Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0267964 (PAA)
 2,561 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

A comparison of two precipitation methods of IgY from normal hen eggs was made. For method I the precipitation agent is represented by PEG 6000, and for method II by organic solvents. The comparative study of some parameters (protein concentration, ovalbumin content, presence of non-specific inhibitors, PAA-gel electrophoresis) shows that method I is more efficient and more convenient than method II. Using this method, we isolated and characterized IgY preparations from hens immunized with circulating influenza virus strains: A/Singapore/6/86 (H1N1), A/Shanghai/11/87 (H3N2) B/Beijing/1/87 and B/Yamagata/16/88 These viral IgY antibody preparations are homogeneous, lacking anti-host cell antibodies and non-specific inhibitors. Their NI titres and HI titres are higher than those found in the sera of immunized birds.
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PMID:Isolation and characterization of egg yolk antibodies IgY from hens immunized with different influenza virus strains. 182 Nov 63

Surface-modified human serum albumin (HSA) nanospheres with a size of around 100 nm in diameter were prepared from poly(amidoamine)-poly(ethylene glycol) copolymer grafted human serum albumin (HSA-PAA-PEG) and poly(thioetheramido acid)-poly(ethylene glycol) copolymer grafted human serum albumin (HSA-PTAAC-PEG). The nanospheres were produced using a pH-coacervation method and cross-linked with glutaraldehyde. The cross-linking efficiency was affected by the type of albumin conjugate used. The zeta potential of the surface-modified nanospheres was significantly lower than that of unmodified particles. The existence of a hydrated steric barrier surrounding the nanospheres was confirmed by electrolyte- and pH-induced flocculation tests. The surface-modified nanospheres showed a reduced plasma protein adsorption on the particle surface compared with unmodified particles.
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PMID:Preparation of surface-modified albumin nanospheres. 910 96

Hydrothermally synthesized acicular nano-apatite (Nap) was used as filler to make composites with a polyethylene glycol/poly(butylene terephthalate) (PEG/PBT) block copolymer (Polyactive 70:30). The Nap had a particle diameter of 9-25 nm and a length of 80-200 nm. The mechanical properties and the physiochemical characteristics of the composites, such as Young's modulus, swelling degree in water and the calcification behaviour, have been determined. It was found that Nap had a strong ability to promote the calcification of composites when incorporated into Polyactive 70:30, while poly(acrylic acid) (PAA) coating of Nap had an adverse effect on the calcification of composites, presumably due to the formation of complexes between PAA and PEG segments. Nap had a prominent stiffening effect for Polyactive 70:30 in the dry state, but had a poor stiffening effect for composites in an aqueous environment due to the hygroscopic nature and/or the formation of aggregates. PAA coating on Nap had almost no additional effect on the mechanical properties of composites either in the dry state or in an aqueous environment. To reinforce the polymer by Nap, achieving a more homogeneous dispersion of Nap in the polymer matrix and surface modifications to render the powders less hygroscopic appear to be necessary.
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PMID:Nano-apatite/polymer composites: mechanical and physicochemical characteristics. 930 14

We have designed a new mucoadhesive drug delivery formulation based on H-bonded complexes of poly(acrylic acid) (PAA) or poly(methacrylic acid) (PMAA) with the poly(ethylene glycol) (PEG), of a (PEG)-drug conjugate. The PEGylated prodrugs are synthesized with degradable PEG-anhydride-drug bonds for eventual delivery of free drug from the formulation. In this work we have used indomethacin as the model drug which is PEGylated via anhydride bonds to the PEG. The complexes are designed first to dissociate as the formulation swells in contact with mucosal surfaces at pH 7.4, releasing PEG-indomethacin, which then hydrolyses to release free drug and free PEG. We found that as MW of PAA increases, the dissociation rate of the complex decreases, which results in decreased rate of release of the drug. On the other hand, the drug release from PEG-indomethacin alone and from solid mixture of PEG-indomethacin+PAA was much faster than that from the H-bonded complexes. Due to the differences in the thermal stability, PMAA complex exhibited slightly faster drug release than that of the PAA complex of comparable MW. These H-bonded complexes of degradable PEGylated drugs with bioadhesive polymers should be useful for mucosal drug delivery.
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PMID:Mucoadhesive drug carriers based on complexes of poly(acrylic acid) and PEGylated drugs having hydrolysable PEG-anhydride-drug linkages. 1106 31

Recent developments in the field of biomaterials are based on molecular design of polymers with improved surface and bulk properties. Novel techniques of surface modification by addition of tethered chains can lead to materials with the ability to recognize biological and pharmaceutical compounds. Methods based on molecular imprinting can increase the recognition capabilities of such systems. Chain tethering can also can improve the mucoadhesive behavior of a delivery device and the effectiveness of a drug by allowing targeting and localization of a drug at a specific site. Acrylic-based hydrogels are well-suited for mucoadhesion due to their flexibility and nonabrasive characteristics which reduce damage-causing attrition to the tissues in contact. However, the adhesive and drug delivery capabilities of these devices can continue to be improved as presently known bioadhesive materials are modified and more bioadhesive materials are discovered. Tethering of long PEG chains on PAA hydrogels and their copolymers can be achieved by grafting reactions involving thionyl chloride, followed by PEG grafting. The ensuing materials exhibit mucoadhesive properties due to enhanced anchoring of the chains with the mucosa. Theoretical calculations can lead to optimization of the tethered structure.
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PMID:Surface modifications and molecular imprinting of polymers in medical and pharmaceutical applications. 1138 82

The organic-inorganic hybrid nanoparticles entrapping oligodeoxynucleotide (ODN) or siRNA were prepared through the self-associating phenomenon of the block copolymer, poly(ethylene glycol)-block-poly(aspartic acid) (PEG-PAA), with calcium phosphate. The nanoparticles have diameters in the range of several hundreds of nanometers depending on the PEG-PAA concentration and revealed excellent colloidal stability due to the steric repulsion effect of the PEG layer surrounding the calcium phosphate core. The loading capacities of ODN and siRNA were fairly high, reaching almost 100% under optimal conditions. The flowcytometric analysis and confocal microscopy observation indicated that the hybrid nanoparticles loaded with ODN were taken up by the cells through the endocytosis mechanism. Furthermore, the calcium phosphate core dissociates in the intracellular environment with appreciably lowered calcium ion concentration compared to the exterior, allowing the release of the incorporated ODN and siRNA in a controlled manner. Eventually, effective intracellular delivery and nuclear localization of these nucleic acid-based drugs were evidenced through the observation of laser confocal microscopy using FITC-labeled ODN. This smart ion-sensitive characteristic of hybrid nanoparticles was further demonstrated by the appreciable silencing of reporter gene expression by siRNA incorporated in the nanoparticles.
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PMID:Block copolymer-coated calcium phosphate nanoparticles sensing intracellular environment for oligodeoxynucleotide and siRNA delivery. 1519 61

The amidase activity of bovine pancreas trypsin in water-soluble complexes with poly(ethylene glycol)-block-poly(alpha,beta-aspartic acid) (PEG-PAA) was evaluated by a colorimetric assay using L-lysine p-nitroanilide as a substrate. The enzymatic reaction of trypsin was accelerated through the complexation with PEG-PAA. By determining the kinetic parameters of the enzymatic reaction of trypsin, it was confirmed that the catalytic rate constant of the complexed trypsin was 15 times higher than that of the native trypsin. From the evaluation of pH dependence of initial reaction rate, it was indicated that this acceleration was induced by a stabilization of the imidazolium ion of the His residue in the catalytic site, the Asp-His-Ser triad, of trypsin due to the Asp units of PEG-PAA. The hydrogen bonded Asp-His pairs are critical constituents in several key enzymatic reactions including serine protease and apurinic endonucleases, and it was expected that the acceleration of the catalytic reaction might occur for other enzymes by the formation of water-soluble complexes with PEG-PAA.
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PMID:Acceleration of enzymatic reaction of trypsin through the formation of water-soluble complexes with poly(ethylene glycol)-block-poly(alpha,beta-aspartic acid). 1576 22

Poly(ethylene glycol) (PEG), a hydrophilic and repulsive polymer to non-specific adsorption, was stamped onto carboxylic acid-enriched polymer surfaces using the micro-contact printing technique. The patterns are stabilized via hydrogen bonds. Areas printed with PEG were then shown to be non-adsorbed with fluorescein isothiocyanate (FITC)-labeled dextran, while the poly(methacrylic acid) (PMAA) regions could via hydrogen bonding. Due to this contrast, well defined dextran patterns were obtained. Tuned with pH and temperature, the PEG molecules could be detached from the surfaces, erasing the template. Moreover, ionization of PMAA at higher pH induced an abrupt transition to an extended conformation, weakening the interactions between PMAA and dextran. Not only the dextran patterns lose their spatial selectivity, but also the overall adsorption amount is much lower. The pH sensitivity was in a quite narrow range, i.e. around pH 5. As the hydrogen bonds are also temperature sensitive, the attach points of PEG molecules on the surfaces disappeared at higher temperature. For poly(acrylic acid) (PAA) photografted surfaces, the pH sensitivity was more complicated due to the formation of the compact complexes of PEG and PAA molecules.
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PMID:Poly(ethylene glycol) micro-patterns as environmentally sensitive template for selective or non-selective adsorption. 1632 82

We developed novel acrylic-based polymers that can be used as mucoadhesive delivery systems. Poly(acrylic acid) hydrogels were modified by grafting adhesion promoter chains such as poly(ethylene glycol) (PEG) onto their back-bone chains, thus promoting the adhesive process by interpenetration. The copolymers synthesized were designated as P(AA-g-EG). Hydrogels were synthesized using PEG of two different molecular weights, 1000 and 2000, and with varying molar feed ratio of AA-EG (20:80, 40:60, 60:40, 80:20, 12:88, 25:75, 44:56, 67:33). The copolymers were synthesized by using free radical solution UV-polymerization. The effects of different PEG-tethered structures on mucoadhesion were studied using a tensiometric testing and the work of adhesion was calculated. Preswollen P(AA-g-EG) copolymer films composed of 40% acrylic acid (AA) and 60% ethylene glycol (EG), containing PEG 1000 tethers, exhibited the highest value for the work of mucoadhesion, 130 x 10(-3)+/-27 x 10(-3) mJ, that is five times higher than the formulation composed of pure PAA. Based on these results and associated molecular analysis, we conclude that the higher mucoadhesive properties of this specific copolymer were the result of the synergistic effects of both monomers. AA functional groups allowed the polymer to form multiple hydrogen bonds with the glycoproteins present in the mucus. PEG tethers possibly acted as mucoadhesive promoters, enhancing interpenetration of polymer chains into the mucus.
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PMID:Design of poly(ethylene glycol)-tethered copolymers as novel mucoadhesive drug delivery systems. 1636 28

In a chemostat, microbial cells reach a steady state condition at which cell biomass production, substrates and the product concentrations remain constant. These features make continuous culture a unique and powerful tool for biological and physiological research. We present a polymer-based microbioreactor system integrated with optical density (OD), pH, and dissolved oxygen (DO) real-time measurements for continuous cultivation of microbial cells. Escherichia coli (E. coli) cells are continuously cultured in a 150 microL, membrane-aerated, well-mixed microbioreactor fed by a pressure-driven flow of fresh medium through a microchannel. Chemotaxisial back growth of bacterial cells into the medium feed channel is prevented by local heating. Using poly(ethylene glycol) (PEG)-grafted poly(acrylic acid) (PAA) copolymer films, the inner surfaces of poly(methyl methacrylate) (PMMA) and poly(dimethylsiloxane) (PDMS) of the microbioreactor are modified to generate bio-inert surfaces resistant to non-specific protein adsorption and cell adhesion. The modified surfaces of microbioreactor effectively reduce wall growth of E. coli for a prolonged period of cultivation. Steady state conditions at different dilution rates are demonstrated and characterized by steady OD, pH, and DO levels.
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PMID:Microchemostat-microbial continuous culture in a polymer-based, instrumented microbioreactor. 1680 95


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