Effect of Surfactants on the Formation,Morphology, and Surface Property of Synthesized SiO2 Nanoparticles

Abstract

This study investigated the effect of cationic, anionic (saturated and unsaturated), and nonionic surfactants on the formation, morphology, and surface properties of silica nanoparticles synthesized by the ammonium‐catalyzed hydrolysis of tetraethoxysilane in alcoholic media. Results indicate that at a relatively low surfactant concentration (1 × 10^?3–1 × 10^?6 M), cationic surfactants significantly affected the growth of silica particles as measured by dynamic light scattering and transmission electron microscopic analyses. In contrast, the anionic and nonionic surfactants showed relatively minor effects in the low concentration range. The magnitude of negative zeta potential was reduced for silica colloids that were synthesized in the presence of cationic surfactant because of charge neutralization. The presence of anionic surfactants only slightly increased the negative zeta potential while the nonionic surfactant showed no obvious effects. At high surfactant concentrations (>1 × 10^?3 M), cationic and anionic surfactants both induced colloid aggregation, while the nonionic surfactant showed no effect on particle size. Raman spectroscopic analysis suggests that molecules of cationic surfactants adsorb on silica surfaces via head groups, aided by favorable electrostatic attraction, while molecules of anionic and nonionic surfactants adsorb via their hydrophobic tails.     

Identification and in vitro antioxidant activities of phenolic compounds isolated from Cynoglossum cheirifolium L.

In an extensive search for bioactive compounds from plant sources, the quantitative and qualitative characterisation of the compounds present in Cynoglossum cheirifolium extracts was studied. Total phenolic and flavonoid contents were determined by spectrophotometric techniques. In vitro antioxidant and radical scavenging profiling was determined through DPPH^? scavenging activity and Ferric reducing antioxidant power (FRAP). Our study showed that leaves produce more phenolic compounds, followed by flowering aerial part. The butanolic fraction obtained from leaves extract exhibited the highest total phenolics (78.65 ± 3.58 mg GAE/g DW) and flavonoids (22.15 ± 4.66 mg CE/g DW). In contrast, this fraction displayed the highest DPPH^? scavenging ability with IC₅₀ values of 0.06 ± 0.003 mg/mL. The RP-HPLC-PDA analysis of phenolic compounds from leaves of C. cheirifolium lets to identify: rosmarinic acid, ferulic acid, caffeic acid, p-coumaric acid, syringic acid, sinapic acid and rutin. The obtained results indicate that this plant represent a valuable source of natural antioxidants.     

Circadian variation and in vitro cytotoxic activity evaluation of volatile compounds from leaves of Piper regnellii (Miq) C. DC. var. regnellii (C. DC.) Yunck (Piperaceae)

Aiming detection of circadian variation in the chemical composition of volatiles from Piper regnellii, the leaves were collected during four different periods (8, 12, 16 and 20 h) in the same day. After extraction by hydrodistillation and GC/MS analysis, no significant variation was observed for the main compounds: germacrene D (45.6 ± 1.5–51.4 ± 3.1%), α–chamigrene (8.9 ± 1.3–11.3 ± 2.7%) and β–caryophyllene (8.2 ± 0.9–9.5 ± 0.3%). Evaluation of in vitro cytotoxicity against several cancer and non-tumourigenic cells indicated promising activity, especially to HeLa (human cervical carcinoma) with IC₅₀ ranging from 11 ± 3 to 17 ± 3 μg/mL. The obtained volatile oils were pooled and subjected to fractionation to afford pure β-caryophyllene, α-chamigrene and germacrene D, being this last compound the more active against HeLa cells with IC₅₀ of 7 ± 1 μg/mL (34 ± 5 μM). Therefore, the predominance of germacrene D in all analysed oils could justify, at least in part, the activity observed for the volatile compounds from P. regnellii leaves.     

Optical Sensing Membrane Based on Tetrabromophenolphthalein Ethyl Ester for the Determination of Cationic Surfactants

Abstract

An optical sensing membrane for detection of cationic surfactants was developed. The optical sensing membrane is 2‐nitrophenyl octyl ether‐plasticized poly(vinyl chloride) membrane incorporating tetrabromophenolphthalein ethyl ester (TBPE). The response of the optical membrane to cationic surfactants was a result of extraction of cationic surfactant into the PVC membrane. The protonated TBPE deprotonates forming an ion associate with the extracted cationic surfactant; simultaneously, the deprotonation of the TBPE is accompanied by a spectral change. Namely, the extracted cationic surfactant changes color of the membrane from yellowish green to blue (absorption maximum: 622 nm). The optical membrane responds to cationic surfactants such as Zephiramine and cetyltrimethylammonium bromide in the concentration range from 1 µM to 100 µM.     

The determination of cationic surfactants in the presence of anionic surfactant in biodegradation test liquors

A method is described for the determination of cationic surfactants in biodegradation test liquors and effluents containing anionic surfactant and other components which interfere with existing colorimetric procedures. The cationic surfactant is concentrated by evaporation of the aqueous sample and separated from the resulting residue by solvent extraction as an ion-association compound. The extract is treated under non-aqueous conditions on Bio-Rad AG 1-X2 resin in the chloride form to remove interfering anionic components. The isolated cationic surfactant is determined colorimetrically as its disulphine blue ion-association compound, extractable into chloroform. The recovery of added cationic surfactants from biodegradation test liquors is generally better than 95 %, and concentrations in the range 0.1–10 mg l^-1 can be determined. The method is suitable for biodegradability test studies where control liquors are available, e.g. OECD Screen and Confirmatory tests. In environmental samples, materials other than cationic surfactant may respond to disulphine blue and these limit severely the application of the procedure.     

Steady-state fluorescence investigations of aqueous binary mixtures of myristyl alcohol based bis-sulfosuccinate anionic gemini surfactant and effect of different conventional surfactants therein

The present research work is associated with the fluorescence investigations of binary aqueous mixed surfactants solutions of anionic bis-sulfosuccinate gemini surfactant (BSGSMA_1,8) and three different conventional surfactants—anionic viz. sodium dodecyl sulfate (SDS), cationic viz. cetyl trimethyl ammonium bromide (CTAB), and nonionic surfactant viz. Triton X 100. Steady-state fluorescence spectroscopy technique has been utilized to examine the micellization behavior of aqueous solution of pure myristyl alcohol-based BSGSMA_1,8 having flexible methylene chain [(CH₂)₈] as spacer group. Critical micelle concentration (CMC), aggregation number (N), and micropolarity of pure and mixed surfactants systems were explored during the investigations. The results revealed the best synergism behavior of prepared gemini BSGSMA_1,8 with SDS as compared to CTAB and Triton X 100. The maximum reduction in the value of pyrene intensity ratio (I₁/I₃) was observed for gemini and SDS mixed surfactant solution. On the other hand, the increased I₁/I₃ value of mixed gemini with Triton X 100 exhibited that mixed surfactant system of anionic gemini BSGSMA_1,8 with non-ionic Triton X 100 is not as compact as other mixed surfactant systems. Aggregation number increased and micropolarity decreased with increased concentration of gemini surfactants.     

Detection of silver(I) ion based on mixed surfactant-adsorbed CdS quantum dots

Mixed cationic and anionic surfactants were adsorbed on cadmium sulfide quantum dots (CdS QDs) capped with mercaptoacetic acid. The CdS QDs can be extracted into acetonitrile with 98 % efficiency in a single step. Phase separation only occurs at a molar ratio of 1:1.5 between cationic and anionic surfactants. The surfactant-adsorbed QDs in acetonitrile solution display stronger and more stable photoluminescence than in water solution. The method was applied for determination of silver(I) ion based on its luminescence enhancement of the QDs. Under the optimum conditions, the relative fluorescence intensity is linearly proportional to the concentration of silver(I) ion in the range between 50 pmol L^?1and 4 μmol L^?1, with a 20 pmol L^?1 detection limit. The relative standard deviation was 1.93 % for 9 replicate measurements of a 0.2 μmol L^?1 solution of Ag(I).

Comparative metabolic profiling of Costus speciosus leaves and rhizomes using NMR,GC-MS and UPLC/ESI-MS/MS

Costus speciosus had been used in oriental systems of medicines, to treat diverse ailments. The present study was focused on NMR, GC-MS and UPLC/ESI-MS/MS-based metabolic profiling of C. speciosus. This metabolic study resulted in the identification of 91 and quantification of 69 metabolites. Caffeic acid derivatives previously unreported in C. speciosus were also identified. High quantity of steroidal saponins namely methyl protogracillin (297.97 ± 0.07 mg/g dried wt.) and dioscin (158.72 ± 0.27 mg/g dried wt.) were observed in butanol fraction of rhizomes. Health care metabolites including caffeic acid (37.88 ± 0.04 mg/g dried wt.) and trehalose (75.12 ± 0.08 mg/g dried wt.) were also detected in ethyl acetate and aqueous fractions of rhizomes, respectively. Metabolites of nutraceutical and biological significance including eremanthine (5.14 ± 0.68%, peak area), tocopherols (~22%), sterols (~25%) were also identified from hexane fractions of rhizomes and leaves using GC-MS. The analytical techniques used had successfully differentiated metabolites composition among leaves and rhizomes.     

Characterization of anionic and cationic functionalized bacterial cellulose nanofibres for controlled release applications

Bacterial cellulose (BC) is a biocompatible biopolymer synthesized by Gluconacetobacter xylinus. In this study, BC was oxidized and aminated to produce hydrogels for biomedical applications, and the products were characterized. A carboxyl (pK_a of 3.9 ± 0.1) content of 1.13 ± 0.02 mmol/g was obtained with the TEMPO-catalyzed oxidation. Epichlorohydrin-mediated amination introduced amine groups (pK_a of 11.0 ± 0.1) up to 1.74 ± 0.06 mmol/g. The oxidation of BC caused a decrease in its ζ-potential to ?103 ± 6 mV, and amination increased the ζ-potential to ?4 ± 6 mV. The fibre diameter decreased after both reactions. The high absolute value of the ζ-potential for oxidized BC led to superior colloidal stability in water, and a 390 % increase in water retention. The oxidized BC hydrogel was also found to increase in water retention fivefold from pH 1 to 7, making it a smart hydrogel. The cationic and anionic BC hydrogels described here could be used for several biomedical applications, including self-assembling drug delivery devices.     

Studies of Interfacial Activities of Four Kinds of Surfactants at Oil/Water Interface

This article aims to compare the interfacial activities of different kinds of surfactants in the same oil/water system. The anionic surfactants of alkylbenzene sulfonates, the polyoxyethylenated nonionic surfactants, the cationic surfactants of alkyl trimethyl ammonium chlorides, and the zwitterionic surfactants of alkyl hydroxyl sulfobetaines were used, and the interfacial tensions of the surfactant solutions against kerosene at different NaCl concentrations were measured. It is found that the interfacial activities of the alkylbenzene sulfonates are high and ultralow interfacial tensions (<0.01 mN/m) can be obtained at proper salinities. While, the nonionic surfactants have relatively low interfacial activities and the minimum tensions are around 0.01 mN/ms. The salinity scanning curves of the alkylbenzene sulfonates and nonionic surfactants decrease first, then increase, showing their interfacial activities can be changed by the salinity effectively. The cationic and zwitterionic surfactants have very low interfacial activities, of which all the tensions are higher than 0.1 mN/ms and are hard to be changed by the salinity. The experimental results may have important reference values for enhanced oil recovery.     

Evaluation of Surface Active Properties and Voltammetric Characterizations of Some New Anionic Copolymer Surfactants

The onset of micelles formations critical micelle concentration, diffusion coefficients as well as particle sizes for some new synthesized anionic copolymer surfactants PSA_4a, PSA_4b, and PSA_4c, were determined and discussed. Three different electrochemical techniques such as cyclic voltammetry (CV), rotating disk voltammetry (RDV), and chronocoulometry (CC) were used in this investigation. The voltammetry of electroactive hydrophobic probe ferrocene solubilized surfactants was investigated in aqueous buffer carbonate solutions of pH 10. The CMC for each PSA_4a, PSA_4b, and PSA_4c, was found to be 3.20 × 10^?4, 4.60 × 10^?4 and 6.30 × 10^?4 M, respectively, using both CV and RDV techniques. The amount of adsorption contribution of ferrocene solubilized surfactants at the glassy carbon electrode was determined from chronocoulometric measurements and it was found in the range from (1.4 to 2.7) × 10^?15 M. The apparent diffusion coefficients were estimated from RDV measurements and the real micelles diffusion coefficients were obtained. Re-quilibrium considerations of ferrocene probe kinetics at the electrode surface were treated according to two different modes of slow- and fast-kinetics. The corrected diffusion coefficient values showed constancy at (5.3 ± 0.1) × 10^?7, (4.8 ± 0.1) × 10^?7, and (3.6 ± 0.4) × 10^?7 cm²/sec for PSA_4a, PSA_4b, and PSA_4c, respectively in the concentration range from 20 to 200 mM. The morphological features of anionic copolymeric surfactants PSA_4a, PSA_4b, and PSA_4c, micelles showed globular self-assembled structure.     

Chemical composition and in vitro antibacterial and antiproliferative activities of the essential oil from the leaves of Psidium myrtoides O. Berg (Myrtaceae)

In this study, the chemical composition and antibacterial and antiproliferative potential of the essential oil obtained from fresh leaves of Psidium myrtoides (PM-EO) against oral pathogens and human tumour cell lines were investigated for the first time. GC-FID and GC-MS analyses showed that trans-β-caryophyllene (30.9%), α-humulene (15.9%), α-copaene (7.8%), caryophyllene oxide (7.3%) and α-bisabolol (5.3%) are the major constituents of PM-EO. The antibacterial activity of PM-EO against a panel of oral pathogens was investigated in terms of their minimal inhibitory concentrations (MIC) using the broth microdilution method. PM-EO displayed moderate activity against Streptococcus mitis (MIC = 100 μg/mL), S. sanguinis (MIC = 100 μg/mL), S. sobrinus (MIC = 250 μg/mL), and S. salivarius (MIC = 250 μg/mL), and strong activity against S. mutans (MIC = 62.5 μg/mL). The antiproliferative activity in normal (GM07492A, lung fibroblasts) and tumour cell lines (MCF-7, HeLa, and M059 J) was performed using the XTT assay. PM-EO showed 50% inhibition of normal cell growth at 359.8 ± 6.3 μg/mL. Antiproliferative activity was observed against human tumour cell lines, with IC₅₀ values significantly lower than that obtained for the normal cell line, demonstrating IC₅₀ values for MCF-7 cells (254.5 ± 1.6 μg/mL), HeLa cells (324.2 ± 41.4 μg/mL) and M059 J cells (289.3 ± 10.9 μg/mL). Therefore, the cytotoxicity of PM-EO had little influence on the antibacterial effect, since it showed antibacterial activity at lower concentrations. Our results suggest that PM-EO is a promising source of new antibacterial and antitumour agents.     

RP-HPLC method for estimation of sesamin in two Zanthoxylum species

Zanthoxylum naranjillo and Z. tingoassuiba (Rutaceae) are traditional herbal medicines with various biological activities including anti-inflammatory, analgesic, and antimalarial action. In this work, we have developed a simple HPLC-DAD method to quantify sesamin, a bioactive lignan present in Z. naranjillo and Z. tingoassuiba; egonol was the internal standard. According to the developed method, 11.07 ± 1.66, 8.69 ± 0.95, and 15.11 ± 0.72 µg/mL sesamin was present in the ethanol extract of Z. naranjillo leaves, in the methanol extract of Z. naranjillo leaves, and in the methanol extract of Z. tingoassuiba bark, respectively. The limits of detection and quantification were 0.32 and 1.06 µg/mL, respectively. The developed method can be easily applied during routine analysis of sesamin in these medicinal plants.     

A versatile amphiprotic cotton fiber for the removal of dyes and metal ions

Adsorption is an efficient method to combat the important issues of water pollution caused by dyes and metal ions. However, due to the surface charge diversity of pollutants, there is a pressing need to develop an all-round, efficient, cheap and environmentally friendly adsorbent. To this end, this work synthesized an amphiprotic adsorbent based on cotton fibers, which were chemically modified with a cationic monomer (3-chloro-2-hydroxypropyl trimethyl ammonium chloride) and anionic monomer (2-acrylamide-2-methyl propane sulfonic acid) respectively. The resultant amphiprotic cotton (AP-cotton) can cope with both of anionic and cationic pollutants. Its adsorption behavior as influenced by the pH value, adsorption time and initial concentration of various adsorbates was investigated. The results demonstrate that the adsorption equilibrium was reached within 4 h for Congo red (CR) and methylene blue (MB), 2 h for Cu²⁺ and 3 h for Pb²⁺, respectively. Adsorption kinetics showed that the adsorption rate was well fitted with the pseudo-second-order rate model, and the best adsorption isotherms fitted the Langmuir model. The Langmuir maximum adsorption capacities were 175.1 mg/g for CR, 113.1 mg/g for MB, 88.9 mg/g for Cu²⁺ and 70.6 mg/g for Pb²⁺, respectively, and the adsorption capacities could be maintained above 90 % after six regenerations. The all-round adsorption capacity and good regeneration performance of AP-cotton benefited from its hollow, flat-banded structure and amphiprotic characteristic. Therefore, AP-cotton exhibited a much better application potential compared with many other reported adsorbents based on natural materials.     

Photochemistry of Flavins in Micelles: Specific Effects of Anionic Surfactants on the Monomerization of Thymine Cyclobutane Dimers Photosensitized by Tetra-O-acyl Riboflavins*

It was found that tetra-o-acyl riboflavins efficiently photosensitize the monomerization of the cis, syn-cyclobutane dimers of 1,3-dimethylthymine and 1,3-dimethyluracil in aqueous solution in the presence of such anionic surfactants as sodium dodecyl sulfate and sodium hexadecyl sulfate at concentrations higher than their critical micelle concentration, while little monomerization of the dimers was photosensitized by the flavins in the absence of the surfactants and even in the presence of cationic and nonionic surfactants.     

Chemical composition and in vitro anticancer,antimicrobial and antioxidant activities of essential oil and methanol extract from Rumex nervosus

Chemical composition, antioxidant, anticancer, and antimacrobial activities of essential oil obtained from leaves of Rumex nervosus has been evaluated here for the first time. GC/MS analysis reveals the presence of Palmitoleic Acid (28.35%) and Palmitic acid, (25. 37%) as their methyl ester as major components. The essential oil showed significant DPPH radical scavenging activity (94.907 ± 0.1089% and 94.003 ± 0.0749%) at concentration (100 and 80) μg/mL respectively. The oil showed promising activity against staph aureus, while showed weak activity against (Hela and 3T3) cell lines. The crude extract / fractions of R. nervosus (leaves) showed significant antioxidant activity at dose (100 and 80) μg/mL. Futhermore the crude showed significant activity against (MCF-7 and MDA-MB-231) cell lines with IC₅₀ (20.5138 ± 0.933 and 25.1728 ± 0.9176) μg/mL respectively, and chloroform fraction showed good activity against (MCF-7 and MDA-MB-231) cell lines with IC₅₀ (31.154 ± 0.965 and 42.269 ± 2.1045) μg/mL.     

Biochemical and Molecular Study of <Emphasis Type="Italic">Carpobrotus edulis</Emphasis> Bioactive Properties and Their Effects on <Emphasis Type="Italic">Dugesia sicula</Emphasis> (Turbellaria,Tricladida) Regeneration

The traditional medicinal properties of Carpobrotus edulis are well recognized, particularly in Tunisia where it is used for wound healing. Thus, in this study, biochemical and molecular properties of its leaves’ bioactive aqueous-acetone extract were investigated. The total phenolic content (TPC) of the extract was estimated to be 184 ± 5 mg/100 g of fresh matter (FM). The qualitative and quantitative polyphenolic profile was determined by ultra performance liquid chromatography with diode array detection (UPLC-DAD) and showed that chlorogenic acid was the major compound (43.7%). The extract exhibits potent antioxidant capacities with IC50 = 56.19 and 58.91 μg/ml, as accessed via the anionic DPPH and cationic ABTS radical scavenging assays, respectively. The extract has high antibacterial properties, especially against the Gram+ Staphylococcus aureus and Bacillus cereus strains. To investigate the extract effect on regeneration, the flatworm Dugesia sicula Lepori, 1948, was used as a model. The macroscopic analysis of planarian cultures in ordinary medium containing phenolic extract at non-toxic concentrations illustrated that the extract caused morphological changes. Additionally, the molecular study through the fluorescence-activated cell sorting (FACS) technique showed that C. edulis polyphenols can harm the stem cells’ development. These results emphasize the ecotoxicological impact of phenolic rejections in the environment on flatworms’ physiology.     

A GC-SIM-MS Method for the Determination of Butylidenephthalide in Rat Plasma and Tissue: Application to the Pharmacokinetic and Tissue Distribution Study

Abstract

Butylidenephthalide is one of the major active components isolated from Rhizoma Chuanxiong. This paper describes a simple, rapid, specific and sensitive method for the quantification of butylidenephthalide in rat plasma and tissue distribution using a liquid-liquid extraction procedure followed by capillary gas chromatography-selected ion monitoring mode-mass spectrometry (GC-SIM-MS) analysis. The calibration curves were linear over the concentration ranging from 0.02–10.0 µg/mL (r > 0.99) for plasma samples and 0.18–7.25 µg/g (r > 0.99) for the tissue samples. The limit of quantification (LOQ) was 1.0 ng/mL or 1.0 ng/g (ten times signal/noise ratio). Within- and between-day precisions expressed as the relative standard deviation (RSD) for the method were 2.39–2.98% and 2.97–4.26%, respectively. The methods of recovery for all samples were greater than 80% at the low, medium, and high concentrations. The method has been successfully applied to a pharmacokinetics study in rats after an oral administration of Butylidenephthalide with a dose of 20.0 mg/kg. The main pharmacokinetic parameters obtained were T _max  = (0.22 ± 0.06) h, C _max = (3 ± 1) µg/mL, AUC = (32 ± 6) h?µg/mL, and K _a  = (8.5 ± 0.8)/h. The results showed that the butylidenephthalide was easily absorbed. The concentrations of butylidenephthalide in rat kidney, lung, heart, and cerebellum were higher than those in other organs. To determine free fraction in serum, samples were filtered using ultrafiltration membranes with a molecular weight cut-off of 10,000 Da and extracted using liquid-liquid extraction. The extracts were evaporated and analyzed by GC-MS. The protein binding in rat plasma, human plasma, and human serum albumin were 83 ± 4%, 94 ± 3%, and 89 ± 3%, respectively.     

Chemical composition,antioxidant and antimicrobial activity of the essential oil from the leaves of Macleaya cordata (Willd) R. Br.

The essential oil from the leaves of Macleaya cordata R.Br. obtained by hydrodistillation was analysed by gas chromatography/mass spectrometry. Sixty-eight compounds consisting of up to 92.53% of the essential oil were identified. Antioxidant activities of the essential oil were evaluated by using DPPH radical scavenging and β-carotene–linoleic acid assays. The essential oil showed moderate antioxidant activity. In addition, the essential oil exhibited potential antimicrobial activity against all tested microorganisms, with diameters of inhibition zones ranging from 8.7 ± 0.5 to 17.2 ± 1.2 mm and minimum inhibitory concentration values from 125 to 500 μg/mL. We selected the most sensitive bacterium Staphylococcus aureus as model to observe of the action of essential oils of M. cordata on the membrane structure by scanning electron microscopy. The treated cell membranes were damaged severely. The results presented here indicate that the essential oil of M. cordata may be potential sources of antioxidant and antimicrobial agents in the future.