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Natural Polymers (natural + polymer)
Selected AbstractsEmulsifying properties of gum kondagogu (Cochlospermum gossypium), a natural biopolymerJOURNAL OF THE SCIENCE OF FOOD AND AGRICULTURE, Issue 8 2009Ganga Modi Naidu Vegi Abstract BACKGROUND: Natural polymers are widely used as emulsifying agents in the food and pharmaceutical industries because of their low cost, biocompatibility and non-toxic nature. In the present study, emulsifying properties of the novel natural biopolymer gum kondagogu (GKG) were investigated. GKG solutions of different concentrations (0.1,0.6% w/v) were prepared in water and emulsified with liquid paraffin oil (40% v/v) in a high-speed homogeniser. Flow properties of the emulsions were measured using a rheometer. Emulsion stability and droplet size distribution were determined by visual observation, photomicrography and laser-scattering particle size distribution analysis. RESULTS: The emulsions prepared with GKG showed pseudoplastic behaviour. The size of oil droplets and the viscosity of emulsions at concentrations of 0.4,0.6% w/v showed little change over time (up to 30 days), indicating that the emulsions were stable. Measurements of the zeta potential of emulsions adjusted to different pH, with and without added electrolyte, showed that the stabilisation of emulsions with GKG was due to mutual repulsion between electrical double layers of particles and adsorption of macromolecules on oil droplets. CONCLUSION: The results of this experimental investigation show that GKG is a good emulsifying agent even at low concentrations, with many potential applications in the food and pharmaceutical industries. Copyright © 2009 Society of Chemical Industry [source] Development and application of polymerase chain reaction primers based on fhcD for environmental detection of methanopterin-linked C1 -metabolism in bacteriaENVIRONMENTAL MICROBIOLOGY, Issue 8 2005Marina G. Kalyuzhnaya Summary In this work we describe development and testing of a novel pair of environmental primers targeting fhcD, a conserved gene in the H4MTP-linked C1 -transfer pathway, and demonstrate that these primers enable confident detection of a broad variety of fhcD genes originating from phylogenetically diverse bacteria. The new primer pair was employed to analyse fhcD diversity in Lake Washington sediment, uncovering the presence of 40 fhcD phylotypes. Based on phylogenetic analyses, the phylotypes identified were affiliated with ,-, ,- and ,-proteobacteria, and Planctomycetes, while a number of sequences formed deep branches suggesting the presence of unknown groups of microorganisms. To assess the physiological potential and the possible substrate repertoire of the fhcD- containing species in Lake Washington, we conducted enrichments of natural populations on a variety of C1 substrates, and observed specific shifts in community structure in response to different C1 substrates. A specific shift in community structure was also observed in the presence of humic acids suggesting that C1 transfer metabolism linked to H4MPT may be part of the degradation pathway for this natural polymer, possibly involving formaldehyde production. Overall, our data suggest that C1 oxidation reactions linked to H4MPT are much more widespread in natural environments than previously thought. [source] Nanofiber Generation of Gelatin,Hydroxyapatite Biomimetics for Guided Tissue Regeneration,ADVANCED FUNCTIONAL MATERIALS, Issue 12 2005H.-W. Kim Abstract The development of biomimetic bone matrices is one of the major goals in the bone-regeneration and tissue-engineering fields. Nanocomposites consisting of a natural polymer and hydroxyapatite (HA) nanocrystals, which mimic the human bone matrix, are thus regarded as promising bone regenerative materials. Herein, we developed a biomimetic nanocomposite with a novel nanofibrous structure by employing an electrospinning (ES) method. The HA precipitate/gelatin matrix nanocomposites are lyophilized and dissolved in an organic solvent, and then electrospun under controlled conditions. With this process, we can successfully generate a continuous fiber with a diameter of the order of hundreds of nanometers. The internal structure of the nanofiber features a typical nanocomposite, i.e., HA nanocrystals well distributed within a gelatin matrix. These nanocomposite fibers improve the bone-derived cellular activity significantly when compared to the pure gelatin equivalent. This method of generating a nanofiber of the biomimetic nanocomposite was effective in producing a biomedical membrane with a composition gradient, which is potentially applicable in the field of guided tissue regeneration (GTR). [source] Estimation of kinetic and mass-transfer parameters for cellulose nitrationAICHE JOURNAL, Issue 10 2006I. V. M. Barbosa Abstract When nitrocellulose is used in the production of gun powders and rocket/missile propellants, rigid control of the cellulose nitration reaction is necessary. Nitrogen content is, by far, the most important parameter to be controlled and only off-line measurements can be performed for that. Although cellulose is a natural polymer whose characteristics may vary, the final product must have its nonuniformities compensated by blending of different batches. In this work, kinetic and mass-transfer parameters are nonlinearly fitted using typical nitration experiments. The required mathematical modeling is carried out using a continuous mixtures approach, which depends only on structural descriptions of the cellulose. The model leads to an algebraic-integro-differential population balance system of equations, solved with an approximant built with block-pulse functions. © 2006 American Institute of Chemical Engineers AIChE J, 2006 [source] A Study on Biomineralization Behavior of N -Methylene Phosphochitosan ScaffoldsMACROMOLECULAR BIOSCIENCE, Issue 10 2004Yu Ji Yin Abstract Summary: Biomimetic growth of calcium phosphate over natural polymer may be an effective approach to constituting an organic/inorganic composite scaffold for bone tissue engineering. In this work, N -methylene phosphochitosan (NMPCS) was prepared via formaldehyde addition and condensation with phosphoric acid in a step that allowed homogeneous modification without obvious deterioration in chitosan (CS) properties. The NMPCS obtained was characterized by using FT-IR and elemental analysis. The macroporous scaffolds were fabricated through a freeze-drying technique. A comparative study on NMPCS and CS scaffold biomimetic mineralization was carried out in different media, i.e, a simulated body fluid (SBF) or alternative CaCl2 and Na2HPO4 solutions respectively. Apatite formation within NMPCS and CS scaffolds was identified with FT-IR, scanning electron microscopy (SEM), energy-dispersive X-ray (EDX) and X-ray diffractometery (XRD). The results revealed alternate soaking of the scaffolds in CaCl2 and Na2HPO4 solutions was better than soaking in SBF solution alone in relation to apatite deposition on the scaffold pore walls. Biomineralization provides an approach to improve nature derived materials, e.g., chitosan derivative NMPCS properties e.g., compressive modulus, etc. SEM image of a NMPCS/apatite composite scaffold. [source] Enzyme degradability of benzylated sisal and its self-reinforced compositesPOLYMERS FOR ADVANCED TECHNOLOGIES, Issue 10 2003Xun Lu Abstract To produce natural polymer based composite materials, sisal fibers were slightly benzylated and then molded into sheets. Because the modified skin portions of the fibers acquired certain thermoplasticity and the unmodified core parts remain constant, the resultant composites fall into the category of self-reinforced ones. The present article is devoted to the evaluation of the materials biodegradability with the help of cellulase. It was found that the inherent biodegradability of plant fibers is still associated with the benzylated sisal and the molded composites, as characterized by structural variation, weight loss and deterioration of mechanical performance of the materials. Reaction temperature and time, pH value of the enzyme solution, and dosage of the enzyme had significant influences on the decomposition behavior of the materials. In principle, the enzymolysis of sisal and its self-reinforced composites is a diffusion-controlled process. Due to the insusceptibility of lignin to cellulase and the hindrance of it to the cellulase solution, the degradation rates of the materials are gradually slowed down with an increase in time. Copyright © 2003 John Wiley & Sons, Ltd. [source] A Versatile "Click" Chemistry Precursor of Functional Polystyrene NanoparticlesADVANCED MATERIALS, Issue 28 2010Lorea Oria The synthesis of a versatile "click" chemistry precursor of functional polystyrene nanoparticles is reported. The resulting nanoparticles thereof offer inherent characteristics of ultrasmall polymeric nanoparticles (size ,4 nm) plus interesting functionalization possibilities, opening the door to new hybrid, soft nano-objects, bridging the gap between synthetic and natural polymers. [source] Formulation and development of a patch containing tamarind fruit extract by using the blended chitosan,starch as a rate-controlling matrixINTERNATIONAL JOURNAL OF COSMETIC SCIENCE, Issue 3 2003J. Viyoch Synopsis A cosmetic patch containing tamarind fruit extract was formulated and developed by blending two types of natural polymers: chitosan with molecular weight of 100 000 and starch such as corn, potato or tapioca starch. The physicochemical characteristics, i.e. flexibility, colour, transparency, integrity, gloss, water sorption and bioadhesion property and the stability of the patch without tamarind content were investigated. Stability test was performed by keeping the prepared patches at 4 °C, at room temperature or at 45 °C for 2 weeks. The results showed that the formulations composed of chitosan:corn starch ratio of 4.5 : 0.5 (CC4.5 : 0.5) and chitosan:tapioca starch ratios of 4.5 : 0.5 (CT4.5 : 0.5) and 4.0 : 1.0 (CT4 : 1) provide patches with favourable physical characteristics, high water sorption, good bioadhesion ability and good stability. After the lyophilized tamarind extract in an amount corresponding to 5% of tartaric acid was incorporated into the formulations of CC4.5 : 0.5, CT4.5 : 0.5 and CT4 : 1, the ability of the patches to adhere to skin was improved. However, after keeping the test patches at room temperature or at 45 °C for 6 weeks, their colours were intensified while their flexibilities and skin adhesion properties decreased. A 12-h in vitro permeation was investigated by studying the cumulative amount of tartaric acid permeated through the Silastic® membrane (Dow-Coming, Midland, MI, USA). The CC4.5 : 0.5 patch tended to give the highest amount of tartaric acid released. The release pattern of all the blended polymeric matrices was exhibited in two distinct phases: the rapid phase, where the flux averaged 3.61 µg min,1 mm,2; and the slow phase, where the flux averaged 1.89 µg min,1 mm,2. Résumé Un patch cosmétique contenant un extrait de fruit de Tamarin a été formulé et développé en mélangeant deux types de polymères naturels, le chitosan d'un poids moléculaire de 100 000 et d'amidon de maïs, de pomme de terre ou d'amidon de tapioca. Les caractéristiques physico chimiques, i.e. de flexibilité, couleur, transparence, intégrité, brillance, pouvoir de sorption de l'eau, la propriété de bio adhésion et la stabilité des patchs sans tamarin ont été déterminées. Le test de stabilité A été effectué en gardant les patchs préparés à 4 °C, température ambiante ou 45 °C pendant 2 semaines. Les résultats montrent que la formulation composée de chitosan:amidon de maïs au taux relatif de 4.5 : 0.5 (CC4.5 : 0.5), de chitosan:amidon de tapioca aux taux relatifs de 4.5 : 0.5 (CT4.5 : 0.5) et de 4.0 : 1.0 (CT4 : 1) conduit aux propriétés physiques les plus favorables, haute sorption d'eau, bonnes capacité de bio adhésion et stabilité. Après que l'extrait lyophilisé de tamarin ait été incorporé au taux correspondant à 5% d'acide tartrique dans les formulations CC4.5 : 0.5, CT4.5 : 0.5 et CT4 : 1, la capacité des patchs à adhérer à la peau a été améliorée. Cependant, la conservation des patchs à température ambiante et à 45 °C pendant 6 semaines conduisait à une intensification de leurs couleurs tandis que leur propriété d'adhésion diminuait. La perméation in vitro sur 12 heures a étéétudiée en suivant le taux cumulé d'acide tartrique passant à travers la membrane de Silastic®. Le CC4.5 : 0.5 tendait à donner le taux le plus élevé d'acide tartrique re largué. Le profil de relarguage de toutes les matrices de polymères montrait deux phases distinctes, l'une, rapide au flux moyen de 3.61 µg min,1 mm,2 et une, plus lente, de flux moyen 1.89 µg min,1 mm,2. [source] Physically crosslinked composite hydrogels of PVA with natural macromolecules: Structure, mechanical properties, and endothelial cell compatibilityJOURNAL OF BIOMEDICAL MATERIALS RESEARCH, Issue 2 2009Y. Liu Abstract Polyvinyl alcohol (PVA) hydrogels have been considered potentially suitable for applications as engineered blood vessels because of their structure and mechanical properties. However, PVA's hydrophilicity hinders its capacity to act as a substrate for cell attachment. As a remedy, PVA was blended with chitosan, gelatin, or starch, and hydrogels were formed by subjecting the solutions to freeze-thaw cycles followed by coagulation bath immersion. The structure-property relationships for these hydrogels were examined by measurement of their swelling, rehydration, degradation, and mechanical properties. For the case of pure PVA hydrogels, the equilibrium swelling ratio was used to predict the effect of freeze thaw cycles and coagulation bath on average molecular weights between crosslinks and on mesh size. For all hydrogels, trends for the reswelling ratio, which is indicative of the crosslinked polymer fraction, were consistent with relative tensile properties. The coagulation bath treatment increased the degradation resistance of the hydrogels significantly. The suitability of each hydrogel for cell attachment and proliferation was examined by protein adsorption and bovine vascular endothelial cell culture experiments. Protein adsorption and cell proliferation was highest on the PVA/gelatin hydrogels. This study demonstrates that the potential of PVA hydrogels for artificial blood vessel applications can be improved by the addition of natural polymers, and that freeze-thawing and coagulation bath treatment can be utilized for fine adjustment of the physical characteristics. © 2009 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 2009 [source] Mercury removal: a physicochemical study of metal interaction with natural materialsJOURNAL OF CHEMICAL TECHNOLOGY & BIOTECHNOLOGY, Issue 11 2009Leticia Carro Abstract BACKGROUND: Mercury is considered one of the most harmful heavy metals to the environment and human health, so recently remediation processes have been developed to eliminate this metal from wastewaters. Metal retention by natural polymers is a good alternative technique to remove heavy metals from solution. RESULTS: A screening of 25 potential mercury sorbents was carried out at three different pH values in order to find appropriate biomass to remove this metal from polluted waters. High sorption capacities were found for many of the materials studied. Four of these materials were selected for further detailed study. Kinetic studies showed short times to reach equilibrium. For S. muticum, sorption isotherms were obtained at several temperatures and a sorption enthalpy value was obtained. Desorption experiments were performed to determine the possibility for recycling of this brown alga. CONCLUSIONS: Different materials have been found to be potentially good adsorbents of mercury. A detailed study showed that S. muticum is an excellent material with a mercury uptake about 200 mg g,1. This brown alga has a fast kinetic process (80% of metal is removed from solution in 30 min), and very high metal uptake over a wide pH range, up to 92% elimination for pH values above 3,4. Copyright © 2009 Society of Chemical Industry [source] Co-electrospun composite nanofibers of blends of poly[(amino acid ester)phosphazene] and gelatinPOLYMER INTERNATIONAL, Issue 5 2010Yi-Jun Lin Abstract Electrospinning is known as a simple and effective fabrication method to produce polymeric nanofibers suitable for biomedical applications. Many synthesized and natural polymers have been electrospun and reported in the literature; however, there is little information on the electrospinning of poly[(amino acid ester)phosphazene] and its blends with gelatin. Composite nanofibers were made by co-dissolving poly[(alaninoethyl ester)0.67(glycinoethyl ester)0.33phosphazene] (PAGP) and gelatin in trifluoroethanol and co-electrospinning. The co-electrospun composite nanofibers from different mixing ratios (0, 10, 30, 50, 70 and 90 wt%) of gelatin to PAGP consisted of nanoscale fibers with a mean diameter ranging from approximately 300 nm to 1 µm. An increase in gelatin in the solution resulted in an increase of average fiber diameter. Transmission electron microscopy and energy dispersive X-ray spectrometry measurements showed that gelatin core/PAGP shell nanofibers were formed when the content of gelatin in the hybrid was below 50 wt%, but homogeneous PAGP/gelatin composite nanofibers were obtained as the mixing ratios of gelatin to PAGP were increased up to 70 and 90 wt%. The study suggests that the interaction between gelatin and PAGP could help to stabilize PAGP/gelatin composite fibrous membranes in aqueous medium and improve the hydrophilicity of pure PAGP nanofibers. Copyright © 2009 Society of Chemical Industry [source] Biodegradable polymers applied in tissue engineering research: a reviewPOLYMER INTERNATIONAL, Issue 2 2007Monique Martina Abstract Typical applications and research areas of polymeric biomaterials include tissue replacement, tissue augmentation, tissue support, and drug delivery. In many cases the body needs only the temporary presence of a device/biomaterial, in which instance biodegradable and certain partially biodegradable polymeric materials are better alternatives than biostable ones. Recent treatment concepts based on scaffold-based tissue engineering principles differ from standard tissue replacement and drug therapies as the engineered tissue aims not only to repair but also regenerate the target tissue. Cells have been cultured outside the body for many years; however, it has only recently become possible for scientists and engineers to grow complex three-dimensional tissue grafts to meet clinical needs. New generations of scaffolds based on synthetic and natural polymers are being developed and evaluated at a rapid pace, aimed at mimicking the structural characteristics of natural extracellular matrix. This review focuses on scaffolds made of more recently developed synthetic polymers for tissue engineering applications. Currently, the design and fabrication of biodegradable synthetic scaffolds is driven by four material categories: (i) common clinically established polymers, including polyglycolide, polylactides, polycaprolactone; (ii) novel di- and tri-block polymers; (iii) newly synthesized or studied polymeric biomaterials, such as polyorthoester, polyanhydrides, polyhydroxyalkanoate, polypyrroles, poly(ether ester amide)s, elastic shape-memory polymers; and (iv) biomimetic materials, supramolecular polymers formed by self-assembly, and matrices presenting distinctive or a variety of biochemical cues. This paper aims to review the latest developments from a scaffold material perspective, mainly pertaining to categories (ii) and (iii) listed above. Copyright © 2006 Society of Chemical Industry [source] | |||||||||||||