Preparation of poly[dl-lactide-co-glycolide]-based microspheres containing protein by use of amphiphilic diblock copolymers of depsipeptide and lactide having ionic pendant groups as biodegradable surfactants by W/O/W emulsion method

To develop the preparative method for poly(dl-lactide-co-glycolide)-based microspheres containing proteins, we prepared microspheres from mixture of poly(dl-lactide-co-glycolide) and polydepsipeptide-block-poly(dl-lactide) having cationic or anionic pendant groups. Since the latter amphiphilic copolymers consisting of hydrophobic poly(dl-lactide) segment and hydrophilic polydepsipeptide segment with amino or carboxyl groups could be converted to cationic or anionic block copolymers, they could act as biodegradable surfactants on the preparation of poly(dl-lactide-co-glycolide)-based microspheres by water-in-oil-in-water emulsion method. The amphiphilic block copolymers were established to stabilize primary emulsions on the preparation of microspheres by scanning electron microscopy. We investigated the effects of the addition of the block copolymers on the entrapment efficiency of protein, the release behavior of protein from microspheres and the stability of protein.     

Mixtures of anionic and cationic surfactants with single and twin head groups: Solubilization and adsolubilization of styrene and ethylcyclohexane

Mixtures of anionic and cationic surfactants with single and twin head groups were used to solubilized styrene and ethylcyclohexane into mixed micelles and adsolubilize them into mixed admicelles on silica and alumina surfaces. Two combinations of anionic and cationic surfactants were studied: (i) a single-head anionic surfactant, sodium dodecyl sulfate (SDS), with a twin-head cationic surfactant, pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD), and (ii) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfonate (SHDPDS), with a single-head cationic surfactant, dodecylpyridinium chloride (DPCl). Mixtures of SDS/PODD showed solubilization synergism (increased oil solubilization capacity) when mixed at a molar ratio of 1∶3; however, the SHD-PDS/DPCl mixture at a ratio of 3∶1 did not show solubilization enhancement over SHDPDS alone. Adsolubilization studies of SDS/PODD (enriched in PODD) adsorbed on negatively charged silica and SHDPDS/DPCl adsorbed on positively charged alumina showed that while mixtures of anionic and cationic surfactants had little effect on the adsolubilization of styrene, the adsolubilization of ethylcyclohexane was greater in mixed SHPDS/DPCl systems than for SHDPDS alone. Finally, it was concluded that whereas mixing anionic and cationic surfactants with single and double head groups can improve the solubilization capacity of micelles or admicelles, the magnitude of the solubilization enhancement depends on the molecular structure of the surfactant and the ratio of anionic surfactant to cationic surfactant in the micelle or admicelle.     

Mixtures of anionic and cationic surfactants with single and twin head groups: Adsorption and precipitation studies

This research reports on the adsorption and precipitation of mixtures of anionic and cationic surfactants having single and twin head groups. The surfactant mixtures investigated were: (i) a single-head anionic surfactant, sodium dodecyl sulfate (SDS), in a mixture with the twin-head cationic surfactant pentamethyl-octadecyl-1,3-propane diammonium dichloride (PODD)—adsorption was studied on negatively charged silica; and (ii) a twin-head anionic surfactant, sodium hexadecyl-diphenyloxide disulfonate (SHDPDS), and the single-head cationic surfactant dodecylpyridinium chloride (DPCI)—adsorption was studied on positively charged alumina. Whereas the mixed surfactant system of SHDPDS/DPCI showed adsorption on alumina that was comparable to the of SHDPDS alone, the mixed surfactant system of SDS/PODD showed increased adsorption on silica as compared with PODD alone. The adsorption of the SDS/PODD mixture increased as the anionic and cationic system approached an equimolar ratio. Precipitation diagrams for mixtures of single- and twin-head surfactant systems showed smaller precipitation areas than for single-head-only surfactant mixtures. Thus, the combination of single- and double-head surfactants helps reduce the precipitation region and can increase the adsorption levels, although the magnitude of the effect is a function of the specific surfactants used.     

Insight into the effect of surface carboxyl and amino groups on the adsorption of titanium dioxide for acid red G

In this study, TiO₂ functionalized with organic groups were prepared to study the effect of carboxyl and amino groups on the adsorption behavior of TiO₂ for the removal of acid red G (ARG) as an anionic dye from aqueous solution. TiO₂ was successfully modified with carboxyl and amino groups by using the hydrolysis method with oxalic acid (OAD, with two carboxyl groups), ethylenediamine (EDA, with two amino groups) and DL-alanine (DLA, with one carboxyl group and one amino group) at low temperature (65 °C) and labeled as OAD-TiO₂, EDA-TiO₂ and DLA-TiO₂, respectively. The ARG uptake by the functionalized TiO₂ samples was largely dependent on the functional groups. The interaction between ARG and the functional organic groups on the TiO₂ samples plays an important role in the adsorption process, which leads to the excellent adsorption performance (higher capacity and faster adsorption rate) of the functionalized TiO₂ samples than that of P25 (commercial TiO₂ without modification). Furthermore, there is no obvious loss of the adsorption capacity for the functionalized TiO₂ even after 5 adsorption-desorption cycles, which indicated the good reusability of the modified TiO₂ samples for anionic dye removal from aqueous solution.     

Adsorption of Congo Red dye by native amine and carboxyl modified biomass of <Emphasis Type="Italic">Funalia trogii</Emphasis>: Isotherms,kinetics and thermodynamics mechanisms

Native, iminodiacetic acid and triethylenetetraamine modified biomasses of Funalia trogii were used for removal of Congo Red dye (CRD) from aqueous medium. The native and modified fungal biomasses were characterized using ATR-FTIR, Zeta potential, contact angle studies and analytical methods. FTIR studies of the native and chemically modified adsorbent preparations show that amine, carboxyl and hydroxyl groups are involved in the adsorption of the model dye (i.e., Congo Red). The maximum adsorption of the CRD on the native, carboxyl and amine groups modified fungal biomasses was obtained at pH 5.0. The amount of adsorbed dye on the adsorbent samples increased as the initial concentration of CRD in the solution increased to 200mg/L. The adsorption capacities of native, carboxyl groups and amine modified fungal preparations were 90.4, 153.6 and 193.7mg/g dry adsorbents, respectively. The data was fitted well with the Langmuir isotherm model, and followed the pseudo-second-order equations. Thermodynamic parameters (ΔG ^o , ΔH ^o and ΔS ^o ) were also calculated. The results showed that triethylenetetraamine (TETA) modified biomass of F. trogii presented an excellent dye removal performance and can be used in various environmental applications such as various micro-pollutants removal from aqueous medium.     

The Binding of Anionic Dyes by Cross-Linked Cationic Starches

Adsorption of anionic dyes on the cross-linked with epichlorohydrin starches containing quaternary ammonium groups (CCS) was investigated and compared with that of modified starches containing only quaternary ammonium groups (CS). The adsorption of anionic dyes on CS and CCS closely follows the Langmuir model of adsorption. The computed Langmuir saturation capacity Q _o increases with increasing degree of substitution (DS) of CS or CCS and has the value from 0.81 mol/kg to 3.22 mol/kg for CCS and from 0.88 mol/kg to 1.87 mol/kg for CS. The effectiveness of the cationic groups in dye binding was about 1 mol/equiv for CSS with DS from 0.47 to 0.62 and all the cationic groups had attached one anionic groups of the dye. Increasing DS of CS decreases the effectiveness of dye binding due to the increase in solubility of CS, and the soluble part of CS binds the dye as a typical soluble polyelectrolyte. CCS are more suitable than CS for the anionic dye adsorption from a textile dyeing solution. DS of CCS should be about 0.5–0.6. They adsorb the anionic dyes in few minutes and acts in the wide range of pH of the solutions. The Langmuir saturation capacity Q _o and the effectiveness of the cationic groups in dye binding increase with an increase of the adsorption temperature. The positive values of the enthalpy and entropy suggest that the adsorption is endothermic and during the adsorption of the anionic dye on CCS the randomness of the system increases.     

Characterization of surface reactivity of graphite fiber by solute adsorption

Solution adsorption techniques have been examined for their applicability in determining the surface reactivity of graphite fiber surfaces. The graphite fibers examined were principally Thornel 50 and HMG 50 which derive from rayon as a precursor. Fiber surface conditions consisted of water sized as synthesized, oxidized in nitrogen-oxygen mixtures at 1200°C and oxidized in hot nitric acid. Ionic solutions NaOH, LiOH, methylene blue chloride, metanil yellow, and chloroplatinic acid were adsorbed from water solution. Adsorption of the cationic dye, methylene blue chloride, and the anionic dye, metanil yellow, from a competitive solvent (water) provide a useful measure of the surface concentration of cationic and anionic adsorption sites for graphite fibers subjected to various surface treatment histories. The untreated water sized fibers are characterized by a predominance of anionic adsorption sites. Nitric acid oxidation treatment leads to a decline in the concentration of anionic adsorption sites, but results in a significant increase in the concentration of cationic adsorption sites. Surface carboxyl and hydroxyl appear to dominate in the adsorption characteristics of acid oxidized fibers but make a minor contribution to the adsorption properties of either untreated or air oxidized graphite fibers. There is good correspondence between the adsorption of the organic dye cation, methylene blue, and inorganic cations, such as sodium and lithium cations. Lithium adsorption is preferred to sodium because of the prevalence of contamination by sodium compounds. The population density of anionic adsorption sites on the untreated graphite fibers is compatible as to order of magnitude with the surface concentration of edge carbons estimated from published data on the crystallography of graphite fibers.     

Co-Formulation of Amphiphilic Cationic and Anionic Cyclodextrins Forming Nanoparticles for siRNA Delivery in the Treatment of Acute Myeloid Leukaemia

Non-viral delivery of therapeutic nucleic acids (NA), including siRNA, has potential in the treatment of diseases with high unmet clinical needs such as acute myeloid leukaemia (AML). While cationic biomaterials are frequently used to complex the nucleic acids into nanoparticles, attenuation of charge density is desirable to decrease in vivo toxicity. Here, an anionic amphiphilic CD was synthesised and the structure was confirmed by Fourier-transform infrared spectroscopy (FT-IR), Nuclear Magnetic Resonance (NMR), and high-resolution mass spectrometry (HRMS). A cationic amphiphilic cyclodextrin (CD) was initially used to complex the siRNA and then co-formulated with the anionic amphiphilic CD. Characterisation of the co-formulated NPs indicated a significant reduction in charge from 34 ± 7 mV to 24 ± 6 mV (p < 0.05) and polydispersity index 0.46 ± 0.1 to 0.16 ± 0.04 (p < 0.05), compared to the cationic CD NPs. Size was similar, 161–164 nm, for both formulations. FACS and confocal microscopy, using AML cells (HL-60), indicated a similar level of cellular uptake (60% after 6 h) followed by endosomal escape. The nano co-formulation significantly reduced the charge while maintaining gene silencing (21%). Results indicate that blending of anionic and cationic amphiphilic CDs can produce bespoke NPs with optimised physicochemical properties and potential for enhanced in vivo performance in cancer treatment.     

A Novel Route to Treat Wastewater Containing Cationic Dyes

The combinations of acetic acid/water co-solvent and KCl were employed as the eluent to regenerate porous magnetic microspheres (PMMs) during treatment of wastewater containing cationic dyes. The effect of acetic acid/water volume ratio and KCl concentration on desorption percentages were systemically investigated. The results indicated that the carboxyl group in acetic acid could produce weak electrostatic attraction with cationic dyes, which was helpful to weaken the interaction between cationic dyes and sulfonic groups. The saturated solution of KCl in acetic acid displayed excellent regeneration capacity for PMMs including methyl violet. This fact was further demonstrated during desorption of basic fuchsin from PMMs. Overall, the present paper provided a novel and simple route to treat wastewater containing cationic dyes and optimized the combination of acetic acid/water co-solvent and KCl for regeneration of PMMs.     

Modification of the surface characteristics of cotton by the introduction of anionic groups,and the mechanism of ion binding

The introduction of carboxymethyl, phosphate and sulfate groups into cotton cellulose considerably modifies the capacity of the cellulose to bind cationic systems. The ion-binding characteristics of these anionic derivatives have been quantitatively studied using the cationic dye methylene blue. Diffuse reflectance spectral measurements demonstrate that two types of sulfated and phosphorylated celluloses can be produced, which differ considerably in the interaction of their anionic groups with the dye. Anionic systems are, in contrast, repelled by the anionic substituents. In this way the resistance of the cotton cellulose to wet soiling can be considerably increased. The mechanism of ion binding to anionic celluloses has been examined and the information utilized to predict methods of modifying the surface characteristics of cotton cellulosee. One of eight papers being published from the Symposium “Surface Active Agents in the Textile Industry, presented at the AOCS Meeting, New Orleans, April 1970.     

Ionic graft copolymerization. V. Graft copolymerization of β-propiolactone onto the trunk polymers containing carboxylic acid,sulfonic acid,and other salts

β-Propiolactone (βPL) was graft-copolymerized onto styrene–divinylbenzene copolymers containing various carboxylates or sulfonates, composed of anions and cations having different electronegativities. In parallel, the mechanism of polymerizations of βPL by relatively neutral catalysts was studied in comparison with the behaviors of graft copolymerizations. In the graft copolymerization onto the trunk polymer containing various carboxylates, a lower electronegativity of countercation favors a higher anionic polymerization activity and the order of rate of polymerization coincides with that of anionic activities of catalysts. On the other hand, in the case of trunk polymer containing sulfonates, a higher electronegativity of countercation favors a cationic polymerization activity, and the order of rate of polymerization coincides with that of cationic activity of catalyst. The order of grafting efficiency at fixed total conversion coincides almost with that of anionic activity. The comparatively higher grafting efficiency in the grafting onto trunk polymer containing carboxylic acid might support an anionic graft copolymerization mechanism by carboxyl anion. The two following mechanisms were proposed for the initiation of the polymerization by the trunk polymer containing sodium sulfonate, in which acrylic acid is transformed from βPL.     

Coagulation and flocculation of dye-containing solutions using a biopolymer (Chitosan)

Chitosan, dissolved in acetic acid, was used for the coagulation–flocculation of an anionic dye (Reactive Black 5). In acidic solutions protonated amine groups of chitosan attract dye sulfonic groups. Increasing chitosan dosage increases dye removal up to a concentration resulting in complete neutralization of anionic charges; above, the excess of cationic charges leads to suspension re-stabilization. Process efficiency increases with decreasing the initial pH of dye solution: the molar ratio between dye molecules and amine groups ([n]) respects the stoichiometry between sulfonic functions and protonated amine groups at initial pH 5; at initial pH 3 a possible dye aggregation phenomenon results in higher molar ratio [n]. The coefficient [n] depends on both the pH and the molecular weight of chitosan. The main mechanism for dye coagulation with chitosan sounds to be charge neutralization at acidic pH.     

多种因素对MIL-101(Cr)选择性吸附水溶液中染料的影响

在多种条件下研究了金属有机框架MIL-101(Cr)对阳离子型染料(亚甲基蓝、罗丹明B)和阴离子型染料(甲基橙、酸性铬蓝K)的吸附性质,主要研究了MIL-101(Cr)对亚甲基蓝和甲基橙的选择性吸附作用。结果表明,中性环境下无论在单组分还是双组分体系中MIL-101(Cr)对阴离子型染料的吸附能力均大于对阳离子型的吸附能力。在pH=3,T=300 K的条件下,选择性系数β可达5.9,但随着pH的增加,选择性系数逐渐降低。相比之下,温度对吸附的选择性影响不大。选择性吸附的机理可以解释为:由于表面带正电荷,MIL-101(Cr)对阴离子型染料产生静电吸引作用;相反,对阳离子型染料的排斥作用而降低了其吸附能力。另外,乙二胺改性提高了MIL-101(Cr)对阴离子型染料的选择吸附性能,而草酸改性降低了选择吸附性。     

Cholic Acid-Derived Facial Surfactants with Long Side-Chain Quaternary Ammonium: Synthesis and Antimicrobial Activity Study

Four cholic acid cationic surfactants containing a flexible long aliphatic chain were synthesized efficiently. A long aliphatic chain was introduced first on the side-chain carboxyl of cholic acid by one-pot condensation reaction of cholic acid and C12–C18 amines using DCC (Dicyclohexylcarbodiimide) and HOBt (N-hydroxybenzotrizole) as condensation agents for the formation of an amide framework. Then reduction of the amide and quaternization gave a cationic group for strengthening hydrophilicity. This strategy offered a very straightforward and efficient method for access to the designed surfactants in good overall yields. Preliminary results show that an increase both in the length of the hydrophobic tail and in the number of charged groups lowered the CMC of cholic acid-derived cationic surfactants. Cholic acid-based cationic surfactants containing a flexible longer aliphatic chain and a quaternary ammonium had the highest antimicrobial activity.     

Preparation and pH‐sensitivity of polyacrylonitrile (PAN) based porous hollow gel fibers

Polyacrylonitrile based porous hollow gel fibers were prepared from PAN hollow fibers by oxidation and subsequent alkaline treatment. Fourier‐transform infrared (FTIR), X‐ray diffraction, and scanning electron microscope (SEM) analyses showed that the PAN porous hollow gel fiber was a kind of amphoteric fiber due to the combination of cationic groups of pyridyl and anionic groups of carboxyl; after gelation the hollow channel and finger‐like pores on the fiber walls were conserved. The effects of cyclization reaction degree, alkaline solution concentration, and alkaline treatment time on the mechanical properties or pH‐sensitive behavior of the porous hollow gel fibers were investigated. The elongation/contraction behavior was studied in detail. It was found that the gel fiber exhibited a large swelling in an alkaline solution and contracting in an acid solution; the swelling change in length was above 90%; the responsive time of elongation/contraction was less than 20 s; the maximum contraction force was 20 N/cm²; and pH‐sensitivity was reversible. © 2008 Wiley Periodicals, Inc. J Appl Polym Sci, 2008     

Effect of the anionic‐group/cationic‐group ratio on the swelling behavior and controlled release of agrochemicals of the amphoteric,superabsorbent polymer poly(acrylic acid‐co‐diallyldimethylammonium chloride)

A series of amphoteric, superabsorbent polymers [poly(acrylic acid‐co‐diallyldimethylammonium chloride)] with different molar ratios of anionic groups to cationic groups were prepared by solution polymerization to investigate their swelling behaviors and the controlled release of agrochemicals. Various factors, including the solution pH, the concentrations of different salt solutions, and the temperature, were studied. The dynamic parameters of hydrogels at different temperatures suggested that diffusion was Fickian at lower temperatures, whereas non‐Fickian diffusion prevailed at higher temperatures. A copolymer hydrogel with a low anionic‐group/cationic‐group ratio showed a higher swelling capacity in water and higher salt tolerance. Also, the anionic‐group/cationic‐group ratio was not the dominant factor in determining the water retention. A poly(acrylic acid‐co‐diallyldimethylammonium chloride) hydrogel could control the release of agrochemicals effectively. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 102: 986–991, 2006     

Anionic/Cationic Membranes Obtained by a Radiation Grafting Method for Use in Waste Water Treatment

Investigations were carried out on different ionic membranes, which were prepared by radiation-induced graft copolymerization. Cationic (low density polyethylene (LPDE)-g-poly(acrylic acid) (PAAc)) and cationic/anionic (LDPE-g-P(AAc/4-vinyl pyridine (4VP)) membranes) were used to elucidate the possibility of their practical use. The metal uptake via their functional groups was determined by using atomic absorption and X-ray fluorescence. The amount of metal uptake by the prepared membranes increased significantly as the pH of the metal feed solution increased (pH ≤ 5·3) and the chelated metal ions were easily desorbed by treating the membrane with 0·1 M HCl for 2h at room temperature. The maximum uptake for a given metal was higher for the cationic/anionic membranes than for the cationic ones. The selectivity of the cationic/anionic membranes towards different metals was investigated using mixtures of two or three metals in the same feed solution. The membranes showed high selectivity towards Fe(III ) ions. Characterization of the graft copolymers containing metals was determined by thermogravimetric analysis (TGA) and X-ray diffraction (XRD). TGA results showed that the decomposition of the graft copolymer in the presence of chelated metal ion occurred at temperatures above 300°C. The XRD of LDPE-g-P(AAc/4VP) treated with Fe(III ) at various concentrations showed that the crystallinity decreased to a certain limiting value. The complexed copolymers could be recycled several times and showed high selectivity to the Fe(III ) ion in the presence of the other metal ions investigated. This may make such grafted membranes acceptable for practical use in waste water treatment. © 1997 SCI     

Relevance of ions in pressurized fluid extraction of carbohydrates and phenolics from barley hull

The removal of total carbohydrates and phenolics from the hull of a new barley variety BT 584 using solid-liquid batch and aqueous pressurized fluid (ethanol or ionic liquid) extractions were evaluated. Using pressurized fluids, temperature was the most significant variable for the extraction of biocompounds from barley hull. The highest phenolics extraction (189.1 ± 3.1 mg/g hull) was obtained using pressurized aqueous ionic liquid while the highest carbohydrates extraction (450.3 ± 7.8 mg/g hull) was obtained using pressurized aqueous ethanol. The predicted solubility of ferulic acid and glucose in water, ionic liquid or carbonic acid, and the acid dissociation constant of the compounds studied allowed proposing an extraction mechanism based on biomass interaction with ionic species formed during pressurized fluid extraction. The anionic species facilitated removal of phenolics while the interaction of cationic/anionic species facilitated removal of carbohydrates from barley hull biomass.     

The Formation of pH-Sensitive Wormlike Micelles in Ionic Liquids Driven by the Binding Ability of Anthranilic Acid

Wormlike micelles are typically formed by mixing cationic and anionic surfactants because of attractive interactions in oppositely charged head-groups. The structural transitions of wormlike micelles triggered by pH in ionic liquids composed of N-alkyl-N-methylpyrrolidinium bromide-based ILs (ionic liquids) and anthranilic acid were investigated. These structures were found responsible for the variations in flow properties identified by rheology and dynamic light scattering, and account for the structures observed with cryogenic transmission electron microscopy (Cryo-TEM). High-viscosity, shear-thinning behavior, and Maxwell-type dynamic rheology shown by the system at certain pH values suggested that spherical micelles grow into entangled wormlike micelles. Light scattering profiles also supported the notion of pH-sensitive microstructural transitions in the solution. Cryo-TEM images confirmed the presence of spherical micelles in the low-viscosity sample and entangled wormlike micelles in the peak viscosity sample. Nuclear magnetic resonance spectroscopy analysis revealed that the pH sensitivity of ionic liquid systems originated from the pH-dependent binding ability of anthranilic acid to the cationic headgroup of ionic liquids.     

Electrical Aspects of Adsorbing Colloid Flotation. XX. NMR Studies of Laurie Acid Solubilization

Abstract

Mixed micelles of dodecanoic acid with sodium dodecylsulfate, Triton X-100 (TX-100, an alkylphenylpolyethoxy alcohol), and dodecyltrimethylammonium chloride were studied. T₁ and nuclear Overhauser enhancement (NOE) measurements were made using dodecanoic acid C-13 labeled at the carboxyl group. Viscosity measurements were made and titration curves run of dodecanoic acid in these mixed micelles. The pK_a of dodecanoic acid increases, as one goes, from cationic to neutral to anionic micelles. Generally the mixed micelles are apparently small and roughly spherical; in acidic solution, however, dodecanoic acid-TX-100 micelles are large with an extended structure. NOE measurements indicate that the carboxyl group is relatively close to the protons in the micelle core, and that the carboxyl group moves out slightly into the aqueous phase on becoming ionized. The NOE of dodecanoic acid-TX-100 micelles indicates interaction between the carboxyl carbon and the protons in the ethoxy chain of TX-100.