nanoparticles as new carriers for the delivery of plasmid DNA. 1145 11

PLA/PLGA was used for biodegradable and biocompatible carriers to achieve sustained release of estradiol. Microspheres were formed by an emulsification-solvent evaporation method, and then their properties and in vitro drug release behavior were examined including amongst others the effects of the concentration of PVA in the aqueous phase, the concentration of PLA in the organic phase, the stirring speed, the volume ratio of O/W, the weight ratio of E2/PLA fed, and the type and molecular weight of the polymers.
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PMID:Preparation and evaluation of poly (D, L-lactic acid) (PLA) or D, L-lactide/glycolide copolymer (PLGA) microspheres with estradiol. 1242 51

Nanoparticles formulated from poly(D,L-lactide-co-glycolide) (PLGA) and poly(lactide) (PLA) are being extensively investigated for different therapeutic applications such as for sustained drug, vaccine, and gene delivery. For many of these applications, it is necessary to study the intracellular distribution as well as the tissue uptake of nanoparticles to optimize the efficacy of the encapsulated therapeutic agent. Fluorescence and electron microscopic techniques are usually used for the above purposes. Colloidal gold particles and fluorescent polystyrene, which are generally used as model particles for electron and fluorescence microscopy, respectively, may not be suitable alternatives to PLGA/PLA nanoparticles for these studies mainly because of the differences in their physical properties and also because they do not contain any therapeutic agent. The aim of the present study was to develop and characterize PLGA nanoparticle formulations that would be suitable for confocal/fluorescence and transmission electron microscopic (TEM) studies. Towards this objective, PLGA nanoparticles containing 6-coumarin as a fluorescent marker and osmium tetroxide as an electron microscopic marker with bovine serum albumin (BSA) as a model protein were formulated. Different physical properties of marker-loaded nanoparticles such as particle size, zeta potential, residual PVA content and protein-loading were compared with those of unloaded nanoparticles and were found to be not significantly different. Furthermore, marker-loaded nanoparticle formulations were non-toxic to the cells as unloaded nanoparticles. Nanoparticles loaded with 6-coumarin were found to be useful for studying intracellular nanoparticle uptake and distribution using confocal microscopy while osmium tetroxide-loaded nanoparticles were found to be useful for studying nanoparticle uptake and distribution in cells and tissue using TEM. It was concluded that 6-coumarin and osmium tetroxide could serve as useful fluorescence and electron microscopy probes, respectively, for incorporation into nanoparticles to study their cellular and tissue distribution.
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PMID:Fluorescence and electron microscopy probes for cellular and tissue uptake of poly(D,L-lactide-co-glycolide) nanoparticles. 1292 82

Temperature-sensitive diblock copolymers, poly(N-isopropylacrylamide)-b-poly(D,L-lactide) (PNIPAAm-b-PLA) with different PNIPAAm contents were synthesized and utilized to fabricate microspheres containing bovine serum albumin (BSA, as a model protein) by a water-in-oil-in-water double emulsion solvent evaporation process. XPS analysis showed that PNIPAAm was a dominant component of the microspheres surface. BSA was well entrapped within the microspheres, and more than 90% encapsulation efficiency was achieved. The in vitro degradation behavior of microspheres was investigated using SEM, NMR, FTIR, and GPC. It was found that the microspheres were erodible, and polymer degradation occurred in the PLA block. Degradation of PLA was completed after 5 months incubation in PBS (pH 7.4) at 37 degrees C. A PVA concentration of 0.2% (w/v) in the internal aqueous phase yielded the microspheres with an interconnected porous structure, resulting in fast matrix erosion and sustained BSA release. However, 0.05% PVA produced the microspheres with a multivesicular internal structure wrapped with a dense skin layer, resulting in lower erosion rate and a biphasic release pattern of BSA that was characterized with an initial burst followed by a nonrelease phase. The microspheres made from PNIPAAm-b-PLA with a higher portion of PNIPAAm provided faster BSA release. In addition, BSA release from the microspheres responded to the external temperature changes. BSA release was slower at 37 degrees C (above the LCST) than at a temperature below the LCST. The microspheres fabricated with PNIPAAm-b-PLA having a 1:5 molar ratio of PNIPAAm to PLA and 0.2% (w/v) PVA in the internal aqueous phase provided a sustained release of BSA over 3 weeks in PBS (pH 7.4) at 37 degrees C.
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PMID:Preparation and characterization of temperature-sensitive poly(N-isopropylacrylamide)-b-poly(D,L-lactide) microspheres for protein delivery. 1460 9

Nanoparticles formulated from biodegradable polymers such as poly(lactic acid) (PLA) and poly(lactide-co-glycolide) (PLGA) are being extensively investigated as non-viral gene delivery systems due to their controlled release characteristics and biocompatibility. PLGA nanoparticles for DNA delivery are mainly formulated by an emulsion-solvent evaporation technique using PVA as a stabilizer generating negatively charged particles and heterogeneous size distribution. The objective of the present study was to formulate cationically modified PLGA nanoparticles with defined size and shape that can efficiently bind DNA. An Emulsion-diffusion-evaporation technique to make cationic nanospheres composed of biodegradable and biocompatible co-polyester PLGA has been developed. PVA-chitosan blend was used to stabilize the PLGA nanospheres. The nanospheres were characterized by atomic force microscopy (AFM), photon-correlation spectroscopy (PCS), and Fourier transform infrared spectroscopy (FTIR). Zeta potential and gel electrophoresis studies were also performed to understand the surface properties of nanospheres and their ability to condense negatively charged DNA. The designed nanospheres have a zeta potential of 10mV at pH 7.4 and size under 200nm. From the gel electrophoresis studies we found that the charge on the nanospheres is sufficient to efficiently bind the negatively charged DNA electrostatically. These cationic PLGA nanospheres could serve as potential alternatives of the existing negatively charged nanoparticles.
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PMID:Preparation and characterization of cationic PLGA nanospheres as DNA carriers. 1473 40

Poly(lactide-co-glycolide) (PLGA), a biocompatible and biodegradable polyester co-polymer of PLA and PGA, has been recognized for its ability to deliver genes. However, gene delivery by PLGA nanoparticles is limited by their negative charge and their poor transport through mucosal barriers. In this study, PLGA nanoparticles were surface modified with cationic chitosan in an effort to improve their gene delivery capability. PLGA nanoparticles were synthesized by emulsion-diffusion-evaporation technique using PVA-chitosan (PLGA1) or PVA-chitosan-PEG (PLGA2) blend as stabilizers. This method is reproducible and produces nanoparticles with hydrodynamic diameter <200 nm. The nanoparticles were characterized by zetasizer, photon correlation spectroscopy and atomic force microscopy. A549 epithelial cells were transfected in vitro with PLGA particles complexed with a reporter plasmid encoding green fluorescent protein. PLGA particles transferred EGFP gene, but were less efficient than the lipofectamine control. The nanoparticles were also tested for their ability to transport across the nasal mucosa in vivo in mice. The results show that both PLGA1 and PLGA2 facilitate gene delivery and expression in vivo with increased efficiency and without causing inflammation, as measured by IL-6. Together, these results indicate that chitosan-modified PLGA nanoparticles have greater potential as gene carriers.
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PMID:Cationic poly(lactide-co-glycolide) nanoparticles as efficient in vivo gene transfection agents. 1565 92

The water soluble peptide, melittin, isolated from bee venom and composed of twenty-six amino acids, was encapsulated in poly (DL-lactic acid, PLA) and poly (DL-lactic-co-glycolic acid, PLGA) microspheres prepared by a multiple emulsion [(W1/O)W2] solvent evaporation method. The aim of this work was to develop a controlled release injection that would deliver the melittin over a period of about one month. The influence of various preparation parameters, such as the type of polymer, its concentration, stabilizer PVA concentration, volume of internal water phase and level of drug loading on the characteristics of the microspheres and drug release was investigated. It was found that the microspheres of about 5 microm in size can be produced in high encapsulation (up to 90%), and the melittin content in the microspheres was up to 10% (w/w). The drug release profiles in vitro exhibited a significant burst release, followed by a lag phase of little or no release and then a phase of constant melittin release. The type of polymer used was a critical factor in controlling the release of melittin from the microspheres. In this study, the rate of peptide release from the microspheres correlated well with the rate of polymer degradation. Moreover, melittin was released completely during the study period of 30 days, which agreed well with the polymer degradation rate.
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PMID:Preparation and characterization of melittin-loaded poly (DL-lactic acid) or poly (DL-lactic-co-glycolic acid) microspheres made by the double emulsion method. 1625 81


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