Hydrophilic Composition Research Articles

The Effect of Hydrophilic Components of Zinc Based Copolymer on its Self Polishing Behavior

The zinc methacrylate copolymers with various monomer compositions were prepared for investigating the effects of zinc methacrylate, 2-methoxyethyl acrylate contents on self polishing behavior. The effect of molecular weight of the self polishing copolymer(SPC) was also investigated. The characterizations of copolymers were performed by fourier transform infrared spectroscopy, proton nuclear magnetic resonance, gel permeation chromatography, and differential scanning calorimetry. The leaching rate of SPC was determined from the reduction of dry film thickness after seawater immersion in a dynamic condition. The experimental results revealed that leaching rate and mechanical property of the film could be controlled by the hydrophilic monomer composition of zinc based copolymer.

Performance Enhancements of Polysulfone Ultrafiltration Membranes through Blending with Functionalized Carbon Nanotubes and Polyaniline Nanofibers

High-performance membranes for protein separation are of great interest. In this study, new type of polysulfone (PSf) composite ultrafiltration membranes are created by blending PSf with polyaniline (PANi) nanofibers and functionalized multi-walled carbon nanotubes (MWNTs) and then casting the mixture solutions via a well-developed non-solvent/solvent induced phase separation technique, using deionized water as the coagulation bath. The compositions, morphologies and properties of as-formed membranes are fully investigated. We demonstrate that membrane characteristics such as porosity, hydrophilicity, conductivity and thermal stability for PSf can be significantly enhanced with the incorporation of hydrophilic and conductive compositions of functionalized-MWNTs and PANi nanofibers. The composite membranes exhibit comparable bovine serum albumin (BSA) selectivities (89-93 vs. 92%) but much improved water fluxes (31.5-88.9 vs. 9.2 gfd/psi) against pure PSf membranes.

Hydrophilic gel composition effect on the molecular association and spectroscopic behavior of rhodamine B

Electronic absorption spectra of rhodamine B dye in aqueous solutions and in a polyacrylamide hydrogel matrix with different structural compositions were studied at room temperature. The transport and the solute–solute interactions of rhodamine B in aqueous solutions across the hydrophilic gels were investigated via exploration of the spectral properties of the dye-loaded hydrogel. The nature of the dye pair interactions in these media was discussed using the Kasha exciton theory. In addition, the monomer–dimer equilibrium of rhodamine B molecules in hydrogels with different compositional percentages was studied by means of UV–vis spectroscopy and least-squares fitting methods.

Formation of vesicular structures by a mono-tethered polyhedral oligomeric silsesquioxane amphiphilic diacid derivative in a solvent mixture

Polyhedral oligomeric silsesquioxane (POSS) molecules contain a silicon/oxygen nano-size cage substituted with organic groups. 2-(Propylcarbamoyl)terephthalic acid heptaisobutyl polyhedral oligomeric silsesquioxane (POSS DCA) is a novel mono-tethered POSS compound which is not commercially available yet and can be regarded as a single-tail surfactant. In contrast to theoretically possible micellization of amphiphilic POSS compounds very rare interest is paid by scientific community to this issue. POSS DCA vesiculation occurred at a very low concentration (0.09 mM) in a mixture of acetone, ethanol and 1-propanol according to the experiments. Critical packing parameter of POSS DCA is bigger than one and it must self-assemble into inverted-micelle morphology in a non-polar solvent. The vesicle formation for POSS DCA in a relatively polar solvent system was mainly attributed to formation of stable various-size intermolecular bridges of ethanol or 1-propanol. Also, π–π interaction between aromatic rings is another driving force. Vesicles can trap both hydrophilic and hydrophobic solvents and change composition of a solvent mixture. For the first time, we studied this property for POSS DCA vesicles in different concentrations by a gas chromatographic method. Significant increase in surface tension was attributed to the changes in solvent system composition due to vesicle formation and variation in vesicles morphology.

Biofilm formation of Candida albicans on implant overdenture materials and its removal

ObjectivesThe purposes of this study were to clarify the surface characteristics of various implant overdenture materials and the capabilities of Candida albicans adherence and biofilm formation on these surfaces, and to investigate the role of salivary mucin in biofilm formation. MethodsSeven commonly used implant and restorative materials were assessed. The surface roughness averages of all materials were limited to 0.07–0.10μm. Contact angles and salivary mucin absorption were measured. After 90-min initial adhesion and 2-day biofilm formation, the amounts of C. albicans were determined by counting colony-forming units and the morphological characteristics were observed by scanning electron microscopy (SEM). The effects of saliva coating and the influences of material surface property on initial adhesion, biofilm formation and its removability were analysed by univariate two-way analysis of variance and multiple linear regression analysis. ResultsSurface contact angle of materials, the index of hydrophobicity, was found to be correlated positively with initial adhesion and biofilm formation of C. albicans. A negative correlation between mucin absorption and removability of Candida biofilm indicates that mucin plays an important role in biofilm formation and its rigidity. SEM observation also revealed fewer Candida cells on saliva-coated Ti than on saliva-coated hydroxyapatite or acrylic resin. ConclusionsThe materials with different hydrophobic property and compositions display diverse manners of salivary mucin absorption, initial adhesion and biofilm formation. The hydrophobic materials encourage enhanced initial adhesion, subsequently resulting in the active biofilm formation. Mucin has decisive effects on Candida immobilization and biofilm development on the materials. Clinical significanceSurface hydrophilic property and composition of materials and salivary proteins, especially mucin, affect the process of Candida biofilm formation and influence the amount and rigidity of formed biofilm. The present data may be applied as a reference for selecting materials in implant overdenture treatment from a microbiological point of view.

SYNTHESIS OF AMPHIPHILIC CHITOSAN DERIVATIVES AND THEIR APPLICATION IN ENCAPSULATION OF QDs

Amphiphilic chitosan derivatives(N-octyl-N-mPEG-chitosan,OPEGC)were successfully synthesized via sequential Schiff base reduction reaction of chitosan with mPEG-aldehyde and n-octanal,with chitosan acting as the backbone of the grafted copolymers,and mPEG-aldehyde providing hydrophilic chain and n-octanal providing hydrophobic alkyl chain,respectively,thereby hydrophobic moiety inclining to segregate into the core of the polymeric micelles,while hydrophilic moiety forming a stabilizing interface between the hydrophobic core and the external medium.The structure of grafted copolymers with both hydrophilic and hydrophobic composition simultaneously was confirmed by characterization employing FTIR and 1H-NMR.In the subsequent procedure,water-soluble quantum dots(QDs),widely used as nanoprobe for medical application,were achieved by incorporation of QDs inside the polymeric micelle core through the hydrophobic interaction between the acyl chain ligand capped on the QDs and the hydrophobic inner core of the polymeric micelles.The size and distribution of the polymeric micelle was determined by dynamic light scattering(DLS),as well the effect of the amount of alkyl chains on the size of the hollow polymeric micelles.The result showed that with grafting level increasing,the size of these nanoparticles diminished accordingly.Moreover,critical micelle concentration(CMC) was determined based on I3/I1 derived from emission spectrum afforded by fluorescence spectroscopy with pyrene as fluorescent probe,with the value of CMC 2.032×10-2mg/mL.At last,the optical properties of OPEGC/QDs were characterized by UV-Vis spectroscopy,fluorescence spectroscopy and the morphology of their assembly formed in water was observed by TEM.The results indicated that the OPEGC/QDs nanoparticles with narrow size distribution were prepared here,which represented good water solubility and high quantum yield.

Effect of polyacrylamide hydrophilic gel composition on photo-physical behavior of Oxazine 750

Electronic absorption spectra of Oxazine 750 dye in aqueous solutions and in polyacrylamide hydrogel matrix with different structural composition were studied at room temperature. The transport and the solute–solute interactions of the ionic dye in aqueous solutions across the hydrophilic gels were investigated via exploring spectral properties of the dye-loaded hydrogel. The nature of the dye pair interactions in these media was discussed using the Kasha exciton theory. In addition, the monomer–dimer equilibrium of Oxazine 750 in hydrogels with different compositional percentage has been determined by means of UV–vis spectroscopy and least square fitting methods.

Effect of hydrophilic gel composition on photo-physical behavior of Oxazine720

The visible absorption spectra of Oxazine 720 dye in aqueous solutions and in polyacrylamide hydrogel matrix with different compositions were studied at room temperature. The spectral properties of the dye-loaded hydrogel were also investigated. The transport and the solute–solute interactions of the ionic dye in aqueous solutions across the hydrophilic gels were calculated. The nature of the interacting pairs in this dye was discussed using the Kasha exciton theory. Also the monomer–dimer equilibrium in this ionic dye in water and in different compositions of hydrogel environment has been investigated by means of UV–Vis spectroscopy.

Hybrid composite membranes of sodium alginate for pervaporation dehydration of 1,4-dioxane and tetrahydrofuran

The study reports on the development of hybrid composite membranes of sodium alginate loaded with hydrophilic alumina-containing Mobile Composition Matter-41 i.e., Al-MCM-41 in different compositions from 3 to 10 wt.% that are used for pervaporation (PV) dehydration of 1,4-dioxane and tetrahydrofuran (THF) from aqueous mixtures in compositions of 10–40 wt.% at 30°C. The PV performance of the hybrid composite membranes was much superior to that of plain NaAlg membrane in terms of selectivity and flux due to increased hydrophilicity of NaAlg membrane in the presence of Al-MCM-41 mesoporous zeolite particles that are also hydrophilic. Membranes crosslinked with glutaraldehyde were characterised by ion exchange capacity, Fourier Transform spectroscopy and X-ray diffraction. Morphology of the membranes was assessed by scanning electron microscopy. Sorption studies have been performed to evaluate the extent of interaction and degree of swelling of the membranes with pure and mixed feed aqueous mixtures of 1,4-dioxane and THF. It is observed that flux and selectivity increased systematically with increasing amount of Al- MCM-41 particles in the NaAlg matrix. In case of hybrid composite membrane containing 10 wt.% Al-MCM-41, selectivity for water was infinity, which was attributed to the combined effects of molecular adhesion between particle surfaces and NaAlg matrix as well as higher selectivity of the composite membrane when compared to plain NaAlg membrane.

Extreme flood events favour floodplain mollusc diversity

Floods are fundamental for the maintenance of floodplain biodiversity. As a result, well-functioning floodplains are characterized by a high spatio-temporal heterogeneity. Most floodplain-organisms need this shifting landscape mosaic to fulfil their environmental requirements and display a range of adaptations to survive floods. However, in temperate areas, where winter floods are common, extraordinary floods occurring in summer, a period of high physiological activity, may seriously impact the floodplain fauna. This is especially true for guilds characterized by low mobility, such as molluscs. Here we examined the immediate and longer-term response of Elbe grassland molluscs to the extreme 2002 Elbe summer flood in terms of abundance, diversity, and community composition by comparing pre- and post-flood data collected with identical methods. The flood favoured the colonization of aquatic species and led to a shift of the community towards a more hydrophilic composition. Both diversity and abundance increased significantly in the first year following the flood but decreased later gradually to the pre-flood levels. The high spatio-temporal habitat heterogeneity played an important part in the maintenance of mollusc diversity by increasing refuge opportunities and favouring the maintenance of various mollusc communities with different environmental requirements within the floodplain.

Poly(L‐lactide)‐b‐poly(ethylene oxide) copolymers with different arms: Hydrophilicity, biodegradable nanoparticles, in vitro degradation, and drug‐release behavior

Biodegradable and amphiphilic poly(L-lactide)-b-poly(ethylene oxide) copolymers with different arms (PLLA-b-PEO having one, two, four, and six arms) were successfully synthesized via a two-step synthetic strategy. The hydrophilicity-hydrophobicity balance of these copolymers was mainly controlled by both the arm number of copolymers (i.e., macromolecular architecture) and the poly(ethylene oxide) (PEO) composition. Biodegradable nanoparticles could be generated by direct injection of these PLLA-b-PEO copolymers solutions into distilled water, and their critical micelles concentrations decreased with the increasing arm number of copolymers. Moreover, both the hydrophilic PEO composition and the arm number of copolymers controlled the average size of PLLA-b-PEO nanoparticles, and the nanoparticles with adjustable sizes (20-85 nm) completely meet the size prerequisite (less than 100 nm) for targeted drug delivery. In vitro degradation of PLLA-b-PEO nanoparticles showed that the PLLA composition gradually increased over the degradation time, and the degree of crystallinity of PLLA block within copolymers increased simultaneously. Furthermore, the nimodipine drug loading efficiency of the PLLA-b-PEO copolymers was apparently higher than that of PLLA homopolymers. The drug-release experiments demonstrated that these biodegradable nanoparticles might be used for a short-time controlled release system. Consequently, this will provide a facile method not only to design new PLLA-based biomaterials from both the macromolecular architecture and the hydrophilicity-hydrophobicity balance, but also to fabricate biodegradable nanoparticles with adjustable sizes for drug delivery.

Soft Patchy Nanoparticles from Solution-Phase Self-Assembly of Binary Diblock Copolymers

The fabrication of highly ordered, defect-free nanostructures is a key challenge in nanotechnology. Bottom-up fabrication approaches require nanobuilding blocks of precisely defined size and shape. In this work we propose a simple approach to obtain one type of building block--soft patchy nanoparticles--suggested by a series of coarse grain molecular dynamics simulations. A binary mixture of two different diblock copolymers with a common hydrophobic block but sufficiently dissimilar hydrophilic blocks reliably self-assembles into a "patchy" spherical micelle in water, with phase separation of the two hydrophilic blocks on the surface of the micelle core. Subsequent crosslinking of the core to solidify the patchy sphere geometry should allow further hierarchical assembly. Altering the hydrophilic versus hydrophobic composition of each polymer yields a change of morphology from "patchy spheres" to "patchy cylinders". Furthermore, by controlling the interaction strength of the blocks with solvent, the patches can be selectively placed either on the outer surface or inside the core of the micelle. The number and size of the patches are found to be largely controlled by the composition of the binary copolymer mixture.

A Topography/Chemical Composition Gradient Polystyrene Surface: Toward the Investigation of the Relationship between Surface Wettability and Surface Structure and Chemical Composition

In this paper, we have prepared of a topography/chemical composition gradient polystyrene (PS) surface, i.e., an orthogonal gradient surface, to investigate the relationship between surface wettability and surface structure and chemical composition. The prepared surface shows a one-dimensional gradient in wettability in the x, y, and diagonal directions, including hydrophobic to hydrophilic, superhydrophobic to hydrophobic, superhydrophobic to superhydrophilic gradients, and so forth. These one-dimensional gradients have different gradient values, gradient range, and contact angle hysteresis, which lie on both the surface roughness and the surface compositions. From the trend of variation of contact angle hysteresis, it can be concluded that the transition from the Cassie's model to the Wenzel's model occurs both by decreasing surface roughness and by increasing surface hydrophilic compositions. Moreover, the transition is more effective via changing surface chemical composition than changing surface roughness herein.

Characterization of the family of Mistic homologues

BackgroundMistic is a unique Bacillus subtilis protein with virtually no detectable homologues in GenBank, which appears to integrate into the bacterial membrane despite an overall hydrophilic composition. These unusual properties have been shown to be useful for high-yield recombinant expression of other membrane proteins through fusion to the C-terminus of Mistic. To better understand the structure and function of Mistic, we systematically searched for and characterized homologous proteins among closely related bacteria.ResultsThree homologues of Mistic were found with 62% to 93% residue identity, all only 84 residues in length, corresponding to the C-terminal residues of B. subtilis Mistic. In every case, the Mistic gene was found partially overlapping a downstream gene for a K+ channel protein. Residue variation amongst these sequences is restricted to loop regions of the protein's structure, suggesting that secondary structure elements and overall fold have been conserved. Additionally, all three homologues retain the functional ability to chaperone fusion partners to the membrane.ConclusionThe functional core of Mistic consists of 84 moderately conserved residues that are sufficient for membrane targeting and integration. Understanding the minimal structural and chemical complexity of Mistic will lead to insights into the mechanistic underpinnings of Mistic-chaperoned membrane integration, as well as how to optimize its use for the recombinant heterologous expression of other integral membrane proteins of interest.

Application of zeta potential measurements for coagulation control: pilot-plant experiences from UK and US waters with elevated organics

At present little is known about the relationship between raw water characteristics, such as natural organic matter (NOM) content, and the universal applicability of coagulation optimisation through surface charge measurement. This research aims to investigate this issue by comparing case study sites in the US (Poudre River, Fort Collins, Colorado) and the UK (Albert Reservoir, Halifax) across periods of elevated organic levels. During the period of April to June 2004 in raw Poudre River water dissolved organic carbon (DOC) levels increased rapidly from 3.5 to 7.4 mg L−1 as a direct result of the spring snowmelt runoff, whereas at Albert reservoir, which is a moorland peat catchment, DOC concentrations varied between 7.8 and 10.1 mg L−1 during the period of January to March 2004. NOM is a highly heterogeneous mixture of organic compounds that vary with regards to acidity, molecular weight, hydrophobicity and charge density. XAD resin adsorption techniques were employed to fractionate the water into its hydrophobic and hydrophilic components. Results revealed that NOM composition and characteristics can vary both temporally and spatially, with increased DOC concentrations associated with both an increase in hydrophobic content and charge density. Optimising coagulation based on a zeta potential range (−10 to +5 mV) produced stable average DOC residuals for both locations, although the exact value is also dependent on the hydrophilic composition of the water and the coagulant used, with alum removing approximately 0.5 mg L−1 less DOC compared with ferric.

Comparison of interfacial characteristics of adhesive bonding to superficial versus deep dentine using SEM and staining techniques

A primary reason for premature failure of Class II composite restorations is recurrent decay at the gingival margin. The integrity of the gingival margin depends on the bond formed with dentine. Using scanning electron microscopy (SEM) and histomorphologic technique, the purpose of this study was to characterise the adhesive/dentine (a/d) bond in dentine sections from the dentinoenamel junction (DEJ) and the cementoenamel junction (CEJ) with commercial adhesives of varying hydrophobic/hydrophilic composition. The occlusal 1/3 of the crown was removed from 20 human third molars, this exposed the surface used for the DEJ sections. The teeth were sectioned occluso-gingivally into equal halves: one-half representing the DEJ; the remaining half was sectioned 4mm deep to the exposed surface (CEJ). Each half was treated with the same adhesive. The teeth were randomly selected for treatment with Single Bond (SB, 3M) or Dentastic UNO (UNO, Pulpdent) using wet bonding technique as per manufacturers' instructions. Thin (3-5mum) sections of native a/d interfaces were cut and stained with Goldner's trichrome for light microscopic (LM) examination. Companion slabs were polished and acid-bleach treated, then analysed with SEM. DEJ sections: SB/dentine specimens had approximately 4mum exposed protein at the interface, UNO infiltrated the depth of the demineralised dentine and encapsulated exposed protein. CEJ sections: SB/dentine specimens had highly variable interface structure with localized exposed protein, UNO/dentine exhibited 3-5mum exposed protein at the interface. The quality of the interface was exaggerated and the above differences were not revealed based on SEM characterisation. As a result of adhesive phase separation, SB does not form structurally integrated a/d bonds at the DEJ or CEJ. The increased hydrophilic composition of UNO contributes to the formation of an integrated a/d bond at the DEJ, but structural differences and increased moisture leads to unprotected protein at the a/d interface in the CEJ sections. The inability of the SEM technique to reveal the complexity of the interface could be related to the modifications of the a/d interface caused by polishing and acid-bleach treatment.

Hydration of protein–protein interfaces

We present an analysis of the water molecules immobilized at the protein-protein interfaces of 115 homodimeric proteins and 46 protein-protein complexes, and compare them with 173 large crystal packing interfaces representing nonspecific interactions. With an average of 15 waters per 1000 A2 of interface area, the crystal packing interfaces are more hydrated than the specific interfaces of homodimers and complexes, which have 10-11 waters per 1000 A2, reflecting the more hydrophilic composition of crystal packing interfaces. Very different patterns of hydration are observed: Water molecules may form a ring around interfaces that remain "dry," or they may permeate "wet" interfaces. A majority of the specific interfaces are dry and most of the crystal packing interfaces are wet, but counterexamples exist in both categories. Water molecules at interfaces form hydrogen bonds with protein groups, with a preference for the main-chain carbonyl and the charged side-chains of Glu, Asp, and Arg. These interactions are essentially the same in specific and nonspecific interfaces, and very similar to those observed elsewhere on the protein surface. Water-mediated polar interactions are as abundant at the interfaces as direct protein-protein hydrogen bonds, and they may contribute to the stability of the assembly.

Effects of scaffold composition and architecture on human nasal chondrocyte redifferentiation and cartilaginous matrix deposition

We investigated whether the post-expansion redifferentiation and cartilage tissue formation capacity of adult human nasal chondrocytes can be regulated by controlled modifications of scaffold composition and architecture. As a model system, we used poly(ethylene glycol)-terephthalate–poly(butylene)-terephthalate block copolymer scaffolds from two compositions (low or high PEG content, resulting in different wettability) and two architectures (generated by compression molding or three-dimensional (3D) fiber deposition) with similar porosity and mechanical properties, but different interconnecting pore architectures. Scaffolds were seeded with expanded human chondrocytes and the resulting constructs assessed immunohistochemically, biochemically and at the mRNA expression level following up to 4 weeks of static culture.For a given 3D architecture, the more hydrophilic scaffold enhanced cell redifferentiation and cartilaginous tissue formation after 4 weeks culture, as assessed by higher mRNA expression of collagen type II, increased deposition of glycosaminoglycan (GAG) and predominance of type II over type I collagen immunostain. The fiber-deposited scaffolds, with a more accessible pore volume and larger interconnecting pores, supported increased GAG deposition, but only if a more hydrophilic composition was used.By applying controlled and selective modifications of chemico-physical scaffold parameters, we demonstrate that both scaffold composition and architecture are instructive for expanded human chondrocytes in the generation of 3D cartilaginous tissues. The observed effects of composition and architecture were likely to have been mediated, respectively, by differential serum protein adsorption and efficiency of nutrient/waste exchange.

Enhanced bone marrow stromal cell adhesion and growth on segmented poly(ether ester)s based on poly(ethylene oxide) and poly(butylene terephthalate).

In previous studies in rats and goats, hydrophilic compositions of the PEOT/PBT block copolymer family have shown in vivo calcification and bone bonding. These copolymers are therefore interesting candidates as scaffolding materials in bone tissue engineering applications. Model studies using goat bone marrow stromal cells, however, showed that it was not possible to culture bone marrow stromal cells in vitro on these hydrophilic copolymers. In this paper two ways of surface modifying these materials to improve in vitro bone marrow stromal cell attachment and growth are discussed. Two different approaches are described: (1) blending of hydroxyapatite (HA) followed by CO(2) gas plasma etching; (2) surface modification using CO(2) gas plasma treatments. It was observed that not only HA but also the CO(2) plasma treatment by itself has a positive effect on bone marrow stromal cell attachment and growth. Gas plasma treatment appeared to be the most successful approach, resulting in a large increase in the amount of bone marrow stromal cells present on the surface (determined by a DNA assay). The amount of DNA present on the plasma-treated copolymer 1000/70/30 PEOT/PBT, based on poly(ethylene oxide, M(w) = 1000, 70 m% soft segment), was comparable to the amount present on PDLLA and significantly higher than the amount present on PCL after 7 days of cell culturing. The fact that after gas plasma treatment bone marrow stromal cells do attach to PEOT/PBT copolymers, enables in vitro bone marrow stromal cell culturing, making bone tissue engineering applications of these materials possible.

Effects of hydrophobic and hydrophilic bile salt mixtures on cholesterol crystallization in model biles

The hydrophilic bile salt ursodeoxycholate is frequently used to dissolve cholesterol gallstones. We have now quantitated crystallization as a function of bile salt hydrophobicity, phospholipid content, cholesterol saturation and total lipid concentration (TLCo). Methods: Crystallization in supersaturated model biles with low phospholipid contents (left two-phase-micelles and crystal-containing-zone) was assessed during 21 days by microscopy and chemical measurement of crystal mass. For model biles with higher phospholipid contents (central three-phase-micelles, vesicles and crystal-containing-zone), lipid distribution into various phases was determined by combined ultracentrifugation–filtration–dialysis methodology (Biochim. Biophys. Acta 1532 (2001) 15–27). Results: In the left two-phase zone, crystal numbers and masses were highest in case of more hydrophilic bile salt composition (TUDC 100%>TC/TUDC 70%/30%>TC 100%>TC/TDC 70%/30%>TDC 100%) and decreased with increasing phospholipid contents, lower TLCo and lower cholesterol saturation index (CSI). In contrast, in the presence of vesicles (three-phase zone), crystallization decreased at increasing bile salt hydrophilicity, with concomitant increased vesicular cholesterol solubilization. Conclusions: Presence of vesicular phases is a prerequisite for inhibition of cholesterol crystallization by tauroursodeoxycholate.