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Polymers Used (polymer + used)
Selected AbstractsPotentiometric Ag+ Sensors Based on Conducting Polymers: A Comparison between Poly(3,4-ethylenedioxythiophene) and Polypyrrole Doped with Sulfonated CalixarenesELECTROANALYSIS, Issue 18 2005Zekra Mousavi Abstract Potentiometric Ag+ sensors were prepared by galvanostatic electropolymerization of 3,4-ethylenedioxythiophene (EDOT) and pyrrole (Py) on glassy carbon electrodes by using sulfonated calixarenes as doping ions. Poly(3,4-ethylenedioxythiophene) (PEDOT) and polypyrrole (PPy) doped with p -sulfonic calix[4]arene (C4S), p -sulfonic calix[6]arene (C6S) and p -sulfonic calix[8]arene (C8S) were compared. PEDOT and PPy doped with poly(styrene sulfonate) (PSS) were also included for comparison. The analytical performance of the conducting polymer-based Ag+ sensors was studied by potentiometric measurements. All conducting polymer and dopant combinations showed sensitivity and selectivity to Ag+ compared to several alkali, alkaline-earth, and transition-metal cations. The type of the conducting polymer used for the fabrication of the electrodes was found to have a more significant effect on the selectivity of the electrodes to Ag+ than the ring size of the sulfonated calixarenes used as dopants. Selected conducting polymer-based sensors were studied by cyclic voltammetry (CV) and energy dispersive analysis of X-rays (EDAX) measurements. Results from the EDAX measurements show that both PEDOT- and PPy-based membranes accumulate silver. [source] Surface Structures and Osteoblast Activity on Biomedical Polytetrafluoroethylene Treated by Long-Pulse, High-Frequency Oxygen Plasma Immersion Ion ImplantationADVANCED ENGINEERING MATERIALS, Issue 5 2010Liping Tong Abstract Polytetrafluoroethylene (PTFE) is a biologically safe polymer used widely in clinical medicine including oral and orthopedic surgery. However, the high bio-inertness of PTFE has hampered wider applications in the biomedical fields. In this work, we extend the treatment time in long-pulse, high-frequency oxygen plasma immersion ion implantation of PTFE and a more superhydrophobic surface with a water contact angle of 160° is created. X-ray photoelectron spectroscopy (XPS) and atomic force microscopy (AFM) reveal that the optimized long-pulse, high-frequency oxygen plasma immersion ion implantation process induces a rougher surface and to a lesser extent alters the surface oxygen concentration on the PTFE. Our data, especially long-term contact angles, suggest that the superhydrophobility stems from surface roughness alteration. Furthermore, the activity of MC3T3-E1 osteoblasts cultured on the treated surfaces is promoted in terms of quantities and morphology. [source] Solvent/non-solvent sintering: A novel route to create porous microsphere scaffolds for tissue regenerationJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2008Justin L. Brown Abstract Solvent/non-solvent sintering creates porous polymeric microsphere scaffolds suitable for tissue engineering purposes with control over the resulting porosity, average pore diameter, and mechanical properties. Five different biodegradable biocompatible polyphosphazenes exhibiting glass transition temperatures from ,8 to 41°C and poly (lactide- co -glycolide), (PLAGA) a degradable polymer used in a number of biomedical settings, were examined to study the versatility of the process and benchmark the process to heat sintering. Parameters such as: solvent/non-solvent sintering solution composition and submersion time effect the sintering process. PLAGA microsphere scaffolds fabricated with solvent/non-solvent sintering exhibited an interconnected porosity and pore size of 31.9% and 179.1 ,m, respectively which was analogous to that of conventional heat sintered PLAGA microsphere scaffolds. Biodegradable polyphosphazene microsphere scaffolds exhibited a maximum interconnected porosity of 37.6% and a maximum compressive modulus of 94.3 MPa. Solvent/non-solvent sintering is an effective strategy for sintering polymeric microspheres, with a broad spectrum of glass transition temperatures, under ambient conditions making it an excellent fabrication route for developing tissue engineering scaffolds and drug delivery vehicles. © 2007 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2008 [source] Sustained Release of 5-Fluorouracil from Polymeric NanoparticlesJOURNAL OF PHARMACY AND PHARMACOLOGY: AN INTERNATI ONAL JOURNAL OF PHARMACEUTICAL SCIENCE, Issue 12 2000PAUL A. McCARRON The use of biodegradable nanoparticles loaded with 5-fluorouracil was investigated as a potential means to sustain the release of this drug. Nanoparticles prepared from four biodegradable polymers were loaded with 5-fluorouracil using three loading concentrations of drug and three different concentrations of added polymer. Washing particles using a centrifugation/re-suspension with ultrasound protocol was found to dislodge the majority of drug, resulting in an over-estimation of incorporation efficiency and low levels of strongly entrapped drug. Increasing the initial 5-fluorouracil concentration before polymer/monomer addition increased the drug loading in both washed and unwashed particles. Increasing the amount of polymer used to make nanoparticles did not increase loadings, but did produce increased amounts of unusable polymer waste. Drug release from nanoparticles was evaluated using a Franz cell diffusion apparatus, which showed an initial burst effect followed by a slower release phase over 24 h. Indeed, nanoparticles prepared from poly(lactide-co-glycolide) released 66% of their 5-fluorouracil payload over this period. It was concluded that 5-fluorouracil-loaded nanoparticles could be readily included into a hydrogel-based delivery system to provide sustained drug release for trans-epithelial drug-delivery applications. [source] Preparation and Characterisation of Pd Nanoclusters in Hyperbranched Aramid Templates to be used in Homogeneous CatalysisMACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 12 2003Daniela Tabuani Abstract In the present paper the potential use of hyperbranched (HB) aramids as metallic solution stabilisers and carriers for homogeneous catalysis is outlined. Aramids, synthesised either from A2,+,B3 reagents [namely, p -phenylenediamine (PPD) and trimesic acid (TMA)] or from an AB2 monomer [i.e., 5-(4-aminobenzamido)isophtalic acid, named ABZAIA], have been used to stabilise palladium nanoclusters dispersed in two solvent media, namely N,N, -dimethylformamide (DMF) and dimethyl sulfoxide (DMSO). The influence of the nature of the polymeric support as well as of the solvent medium on both cluster dimensions and stability of the solutions has been investigated. Indeed, the interactions between the polymeric support and the metallic precursor (PdCl2), as revealed by 1H NMR spectroscopy, involve only the amino groups of the HB aramids. Metal nanocluster dimensions and stability are strongly dependent on the polymer used as a stabilizer. Transmission electron microscopy (TEM) analysis has shown that the presence of HB polymer in the solution reduces cluster dimensions and allows the obtaining of stable systems. The low concentration of NH2 end groups in the poly(AB2) system leads to the formation of Pd particles of rather low dimensions with a high tendency to aggregate. All prepared solutions are stable under inert atmosphere for at least a month, with an improved stabilisation when using the poly(A2,+,B3) system for more than five months. A TEM micrograph of poly(ABZAIA)/Pd from a DMSO solution. [source] A Cationic Water-Soluble Poly(p -phenylenevinylene) Derivative: Highly Sensitive Biosensor for Iron-Sulfur Protein Detection,MACROMOLECULAR RAPID COMMUNICATIONS, Issue 10 2006Fan Cheng Abstract Summary: A new water-soluble cationic ammonium-functionalized poly(p -phenylenevinylene) (PPV-NEtMe) was successfully synthesized and exhibited high sensitivity (Ksv,=,6.9,×,107M,1) on rubredoxin, a type of anionic iron-sulfur (Fe-S) proteins. Further investigation showed that the biosensitivity of the cationic conjugated polymer is strongly dependent on the nature of the buffer solution and the concentration of the conjugated polymer used in the analyses. The schematic diagram of anionic rubredoxin detected by PPV-NEtMe. [source] A model to quantify encrustation on ureteric stents, urethral catheters and polymers intended for urological useBJU INTERNATIONAL, Issue 4 2000S.K.S. Choong Objective To validate an encrustation model and to quantify encrustation on currently used urological devices and polymers intended for urological use. Materials and methods An encrustation model was validated: (i) to measure the amount of calcium leaching from the glass model and from the polymer used; (ii) to determine whether the use of a single-source or pooled urine produced similar results; (iii) to determine in vitro encrustation; and (iv) to compare the results of in vivo implantation of the same materials into the bladders of rodents with the in vitro results. A test polymer (a ureteric stent, a urethral catheter or a biomaterial) and a control silicone polymer were housed separately but received human urine from the same reservoir and under the same conditions (pH 6.0 and 37 °C) for 5 days. The amount of calcium encrustation on each polymer was measured using atomic absorption spectroscopy. Each experiment was repeated at least four times and the results expressed as an encrustation index, defined as the ratio of encrustation of the test and reference polymers. Results The amount of calcium leaching from the glass model and polymers tested was insignificant. The use of a single-source or pooled urine gave the same results in the encrustation model. The in vitro results correlated with in vivo implantation of disks into the bladders of rats. Among the commonly used ureteric stents tested, the Cook C-Flex ureteric stents encrusted least. Hydrogel-coated ureteric stents encrusted more than uncoated stents. The Bard polytetrafluoroethylene short-term urethral catheter encrusted more than the Bard hydrogel-coated long-term catheter. A plasma-activated surface modification of a synthetic biomaterial with hyaluronic acid encrusted less than silicone, a long-term biomaterial widely regarded as the ,gold standard'. Conclusion This validated encrustation model is the first to quantify encrustation on currently available ureteric stents and urethral catheters. A novel coating for a biomaterial was identified using the encrustation model, and which encrusted less than silicone. [source] Glycochips from Polyanionic Glycopolymers as Tools for Detecting Shiga ToxinsCHEMBIOCHEM, Issue 17 2007Hirotaka Uzawa Dr. Abstract An alternating layer-by-layer adsorption methodology was applied to the assembly of glycochips by using synthetic polyanionic glycopolymers. Three glycochips carrying globobioside (Gb2), ,-lactoside (, -Lac), or , - D -mannoside (, -Man) residues were prepared, and used for the detection of Shiga toxins, Stx-1 and Stx-2, by using surface plasmon resonance (SPR). Using this method, we could confirm that both Stx-1 and Stx-2 show binding specificity for the Gb2 glycochip as well as a weak affinity for the , -Lac glycochip. The affinity constants of these toxins depended strongly on the sugar content of the Gb2 polymer used to prepare the glycochip. Greater affinity was observed for chips with a higher sugar content (up to 43,%) in the Gb2 glycopolymer. The maximal affinity constants of Stx-1 and Stx-2 (Ka=108,109,M,1) enabled highly sensitive and facile analysis (10 ng,mL,1, 30 min). When Gb2 glycopolymers were used as competitors, Stx-1 and Stx-2 behaved differently from one another in terms of their SPR response; this allowed us to perform discriminative analysis between the two toxins. [source] Protein separations using polyelectrolyte multilayer coatings with molecular micelles in open tubular capillary electrochromatographyELECTROPHORESIS, Issue 4 2008Candace A. Luces Abstract Novel polyelectrolyte multilayer (PEM) coatings for enhanced protein separations in open tubular CEC (OT-CEC) are reported. Use of four cationic polymers (poly- L -lysine, poly- L -ornithine, poly- L -lysine-serine, and poly- L -glutamic acid-lysine), and three anionic molecular micelles, sodium poly(N -undecanoyl- L -leucyl-alaninate) (poly- L -SULA), sodium poly(N -undecanoyl- L -leucyl-valinate) (poly- L -SULV), and sodium poly(undecylenic sulfate) (poly-SUS) were investigated in PEM coatings for protein separations. The simultaneous effects of cationic polymer concentration, number of bilayers, temperature, applied voltage, and pH of the BGE on the separation of four basic proteins (,-chymotrypsinogen A, lysozyme, ribonuclease A, and cytochrome c) were analyzed using a Box Behnken experimental design. The influence of NaCl on the run-to-run reproducibility was investigated for PEM coatings containing each cationic polymer. All coatings exhibited excellent reproducibilities with a %RSD of the EOF less than 1% in the presence of NaCl. Optimal conditions were dependent on both the cationic and anionic polymers used in the PEM coatings. Poly- L -glutamic acid-lysine produced the highest resolution and longest migration time. The use of molecular micelles to form PEM coatings resulted in better separations than single cationic coatings. Chiral poly- L -SULA and poly- L -SULV resulted in higher protein resolutions as compared to the achiral, poly-SUS. Furthermore, the use of poly- L -SULV reversed the elution order of lysozyme and cytochrome c when compared to poly- L -SULA and poly-SUS. [source] Assembling DNA into Advanced Materials: From Nanostructured Films to Biosensing and Delivery Systems,ADVANCED MATERIALS, Issue 21 2007Abstract The past decade has witnessed a rapid expansion in the design and assembly of engineered materials for biological applications. However, such applications place limitations on the molecular building blocks that can be used. Requirements for polymer-based building blocks include biocompatibility, biodegradability, and stimuli-responsive behavior. Many traditional polymers used in materials science are limited in at least one of these areas, so new polymers need to be explored. As we outline here, DNA is one such polymer that shows promise in developing the next generation of ,smart' materials for biomedical and diagnostic applications. [source] Effect of chain architecture on biaxial orientation and oxygen permeability of polypropylene filmJOURNAL OF APPLIED POLYMER SCIENCE, Issue 3 2008P. Dias Abstract Films of two isotactic propylene homopolymers prepared with different catalysts and a propylene/ethylene copolymer were biaxially oriented under conditions of temperature and strain rate that were similar to those encountered in a commercial film process. The draw temperature was varied in the range between the onset of melting and the peak melting temperature. It was found that the stress response during stretching depended on the residual crystallinity in the same way for all three polymers. Biaxial orientation reduced the oxygen permeability of the oriented films, however, the reduction did not correlate with the amount of orientation as measured by birefringence, with the fraction of amorphous phase as determined by density, or with free volume hole size as determined by PALS. Rather, the decrease in permeability was attributed to reduced mobility of amorphous tie molecules. A single one-to-one correlation between the oxygen permeability and the intensity of the dynamic mechanical ,-relaxation was demonstrated for all the polymers used in the study. © 2007 Wiley Periodicals, Inc. J Appl Polym Sci, 2008 [source] Laser Raman spectroscopic investigations of biodegradable vehicle of active agents eluting LVM 316 stainless steel cardiovascular stents for in vivo degradation characteristicsJOURNAL OF RAMAN SPECTROSCOPY, Issue 4 2010S. K. Sudheer Abstract Laser Raman spectroscopy is an effective tool for the study of biodegradable polymers, which play a vital role in the new developments in coronary implants such as stents. There is much excitement around the potential capabilities of synthetic biodegradable polymers and the effect they will have on the design and function of implanted devices. In the present investigation, heparin-conjugated biodegradable copolymers were evaluated for their durability as drug-eluting stent coatings. Laser Raman spectroscopic studies were carried out and spectra recorded and analyzed of explanted stents coated with different amounts of polymer alone, showing the existence of different levels at different quantities of polymer. The polymer was detected on every stent analyzed. On the stents coated with a thick layer of polymer, a firm layer of polymer still existed on the stent. In contrast, this layer was degraded and spread around on the stents coated with only a thin layer of the polymer. This indicates that the polymers used in the stents in the present investigation exhibit acceptable biodegradability. Such polymers can be used as efficient drug carriers, as these materials show good degradation after the stipulated period. Copyright © 2009 John Wiley & Sons, Ltd. [source] Measurement of aroma compound self-diffusion in food models by DOSYMAGNETIC RESONANCE IN CHEMISTRY, Issue 6 2004Thierry Gostan Abstract Self-diffusion measurement of solutes in polymer gels has been investigated using pulsed gradient spin echo NMR spectroscopy. However, few data are available on the self-diffusion of small solutes in natural polysaccharide polymers used as thickeners in the food industry. Since aroma diffusion in food matrices could have an impact on flavor release, this is an interesting and economic challenge. Diffusion ordered spectroscopy (DOSY) resolves diffusion data for each component in complex mixtures. We used DOSY with the inverse Laplace transform approach with the maximum entropy algorithm to investigate diffusion of two aroma compounds, ethyl butanoate and linalool, in an ,-carrageenan matrix as the food model. We showed that the self-diffusion coefficient values of small molecules in a polysaccharide matrix could be easily extracted using this method. We then investigated the impact of the gelling state of ,-carrageenan matrices on the self-diffusion of ethyl butanoate. Copyright © 2004 John Wiley & Sons, Ltd. [source] Detection of volatile organic compounds using a polythiophene derivativePHYSICA STATUS SOLIDI (A) APPLICATIONS AND MATERIALS SCIENCE, Issue 7 2010V. C. Gonçalves Abstract Conjugated polymers have been subject of great interest in the recent literature from both fundamental point of view and applied science perspective. Among the several types of conjugated polymers used in recent investigations, polythiophene and its derivatives have attracted considerable attention over the past 20,years due to their high mobility and other remarkable solid-state properties. They have potential applications in many fields, such as microelectronic devices, catalysts, organic field-effect transistors, chemical sensors, and biosensors. They have been studied as gas and volatile organic compounds (VOCs) sensors using different principles or transduction techniques, such as optical absorption, conductivity, and capacitance measurements. In this work, we report on the fabrication of gas sensors based on a conducting polymer on an interdigitated gold electrode. We use as active layer of the sensor a polythiophene derivative: poly (3-hexylthiophene) (P3HT) and analyzed its conductivity as response for exposure to dynamic flow of saturated vapors of six VOCs [n -hexane, toluene, chloroform, dichloromethane, methanol, and tetrahydrofuran (THF)]. Different responses were obtained upon exposure to all VOCs, THF gave the higher response while methanol the lower response. The influence of moisture on the measurements was also evaluated. [source] Synthesis and characterization of novel thermoplastic poly(oligophosphazene-urethane)sPOLYMER INTERNATIONAL, Issue 6 2009Yubo Zhou Abstract BACKGROUND: Polyurethanes are some of the most popular polymers used in a variety of products, such as coatings, adhesives, flexible and rigid foams, elastomers, etc. Despite the possibility of tailoring their properties, polyurethanes suffer a serious disadvantage of poor thermal stability. Many attempts have been made in order to improve the thermal stability of polyurethanes. RESULTS: A new hydroxyl-terminated oligomer containing sulfone groups, 2,2-bis(4-hydroxy-4,4-sulfonyldiphoneloxy)tetraphenoxyoligocyclotriphosphazene (HSPPZ), was synthesized. HSPPZ was characterized using Fourier transform infrared (FTIR), NMR and gel permeation chromatography analyses. A series of novel thermoplastic poly(oligophosphazene-urethane)s were then synthesized via the reaction of NCO-terminated polyurethane prepolymer with HSPPZ containing chain-extender diols. Their structure and properties were investigated using FTIR spectroscopy, thermogravimetric analysis, differential scanning calorimetry, X-ray diffraction, water contact angle measurement and tensile measurements. CONCLUSION: Compared to conventional thermoplastic polyurethanes, poly(oligophosphazene-urethane)s exhibit better thermal stability, low-temperature resistance and hydrophobicity, but their mechanical properties are slightly poorer. Copyright © 2009 Society of Chemical Industry [source] Modification of polystyrene properties through grafting with N -vinylcarboxamido-2-methylpropane sulfonic acid monomerPOLYMER INTERNATIONAL, Issue 12 2004A Aggour Abstract Polystyrene (PS) possesses good mechanical properties, but its surface is relatively inert and hydrophobic. Grafting of N -vinylcarboxamido-2-methylpropane sulfonic acid (VCMP) is useful to hydrophilize the PS surface. Grafting was performed using benzoyl peroxide (BPO) as an initiator in toluene:methanol solvent mixture (3:1 volume ratio). The influence of the main factors on grafting, such as temperature, time, concentrations of initiator, PS and VCMP, has been studied. The results show that the initial rate of polymerization and percentage of grafting are enhanced by increased temperature. Furthermore, the specific rate constants of the first order reaction/are determined, and the activation energy of the grafting reaction is estimated. The grafting parameters are established and a suitable mechanism of the reaction is proposed. The grafted PS is to characterized through infrared spectra, intrinsic viscosity, thermogravimetric analysis (TGA) and differential gravimetric analysis (DTG). The kinetics of thermal degradation and the order of the thermal stabilities are given. Also the decomposition activation energies of the thermal degradation are determined, and confirm the thermal stabilities of the polymers used. © 2004 Society of Chemical Industry [source] Metallocene based polyolefin: a potential candidate for the replacement of flexible poly (vinyl chloride) in the medical fieldPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 9 2010M. C. Sunny Abstract A comparative assessment of the performance properties of metallocene polyolefin (m-PO) with those of plasticized poly (vinyl chloride) (pPVC) and ethylene vinyl acetate (EVA) copolymer having 18% vinyl acetate content (EVA-18), the two common polymers used for flexible medical products, is carried out. The preliminary evaluation of the processability, mechanical properties, and thermal stability of the new material, m-PO is described. The processability parameters like mixing torque and melt viscosity of m-PO are found to be comparable with those of pPVC and EVA-18. Mechanical properties such as tensile strength, elongation at break, and tear strength (TS) of m-PO are much higher than that of pPVC and EVA-18. Thermo gravimetric analysis (TGA) indicates that the thermal degradation of m-PO takes place only at temperatures above 340°C and can be processed at 170°C without much damage. Oxygen and carbon dioxide permeabilities of m-PO at three different temperatures (10, 25, and 40°C) are evaluated and compared with those of pPVC and EVA-18. It could be seen that the permeabilities of both the gases for m-PO at three temperatures were lower than those of pPVC and EVA. Biological evaluation of m-PO is carried out by assessing its cytotoxicity, hemolytic property, and blood clotting initiation. The cytotoxicity studies indicate that m-PO is non-toxic to the monolayer of L929 mammalian fibroblast cell lines on direct contact or the exposure of its extract. Non-hemolytic property of m-PO by direct contact as well as test on extract is revealed both in static and in dynamic conditions. Blood clotting time experiments indicate that the initiation of blood clotting due to m-PO is faster than that of pPVC and EVA-18. Copyright © 2009 John Wiley & Sons, Ltd. [source] Evaluation of pyridoindoles, pyridylindoles and pyridylpyridoindoles as matrices for ultraviolet matrix-assisted laser desorption/ionization time-of-flight mass spectrometryRAPID COMMUNICATIONS IN MASS SPECTROMETRY, Issue 23 2001Hiroshi Nonami In an effort to gain an understanding of the processes governing ultraviolet matrix-assisted laser desorption/ionization (UV-MALDI), direct comparison was made of the mass spectra of proteins, carbohydrates and synthetic polymers (polyethylene glycol, polyester and polyamide) by using pyridylindoles, pyridoindoles and pyridylpyridoindoles as UV (337,nm)-MALDI-TOFMS matrices in positive and negative ion mode. In order to study the combined effect of the indole N-H and the pyridine nitrogen of the MALDI matrix on the desorption/ionization process in MALDI, compounds were selected that include either or both of these functions in their structure. Within the compounds studied only those that possess simultaneously both functions in a 1,4-relation behave as very good matrices for proteins. These compounds also work as matrices for some carbohydrates and synthetic polymers used as analytes in the present study. Some of the compounds were also found to be useful for the post-source decay (PSD) analysis of cyclodextrins in positive and negative ion mode. In several cases we also examined the matrix behavior of the corresponding N-methylindole derivatives. Copyright © 2001 John Wiley & Sons, Ltd. [source] Pharmacokinetic study on the mechanism of interaction of sulfacetamide sodium with bovine serum albumin: a spectroscopic methodBIOPHARMACEUTICS AND DRUG DISPOSITION, Issue 2-3 2010Praveen N. Naik Abstract The binding of sulfacetamide sodium (SAS) to bovine serum albumin (BSA) was investigated by spectroscopic methods, namely fluorescence, FT-IR and UV-vis absorption spectral studies. The binding parameters were evaluated by a fluorescence quenching method. The thermodynamic parameters, ,H0, ,S0and ,G0 were observed to be ,49.03,k,J,mol,1, ,99.9,J,K,1,mol,1 and ,18.96,k,J,mol,1, respectively. These indicated that the hydrogen bonding and weak van der Waals forces played major roles in the interaction. Based on Förster's theory of non-radiation energy transfer, the binding average distance, r, between the donor (BSA) and acceptor (SAS) was evaluated and found to be 3.72,nm. The spectral results showed that binding of SAS to BSA induced conformational changes in BSA. The effect of common ions and some of the polymers used in drug delivery for controlled release were also tested on the binding of SAS to BSA. Copyright © 2010 John Wiley & Sons, Ltd. [source] Retrovirus-Polymer Complexes: Study of the Factors Affecting the Dose Response of TransductionBIOTECHNOLOGY PROGRESS, Issue 2 2007Natalia Landázuri We have previously shown that complexes of Polybrene (PB), chondroitin sulfate C (CSC), and retrovirus transduce cells more efficiently than uncomplexed virus because the complexes are large and sediment, reaching the cells more rapidly than by diffusion. Transduction reaches a peak at equal weight concentrations of CSC and PB and declines when the dose of PB is higher or lower than CSC. We hypothesized that the nonlinear dose response of transduction was a complex function of the molecular characteristics of the polymers, cell viability, and the number of viruses incorporated into the complexes. To test this hypothesis, we formed complexes using an amphotropic retrovirus and several pairs of oppositely charged polymers and used them to transduce murine fibroblasts. We examined the effect of the type and concentration of polymers used on cell viability, the size and charge of the complexes, the number of viruses incorporated into the complexes, and virus binding and transduction. Transduction was enhanced (2.5- to 5.5-fold) regardless of which polymers were used and was maximized when the number of positive charge groups was in slight excess (15,28%) of the number of negative charge groups. Higher doses of cationic polymer were cytotoxic, whereas complexes formed with lower doses were smaller, contained fewer viruses, and sedimented more slowly. These results show that the dose response of transduction by virus-polymer complexes is nonlinear because excess cationic polymer is cytotoxic, whereas excess anionic polymer reduces the number of active viruses that are delivered to the cells. [source] | |||||||||||||||||||||||||||||||