ELECTROANALYSIS, Issue 18 2003
Moritz Beissenhirtz
Abstract A method for the characterization of antioxidants is introduced, which allows the measurement of pure hydrophilic and hydrophobic substances as well as complex cosmetic creams. The sensor is based on cytochrome c covalently immobilized on a gold wire electrode working in mixtures of phosphate buffer and organic solvents. It is combined with a superoxide generating enzyme system. The decrease of the superoxide concentration in the test solution by the added antioxidants is detected and used for the quantification of their antioxidative efficiency. Electrochemical properties of immobilized cytochrome c, such as formal potential and heterogeneous electron transfer rate constant, have been investigated in mixtures of aqueous buffer and DMSO, methanol, butanediol, and THF. The maximum organic solvent content for quasi-reversible electrode behavior was correlated to spectroscopic measurements. The activity of the radical producing enzyme in such media was determined and the radical generation characterized. The antioxidative properties of pure substance such as ascorbic acid and Biochanin A as well as of five anti-ageing cosmetic creams were studied. This showed also the influence of matrix composition on the efficiency of antioxidative supplements. [source]

Hydrophilic and Antimicrobial Zeolite Coatings for Gravity-Independent Water Separation,

ADVANCED FUNCTIONAL MATERIALS, Issue 2 2005

Abstract Condensing heat exchangers onboard manned spacecraft require hydrophilic fin surfaces to facilitate wetting and wicking of condensate to achieve gravity-independent water separation in the zero- or micro-gravity environment of space. In order to prevent the proliferation of microbes, the coating must also be biocidal. Here we show for the first time that zeolite,A and ZSM-5 coatings deposited via in-situ crystallization on stainless steel and aluminum alloys have excellent hydrophilicity, biocidal properties, and adhesion. Water contact angles below 5° were obtained on most substrates tested. When silver-ion exchange is carried out on the zeolite,A coating, it becomes highly antibacterial. This biocidal capability of zeolite,A is regenerative by repeated ion exchange. All coatings exhibit the highest rating of 5B as determined by adhesion test ASTM D-3359-02 (American Society for Testing and Materials). These properties, in addition to zeolite coating's low-temperature crystallization process and demonstrated corrosion resistance, make zeolite coatings advantageous over the current sol,gel coatings and well suited for use in condensing heat exchangers onboard manned spacecraft. [source]

Highly Functional Poly(meth)acrylates via Cascade Reaction

MACROMOLECULAR CHEMISTRY AND PHYSICS, Issue 2 2009
Dragos Popescu
Abstract A new route to the synthesis of highly functional and reactive polymethacrylates via cascade reactions comprising enzymatically and chemically catalyzed steps is presented. Transacylation of methyl acrylate and methyl methacrylate as substrates with different functional alcohols in the presence of Novozyme 435 leads to a mixture of functional monomers, which in a subsequent step was copolymerized via free radical polymerization, resulting in polymethacrylates with predefined functionalities. Hydrophilic, hydrophobic, as well as ionic methacrylate repeating units were assembled in a copolymer and adjusted for surface coatings. [source]

A "Click" Strategy for Tuning in situ the Hydrophilic,Hydrophobic Balance of AB Macrosurfactants

MACROMOLECULAR RAPID COMMUNICATIONS, Issue 12-13 2008
Zoya Zarafshani
Abstract The self-organization of amphiphilic block copolymers in water strongly depends on their molecular structure, in particular on their hydrophilic,hydrophobic balance. Herein, a simple method for tuning the amphiphilicity of polymeric macrosurfactants in aqueous medium is proposed. This concept relies on the "click" ligation of an amphiphilic block copolymer (AB type) and a hydrophilic homopolymer (B type). In the present communication, the validity of this approach was examined with model polymers based on polystyrene (PS) and poly[oligo (ethylene glycol) acrylate] (POEGA) segments. A well-defined , -azido functional diblock copolymer PS- b -POEGA and an , -alkyne functional homopolymer POEGA were prepared using atom transfer radical polymerization. These two polymers could be efficiently coupled to each other via copper-catalyzed azide,alkyne click chemistry in aqueous medium. Moreover, in this coupling strategy, an ester group was introduced at the junction between AB and B segments. This labile moiety may be "cut" by hydrolysis. [source]

Synthesis of hydrophilic/CO2 -philic poly(ethylene oxide)- b -poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) block copolymers via controlled/living radical polymerizations and their properties in liquid and supercritical CO2

JOURNAL OF POLYMER SCIENCE (IN TWO SECTIONS), Issue 10 2004
Zhi Ma
Abstract Hydrophilic/CO2 -philic poly(ethylene oxide)- b -poly(1,1,2,2-tetrahydroperfluorodecyl acrylate) block copolymers were synthesized via reversible addition,fragmentation chain transfer (RAFT) polymerization, iodine transfer polymerization (ITP), and atom transfer radical polymerization (ATRP) in the presence of either degenerative transfer agents or a macroinitiator based on poly(ethylene oxide). In this work, both RAFT and ATRP showed higher efficiency than ITP for the preparation of the expected copolymers. More detailed research was carried out on RAFT, and the living character of the polymerization was confirmed by an ultraviolet (UV) analysis of the SC(S)Ph or SC(S)SC12H25 end groups in the polymer chains. The quantitative UV analysis of the copolymers indicated a number-average molecular weight in good agreement with the value determined by 1H NMR analysis. The properties of the macromolecular surfactants were investigated through the determination of the cloud points in neat liquid and supercritical CO2 and through the formation of water-in-CO2 emulsions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 42: 2405,2415, 2004 [source]

Immobilized Cytochrome c Sensor in Organic/Aqueous Media for the Characterization of Hydrophilic and Hydrophobic Antioxidants

Online CIEF-ESI-MS in glycerol,water media with a view to hydrophobic protein applications

ELECTROPHORESIS, Issue 23 2009
Meriem Mokaddem
Abstract A new online coupling of CIEF with ESI-MS has been developed in glycerol,water media. This improved protocol provides: (i) the electric continuity during the whole analysis by a discontinuous filling of the capillary with 60:40 (cm/cm) catholyte/proteins,ampholyte mixture; (ii) the use of an anticonvective medium, i.e. 30:70 glycerol/water, v/v, compatible with MS detection and as an aid to hydrophobic protein solubilization and (iii) the use of unmodified bare fused-silica capillaries, as the glycerol/water medium strongly reduces EOF. Focusing was performed in positive polarity and cathodic mobilization was achieved by both voltage and pressure application. The setup was optimized with respect to analysis time, sensitivity and precision on pI determination. The optimized anolyte and catholyte were composed of 50,mM formic acid/1,mM glutamic acid (pH 2.35) and 100,mM NH3/1,mM lysine (pH 10.6), respectively. The effects of ampholyte concentration, focusing time and ESI parameters were presented for model proteins and discussed. This new integrated protocol should be an easy and effective additional tool in the field of proteome analysis, providing a means for the characterization of a large number of hydrophilic and hydrophobic proteins. [source]

Preparation and characterization of temperature-responsive capillary electrochromatographic column using poly(N -isopropylacrylamide)

ELECTROPHORESIS, Issue 4 2009
Rongji Dai
Abstract Poly(N -isopropylacrylamide) is a temperature-responsive polymer, which is hydrophilic at low temperature but hydrophobic at high temperature. Using this characteristic, the polymer was bonded to the inner surface of fused-silica capillary to prepare a temperature-responsive column to study the separation behavior in electrochromatography. [source]

Electrokinetic instability effects in microchannels with and without nanofilm coatings

ELECTROPHORESIS, Issue 24 2008
Lung-Ming Fu
Abstract This paper presents a parametric experimental investigation into the electrokinetic instability (EKI) phenomenon within three different types of microfluidic device, namely T-type, cross-shaped, and cross-form with an expansion configuration. The critical electric field strength at which the EKI phenomenon is induced is examined as a function of the conductivity ratio, the microchannel width, the expansion ratio, and the surface treatment of the microchannel walls. It is found that the critical electric field strength associated with the onset of EKI is strongly dependent on the conductivity ratio of the two samples within the microfluidic device and reduces as the channel width increases. The surfaces of the microchannel walls are coated with hydrophilic or hydrophobic organic-based spin-on-glass (SOG) nanofilms for glass-based microchips. The experimental results indicate that no significant difference exists in the critical electric field strengths in the hydrophilic or hydrophobic SOG-coated microchannels, respectively. However, for a given conductivity ratio and microchannel width, the critical strength of the electric field is slightly lower in the SOG-coated microchannels than in the non-coated channels. In general, the results presented in this study demonstrate the potential for designing and controlling on-chip assays requiring the manipulation of samples with high conductivity gradients, and provide a useful general reference for avoiding EKI effects in capillary electrophoresis analysis applications. [source]

Nanostructured copolymer gels for dsDNA separation by CE

ELECTROPHORESIS, Issue 23 2008
Fen Wan
Abstract Pluronics are triblock copolymers of poly(ethylene oxide)-poly(propylene oxide)-poly(ethylene oxide) that are able to form many different ordered nanostructures at appropriate polymer concentrations and temperatures in selective solvents. These nanostructured "gels" showed desirable criteria when used as DNA separation media, especially in microchip electrophoresis, including dynamic coating and viscosity switching. A ternary system of F127 (E99P69E99)/TBE buffer/1-butanol was selected as a model system to test the sieving performance of different nanostructures in separating dsDNA by CE. The nanostructures and their lattice constants were determined by small-angle X-ray scattering. Viscosity measurements showed the sol,gel transition phenomena. In addition to the cubic structure, successful electrophoretic separation of dsDNA in 2-D hexagonally packed cylinders was achieved. Results showed that without further optimization, ,X174 DNA,Hae III digest was well separated within 15,min in a 7-cm separation channel, by using F127/TBE/1-butanol gel with a 2-D hexagonal structure. A mechanism for DNA separations by those gels with both hydrophilic and hydrophobic domains is discussed. [source]

Confinement effects on the morphology of photopatterned porous polymer monoliths for capillary and microchip electrophoresis of proteins

ELECTROPHORESIS, Issue 14 2008
Mei He
Abstract We find that the morphology of porous polymer monoliths photopatterned within capillaries and microchannels is substantially influenced by the dimensions of confinement. Porous polymer monoliths were prepared by UV-initiated free-radical polymerization using either the hydrophilic or hydrophobic monomers 2-hydroxyethyl methacrylate or butyl methacrylate, cross-linker ethylene dimethacrylate and different porogenic solvents to produce bulk pore diameters between 3.2 and 0.4,µm. The extent of deformation from the bulk porous structure under confinement strongly depends on the ratio of characteristic length of the confined space to the monolith pore size. The effects are similar in cylindrical capillaries and D-shaped microfluidic channels. Bulk-like porosity is observed for a confinement dimension to pore size ratio >10, and significant deviation is observed for a ratio <5. At the extreme limit of deformation a smooth polymer layer ,300 nm thick is formed on the surface of the capillary or microchannel. Surface tension or wetting also plays a role, with greater wetting enhancing deformation of the bulk structure. The films created by extreme deformation provide a rapid and effective strategy to create robust wall coatings, with the ability to photograft various surface chemistries onto the coating. This approach is demonstrated through cationic films used for electroosmotic flow control and neutral hydrophilic coatings for electrophoresis of proteins. [source]

Electrokinetic-driven microfluidic system in poly(dimethylsiloxane) for mass spectrometry detection integrating sample injection, capillary electrophoresis, and electrospray emitter on-chip

ELECTROPHORESIS, Issue 24 2005
Sara Thorslund
Abstract A novel microsystem device in poly(dimethylsiloxane) (PDMS) for MS detection is presented. The microchip integrates sample injection, capillary electrophoretic separation, and electrospray emitter in a single substrate, and all modules are fabricated in the PDMS bulk material. The injection and separation flow is driven electrokinetically and the total amount of external equipment needed consists of a three-channel high-voltage power supply. The instant switching between sample injection and separation is performed through a series of low-cost relays, limiting the separation field strength to a maximum of 270,V/cm. We show that this set-up is sufficient to accomplish electrospray MS analysis and, to a moderate extent, microchip separation of standard peptides. A new method of instant in-channel oxidation makes it possible to overcome the problem of irreversibly bonded PDMS channels that have recovered their hydrophobic properties over time. The fast method turns the channel surfaces hydrophilic and less prone to nonspecific analyte adsorption, yielding better separation efficiencies and higher apparent peptide mobilities. [source]

Monomeric and polymeric anionic gemini surfactants and mixed surfactant systems in micellar electrokinetic chromatography.

ELECTROPHORESIS, Issue 2 2005
Part II: Characterization of chemical selectivity using two linear solvation energy relationship models
Abstract Sodium di(undecenyl) tartarate monomer (SDUT), a vesicle-forming amphiphilic compound possessing two hydrophilic carboxylate headgroups and two hydrophobic undecenyl chains, was prepared and polymerized to form a polymeric vesicle (i.e., poly-SDUT). The anionic surfactants of SDUT and poly-SDUT (carboxylate head group) and sodium dodecyl sulfate, SDS (sulfate head groups) as well as mixed surfactant systems (SDS/SDUT, SDS/poly-SDUT, and SDUT/poly-SDUT) were applied as pseudostationary phases in micellar electrokinetic chromatography (MEKC). Two linear solvation energy relationship (LSER) models, i.e., solvatochromic and solvation parameter models, were successfully applied to investigate the effect of the type and composition of pseudostationary phases on the retention mechanism and selectivity in MEKC. The solvatochromic and solvation parameter models were used to help understand the fundamental nature of the solute-pseudostationary phase interactions and to characterize the properties of the pseudostationary phases (e.g., solute size and hydrogen bond-accepting ability for all pseudostationary phases). The solute types were found to have a significant effect on the LSER system coefficients and on the predicted retention factors. Although both LSER models provide the same information, the solvation parameter model is found to provide much better results both statistically and chemically than the solvatochromic model. [source]

Characterization of the surface hydrophobicity of filamentous fungi

ENVIRONMENTAL MICROBIOLOGY, Issue 2 2003
Theo H. M. Smits
Summary A method for the quantitative analysis of the hydrophobicity of the mycelial mat of filamentous fungi based on contact angle measurements is presented. It was tested for a range of fungi belonging to the classes of basidiomycetes, ascomycetes and deuteromycetes. The measured contact angles of the mycelial mats ranged between hydrophilic (<30°) for the deuteromycetes Fusarium oxysporum Fo47 GUS1 and Trichoderma harzianum P1[pZEGA1] and hydrophobic (>60°) for the ascomycete Cladosporium sp. DSE48.1b and the basidiomycetes Paxillus involutus WSL 37.7, Hebeloma crustiliniforme WSL 6.2, Suillus bovinus WSL 48.1 and Laccaria bicolor WSL 73.1. For some fungi, variations in the hydrophobicity of the mycelium depending on the growth medium, the physiological state and the exposure to water were distinguished. [source]

Disposition of perfluorinated acid isomers in sprague-dawley rats; Part 1: Single dose

ENVIRONMENTAL TOXICOLOGY & CHEMISTRY, Issue 3 2009
Jonathan P. Benskin
Abstract Perfluorinated acids (PFAs) and their precursors (PFA-precursors) exist in the environment as linear and multiple branched isomers. These isomers are hypothesized to have different biological properties, but no isomer-specific data are currently available. The present study is the first in a two-part project examining PFA isomer-specific uptake, tissue distribution, and elimination in a rodent model. Seven male Sprague-Dawley rats were administered a single gavage dose of approximately 500 ,g/kg body weight perfluorooctane sulfonate (C8F17SO3,, PFOS), perfluorooctanoic acid (C7F15CO2H, PFOA), and perfluorononanoic acid (C8F17CO2H, PFNA) and 30 ,g/kg body weight perfluorohexane sulfonate (C6F13SO3,, PFHxS). Over the subsequent 38 d, urine, feces, and tail-vein blood samples were collected intermittently, while larger blood volumes and tissues were collected on days 3 and 38 for isomer analysis by high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS). For all PFAs, branched isomers generally had lower blood depuration half-lives than the corresponding linear isomer. The most remarkable exception was for the PFOS isomer containing an alpha-perfluoromethyl branch (1m -PFOS), which was threefold more persistent than linear PFOS, possibly due to steric shielding of the hydrophilic sulfonate moiety. For perfluoromonomethyl-branched isomers of PFOS, a structure,property relationship was observed whereby branching toward the sulfonate end of the perfluoroalkyl chain resulted in increased half-lives. For PFHxS, PFOA, and PFOS, preferential elimination of branched isomers occurred primarily via urine, whereas for PFNA preferential elimination of the isopropyl isomer occurred via both urine and feces. Changes in the blood isomer profiles over time and their inverse correlation to isomer elimination patterns in urine, feces, or both provided unequivocal evidence of significant isomer-specific biological handling. Source assignment based on PFA isomer profiles in biota must therefore be conducted with caution, because isomer profiles are unlikely to be conserved in biological samples. [source]

Blood,brain barrier damage and brain penetration of antiepileptic drugs: Role of serum proteins and brain edema

EPILEPSIA, Issue 4 2009
Nicola Marchi
Summary Purpose:, Increased blood,brain barrier (BBB) permeability is radiologically detectable in regions affected by drug-resistant epileptogenic lesions. Brain penetration of antiepileptic drugs (AEDs) may be affected by BBB damage. We studied the effects of BBB damage on brain distribution of hydrophilic [deoxy-glucose (DOG) and sucrose] and lipophilic (phenytoin and diazepam) molecules. We tested the hypothesis that lipophilic and hydrophilic drug distribution is differentially affected by BBB damage. Methods:, In vivo BBB disruption (BBBD) was performed in rats by intracarotid injection of hyperosmotic mannitol. Drugs (H3-sucrose, 3H-deoxy-glucose, 14C-phenytoin, and C14-diazepam) or unlabeled phenytoin was measured and correlated to brain water content and protein extravasation. In vitro hippocampal slices were exposed to different osmolarities; drug penetration and water content were assessed by analytic and densitometric methods, respectively. Results:, BBBD resulted in extravasation of serum protein and radiolabeled drugs, but was associated with no significant change in brain water. Large shifts in water content in brain slices in vitro caused a small effect on drug penetration. In both cases, total drug permeability increase was greater for lipophilic than hydrophilic compounds. BBBD reduced the amount of free phenytoin in the brain. Discussion:, After BBBD, drug binding to protein is the main controller of total brain drug accumulation. Osmotic BBBD increased serum protein extravasation and reduced free phenytoin brain levels. These results underlie the importance of brain environment and BBB integrity in determining drug distribution to the brain. If confirmed in drug-resistant models, these mechanisms could contribute to drug brain distribution in refractory epilepsies. [source]

Synthesis and Molecular Structures of Nickel(II) and Cobalt(III) Complexes with 2-(Arylimino)-3-(hydroxyimino)butane

EUROPEAN JOURNAL OF INORGANIC CHEMISTRY, Issue 14 2003
Ennio Zangrando
Abstract We report new series of NiII and CoIII complexes with nitrogen-donor chelating ligands of the (E,E)-2-(arylimino)-3-(hydroxyimino)butane type (Ar,N,N,OH). These ligands are characterized by a hydrophilic (OH group) and a hydrophobic region (aryl group). NiII derivatives were obtained either as trimers of formula [Ni3(Ar,N,N,OH)3Br4(OH)][Br], with the hydrophobic groups oriented on the same side, or as bis(chelated) derivatives with cis geometry, depending on the steric hindrance of the aryl groups. CoIII complexes were obtained only as bis(chelated) derivatives, with the two ligands coplanar. The "iso -oriented" arrangement of ligands in bis(chelated) CoIII complexes is favored by weak interactions between the two ligands, namely O,H···O hydrogen bond and stacking interactions between the aryl groups. CoIII complexes might find application as catalysts for living or controlled radical polymerization of polar olefins, and preliminary results are reported. (© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2003) [source]

Proteolytically Degradable Photo-Polymerized Hydrogels Made From PEG,Fibrinogen Adducts,

ADVANCED ENGINEERING MATERIALS, Issue 6 2010
Daniel Dikovsky
Abstract We develop a biomaterial based on protein,polymer conjugates where poly(ethylene glycol) (PEG) polymer chains are covalently linked to multiple thiols on denatured fibrinogen. We hypothesize that conjugation of large diacrylate-functionalized linear PEG chains to fibrinogen could govern the molecular architecture of the polymer network via a unique protein,polymer interaction. The hypothesis is explored using carefully designed shear rheometry and swelling experiments of the hydrogels and their precursor PEG/fibrinogen conjugate solutions. The physical properties of non-cross-linked and UV cross-linked PEGylated fibrinogen having PEG molecular weights ranging from 10 to 20,kDa are specifically investigated. Attaching multiple hydrophilic, functionalized PEG chains to the denatured fibrinogen solubilizes the denatured protein and enables a rapid free-radical polymerization cross-linking reaction in the hydrogel precursor solution. As expected, the conjugated protein-polymer macromolecular complexes act to mediate the interactions between radicals and unsaturated bonds during the free-radical polymerization reaction, when compared to control PEG hydrogels. Accordingly, the cross-linking kinetics and stiffness of the cross-linked hydrogel are highly influenced by the protein,polymer conjugate architecture and molecular entanglements arising from hydrophobic/hydrophilic interactions and steric hindrances. The proteolytic degradation products of the protein,polymer conjugates proves to be were different from those of the non-conjugated denatured protein degradation products, indicating that steric hindrances may alter the proteolytic susceptibility of the PEG,protein adduct. A more complete understanding of the molecular complexities associated with this type of protein-polymer conjugation can help to identify the full potential of a biomaterial that combines the advantages of synthetic polymers and bioactive proteins. [source]

Functionalized Poly(D,L -lactide) for Pulmonary Epithelial Cell Culture

ADVANCED ENGINEERING MATERIALS, Issue 4 2010
Yuan-Min Lin
Functional groups on a material surface affect the response of many cell types. As part of our strategy aimed at engineering lung tissue, we introduced functional groups into the surface of Poly(D,L -lactide) (PDLLA) films to improve its suitability for the culture of mature pulmonary epithelial cells (A549 line) using two different methods. The first method, aminolysis, can introduce primary amines into PDLLA films by transesterification using 1,15% of ethylenediamine in isopropanol. The second method, a branching modification, can generate amine-terminated or carboxylic acid-terminated tree-like branched architectures. All modified PDLLA surfaces exhibited lower water contact angles, i.e. are more hydrophilic than unmodified PDLLA. PDLLA treated with 15% ethylenediamine exhibited a rougher surface than the control, and PDLLA with branching modification had a droplet-like surface topography as visualized by atomic force microscopy (AFM). PDLLA treated with 15% ethylenediamine and branching modification with two and three generations enhanced the attachment of pulmonary epithelial cells measured using Hoechst dye. Immunostaining demonsatrated that amine-terminated branched architectures allowed for better focal adhesion point formation than the control 24,h after cell seeding. Furthermore, they also induced higher A549 cell populations and levels of activity after 4 days in culture measured using Hoechst dye and WST1 cell proliferation reagents, respectively. In contrast, carboxylic acid-terminated branching architectures were found to reduce the cell population size after 4 days. It was concluded that the concentration, type and distribution of surface functional groups can affect significantly the behavior of pulmonary epithelial cells growing on a PDLLA surface, and PDLLA film modified with two or three generations of amine-terminated branched architectures is a suitable 2D scaffold for the culture of of pulmonary epithelial cells. [source]

A Post-Modification Strategy for the Synthesis of Uniform, Hydrophilic/Hydrophobic Patterned ,-Hydroxy Acid Oligomers

EUROPEAN JOURNAL OF ORGANIC CHEMISTRY, Issue 31 2009
Nadja Franz
Abstract Hydrophilic/hydrophobic patterning is a well-established design strategy to guide secondary structure formation of both natural as well as non-natural oligomers and polymers. This contribution explores the feasibility of a new approach for the synthesis of uniform, sequence-defined, hydrophilic/hydrophobic patterned oligo(,-hydroxy acid)s. The proposed strategy is based on post-modification of a reactive oligoester scaffold composed of an alternating sequence of hydrophobic [(2S)-2-hydroxy-4-methylpentanoic acid] and masked hydrophilic [(2S)-2-hydroxypent-4-enoic acid] ,-hydroxy acids. The use of (2S)-2-hydroxypent-4-enoic acid instead of a complex side-chain-protected hydrophilic building block obviates the need for additional protective group chemistry during chain extension. In a subsequent post-modification step, the allyl side chains can be quantitatively modified via free-radical addition of different ,-functional thiols to afford hydrophilic/hydrophobic patterned oligoesters. The proposed synthetic strategy provides an interesting alternative to rapidly generate libraries of foldamers with identical chain length and monomer sequence but different side-chain functionalities.(© Wiley-VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2009) [source]

Highly Porous Nano- and Microstructured Films Loaded with Bioactive Agents for Biomedical Applications: Structure,Release Profile Effects

ADVANCED ENGINEERING MATERIALS, Issue 8 2009
Adi Rachelson
The current study focuses on the nanostructuring of our new drug-eluting porous films and its effect on the drug release profile of both hydrophilic and hydrophobic drugs. Nanostructuring was obtained using both the dispersion and the condensation methods of emulsion processing. These new highly porous nanostructured films can be used as basic elements of various drug-eluting medical devices. [source]

Adapted DAX-8 fractionation method for dissolved organic matter (DOM) from soils: development, calibration with test components and application to contrasting soil solutions

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 6 2009
F. Amery
Summary Most methods to fractionate natural dissolved organic matter (DOM) rely on sorption of acidified DOM samples onto XAD-8 or DAX-8 resin. Procedural differences among methods are large and their interpretation is limited because there is a lack of calibration with DOM model molecules. An automated column-based DOM fractionation method was set up for 10-ml DOM samples, dividing DOM into hydrophilic (HPI), hydrophobic acid (HPOA) and hydrophobic neutral (HPON) fractions. Fifteen DOM model components were tested in isolation and in combination. Three reference DOM samples of the International Humic Substances Society were included to facilitate comparison with other methods. Aliphatic low-molecular-weight acids (LMWAs) and carbohydrates were classified as HPI DOM, but some LMWAs showed also a partial HPO character. Aromatic LMWAs and polyphenols partitioned in the HPOA fraction, menadione (quinone) and geraniol (terpenoid) in HPON DOM. Molecules with log Kow > 0.5 had negligible HPI fractions. The HPO molecules except geraniol had specific UV absorbance (SUVA, measure for aromaticity) >3 litres g,1 cm,1 while HPI molecules had SUVA values <3 litres g,1 cm,1. Distributions of DOM from eight soils ranged from 31 to 72% HPI, 25 to 46% HPOA and 2 to 28% HPON of total dissolved organic carbon. The SUVA of the HPI DOM was consistently smaller compared with the HPOA DOM. The SUVA of the natural DOM samples was not explained statistically by fractionation and the variation coefficient of SUVA among samples was not reduced by fractionation. Hence, fractionation did not reduce the variability in this DOM property, which casts some doubts on the practical role of DOM fractionation in predicting DOM properties. [source]

Dissolved organic phosphorus and sulphur as influenced by sorptive interactions with mineral subsoil horizons

EUROPEAN JOURNAL OF SOIL SCIENCE, Issue 3 2001
K. KaiserArticle first published online: 6 JAN 200
Summary This study tested the hypothesis that, like dissolved organic nitrogen (N), dissolved organic phosphorus (P) and sulphur (S) are more mobile in soil than is organic carbon (C). To do so, I compared the sorption of organic P and S to subsoil materials with that of organic C. Soil samples were equilibrated with water-soluble organic matter from the forest floor at pH 4 and in the equilibrium solutions organic C, P, and S, and their distributions between the hydrophilic and hydrophobic fraction were determined. Sorption of C within the organic matter did not differ from that of P and S. However, the hydrophilic fraction contained the vast majority of P and S and sorbed far less than the hydrophobic fraction. So the overall retention of organic P and S was smaller than that of organic C. This result suggested that dissolved organic matter is more important in the loss of plant nutrients than in the release of C from soil. [source]

The solution structure of gomesin, an antimicrobial cysteine-rich peptide from the spider

FEBS JOURNAL, Issue 4 2002
Nicolas Mandard
Gomesin is the first peptide isolated from spider exhibiting antimicrobial activities. This highly cationic peptide is composed of 18 amino-acid residues including four cysteines forming two disulfide linkages. The solution structure of gomesin has been determined using proton two-dimensional NMR (2D-NMR) and restrained molecular dynamics calculations. The global fold of gomesin consists in a well-resolved two-stranded antiparallel ,,sheet connected by a noncanonical ,,turn. A comparison between the structures of gomesin and protegrin-1 from porcine and androctonin from scorpion outlines several common features in the distribution of hydrophobic and hydrophilic residues. The N- and C-termini, the ,,turn and one face of the ,,sheet are hydrophilic, but the hydrophobicity of the other face depends on the peptide. The similarities suggest that the molecules interact with membranes in an analogous manner. The importance of the intramolecular disulfide bridges in the biological activity of gomesin is being investigated. [source]

Adhesion of Enterococcus faecalis 1131 grown under subinhibitory concentrations of ampicillin and vancomycin to a hydrophilic and a hydrophobic substratum

FEMS MICROBIOLOGY LETTERS, Issue 1 2001
Amparo M Gallardo-Moreno
Abstract The effect of two subinhibitory antibiotic concentrations of ampicillin and vancomycin during growth on the adhesion of Enterococcus faecalis 1131 to glass and silicone rubber was studied in a parallel plate flow chamber. Initial deposition rates and numbers of adhering bacteria after 4 h were higher on hydrophilic glass than on hydrophobic silicone rubber, regardless of growth conditions. The presence of 1/4 minimal inhibitory concentration (MIC) of ampicillin during growth reduced enterococcal adhesion to both substrata, but growth in the presence of 1/4 MIC vancomycin did not affect the adhesion of E. faecalis. Moreover, enterococcal adhesion increased after growth in the presence of 1/8 MIC vancomycin. The increased adhesion after growth in the presence of subinhibitory concentrations of vancomycin may have strong implications for patients living with implanted biomaterials, as they may suffer adverse effects from use of this antibiotic, especially since bacteria once adhered are less sensitive to antibiotics. [source]

Random Copolymer Films with Molecular-Scale Compositional Heterogeneities that Interfere with Protein Adsorption

ADVANCED FUNCTIONAL MATERIALS, Issue 21 2009
Salmaan H. Baxamusa
Abstract Smooth surfaces with compositional heterogeneities at a molecular-length scale are presented with the goal of disrupting surface,protein interactions. These surfaces are synthesized by utilizing photoinitiated chemical vapor deposition (piCVD) to deposit thin films of random copolymers consisting of highly hydrophilic and highly hydrophobic comonomers. Swellability, wettability, and surface roughness could be systematically controlled by tuning the copolymer composition. The surface composition was dynamic, and the surface reconstructed based on the hydration state of the film. Proteins adsorbed to the copolymer films less readily than to either of the respective homopolymers, indicating a synergistic effect resulting from the random copolymer presenting molecular-scale compositional heterogeneity. These results provide direct evidence that protein adsorption can be disrupted by such surfaces and a simple analytical model suggests that the heterogeneities occur over areas encompassing 4,5 repeat units of the polymer. The synthetic method used to create these films can be used to coat arbitrary geometries, enabling practical utility in a number of applications. [source]

Tailoring Macromolecular Expression at Polymersome Surfaces

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2009
Adam Blanazs
Abstract A series of amphiphilic ABC triblock copolymers are synthesized by atom transfer radical polymerization, wherein the ,A' and ,C' blocks are hydrophilic and the pH-sensitive ,B' block can be switched from hydrophilic in acidic solution to hydrophobic at pH 7. Careful addition of base to the molecularly dissolved copolymer in acidic solution readily induces the self-assembly of such triblock copolymers at around neutral pH to form pH-sensitive polymersomes (a.k.a. vesicles) with asymmetric membranes. By systematic variation of the relative volume fractions of the ,A' and ,C' blocks, the chemical nature of the polymer chains expressed at the interior or exterior corona of the polymersomes can be selected. Treatment of primary human dermal fibroblast cells with these asymmetric polymersomes demonstrates the biological consequences of such spatial segregation, with both polymersome cytotoxicity and endocytosis rates being dictated by the nature of the polymersome surface chemistry. The pH-sensitive nature of the polymersomes readily facilitates their dissociation after endocytosis due to the relatively low endosomal pH, which results in the rapid release of an encapsulated dye. Selective binding of anionic substrates such as DNA within the inner cationic polymersome volume, coupled with a biocompatible exterior, leads to potential gene delivery applications for these pH-sensitive asymmetric nanovectors. [source]

Cell surface hydrophobicity of Candida albicans isolated from elder patients undergoing denture-related candidosis

GERODONTOLOGY, Issue 2 2009
Roberta Diavana De Souza
Background:, The virulence potential of Candida albicans strains enrolled in denture-related candidosis still remains uncertain. Candida albicans cells with higher cell surface hydrophobicity (CSH) rates, so-called hydrophobic, present higher adhesion success in different host tissues than cells with lower rates, or even hydrophilic. Objective:, The proposition of this study was to evaluate the differences in the CSH of strains isolated from denture users with and without denture-related candidosis. Material and methods:, The strains were obtained from two paired groups of patients living a same retirement house. Fungal cells were submitted to CSH evaluation by the hydrocarbon partition test using xylene. Results:, The measures revealed that the yeasts from patients with candidosis had CSH values ranging from 4.52% to 12.24%, with an average of 8.22 ± 2.92%. In the countergroup, the CSH ranged from 3.86% to 14.36%, with an average of 8.38 ± 3.76%. The difference between the groups were considered not relevant (p = 0.997). Conclusion:, The results let to the inference that natural populations of C. albicans from patients with and without clinical manifestation denture-related candidosis do not differ one from the other regarding to CSH. [source]

Nanosensor Design Packages: A Smart and Compact Development for Metal Ions Sensing Responses,

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2007
A. El-Safty
Abstract With recent advances in mesostructured materials and nanotechnologies, new methods are emerging to design optical sensors and biosensors, and to develop highly sensitive solid sensors. Here, highly sensitive, low cost, simple nanosensor designs for naked-eye detection of toxic metal ions are successfully developed by the immobilization of commercially available ,,,,,,,-tetrakis(1-methylpyridinium-4-yl)porphine p -toluenesulfonate (TMPyP) and diphenylcarbazide (DPC), and chemically synthesized 4- n -dodecyl-6-(2-thiazolylazo) resorcinol (DTAR) and 4- n -dodecyl-6-(2-pyridylazo) phenol (DPAP) chromophore molecules into spherical nanosized cavities and surfaces. A rational strategy was crucial to develop optical nanosensors that can be used to control accurate recognition and signaling abilities of analyte species for ion-sensing purposes. This is the first reported evidence of the significant key factors of the development of receptors as ,indicator dyes' and surface-confinement materials as ,carriers' to broadening the applicability of optical chemical sensors for selective discrimination of trace levels of toxic analytes. In all the nanosensor design techniques presented here, a dense pattern of immobilized hydrophobic ,neutral' and hydrophilic ,charged' chromophores with intrinsic mobility, as a result of extremely robust constructed sequences on nanoscale structures, is a key to enhancing the sensing functionality of optical nanosensors. These nanosensor designs can be used as cage probe sinks with reliable control, for the first time, over the colorimetric recognition of cadmium ions to low levels of concentration in the range of 10,9 to 10,10M. Optimization of control sensing conditions is established to achieve enhanced signal response and color intensities. These chemical nanosensors are reversible and have the potential to serve effectively in on-site field analysis of environmental samples, which eliminates the necessity for instrument-dependent analysis. Moreover, these new classes of optical cage sensors exhibit long-term stability of signaling and recognition functionalities that in general provide extraordinary sensitivity, selectivity, reusability, and fast kinetic detection and quantification of various deleterious metal ions in our environment. [source]

Synthesis of Hexagonal-Phase NaYF4:Yb,Er and NaYF4:Yb,Tm Nanocrystals with Efficient Up-Conversion Fluorescence,

ADVANCED FUNCTIONAL MATERIALS, Issue 18 2006
S. Yi
Abstract IR-to-visible up-conversion fluorescent nanocrystals of hexagonal-phase NaYF4:20,%Yb,2,%Er and NaYF4:20,%Yb,2,%Tm have been synthesized by decomposition of multiprecursors of CF3COONa, (CF3COO)3Y, (CF3COO)3Yb, and (CF3COO)3Er/(CF3COO)3Tm in oleylamine at 330,°C. The average particle size is 10.5,±,0.7,nm (from random measurements of 200,particles from five transmission electron microscopy images) and 11.1,±,1.3,nm (from dynamic-light-scattering measurements). The up-conversion fluorescence intensity of the hexagonal nanocrystals in this work is much higher than that of other cubic-phase NaYF4:Yb,Er nanocrystals, including the ones in this work (by a factor of 7.5). Mechanisms for nucleation and growth of the hexagonal-phase nanoparticles are proposed. These nanocrystals are easily dispersed in organic solvents, producing a transparent colloidal solution. The hydrophobic surfaces of the particles are made hydrophilic using a bipolar surfactant. These nanoparticles and their dispersions in various media have potential applications in optical nanodevices and bioprobes. [source]