Home About us Contact
|
Home About us Contact | ||
|
|
||
Hydrophilic Polymers (hydrophilic + polymer)
Selected AbstractsHydrophilic Polymers with Potassium Salt and Microporous Polysaccharides for Use as Hemostatic AgentsDERMATOLOGIC SURGERY, Issue 12 2007JULIA HO MD BACKGROUND Postoperative bleeding can lead to complications such as hematoma, infection, dehiscence, and an unscheduled office visit. Topical hemostatic agents can be used to aid in hemostasis. OBJECTIVE The objective is to familiarize physicians with topical hemostatic agents,hydrophilic polymers with potassium salts (Urgent QR powder) and microporous polysaccharide hemispheres (Bleed-X). METHODS Two hemostatic agents, microporous polysaccharide hemospheres and hydrophilic polymers with potassium salt, are discussed. The literature is reviewed. RESULTS Numerous types of hemostatic agents exist. Topical hemostatic agents are safe, cost-effective, and efficient. CONCLUSION Microporous polysaccharide hemospheres and hydrophilic polymers with potassium salts can be an adjunct to hemostasis after cautery and ligation. Patients can apply hemostatic agents if they experience any bleeding leading to decreased office visits. Hemostatic agents used intraoperatively shorten bleeding time and enable the physician to use less cautery. Using hemostatic agents can lead to fewer hematomas, infections, and office visits. [source] Polymer-Controlled Crystallization of Unique Mineral SuperstructuresADVANCED MATERIALS, Issue 4 2010Shao-Feng Chen Abstract The origin of complex superstructures of biomaterials in biological systems and the amazing self-assembly mechanisms of their emergence have attracted a great deal of attention recently. Mimicking nature, diverse kinds of hydrophilic polymers with different functionalities and organic insoluble matrices have been designed for the morphogenesis of inorganic crystals. In this Research News, emerging new strategies for morphogenesis and controlled crystal growth of minerals, that is, selective adsorption and mesoscale transformation for highly ordered superstructures, the combination of a synthetic hydrophilic polymer with an insoluble matrix, a substrate, or the air/solution interface, and controlled crystallization in a mixed solvent are highlighted. It is shown that these new strategies can be even further extended to morphogenesis and controlled crystallization of diverse inorganic or inorganic,organic hybrid materials with structural complexity, structural specialties, and improved functionalities. [source] Development of clinical dosage forms for a poorly water-soluble drug II: Formulation and characterization of a novel solid microemulsion preconcentrate system for oral delivery of a poorly water-soluble drugJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 5 2009Ping Li Abstract The solution of a poorly water-soluble drug in a liquid lipid,surfactant mixture, which served as a microemulsion preconcentrate, was converted into a solid form by incorporating it in a solid polyethylene glycol (PEG) matrix. The solid microemulsion preconcentrates thus formed consisted of Capmul PG8 (propylene glycol monocaprylate) as oil, Cremophor EL (polyoxyl 35 castor oil) as surfactant, and hydrophilic polymer PEG 3350 as solid matrix. The drug (aqueous solubility: 0.17 µg/mL at pH 1,8 and 25°C) was dissolved in a melt of the mixture at 65,70°C and then the hot solution was filled into hard gelatin capsules; the liquid gradually solidified upon cooling below 55°C. The solid system was characterized by differential scanning calorimetry (DSC), scanning electron microscopy (SEM), confocal Raman microscopy (CRM), and the dispersion testing in water. It was confirmed that a solid microemulsion preconcentrate is a two-phase system, where clusters of crystalline PEG 3350 formed the solid structure (m.p. 55,60°C) and the liquid microemulsion preconcentrate dispersed in between PEG 3350 crystals as a separate phase. The drug remained dissolved in the liquid phase. In vitro release testing showed that the preconcentrate dispersed readily in water forming a microemulsion with the drug dissolved in the oil particles (<150 nm) and the presence of PEG 3350 did not interfere with the process of self-microemulsification. © 2008 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 98:1750,1764, 2009 [source] Polymers effect on estradiol partition coefficient between powdered human stratum corneum and waterJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 12 2002Ronald C. Wester Abstract Macromolecules have gained interest as drug entities unto themselves and as transport facilitators to alter initial phases of percutaneous absorption. Two macromolecular polymers (MW 2081 and 2565) were designed to hold cosmetics and drugs to the skin surface by altering initial chemical and skin partitioning. The effect of these polymers on the partition coefficient (PC) of estradiol with powdered human stratum corneum (PHSC) and water was determined. There was no statistically significant effect on the PC when the concentration of estradiol was increased 100-fold (0.028,2.8 ,g/mL), when the incubation time was increased from 0 to 24 h, or when PHSC was delipidized. The addition of a liphophilic polymer had no effect on the PC; however, the hydrophilic polymer showed a significant polymer concentration-dependent increase (p,<,0.01) in log PC for estradiol concentrations. Thus, a macromolecular chemical has the potential to alter the partitioning of chemical into the outer layers of skin, the first step in percutaneous absorption. © 2002 Wiley-Liss, Inc. and the American Pharmaceutical Association J Pharm Sci 91:2642,2645, 2002 [source] Dissolution of artemisinin/polymer composite nanoparticles fabricated by evaporative precipitation of nanosuspensionJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 4 2010Mitali Kakran Abstract Objectives An evaporative precipitation of nanosuspension (EPN) method was used to fabricate composite particles of a poorly water-soluble antimalarial drug, artemisinin, with a hydrophilic polymer, polyethylene glycol (PEG), with the aim of enhancing the dissolution rate of artemisinin. We investigated the effect of polymer concentration on the physical, morphological and dissolution properties of the EPN-prepared artemisinin/PEG composites. Methods The original artemisinin powder, EPN-prepared artemisinin nanoparticles and artemisinin/PEG composites were characterised by scanning electron microscopy, Fourier-transform infrared spectroscopy, differential scanning calorimetry (DSC), X-ray diffraction (XRD), dissolution testing and HPLC. The percentage dissolution efficiency, relative dissolution, time to 75% dissolution and mean dissolution time were calculated. The experimental drug dissolution data were fitted to various mathematical models (Weibull, first-order, Korsemeyer,Peppas, Hixson,Crowell cube root and Higuchi models) in order to analyse the release mechanism. Key findings The DSC and XRD studies suggest that the crystallinity of the EPN-prepared artemisinin decreased with increasing polymer concentration. The phase-solubility studies revealed an AL -type curve, indicating a linear increase in drug solubility with PEG concentration. The dissolution rate of the EPN-prepared artemisinin and artemisinin/PEG composites increased markedly compared with the original artemisinin powder. Conclusions EPN can be used to prepare artemisinin nanoparticles and artemisinin/PEG composite particles that have a significantly enhanced dissolution rate. The mechanism of drug release involved diffusion and erosion. [source] Modification of pLL/DNA complexes with a multivalent hydrophilic polymer permits folate-mediated targeting in vitro and prolonged plasma circulation in vivoTHE JOURNAL OF GENE MEDICINE, Issue 5 2002Christopher M. Ward Abstract Background Gene delivery vectors based on poly(L -lysine) and DNA (pLL/DNA complexes) have limited use for targeted systemic application in vivo since they bind cells and proteins non-specifically. In this study we have attempted to form folate-targeted vectors with extended systemic circulation by surface modification of pLL/DNA complexes with hydrophilic polymers. Methods pLL/DNA complexes were stabilised by surface modification with a multivalent reactive polymer based on alternating segments of poly(ethylene glycol) and tripeptides bearing reactive ester groups. Folate moieties were incorporated into the vectors either by direct attachment of folate to the polymer or via intermediate poly(ethylene glycol) spacers of 800 and 3400,Da. Results Polymer-coated complexes show similar morphology to uncoated complexes, their zeta potential is decreased towards zero, serum protein binding is inhibited and aqueous solubility is substantially increased. Intravenous (i.v.) administration to mice of coated complexes produced extended systemic circulation, with up to 2000-fold more DNA measured in the bloodstream after 30,min compared with simple pLL/DNA complexes. In further contrast to simple pLL/DNA complexes, coated complexes do not bind blood cells in vivo. Folate receptor targeting is shown to mediate targeted association with HeLa cells in vitro, leading to increased transgene expression. We demonstrate for the first time that DNA uptake via the folate receptor is dependent on pEG spacer length, with the transgene expression relatively independent of the level of internalised DNA. Conclusions We show increased systemic circulation, decreased blood cell and protein binding, and folate-targeted transgene expression using pLL/DNA complexes surface-modified with a novel multireactive hydrophilic polymer. This work provides the basis for the development of plasma-circulating targeted vectors for in vivo applications. Copyright © 2002 John Wiley & Sons, Ltd. [source] Hydrophilic Polymers with Potassium Salt and Microporous Polysaccharides for Use as Hemostatic AgentsDERMATOLOGIC SURGERY, Issue 12 2007JULIA HO MD BACKGROUND Postoperative bleeding can lead to complications such as hematoma, infection, dehiscence, and an unscheduled office visit. Topical hemostatic agents can be used to aid in hemostasis. OBJECTIVE The objective is to familiarize physicians with topical hemostatic agents,hydrophilic polymers with potassium salts (Urgent QR powder) and microporous polysaccharide hemispheres (Bleed-X). METHODS Two hemostatic agents, microporous polysaccharide hemospheres and hydrophilic polymers with potassium salt, are discussed. The literature is reviewed. RESULTS Numerous types of hemostatic agents exist. Topical hemostatic agents are safe, cost-effective, and efficient. CONCLUSION Microporous polysaccharide hemospheres and hydrophilic polymers with potassium salts can be an adjunct to hemostasis after cautery and ligation. Patients can apply hemostatic agents if they experience any bleeding leading to decreased office visits. Hemostatic agents used intraoperatively shorten bleeding time and enable the physician to use less cautery. Using hemostatic agents can lead to fewer hematomas, infections, and office visits. [source] Polymer-Controlled Crystallization of Unique Mineral SuperstructuresADVANCED MATERIALS, Issue 4 2010Shao-Feng Chen Abstract The origin of complex superstructures of biomaterials in biological systems and the amazing self-assembly mechanisms of their emergence have attracted a great deal of attention recently. Mimicking nature, diverse kinds of hydrophilic polymers with different functionalities and organic insoluble matrices have been designed for the morphogenesis of inorganic crystals. In this Research News, emerging new strategies for morphogenesis and controlled crystal growth of minerals, that is, selective adsorption and mesoscale transformation for highly ordered superstructures, the combination of a synthetic hydrophilic polymer with an insoluble matrix, a substrate, or the air/solution interface, and controlled crystallization in a mixed solvent are highlighted. It is shown that these new strategies can be even further extended to morphogenesis and controlled crystallization of diverse inorganic or inorganic,organic hybrid materials with structural complexity, structural specialties, and improved functionalities. [source] Gas permeation related to the moisture sorption in films of glassy hydrophilic polymersJOURNAL OF APPLIED POLYMER SCIENCE, Issue 6 2010F.L. Laksmana Abstract The purpose of this article is to elucidate the effect of integral sorption of moisture on gas permeation in glassy hydrophilic polymers. The oxygen and the simultaneous moisture sorption into various hydroxypropyl methylcellulose (HPMC) films were measured under a wide range of relative humidities using sorption analyzer equipment. Correspondingly, the oxygen permeability at different ambient conditions was measured using an oxygen detector. The solubility of oxygen in the HPMC film was found to be affected by the amount of water and therefore by the water state. At low moisture content, the water molecules are present as bound water, which promotes the sorption of oxygen in the HPMC films. At moisture content higher than 5%, water clusters are rapidly formed, which increase the affinity of HPMC polymer towards water rather than towards oxygen molecules, resulting in a decrease of oxygen solubility in the polymer. This was found to be the governing factor for the reduction in the oxygen permeability in glassy HPMC films at high water activity. This proposes a specific interaction between moisture sorption and oxygen transport in coating films like HPMC, which is of important aspect in the coating design and formulation. © 2010 Wiley Periodicals, Inc. J Appl Polym Sci, 2010 [source] Design and In vitro evaluation of a film-controlled dosage form self-converted from monolithic tablet in gastrointestinal environmentJOURNAL OF PHARMACEUTICAL SCIENCES, Issue 11 2010Tingting Zhang Abstract The purpose of this study is to design an easily manufactured sustained drug delivery system, which can be converted to a film coated system during the dissolution process and then control the drug release according to near zero-order kinetics. Two kinds of pH-sensitive and oppositely charged hydrophilic polymers, chitosan and alginate, were physically mixed as the matrix. Slightly water-soluble drugs such as theophylline, aspirin, and acetaminophen were utilized as model drugs. In vitro drug release and swelling tests were undertaken in simulated gastrointestinal environments. The formation and properties of the film formed during the dissolution process were identified using different techniques. It was demonstrated that formation of the film was based on the interaction of the polymers on tablet surface with the change of system pH. In 0,4,h drug release depended on the intrinsic properties of the polymers, however, characteristics of the film played a leading role in controlling drug release after 4,h. By studying the ratio of relaxation over Fickian diffusion and relationship between tablets swelling and drug release, it was revealed that the film probably modified drug release behavior by limiting polymer erosion. The in vivo behavior of this hydrophilic matrix system will be investigated. © 2010 Wiley-Liss, Inc. and the American Pharmacists Association J Pharm Sci 99:4678,4690, 2010 [source] Template-directed patterning of polymers and biomaterialsMICROSCOPY RESEARCH AND TECHNIQUE, Issue 6 2007Amol Chandekar Abstract A novel method of patterning surfaces with synthetic or biological polymers is demonstrated. It consists of using microcontact printing to pattern a gold surface with an adsorbate that imparts hydrophilicity; the remainder of the surface is covered with one that imparts hydrophobicity. 16-Mercaptohexadecanoic acid (MHDA) and 1H,1H,2H,2H-perfluorodecanethiol, respectively, have been used as the hydrophilic and hydrophobic adsorbates. This functionalized gold surface then serves as a template for patterning hydrophilic polymers and biomaterials, which are either spin-coated or drop-cast onto the surface. Using this methodology, it is shown by atomic force microscopy, scanning electron microscopy (SEM), and fluorescence microscopy that micron-scale patterns of a poly(ethylene)- block -poly(ethylene oxide) copolymer, poly- L -tryptophan, and bovine collagen can be fabricated, with these mimicking the MHDA patterns. For the block copolymer, it is found by atomic force microscopy that the heights of the polymer patterns decrease as their widths decrease. This is believed to be due to the inherent instability of tall, narrow polymer structures and the tendency of the polymer to minimize its exposed surface area. For poly- L -tryptophan, two different molecular weights of this polyamino acid have been studied, and different morphologies within the patterned regions are observed. While oligomeric poly- L -tryptophan (1,000,5,000 g/mol) gives smooth MHDA-covered patterns, the higher molecular weight (15,000,50,000 g/mol) yields fibrous ones. Microsc. Res. Tech., 2007. © 2007 Wiley-Liss, Inc. [source] The physiological relevance of wet versus dry differential scanning calorimetry for biomaterial evaluation: a technical notePOLYMER INTERNATIONAL, Issue 10 2010Dimitrios I Zeugolis Abstract Collagen and its denatured form, gelatin, have been extensively used as scaffolds for tissue engineering and tissue repair applications. Denaturation temperature, commonly measured using differential scanning calorimetry (DSC), for biomaterial applications is a significant physical property that will determine the stability of a potential implant at body temperature. In order to imitate a clinical setting, DSC should be run under fully hydrated conditions. We show here that for hydrophobic polymers such as poly(,-caprolactone) and chitosan there is no significant difference between dry and wet DSC operation (p > 0.05). In contrast, for hydrophilic polymers such as collagen, gelatin, poly(ethylene glycol) (40 kDa) and poly(ethylene oxide) (900 kDa) significant differences occur between measurements in the dry and the wet state (p < 0.0011). Moreover, we demonstrate that only when wet DSC is carried out are we able to separate the unique crystalline structure of collagen from its randomly coiled heat-denatured by-product gelatin (p < 0.0005). We therefore recommend running DSC under fully hydrated conditions when the function and properties of a biomaterial are under investigation. Copyright © 2010 Society of Chemical Industry [source] Gene transfer with modified polyethyleniminesTHE JOURNAL OF GENE MEDICINE, Issue S1 2004Antoine Kichler Abstract Branched and linear polyethylenimines (PEIs) have proven to be efficient and versatile agents for gene delivery in vitro. In addition, systemic administration of positively charged DNA/PEI complexes results in significant reporter gene expression in lungs. However, re-targeting of complexes to organs other than the lung is hampered by non-specific interactions of polyplexes with blood components and non-target cells. Thus, despite considerable transfectional activity, the properties of PEIs need to be further improved. Therefore, various modifications of PEIs have been explored in recent years. For example, to increase the circulation half-life of the DNA complexes, the surface charge of the particles was shielded by grafting hydrophilic polymers such as polyethylene glycols (PEGs) onto their surface. Alternatively, incorporation of certain ligands into the DNA complexes also resulted in charge shielding even without PEGylation. Herein, I review the most recent PEI derivatives, with a special focus on PEGylated and targeted polymers. Copyright © 2004 John Wiley & Sons, Ltd. [source] Modification of pLL/DNA complexes with a multivalent hydrophilic polymer permits folate-mediated targeting in vitro and prolonged plasma circulation in vivoTHE JOURNAL OF GENE MEDICINE, Issue 5 2002Christopher M. Ward Abstract Background Gene delivery vectors based on poly(L -lysine) and DNA (pLL/DNA complexes) have limited use for targeted systemic application in vivo since they bind cells and proteins non-specifically. In this study we have attempted to form folate-targeted vectors with extended systemic circulation by surface modification of pLL/DNA complexes with hydrophilic polymers. Methods pLL/DNA complexes were stabilised by surface modification with a multivalent reactive polymer based on alternating segments of poly(ethylene glycol) and tripeptides bearing reactive ester groups. Folate moieties were incorporated into the vectors either by direct attachment of folate to the polymer or via intermediate poly(ethylene glycol) spacers of 800 and 3400,Da. Results Polymer-coated complexes show similar morphology to uncoated complexes, their zeta potential is decreased towards zero, serum protein binding is inhibited and aqueous solubility is substantially increased. Intravenous (i.v.) administration to mice of coated complexes produced extended systemic circulation, with up to 2000-fold more DNA measured in the bloodstream after 30,min compared with simple pLL/DNA complexes. In further contrast to simple pLL/DNA complexes, coated complexes do not bind blood cells in vivo. Folate receptor targeting is shown to mediate targeted association with HeLa cells in vitro, leading to increased transgene expression. We demonstrate for the first time that DNA uptake via the folate receptor is dependent on pEG spacer length, with the transgene expression relatively independent of the level of internalised DNA. Conclusions We show increased systemic circulation, decreased blood cell and protein binding, and folate-targeted transgene expression using pLL/DNA complexes surface-modified with a novel multireactive hydrophilic polymer. This work provides the basis for the development of plasma-circulating targeted vectors for in vivo applications. Copyright © 2002 John Wiley & Sons, Ltd. [source] | |||||||||||||