Sulfosuccinate Sodium Salt Research Articles

Synthesis of nanocrystalline hydroxyapatite using surfactant template systems: Role of templates in controlling morphology

Hydroxyapatite (HA) nanopowder was synthesized by reverse microemulsion technique using calcium nitrate and phosphoric acid as starting materials in aqueous phase. Cyclohexane, hexane, and isooctane were used as organic solvents, and Dioctyl sulfosuccinate sodium salt (AOT), dodecyl phosphate (DP), NP5 (poly(oxyethylene) 5 nonylphenol ether), and NP12 (poly(oxyethylene) 12 nonylphenol ether) as surfactants to make the emulsion. Effect of synthesis parameters, such as type of surfactant, aqueous to organic ratio (A/O), pH and temperature on powder characteristics were studied. It was found that the surfactant templates played a significant role in regulating the morphology of the nanoparticle. Hydroxyapatite nanoparticle of different morphologies such as spherical, needle shape or rod-like were obtained by adjusting the conditions of the emulsion system. Synthesized powder was characterized using X-ray diffraction (XRD), BET surface area and transmission electron microscopy (TEM). Phase pure HA nanopowder with highest surface area of 121 m 2/g were prepared by this technique using NP5 as a surfactant. Densification studies showed that this nanoparticle can give about 98% of their theoretical density. In vitro bioactivity of the dense HA compacts was confirmed by excellent apatite layer formation after 21 days in SBF solution. Cell material interaction study showed good cell attachment and after 5 days cells were proliferated on HA compacts in OPC1 cell culture medium. The results imply this to be a versatile approach for making hydroxyapatite nanocrystals with controlled morphology and excellent biocompatibility.

Kinetic analysis of hydrogen production using anaerobic bacteria in reverse micelles

The micellar formation and entrapment of bacteria cell in reverse micelles were investigated by ultraviolet spectrum (UV), fluorescence spectrum, and scanning electron microscope (SEM). The hydrogen production in reverse micelles was confirmed. The Gompertz equation was employed to evaluate the hydrogen-producing behavior in reverse micellar systems. Different systems including dioctyl sulfosuccinate sodium salt (AOT)–isooctane, sodium dodecyl sulfate (SDS)–benzene and SDS–carbon tetrachloride (CCl 4) reverse micelles were analysized. The results revealed that the maximum rate of hydrogen production ( R m) was also suitable to formulate the relationship between hydrogen-producing rate and hydrogen productivity in reverse micelles.

Determination of nucleic acid by [tetra‐(3‐methoxy‐4‐hydroxyphenyl)]–Tb3+ porphyrin as the fluorescence spectral probe in bis(2‐ethylhexyl)sulfosuccinate sodium salt micelle system

A new system for the determination of nucleic acid by rare earth metallic porphyrin of [tetra-(3-methoxy-4-hydroxyphenyl)]-Tb3+ [T(3-MO-4HP)-Tb3+] porphyrin as fluorescence spectral probe has been developed in this paper. Nucleic acid can enhance the fluorescence intensity of the T(3-MO-4HP)-Tb3+ porphyrin in the presence of bis(2-ethylhexyl)sulfosuccinate sodium salt(AOT) micelle. In pH 8.00 Tris-HCl buffer solution, under optimum conditions, the enhanced fluorescence intensity is in proportion to the concentration of nucleic acids in the range of 0.05-3.00 microg mL(-1) for calf thymus DNA (ct DNA) and 0.03-4.80 microg mL(-1) for fish sperm DNA(fs DNA). Their detection limits are 0.03 and 0.01 microg mL(-1), respectively. In addition, the binding interaction mechanism between T(3-MO-4HP)-Tb(3+) porphyrin and ct DNA is also investigated by resonance scattering and fluorescence spectra. The maximum binding number is calculated by molar ratio method. The new system can be used for the determination of nucleic acid in pig liver, yielding satisfactory results.

Determination of ultra trace amounts of protein by 4-chlorosulfo-(2′-hyaroxylphenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] as the fluorescence spectral probe in AOT microemulsion

Experiments indicated that protein can enhance the fluorescence of the 4-chlorosulfo-(2′-hydroxylophenylazo)-rhodanine-Ti(IV) complex [ClSARP-Ti(IV)] in the presence of bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) microemulsion. Based on this, a sensitive and reproducible fluorometric method for the determination of micro amount protein was developed. The calibration curves of four proteins were given. Under the optimum experimental conditions, the enhanced fluorescence intensity of the system was in proportional to the concentration of protein in the range of 0.1–11 μg mL −1 for bovine serum albumin (BSA), 1.0–10 μg mL −1 for human serum albumin (HSA), 1.0–50 μg mL −1 for ovalbumin (Ova) and 2.5–18 μg mL −1 for γ-globulins (γ-G). Their detection limits were 0.070, 0.071, 0.33 and 0.22 μg mL −1, respectively. The ClSARP-Ti(IV) complex as a spectral probe can be used to the determination of protein in milk powder and oatmeal yielding with satisfactory results. Therefore, the proposed method is one of the most sensitive methods available. In addition, the interaction mechanism of this system is studied by multi-techniques.

Effects of Additives on the Thermostability of Chloroperoxidase

The effects of several polyhydroxy compounds (glucose, fructose, gumsugar, galactose, trehalose, dextran, xylose, PEG200, glycerin) and surfactant (dioctyl sulfosuccinate sodium salt, AOT) on the catalytic activity and thermal stability of chloroperoxidase (CPO) in aqueous systems were investigated at various temperatures. A 25% superactivity was found in AOT solutions at 25 degrees C, and it could be maintained during the 882 h. PEG200 and glycerin were proven to be the most efficient stabilizer for CPO in temperatures ranging from 25 to 60 degrees C. Trehalose is more helpful than other sugars for extended storage of CPO. These results are promising in view of industrial applications of this versatile biological catalyst. The protective mechanism of various additives on CPO was discussed.

Bio-hydrogen production of anaerobic bacteria in reverse micellar media

Biohydrogen production using anaerobic mixed bacteria in dioctyl sulfosuccinate sodium salt (AOT)/isooctane/water reverse micelles has been investigated. It was found that hydrogen production was enhanced by optimizing some relevant parameters, such as surfactant concentration, water content ( w 0), initial pH, temperature, and substrate concentration. The maximum hydrogen productivity was obtained as 3.51 mol H 2/mol glucose, which was 2.28-fold in aqueous solutions. Analysis of volatile fatty acid suggested that variation of AOT concentration resulted in a dominated metabolic alteration of microorganisms, whereas the dominated acetic acid products were always found at a wide range of water content ( w 0), which was much different with the dominated butyric acid products in aqueous phase. Peak value of hydrogen productivity occurred at initial pH 7.5 in aqueous solutions in contrast that hydrogen production kept stable at pH range from 7.0 to 8.5 in reverse micellar systems. Temperatures of 30–35 °C were optimum for hydrogen production both in aqueous phase and reverse micellar systems. Organic substrates such as glucose, sucrose and starch, were found with similar behaviors that increasing substrate concentration (>11.1 g/l) had no apparent enhancement for hydrogen production in reverse micellar systems.

Biochemical and structural characterisation of cutinase mutants in the presence of the anionic surfactant AOT

The reactivity, stability and unfolding of wild-type (WT) Fusarium solani pisi cutinase and L153Q, S54D and T179C variants were studied in the absence and presence of the dioctyl sulfosuccinate sodium salt (AOT) surfactant. In the absence of surfactant the S54D variant catalytic activity is similar to that of the WT cutinase, whereas L153Q and T179C variants show a lower activity. AOT addition induces an activity reduction for WT cutinase and its variants, although for low AOT concentrations a small increase of activity was observed for S54D and T179C. The enzyme deactivation in the presence of 0.5 mM AOT is relatively slow for the S54D and T179C variants when compared to wild-type cutinase and L153Q variant. These results were correlated with secondary and tertiary structure changes assessed by the CD spectrum and fluorescence of the single tryptophan and the six tyrosine residues. The WT cutinase and S54D variant have similar secondary and tertiary structures that differ from those of T179C and L153Q variants. L153Q, S54D and T179C mutations prevent the formation of hydrophobic crevices responsible for the unfolding by anionic surfactants, with the consequent decrease of the AOT–cutinase interactions.

Improving activity and stability of cutinase towards the anionic detergent AOT by complete saturation mutagenesis

Cutinase is an enzyme suitable for detergent applications as well as for organic synthesis in non-aqueous solvents. However, its inactivation in the presence of anionic surfactants is a problem which we have addressed by creating a complete saturation library. For this, the cutinase gene from Fusarium solani pisi was mutated to incorporate all 19 possible amino acid exchanges at each of the 214 amino acid positions. The resulting library was screened for active variants with improved stability in the presence of the anionic surfactant dioctyl sulfosuccinate sodium salt (AOT). Twenty-four sites in cutinase were discovered where amino acid replacements resulted in a 2-11-fold stability increase as compared to the wild-type enzyme.

P450cam biocatalysis in surfactant‐stabilized two‐phase emulsions

Cytochrome P450 monooxygenases (P450s) are powerful biocatalysts that have the ability to oxidize a broad range of substrates, often at non-reactive carbon centers. However, incorporation of P450s into synthetic schemes has so far been limited to a few whole-cell transformations. P450 substrates are often hydrophobic and have low water solubility, limiting the amount of product that can be produced. To help overcome this limitation, we have examined P450cam activity in two-phase hexane/water emulsions with and without the anionic surfactant, bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT). Hydroxylation of camphor to hydroxycamphor by the three- component P450cam system was chosen as the model reaction, and regeneration of NADH was accomplished with yeast alcohol dehydrogenase (YADH). P450cam was activated in the surfactant-free emulsions, and addition of AOT improved the activity even further, at least over the range of camphor concentrations for which initial rates were readily measurable in all media. The largest observed rate enhancement was 4.5-fold. Nearly 50-times more product was formed in the surfactant-stabilized emulsions than was achieved in aqueous buffer, with total turnover numbers reaching 28,900 for P450cam and 11,800 for YADH. In the absence of surfactant, the two-phase reaction appeared to be mass-transfer limited, while inclusion of AOT alleviated transport limitations and/or afforded a larger interfacial area for P450 activation. The oxidation of hydroxycamphor to 2,5-diketocamphane was also observed, owing to the large concentration of hydroxycamphor relative to camphor in the aqueous phase of the two-phase emulsion. This competing reaction was accompanied by the uncoupled oxidation of NADH (i.e., NADH oxidation without formation of 2,5-diketocamphane), which reduced the availability of NADH for camphor oxidation and further limited the yield of hydroxycamphor in the two-phase emulsions. These results indicate that a surfactant-stabilized two-phase emulsion is a promising reaction medium for practical P450 biocatalysis, although its effectiveness for a given P450/substrate combination can depend on several factors, including competitive or sequential reactions, product inhibition, and NAD(P)H uncoupling.

Dye-Sensitized Solar Cells Based on Nanocrystalline Titania Electrodes Made at Various Sintering Temperatures

Dye-sensitized solar cells were made by using nanocrystalline titania deposited on Fluorine-doped SnO2 (FTO) electrodes. Nanocrystalline titania deposition was made by the sol-gel method using reverse micelles of bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) in cyclohexane as reaction medium. This surfactant could be easily removed from the deposited nanocomposite organic-inorganic film by simple rinsing with distilled water, without affecting titania adherence on FTO electrode. These nanocrystalline titania electrodes were used to make solar cells either without sintering or after sintering at various temperatures. Sintering extensively affected short circuit current but had small effect on device open-circuit voltage. Thus satisfactory photovoltaic response could be obtained even with devices made of non-sintered (room-temperature) titania.

Simple Procedure of Making Room Temperature Mesoporous TiO2 Films with High Purity and Enhanced Photocatalytic Activity

A simple and benign procedure was developed to synthesize room-temperature titania (TiO2) films consisting of nanoparticles. TiO2 nanoparticles were synthesized using a sol-gel method employing the controlled hydrolysis and condensation reactions of titanium isopropoxide in the inner aqueous phase of reverse micellar solution of amphiphilic bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT). The organic–inorganic TiO2 composite nanoparticles were deposited on glass substrates by dip coating, and all the organics including AOT in the sol-gel network were drifted with pure water instead of thermal treatment. Pure TiO2 films consisting of nanoparticles were formed with a high surface area of 547 m2/g and a pore volume of 0.486 cm3/g. The thickness of the films was found to be dependent on AOT concentration and the particular time when the substrates were dipped in the sol as the polycondensation reaction was still in progress. The structural properties of the films were characterized by scanning electron mic...

Silica Particle Formation in Confined Environments via Bioinspired Polyamine Catalysis at Near‐Neutral pH

Big or small, AOT can do it all! In nature, silica formation occurs at neutral to slightly acidic pH conditions with structural control over multiple length scales. Polyamine-containing emulsions and micelles are thought to play an active role in directing the growth of these structures. To mimic this process, silicic acid and poly(ethylene imine) were confined within bis(2-ethylhexyl) sulfosuccinate sodium salt (AOT) reverse micelles (see sketch). Varying the reaction conditions yields silica particles that differ dramatically in both morphology and size.

Preparation and characterization of highly dispersed nanocrystalline rutile powders

A highly dispersed nanocrystalline rutile powder (NRP) having ultrafine and narrow-distributed diameters was successfully prepared via an improved conventional liquid one-step method by introducing dioctyl sulfosuccinate sodium salt (AOT) surfactant in the peptization reaction anaphase. The average grain size of the product is 10–20 nm. The effects of the titanium tetrabutoxide (Ti(OBu) 4) to ethanol volumetric ratio, the precipitation temperature, the peptization temperature and the presence of dioctyl sulfosuccinate sodium salt (AOT) on the preparation of NRP were studied. A new procedure for synthesizing NRP is proposed, and the optimum conditions for preparing NRP were obtained. The TEM, XRD, SEM and FT-IR results were also investigated in this work.

Acellular Synthesis of a Human Enamel‐like Microstructure

Dental enamel is the outermost layer of teeth and the hardest mineralized tissue in the human body. It consists of nanorod-like hydroxyapatite (HA) crystals arranged into a highly organized micro-architectural unit called an enamel prism. These special units play an important role in determining the unique physicochemical properties of dental enamel. Cells (ameloblasts) and enamel proteins are thought to be intimately involved in vivo in producing this unique structure. The aim of this research was to create a similar structure directly by crystal growth without using cells and/or enamel proteins. Using a hydrothermal method we have been able to synthesize these prism-like structures, consisting of fluorapatite (FA) crystals, which are similar to the dimensions of those seen in human enamel. Dental pulp stem cells (DPSCs) were cultured on these crystals and showed the excellent biocompatibility of the FA crystals. The growth mechanism of this structure is outlined and its use in tissue repair is discussed. Ninety-five percent (by volume) of human enamel is comprised of nanorod-like calcium hydroxyapatite crystals, which have an approximate cross section of 25–100 nm and an undetermined length of 100 nm to 100 lm or longer along the c-axis. The typical human enamel prism structure is approximately 5 lm in cross section, and can span the entire enamel thickness, that is, approximately 1–2 mm in length. The prevailing theory is that the ameloblasts secrete amelogenin, a major enamel protein constituting approximately 90 % of all organic matrix material in developing enamel, and this protein plays a vital role in enabling crystallites to form a well-organized prism pattern. These prisms project from the dentino–enamel junction to the enamel surface. The prisms are aligned parallel to each other and separated by an interprismatic structure to form a densely compacted enamel layer. Unlike other calcified tissues, such as dentin and bone, there are no living cells in the mature enamel. The ameloblast cells die after the enamel is formed. Thus, when the enamel is damaged, the body has no ability to regenerate it. The approach to create artificial bone and tooth structures has attracted the interest of many researchers. Kniep and co-workers have described a fluorapatite–gelatine system that resembles the biosystem hydroxyapatite–collagen in both bone and dentine. Recently, Yamagishi et al. have reported a paste of fluoridated hydroxyapatite that could be used to repair a small carious lesion. Although the interface between the precipitated layer from the paste and the tooth surface contains elongated crystals some of which are orientated towards the tooth surface, the unique enamel prism structure is not visible from the transmission electron microscopy (TEM) images. In our previous paper, we reported a way to mimic the natural biomineralization process to create these special structures by modifying synthetic hydroxyapatite nanorods with surfactants that allow the nanorods to self-assemble into an enamel prismlike structure at a water/air interface. However, those self-assembled enamel prism-like structures are small, only about 400 nm in length and 100 nm in cross section, and dispersed randomly. Very recently, Fowler et al. reported that they were able to synthesize an HA bundle structure directly from a solution containing the surfactant bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT), water, and oil. These bundles were only 750 nm to 1 lm in length, 250–350 nm wide and they were dispersed randomly. These unique structures, therefore, have limited applications, and the introduction of other chemicals, for example AOT may cause unnecessary biological effects. The development of nanotechnology has created many ways to grow 1D nanostructures. Among them, the hydrothermal method is a widely adopted technique to create nanorods, nanowires, and whiskers and has already been shown to be an effective way to create long hydroxyapatite nanorods and whiskers. In this study, we demonstrate a direct growth method to produce fluorapatite dental enamel prismlike structures using a hydrothermal technique. A film of compacted well-aligned FA crystals, which was grown on metal plates, had a structure C O M M U N IC A TI O N S

Microgel, nanogel and hydrogel–hydrogel semi-IPN composites for biomedical applications: synthesis and characterization

Quaternary ammonium salt hydrogels from a cationic monomer, (3-acrylamidopropyl)-trimethylammonium chloride (APTMACl), in a variety sizes such as bulk, micro- and nano- has been prepared. The synthesis of micro- and nanogels were carried out in the microenvironment of water-in-oil microemulsions using two types of surfactants, namely, L-α- phosphatidylcholine (lecithin) and dioctyl sulfosuccinate sodium salt (AOT). Additionally, hydrogel–hydrogel composite semi-interpenetrating polymer networks (semi-IPN) was synthesized by dispersing previously prepared micro/nanogel into neutral monomers such as acrylamide (AAm) or 2-hydroxylethyl methcarylate (HEMA) before network formation. Hydrogel swelling and pH response behaviors have been investigated for bulk gels. Morphology, structure, and size of nano-, micro- and bulk materials were explored utilizing transmission electron microcopy (TEM), scanning electron microscopy (SEM) and atomic force microscopy (AFM). It was confirmed with gel electrophoresis that completely charged nanogel form a strong complex with DNA.

Tailoring of Horseradish Peroxidase Activity in Cationic Water-in-Oil Microemulsions

Horseradish peroxidase (HRP) in cationic water-in-oil (W/O) microemulsions has always been ignored in reverse micellar enzymology, mainly because cationic surfactants are inhibitors of enzyme peroxidase. In the present study, for the first time, we have successfully introduced the cationic W/O microemulsion as an attractive host for efficient HRP activity. To this notion, much improved activity of HRP was observed in the W/O microemulsion of cetyltrimethylammonium bromide (CTAB) with an increase in n-hexanol concentration and W0 ([water]/[surfactant]), presumably due to the increased interfacial area of the microemulsions. In support of our above observation, six surfactants were synthesized with an increased headgroup size where the methyl groups of CTAB were subsequently replaced by the n-propyl and 2-hydroxyethyl groups, respectively, to prepare mono-, di-, and tripropylated/hydroxyethylated n-hexadecylammonium bromide. The peroxidase activity enhanced with headgroup size and also followed an overall trend similar to that found in the case of CTAB. Possibly, the reduced positive charge density at the augmented interfacial area by means of increase, either in headgroup size, cosurfactant concentration, and/or W0, is not capable of inactivating HRP. Also, the larger space at the interface may facilitate easier solubilization of the enzyme and increase the local concentration of enzyme and substrate, leading to the higher activity of HRP. The best activity was obtained with surfactant N-hexadecyl-N,N,N-tripropylammonium bromide, the highest ever found in any cationic W/O microemulsions, being almost 3 times higher than that found in water. Strikingly, this observed highest activity is comparable with that observed in an anionic bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT)-based system, the best W/O microemulsions used for HRP.

Dynamics of Solvent and Rotational Relaxation of Glycerol in the Nanocavity of Reverse Micelles

The dynamics of solvent and rotational relaxation of Coumarin 480 and Coumarin 490 in glycerol containing bis-2-ethyl hexyl sulfosuccinate sodium salt (AOT) reverse micelles have been investigated with steady-state and time-resolved fluorescence spectroscopy. We observed slower solvent relaxation of glycerol confined in the nanocavity of AOT reverse micelles compared to that in pure glycerol. However, the slowing down in the solvation time on going from neat glycerol to glycerol confined reverse micelles is not comparable to that on going from pure water or acetonitrile to water or acetonitrile confined AOT reverse micellar aggregates. While solvent relaxation times were found to decrease with increasing glycerol content in the reverse micellar pool, rotational relaxation times were found to increase with increase in glycerol content.

Complex Formation of Semifluorinated γ-Cyclodextrin and Surfactants in Liquid Carbon Dioxide

γ-Cyclodextrins functionalized at the 6-position with perfluoro butanoate groups were prepared from the esterification reaction between γ-cyclodextrin and perfluorobutanoic acid. The semifluorinated γ-cyclodextrin derivatives exhibited amphiphilic behavior and an apparent solubility in densified CO2. They can form soluble complexes with surfactants such as bis(2-ethylhexyl)sulfosuccinate sodium salt (AOT) and N-lauroylsarcosine sodium salt in liquid CO2. The complex with AOT was confirmed visually and by differential scaning calorimetry (DSC), which did not show the characteristic melting endotherm of AOT. The formation of complexes of the single-tail surfactant N-lauroylsarcosine sodium salt and γ-cyclodextrins was also investigated.

Conductive polypyrrole nanofibers via electrospinning: Electrical and morphological properties

Conductive polypyrrole nanofibers with diameters in the range of about 70–300 nm were obtained using electrospinning processes. The conductive nanofibers had well-defined morphology and physical stability. Two methods were employed. Electrospun nanofibers were prepared from a solution mixture of polypyrrole (PPy), and poly(ethylene oxide) (PEO) acted as a carrier in order to improve PPy processability. Both the electrical conductivity and the average diameter of PPy nanofibers can be controlled with the ratio of PPy/PEO content. In addition, pure (without carrier) polypyrrole nanofibers were also able to be formed by electrospinning organic solvent soluble polypyrrole, [(PPy3) + (DEHS) −] x , prepared using the functional doping agent di(2-ethylhexyl) sulfosuccinate sodium salt (NaDEHS) [Jang KS, Lee H, Moon B. Synth Met 2004;143:289–94. [24]]. Electrospun blends of sulfonic acid (SO 3H)-bearing water soluble polypyrrole, [PPy(SO 3H)–DEHS], with PEO acting as a carrier, are also reported. The factors that facilitate the formation of electrical conduction paths through the electrospun nanofiber segments are discussed.

Porous poly(methylmethacrylate) and poly(methylmethacrylate-co-acrylamide)

The characteristics of two types of porous polymers: poly(methyl methacrylate) and copolymers of methyl methacrylate and acrylamide were investigated in this study. Poly(methyl methacrylate) was synthesized in suspension, using ethylene glycol dimethacrylate as the cross-linking agent, poly(vinyl pyrrolidone) as the protective colloid, and benzoyl peroxide as the initiator. The synthesis of poly(methyl methacrylate-co-acrylamide) was initiated in emulsion in the presence of dioctyl sulfosuccinate sodium salt, followed by a sol-gel process, and completely reacted to the solid state. Potassium persulfate was used as the initiator, and tetramethylol glycoluril as the cross-linking agent. Both types of syntheses were carried out in the presence of ethyl acetate. The porosity, specific surface and distribution of the pore sizes of the obtained polymers were determined by mercury porosimetry. The polymers were used as inert carriers for the immobilization of enzymes and whole cells of Saccharomyces cerevisiae yeast.