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Unmodified Polymer (unmodified + polymer)
Selected AbstractsEvaluation of the inhibition effect of thiolated poly(acrylates) on vaginal membrane bound aminopeptidase N and release of the model drug LH-RHJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 5 2002Claudia Valenta The purpose of this study was to evaluate the inhibitory effect of thiolated carbopol 974P (carbcys) on the enzymatic activity of vaginal aminopeptidase N in-vitro. Mediated by a carbodiimide, L-cysteine was covalently linked to carbopol 974P. Depending on the weight ratio of polymer to cysteine during the coupling reaction, resulting conjugates displayed 31.3,54.4 ,mol thiol groups per g polymer. The inhibitory effect of carb-cys conjugates was evaluated towards isolated aminopeptidase N and aminopeptidase-N-like activity of excised vaginal mucosa covered with native mucus, respectively. Enzymatic activity was assayed spectrophotometrically using L-leucine- p -nitroanilide (L-leu-pNA) as a synthetic substrate. Carb-cys thereby showed a significantly higher inhibitory effect than unmodified polymer towards both isolated enzyme and vaginal mucosa. Moreover, enzyme inhibition was strongly dependent on the amount of thiol groups being immobilised. The more thiol groups available the higher was the inhibitory effect. Due to its additional high cohesive properties and the possibility of a sustained drug release, which could be shown for the model drug LH-RH, carb-cys appears interesting for the development of vaginal peptide drug-delivery systems. [source] Use of N -(N,-arylamino)maleimides to improve the thermal properties of poly(vinyl chloride) through chemical modification and graft copolymerizationJOURNAL OF VINYL & ADDITIVE TECHNOLOGY, Issue 4 2008Abir S. Abdel-Naby The reaction of poly(vinyl chloride) (PVC) with N -(N,-arylamino)maleimide derivatives was studied. The thermal stability of the modified polymer was improved markedly when compared with that of the unmodified polymer. The stability improvement was attributed to the replacement of the labile chlorine atoms by more stable organic groups. The modified polymer also showed a lower extent of discoloration when compared with that of unmodified PVC. In order to introduce a polymeric stabilizer into PVC, the dienophilic monomer was chemically grafted onto the polymeric chains. The mechanism of the chemical modification as well as that of the graft copolymerization are discussed. J. VINYL ADDIT. TECHNOL., 2008. © 2008 Society of Plastics Engineers. [source] Surface properties of poly(lactic/glycolic acid),pluronic® blend filmsPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 11-12 2003É. Kiss Abstract Poly(dl -lactide) (PLA) and two of its random copolymers with glycolic acid, poly(dl -lactide- co -glycolide) (PLGA) with 75/25 and 50/50 component ratios of lactide/glycolide were blended with poly(ethylene oxide)/poly(propylene oxide)/poly(ethylene oxide) (PEO,PPO,PEO) triblock non-ionic surfactants, known by the Pluronic® trade names of PE6100, PE6400 and PE6800. The surface chemical compositions of the blended films were identified by X-ray photoelectron spectroscopy (XPS). Based on the component of the carbon signal assigned to the ether carbon of the Pluronic® molecule, quantification of the surface accumulation of the Pluronic® additive, compared to its bulk concentration, was performed. The data demonstrated that PEO-containing surfaces were prepared by the blending process. A significant surface hydrophilization, characterized by wettability measurements, was obtained by applying the Pluronics® at a concentration of 1.0,9.1,wt% in the blends. The composition of the surface layer and, in accordance with this, the wettability of the film were found to be dependent on the type of Pluronic® and on the composition of the unmodified polymer. Protein adsorption on the polymer films was measured by the FT-IR ATR spectroscopic technique. The adsorbed amount of bovine serum albumin onto PLA was highly reduced when the polymer was blended with a Pluronic®. The increased hydrophilicity and the reduced protein adsorption properties of the PLA and PLGA obtained by blending with PEO compounds might contribute to their applications as drug carrier systems with great potential. Copyright © 2003 John Wiley & Sons, Ltd. [source] Oral peptide delivery: in-vitro evaluation of thiolated alginate/poly(acrylic acid) microparticlesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 9 2007Alexander Greimel ABSTRACT The purpose of this study was to develop an oral thiomer-based microparticulate delivery system for insulin by ionic gelation. The microparticulate matrix consisted of either poly(acrylic acid)-cysteine (PAA-Cys) and alginate-cysteine (Alg-Cys) or the corresponding unmodified polymers (PAA, Alg). Two different viscosities of alginates were provided for the study, low and medium. Three different types of microparticles were prepared via ionic gelation with calcium (Alg, AlgPAA and AlgPAA-Cys) and their different properties evaluated in-vitro (particle size and shape, drug loading and release profile, swelling and stability). The mean particle size of all formulations ranged from 400 to 600 ,m, revealing the lowest for thiolated microparticles. SEM micrographs showed different morphological profiles for the three different types of microparticles. Encapsulation efficiency of insulin increased within the following rank order: Alg (15%) < AlgPAA (40%) < AlgPAA-Cys (65%). Alginate and AlgPAA microparticles displayed a burst release after 30 min, whereas the thiolated particles achieved a controlled release of insulin over 3 h. The swelling ratio was pH dependent: in simulated intestinal fluid microparticles exhibited a much higher water uptake compared with simulated gastric fluid. Due to the formation of intraparticulate disulfide bonds during the preparation process, thiolated particles revealed a higher stability. It was also observed that the viscosity of the two alginates used had no influence on the properties of the particles. According to these results AlgPAA-Cys microparticles obtained by ionic gelation and stabilized via disulfide bonds might be an alternative tool for the oral administration of therapeutic peptides. 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