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

Eighty bovine incisors were ground on 320-grit silicone carbide paper and cleaned with fluoride-free prophylaxis paste. The enamel surface conditions were: 1. no conditioning; 2. salicylic acid (10%, 10s); 3. benzoic acid (10%, 10s); 4. air polishing with sodium hydrogen carbonate/Prophy-Jet; 5. Prophy-Jet, followed by polyacrylic acid (PAA, 10%, 10 s); 6. PAA, followed by saliva contamination; 7. PAA; 8. phosphoric acid (37%, 10 s). Fuji Ortho II LC (GC) was used as a bracket adhesive in groups 1 t0 7, and in group 8 Concise orthodontic (3M). Stainless steel lingual buttons were placed by hand. Polymerisation with visible light was carried out 20 s from mesial, distal, incisal and gingival. After 24 h storage in tap water at room temperature the shear bond strengths were tested in accordance with ISO specification TC 106/SC/WG16. Mean values of the groups were compared using Student's t-test. Group 7 (PAA) attained the highest mean shear strength (in comparison with control group): 28 MPa. This was both significantly different from the control group (Concise, 33 MPa) and highly significant in comparison with the other groups (< 16 MPa). The shear bond strength of Fuji Ortho II LC on PAA conditioned enamel indicates the clinical applicability of this material.
 ...
PMID:Light-cured glass ionomer cement as a bracket adhesive with different types of enamel conditioners. 920 Aug 93

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.
 ...
PMID:Nano-apatite/polymer composites: mechanical and physicochemical characteristics. 930 14

The axi-symmetric drop-shape analysis-pendant drop technique has been used to measure interfacial tension at the chlorobenzene-water interface in the presence of adsorbed films of dimyristoylphosphatidylcholine (DMPC), dipalmitoylphosphatidylcholine (DPPC), DMPC-cholesterol, DPPC-cholesterol, DMPC-cholesterol-dicetyl phosphate (DCP) and DPPC-cholesterol-DCP. A surface-pressure function, pi * = pi lipid-polymer -pi lipid (where pi lipid is the surface pressure of the mono-layer without polymer and pi lipid-polymer is the surface pressure of the lipid mono-layer and adsorbed polymer at equilibrium at the chlorobenzene-water interface) was used to characterize the interaction of eight water-soluble polymers with the lipid films. The equation, delta pi * = pi II*-pi I* (where the subscripts II and I denote the higher and lower lipid composites, respectively) was used to determine the differential effect of cholesterol and DCP on mono-layer characteristics in the presence of 1% w/v polymer. Cholesterol or polymer individually condensed DMPC films and expanded DPPC films. However, composite films of DMPC-cholesterol-DCP and carboxymethylchitin (CM-chitin), poly(acrylic acid) (PAA) or poly(vinyl alcohol) (PVA) were more expanded than DMPC films whereas composite films of DPPC were neither more condensed nor expanded than DPPC films. A polymer impact ratio, P* = pi lipid-polymer/pi lpolymer was calculated and the polymers were ranked in order of their impact on the lipid film. PVA and polysaccharides gave low and high P* values, respectively, corresponding to high and low levels of film interaction, whereas PAA and hydrophobized polysaccharides gave intermediate values, indicating their affinity for and penetration of interfacial films with little disruption of the mono-layer. The results show that measurement of interfacial pressures at the chlorobenzene-water interface might be advantageous for evaluating the action of polymers on biological membranes.
 ...
PMID:An interfacial tension model of the interaction of water-soluble polymers with phospholipid composite monolayers. 933 Jan 96

Ultrafiltration (UF) membranes from polysulfone (PSf) were functionalized by heterogeneous photo-initiated graft copolymerization of acrylic acid (AA). With radiation susceptible PSf, only proper selection of the UV energy (lambda > 350 nm; for selective excitation of the photoinitiator) yielded membranes with preserved UF barrier layer. Possibilities for adjusting structure and morphology of the graft polymer (g-PAA) layer by variation of functionalization parameters such as AA concentration and UV irradiation time were investigated. Very long grafted chains (Mw > 10(5) g mol(-1)) at varied grafting density (GD = 0.01 ... 1.2 nmol cm(-2), relative to the outer surface area) were obtained. Partial penetration of the UF barrier layer by g-PAA was verified. Covalent immobilization of bovine serum albumin (BSA), gamma-globulin (gamma-Gl) and alkaline phosphatase (APh) was achieved by coupling with a water soluble carbodiimide. Bound BSA and gamma-Gl amounts were up to gamma = 10 microg cm(-2), for membranes accessible only from the outer surface thus not using the entire pore volume. Locally addressed covalent protein immobilization after photo-patterning the PSf surface could be visualized with a fluorescent FITC-BSA conjugate. A strong salt effect onto immobilized APh activity (increase with NaCl concentration) was observed, indicating internal transport/accessibility limitations in the g-PAA layer. Correlations between PAA structure (Mw, GD) and accessibility (from BSA or gamma-G1 binding and APh activity) could be established. The 'tentacle' g-PAA functionalized PSf UF membranes having preserved UF barrier and, e.g., with surface-bound receptors will find application in cell cultures under diffusion or perfusion conditions.
 ...
PMID:Ultrafiltration membrane surfaces with grafted polymer 'tentacles': preparation, characterization and application for covalent protein binding. 972 Aug 86

A method for the preparation of poly(acrylic acid) (PAA) microspheres crosslinked with beta-cyclodextrin (beta-CD) is described. The method is based on a water-in-oil (w/o) emulsion solvent evaporation technique which facilitates a condensation reaction between PAA and beta-CD. Aqueous solutions of PAA and beta-CD were used as the dispersed phase and food grade olive oil was used as the continuous phase. The effect of homogenization speed (used in the preparation of the emulsion), phase volume ratio and cyclodextrin-polymer load on the particle size of the microspheres produced was investigated in a replicated factorial design. Microspheres were sized by light microscopy. The particle size of the microspheres was influenced by all three variables with two significant first order interactions between the variables being observed (homogenization speed with phase volume ratio and homogenization speed with load). A second order interaction between the three principal factors was also observed. Particle size ranged from 16 to 150 microns, depending on the production variables employed. The yield for the technique was 69.5 +/- 9.5%. Using selected conditions, microspheres of 15-25 microns size were prepared from a range of PAA with different weight average molecular weights (Mw). These particles were then characterized for beta-CD, free carboxylic acid group content and residual oleic acid.
 ...
PMID:Preparation and characterization of beta-cyclodextrin and poly(acrylic acid) microspheres. 974 18

Microspheres composed of the hydrophilic polymer poly(acrylic acid) (PAA), with and without beta-cyclodextrin (beta-CD), were prepared by a water-in-oil (w/o) solvent evaporation technique. Microspheres were characterised for particle size, beta-CD and residual oil content. The type of matrix formed during microsphere synthesis was investigated by solid state carbon 13C NMR, in vitro release of beta-CD and swelling measurements. A high encapsulation efficiency of the beta-CD was observed (?90%). The in vitro release of beta-CD in water over 24 h was initially rapid ( approximately 70% in 3 h) with no further loss thereafter, suggesting potential covalent binding of the residual beta-CD. NMR indicated that in the presence of beta-CD, two concomitant chemical processes occur during microsphere synthesis: (i) esterification of the hydroxyl group(s) of the beta-CD with the carboxylic acid groups of the PAA; and (ii) the formation of intra-/inter-polymer acid anhydrides.
 ...
PMID:Investigations into the structure and composition of beta-cyclodextrin/poly(acrylic acid) microspheres. 1037 Jan 86

The effects of excipients on the protein stability during lyophilization as well as the storage stability of lyophilized bilirubin oxidase (BO) and beta-galactosidase (GA) formulations were studied using four polymer excipients: dextran, polyvinylalcohol (PVA), poly(acrylic acid) (PAA), and alpha, beta-poly(N-hydroxyethyl)-L-aspartamide (PHEA). Denaturation of BO and GA during lyophilization largely depended on the excipient used. Dextran appeared to cause severe damage to proteins, whereas PHEA protected proteins effectively from denaturation. Storage stability of BO and GA formulations also depended on the excipients, such that the formulations containing dextran and PAA were relatively unstable. Storage stability was improved by absorption of a small amount of water for all the formulations studied. Absorption of a larger amount of water, however, decreased the storage stability of the formulations containing PVA, PAA or PHEA. In contrast, the storage stability of formulations containing dextran did not decrease noticeably with increasing water. This may be because formulations containing dextran have a higher glass transition temperature than formulations containing PVA, PAA or PHEA when a large amount of water is absorbed.
 ...
PMID:Effect of polymer excipients on the enzyme activity of lyophilized bilirubin oxidase and beta-galactosidase formulations. 1070 20

Bioadhesive vaginal tablets were prepared using poly(acrylic acid) (PAA); Methylcellulose (MC), carboxymethyl cellulose (CMC), hydroxypropyl cellulose (HPC) and hydroxypropylmethyl cellulose (HPMC) as bioadhesive polymers in different concentrations and acyclovir as drug by direct compression technique (DCT) and wet granulation technique (WGT). Physical tests were applied to the tablets. The swelling behavior of vaginal tablets in distilled water, lactic solution and cow vagina, acyclovir release rate in lactic solution and bioadhesion to vaginal mucosa in cow vagina, in situ, were investigated. Swelling of the tablets containing HPC, CMC and MC was very rapid and caused disintegration of the tablets. The swelling behaviour of the tablets containing HPMC lasted 6 h in lactic solution. The force (N) necessary to detach the tablets from the vaginal tissue was found to depend on concentration and type of the bioadhesive polymer. The tablets containing HPMC needed the most detachment force.
 ...
PMID:Studies on vaginal bioadhesive tablets of acyclovir. 1079 44

The aim of this work was to develop a calcium phosphate cement (CPC) providing controlled release of the antibiotic gentamicin sulfate (GS) over at least 1 week. The CPC was made of beta-tricalcium phosphate [beta-TCP; beta-Ca(3)(PO(4))(2)], monocalcium phosphate monohydrate [MCPM; Ca(H(2)PO(4))(2). H(2)O] and water. Release of GS was controlled by admixture of poly(acrylic acid) (PAA). The effects on the GS release kinetics of the molecular weight of PAA, of the amount of admixed PAA, and of the pH of the release medium were investigated. A typical cement sample weighed 3.6 g and contained 100 mg of GS and between 0 and 150 mg of PAA. In the following, PAA content is expressed as the weight ratio, lambda, with respect to GS. At a low PAA content in the CPC (lambda < 0.7), GS was released over 1-2 days according to a square-root-of-time kinetics, but not all GS was released. The unreleased GS fraction increased from 0 to 58% with an increase of PAA content (up to lambda = 0.7). At high PAA content (lambda > 0.7), GS was released over a period of up to 8 days according to a combination of a square-root-of-time and a zero-order kinetics. The total GS fraction released increased again from 58 to 100% with an increase of the amount of PAA (up to lambda = 1.5). These observations were explained by molecular interaction between PAA and GS resulting in gel formation. The maximum fraction of GS released from the cement was indeed a function of the solubility of the PAA-GS (coacervate) complex in the release medium. Thus, GS release was controlled by two mechanisms: (1) diffusion of free GS molecules through the porous cement (square-root-of-time kinetics); and (2) dissociation of GS from the PAA-GS complex (zero-order kinetics). The first mechanism was predominant at low lambda, whereas the second mechanism became important at high lambda and later release times. As the solubility of the PAA-GS complex decreased with an increase in PAA molecular weight, the higher molecular weight PAA yielded more prolonged release periods of up to 8 days. Interestingly, the use of 450 kDa PAA at lambda = 1.00 provided an almost constant release profile over a period of 7 days. Gel formation between PAA and GS was explained in terms of hydrogen bonding of PAA carboxyl groups with GS amino groups. The molar ratio between carboxyl groups and amino groups in the gel was estimated to be approximately 1.9. In conclusion, admixture of PAA into calcium phosphate cement appeared to be a very elegant tool to control the release of the antibiotic over a period of 7 to 8 days.
 ...
PMID:Control of gentamicin release from a calcium phosphate cement by admixed poly(acrylic acid). 1098 May 1

The uptake of glucose oxidase (GOx) onto a polycationic redox polymer (PAA-Os)-modified surface, by adsorption from dilute aqueous GOx solutions, was followed by the quartz crystal microbalance (QCM) and shows double exponential kinetics. The electrochemistry of the layer-by-layer-deposited redox-active polymer was followed by cyclic voltammetry in glucose-free solutions, and the enzyme catalysis mediated by the redox polymer was studied in beta-D-glucose-containing solutions. AFM studies of the different layers showed the existence of large two dimension enzyme aggregates on the osmium polymer for 1 microM GOx and less aggregation for 50 nM GOx solutions. When the short alkanethiol, 2,2'-diaminoethyldisulfide was preadsorbed onto gold, a monoexponential adsorption law was observed, and single GOx enzyme molecules could be seen on the surface where the enzyme was adsorbed from 50 nM GOx in water.
 ...
PMID:Layer-by-layer self-assembly of glucose oxidase and Os(Bpy)2CIPyCH2NH-poly(allylamine) bioelectrode. 1130 46


<< Previous 1 2 3 4 5 6 7 8 9 10 Next >>