Water-insoluble Dye Research Articles

Complexes of 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane bromides with lanthanum nitrate: Aggregation and interaction with biomolecules

Aggregation of new multifunctional amphiphilic complexes of 1-alkyl-4-aza-1-azoniabicyclo[2.2.2]octane bromides (Alk = CnH2n+1, n = 14, 16, 18) with lanthanum nitrate, their solubilization activity and complexation ability toward biopolyanions, as well as antimicrobial properties have been studied to establish the influence of the structure of these compounds on the functional activity. The critical micelle concentration, aggregation numbers and size characteristics of metallosurfactant in aqueous solutions, complexation of metallosurfactants with oligonucleotide, DNA and bovine serum albumin (BSA) have been determined by fluorescence spectroscopy, spectrophotometry, dynamic and electrophoretic light scattering, and circular dichroism techniques. The results have been compared with the properties of metal-free surfactant (ligand), as well as the composition of ligand with inorganic salt. Beneficial effect of the metallosurfactants hydrophobicity on the solubilizing ability of metallomicellar solutions with respect to the water-insoluble dye Orange OT and the high complexing ability of metallomicelles with respect to the DNA decamer (oligonucleotide), DNA and BSA have been established. Metallocomplex bearing hexadecyl ligand effectively interacted with BSA and bound to the tryptophan amino acid residue of the polypeptide.

Спектральные зависимости оптического поглощения и показателя преломления композиции из родамина Б, в молекулярной форме иммобилизированного в полимерной пленке, от концентрации ионов свинца в воде

The dependence of the adsorption and refractometric parameters of a polymer composition containing rhodamine B in the molecular state on the concentration of lead ions is studied. The studied dependences are the basis of the rapid method for determining the concentration of lead ions in water, and its high sensitivity is shown to be 0.001 mg / l, which is lower than the maximum permissible concentration. The use of a water-insoluble dye as a material sensitive to the presence of lead ions shows the possibility of creating a stable sensor based on the studied effect. The application of the method of disturbed total internal reflection to determine the concentration of lead according to the above optical parameters is considered.

Functional properties of metallocomplexes with glucamine moiety/Ctab micellar systems

Mixed supramolecular systems alkylated N-methyl-d-glucamine (Alk = C n H2n+1, n = 12, 16)/cetyltrimethylammonium bromide (Ctab) (1:1) and a metallocomplex of alkylated N-methyl-d-glucamine with lanthanum (III) nitrate (La(NO3)3)/Ctab (1:1) were fabricated. Their aggregation behavior and functional activity (solubilization and biological properties) were studied. The aggregation parameters (critical micelle concentration, aggregation number and size and shape of aggregates) and solubilizing ability of the systems were determined by fluorimetry of pyrene, transmission electron microscopy and the solubilization of the water-insoluble dye Orange OT. A significant dependence of the micelle-forming properties of systems on the presence of hydrophobic probes was determined. There was an increase in the aggregation threshold of mixed systems in the presence of pyrene, and Orange OT had a beneficial effect on their structural rearrangement. The high solubilization activity of the mixed systems significantly exceeded that of individual Ctab solutions (up to 70 times). The antibacterial effect of N-methyl-d-glucamine derivatives was established.

Phase behavior and microstructure of sugar surfactant-ionic liquid microemulsions

Microemulsions have been explored as a unique and versatile reaction media for a variety of chemical reactions, viz. nanoparticle preparation, organic synthesis, bio-organic synthesis etc. The phase behavior and microstructure of a ternary system water/1-butyl-3-methylimidazolium hexafluorophosphate/Sugar Surfactant was studied as a function of temperature and sugar surfactant mass fraction, γ. In the present study, a hydrophobic ionic liquid 1-butyl-3-methylimidazolium hexafluorophosphate was used to replace commonly used organic solvents (n-alkanes) as an oil/non-polar phase substitute in ternary microemulsion formulations, wherein, a sugar based alkyl polyglycoside nonionic surfactant was used instead of a conventional nonionic surfactant (i.e., alkyl polyoxyethylene ether class) to solubilize hydrophobic ionic liquid and water. The effect of alkanols of variable chain length (octanol, decanol and dodecanol) as co-surfactant on the phase behavior and microstructure of ionic liquid/sugar surfactant/water ternary microemulsion systems was also investigated. The ability of nonionic sugar-based surfactant n-decyl β-D-maltoside, and n-dodecyl β-D-maltoside, to solubilize oil (hydrophobic ionic liquid) and water, i.e., was evaluated. Moreover, phase behavior and microstructure of ternary systems, 1-butyl-3-methylimidazolium tetrafluoroborate:water (1:1)/sugar surfactant/n-alkanes (alkanes of varying chain length, i.e., octane, decane and dodecane) was also studied. Solubilization of a water insoluble dye, Sudan Red, in selected microemulsion systems was also investigated.

Emulsion copolymerization of vinyl monomers from soybean and olive oil: Effect of counterpart aqueous solubility

Highly hydrophobic vinyl monomers from soybean (SBM) and olive (OVM) oil with different amounts of unsaturation were copolymerized in emulsion with significantly more soluble in water comonomers, methyl methacrylate (MMA), vinyl acetate (VA), and methyl acrylate (MA). Our intention was to demonstrate that higher aqueous solubility of the comonomer impacts the mechanism of the emulsion process by balancing latex particle homogeneous and heterogeneous (micellar) nucleation.Using an experimental method based on water insoluble dye Blue 70, it is shown that particle nucleation indeed depends to a great extent on aqueous solubility of the comonomer, along with the plant oil-based monomer (POBM) content in the feed. Upon addition of POBM into the monomer mixture with MMA (aq.solubility 1.5 wt%), the latex polymer particles originating from micellar nucleation essentially increased. In copolymerization of POBM with MA (aqueous solubility 4.9 wt%), this effect is even more pronounced. Those findings clearly indicate that copolymerization loci change when monomer feed hydrophobicity increases, and the magnitude of this effect is dependent on the comonomer aqueous solubility.Experimentally determined changes in reaction order with respect to emulsifier and initiator upon addition of POBM confirm that kinetics of emulsion copolymerization is impacted by comonomer aqueous solubility. The latter finding can be indicative of changing latex particle nucleation mode when monomer feed hydrophobicity changes.Overall, the portion of latex particles originating through micellar nucleation is higher in the copolymerization of more unsaturated SBM (with both MMA and MA) in comparison to OVM. No impact of POBM content on the reaction kinetics was observed in copolymerization with VA (aq. solubility 2.5 wt%). Here, high reactivity of growing PVA radicals in chain transfer reactions makes the presence of POBM in monomer feed kinetically irrelevant.

Influence of Kosmotropes and Chaotropes on the Krafft Temperature and Critical Micelle Concentration of Tetradecyltrimethylammonium Bromide in Aqueous Solution

The study aims to show the effect of some Hofmeister series anions on the Krafft temperature (TK) and the critical micelle concentration (CMC) of tetradecyltrimethylammonium bromide (TTAB) in aqueous solution. The TK of TTAB decreases in the presence of strong kosmotropes and moderate chaotropes but increases in the presence of strong chaotropes. Strong kosmotropes and moderate chaotropes remain hydrated in the bulk phase of the aqueous solution and promote dispersion of the surfactant. On the other hand, strong chaotropes form contact ion pairs with the cationic part of TTAB and exhibit salting out effects showing an increase in TK. The CMC of TTAB decreases in the presence of all ions irrespective of their chaotropic and kosmotropic nature. This can be ascribed to screening of the micelle surface charge by the added counterions. The standard Gibbs energy ( $$ \Delta G_{\text{m}}^{\text{o}} $$ ) of micellization was found to be negative, indicating spontaneity of the process. Solubilization of a water-insoluble dye, Sudan II in TTAB micelles, was quantified by the molar solubilization ratio (MSR). The MSR value was found to be higher in the presence of NaCl compared to that in pure water indicating that the added NaCl facilitated solubilization of the dye.

Synthesis, biological evaluation and structure-activity relationships of self-assembled and solubilization properties of amphiphilic quaternary ammonium derivatives of quinuclidine

This work deals with development of polyfunctional biocompatible cationic surfactant systems based on bioactive saturated bicyclic alkaloid quinuclidine. It is focused on the effect of the chemical structure of surfactants on their aggregation behavior, their physicochemical estimation of solubility of model water insoluble dye Orange OT and drugs, quercetin and rutin, microbiology and cytotoxicity. Quaternary ammonium derivatives of quinuclidine (Q-Nuc-n) with different hydrophobicity (R = CnH2n+1, where n = 14, 16, 18) were synthesized. Self-assembly of Q-Nuc-n was investigated by tensiometry, conductometry, spectrophotometry, fluorimetry and dynamic light scattering. The critical micelle concentration, thermodynamic and adsorption parameters at water-air interface, size and aggregation numbers of Q-Nuc-n micelles were determined. The looser packing of surfactant molecules in Q-Nuc-n micelles compared to its analogues, quaternized derivatives of 1,4‑diazabicyclo[2.2.2]octane (DABCO-n), was established. The hydrophobic dye Orange OT and drugs quercetin and rutin were solubilized in micellar Q-Nuc-n solutions better than in solutions of classical surfactant CTAB and its analogue DABCO-n. Solubilization capacity of Q-Nuc-18 is 5 times higher than that of classical surfactant CTAB. Q-Nuc-18 1.95 μg·mL−1 has also bactericidal and fungicidal activity 2 times (against S. aureus 209P) and 8 times (against B. cereus 8035) higher than antibiotics Norfloxacin and antifungal Ketoconazole. Q-Nuc-16 has the highest bactericidal activity. It is 6 times (against S. aureus 209P) and 15 times (against B. cereus 8035) higher than the bactericidal activity value of Norfloxacin. Synthesized cationic surfactants based on quinuclidine are new multifunctional biocompatible compounds with high potential in nanomedicine and biotechnology.

Biocompatible Unimolecular Micelles Obtained via the Passerini Reaction as Versatile Nanocarriers for Potential Medical Applications.

A Passerini three-component polymerization was performed for the synthesis of amphiphilic star-shaped block copolymers with hydrophobic cores and hydrophilic coronae. The degree of polymerization of the hydrophobic core was varied from 5 to 10 repeating units, and the side chain ends were conjugated by performing a Passerini-3CR with PEG-isocyanide and PEG-aldehyde (950 g/mol). The resulting amphiphilic star-shaped block copolymers contained thioether groups, which could be oxidized to sulfones in order to further tune the polarity of the polymer chains. The ability of the amphiphilic copolymers to act as unimolecular micellar encapsulants was tested with the water-insoluble dye Orange II, the water-soluble dye Para Red and the macrolide antibiotic azithromycin. The results showed that the new copolymers were able to retain drug cargo at pH levels corresponding to circulating blood and selectively release therapeutically effective doses of antibiotic as measured by bacterial cell kill. The polymers were also well-tolerated by differentiated THP-1 macrophages in the absence of encapsulated drugs.

Complexes of 1-hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide with transition metal nitrates. Micelle-forming, solubilizing, and adsorption properties

Amphiphilic complexes of 1-hexadecyl-4-aza-1-azoniabicyclo[2.2.2]octane bromide (D-16) with nitrates of transition metals (La3+, Cu2+, Ni2+, and Co2+) have been synthesized and characterized. Absorption spectrophotometry in the UV, visible, and IR regions, as well as 1Н NMR spectroscopy, have been employed to study their spectral properties in water and organic media. Adsorption properties and micelleforming and solubilizing abilities of the amphiphilic complexes have been investigated in aqueous solutions by the methods of tensiometry and conductometry, as well as by solubilization of a water-insoluble dye (Orange OT). The values of the critical micelle concentration, adsorption parameters at a water/air interface, and solubilization capacity S of complex micelles have been determined. It has been shown that the most pronounced decrease in the critical micelle concentration (as large as two to three times) and differences in the adsorption characteristics and the S values as compared with those of ligand D-16 are observed for complexes of copper and lanthanum. The S values for these complexes are 1.3−2.5 and 3−6.5 times higher than those for D-16 and cetyltrimethylammonium bromide, respectively.

Nile red nanosuspensions as investigative model to study the follicular targeting of drug nanocrystals

The strategy of formulating poorly soluble actives as nanosuspension has been explored by more than a thousand research papers, with some medicinal products for oral and intravenous use having reached the market or advanced clinical trials. Interestingly, there is a limited number of reports of nanosuspensions formulated for dermal and transdermal drug delivery. In the present work, a nanocrystals suspension of the fluorescent, water-insoluble dye Nile Red, is prepared through a media milling technique and exploited to characterize the fate of the nanosuspended drug when applied on the skin. More in detail, the accumulation of Nile Red nanocrystals inside the hair follicles is evidenced by scanning electron microscopy, and the diffusion of drug molecules in the different skin layers is evaluated by confocal microscopy and skin permeation studies. Overall, the combination of the analytical techniques provide a description of the mechanisms underlying dermal accumulation, and transdermal penetration of a drug formulated as a nanosuspension.

Targeted Plasma Membrane Delivery of a Hydrophobic Cargo Encapsulated in a Liquid Crystal Nanoparticle Carrier

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. Recently, nanoparticles (NPs) have shown significant promise in the development of such delivery systems. Here, a liquid crystal NP (LCNP)-based delivery system has been employed for the controlled delivery of a water-insoluble dye, 3,3′-dioctadecyloxacarbocyanine perchlorate (DiO), from within the NP core to the hydrophobic region of a plasma membrane bilayer. During the synthesis of the NPs, the dye was efficiently incorporated into the hydrophobic LCNP core, as confirmed by multiple spectroscopic analyses. Conjugation of a PEGylated cholesterol derivative to the NP surface (DiO-LCNP-PEG-Chol) enabled the binding of the dye-loaded NPs to the plasma membrane in HEK 293T/17 cells. Time-resolved laser scanning confocal microscopy and Förster resonance energy transfer (FRET) imaging confirmed the passive efflux of DiO from the LCNP core and its insertion into the plasma membrane bilayer. Finally, the delivery of DiO as a LCNP-PEG-Chol attenuated the cytotoxicity of DiO; the NP form of DiO exhibited ~30-40% less toxicity compared to DiOfree delivered from bulk solution. This approach demonstrates the utility of the LCNP platform as an efficient modality for the membrane-specific delivery and modulation of hydrophobic molecular cargos.

Targeted Plasma Membrane Delivery of a Hydrophobic Cargo Encapsulated in a Liquid Crystal Nanoparticle Carrier.

The controlled delivery of drug/imaging agents to cells is critical for the development of therapeutics and for the study of cellular signaling processes. Recently, nanoparticles (NPs) have shown significant promise in the development of such delivery systems. Here, a liquid crystal NP (LCNP)-based delivery system has been employed for the controlled delivery of a water-insoluble dye, 3,3'-dioctadecyloxacarbocyanine perchlorate (DiO), from within the NP core to the hydrophobic region of a plasma membrane bilayer. During the synthesis of the NPs, the dye was efficiently incorporated into the hydrophobic LCNP core, as confirmed by multiple spectroscopic analyses. Conjugation of a PEGylated cholesterol derivative to the NP surface (DiO-LCNP-PEG-Chol) enabled the binding of the dye-loaded NPs to the plasma membrane in HEK 293T/17 cells. Time-resolved laser scanning confocal microscopy and Förster resonance energy transfer (FRET) imaging confirmed the passive efflux of DiO from the LCNP core and its insertion into the plasma membrane bilayer. Finally, the delivery of DiO as a LCNP-PEG-Chol attenuated the cytotoxicity of DiO; the NP form of DiO exhibited ~30-40% less toxicity compared to DiOfree delivered from bulk solution. This approach demonstrates the utility of the LCNP platform as an efficient modality for the membrane-specific delivery and modulation of hydrophobic molecular cargos.

Use of hybrid composite particles prepared using alkoxysilane-functionalized amphiphilic polymer precursors for simultaneous removal of various pollutants from water

In this study, we present new inorganic-organic hybrid particles and their possible application as an adsorbent for simultaneous removal of hydrophobic and hydrophilic pollutants from water. These hybrid particles were prepared using tailor-made alkoxysilane-functionalized amphiphilic polymer precursors (M-APAS), which have amphiphilic polymers and reactive alkoxysilane groups attached to the same backbone. Through a single conventional sol-gel process, the polymerization of M-APAS and the chemical conjugation of M-APAS onto silica nanoparticles was simultaneous, resulting in the formation of hybrid particles (M-APAS-SiO2) comprised of hyperbranch-like amphiphilic polymers bonded onto silica nanoparticles with a relatively high grafting efficiency. A test for the adsorption of water-soluble dye (organe-16) and water insoluble dye (solvent blue-35) onto the hybrid particles was performed to evaluate the possibility of adsorbing hydrophilic and hydrophobic compound within the same particle. The hybrid particle was also evaluated as an adsorbent for the removal of contaminated water containing various pollutants by wastewater treatment test. The hybrid particle could remove phenolic compounds from wastewater and the azo dye reactive orange-16 from aqueous solutions, and it was easily separated from the treated wastewater because of the different densities involved. These results demonstrate that the hybrid particles are a promising sorbent for hydrophilic and/or hydrophobic pollutants in water.

Effects of Added Salts on Surface Tension and Aggregation of Crown Ether Surfactants.

Two crown ether surfactants, dodecanoyloxymethyl- (C11Φ6) and octanoyloxymethyl-18-crown-6 (C7Φ6), were synthesized and the surface tension dependence on surfactant concentration of their aqueous solutions was measured both in the absence and presence of alkali chlorides to confirm the critical micelle concentration (CMC) is highest for the added cation that have an ionic diameter comparable to the hole size of the crown ether ring and that several break points on the surface tension vs. concentration curves occur for these crown ether surfactants. For C11Φ6 and C7Φ6, in the absence of salt, the surface tension vs. concentration curves had two break points. Using the solubilization of a water-insoluble dye as an indicator, we found that the break point at the higher concentration (m0) for C7Φ6 was due to micelle formation. Two break points were also observed for the aqueous solution of C11Φ6 in the presence of NaCl, KCl, RbCl, and CsCl salts at concentrations of 0.22 mol kg(-1) and for C7Φ6 with 0.22 mol kg(-1) KCl added. The CMC (m0) was found to be the highest for solutions containing K(+) salts because K(+) has an ionic diameter comparable to the hole size of 18-crown-6 ring. Furthermore, the CMC decreased as the ionic diameters of the added cations deviated from the hole size. The molecular areas at two break points, estimated by the Gibbs adsorption isotherm, except for that at the break point at mI of C7Φ6, were very small for an adsorbed monolayer. Further investigation is required to elucidate the reason for the break point at mI.

Effects of added salts on adsorbed film and premicelle formation of crown ether surfactants

Abstract Two crown ether surfactants, dodecanoyloxymethyl- (C11Φ5) and octanoyloxymethyl-15-crown-5 (C7Φ5), were synthesized and the concentration dependence of surface tension of their aqueous solutions was measured in the absence and the presence of various salts to study the effect of coexistent cation on adsorbed film and aggregation behavior of crown ether surfactants. In the absence of salt, the surface tension vs. concentration curves had two break points for both C11Φ5 and C7Φ5. The break point at the higher concentration (m0) was confirmed to be attributed to the micelle formation by the solubilization of water-insoluble dye and the concentration dependence of proton chemical shifts. Another break point at the lower concentration (mI) would be caused by the formation of premicellar aggregates. For C11Φ5 in the presence of KCl two break points were also observed. At about 0.05 mol kg−1 KCl, m0 and mI were minimized. The cause would be that the salting-out effect of KCl dominates below 0.05 mol kg−1 but above it the repulsive interaction between charged head groups of C11Φ5 complex with K+ becomes larger than it. Two break points were also observed for C11Φ5 in the presence of LiCl, NaCl, CsCl and NH4Cl of 0.22 mol kg−1. It has been found that the critical micelle concentration (m0) are the highest for Na+ having an ionic diameter comparable to the hole size of 15-crown-5 ring and decrease as an ionic diameter of added cation departs from the hole size. The aggregation number of premicelle, which was estimated from the surface excesses at mI and m0 on the assumption of two step micellization, has been about 4 in the absence of salt, about 3 for Li+ hydrated strongly and about 2 for all other cations.

Photocatalytic disassembly of tertiary amine-based dendrimers to monomers and their application to the ‘catch and release’ of a dye in aqueous solution

Covalent bond disassembly of tertiary amine based dendrimers and their application to the ‘catch and release’ of a water-insoluble dye are reported.

Going deep: Single cell physiology and cell function

function as well as killing assays is of relevance in manyhigh-throughput assays where numerous different effectors,targets, or treatments have to be analyzed. In order to quanti-tate cell function modification by chemical or biologicalagents, several cell-based assays have been developed in thepast. For example, standardized polychromatic (11-color)cytokine expression assays are available to simultaneouslymeasure the intracellular production of five (1) or more cyto-kines in combination with phenotypic markers. Intracellularsignaling patterns can be investigated also, using multiplexedphosphoflow assays (2). In addition, for reliable quantitation,new multiplexed assays are in demand to reduce the numberof assays required, as well as the number of animals needed forreliable results.Inosine triphosphatase (ITPase) polymorphism has beenassociated with several diseases as well as advantageous or dis-advantageous response to therapy. In most studies ITPaseexpression was measured in erythrocyte lysates. However, itwas found that leukocytes express ITPase at substantiallyhigher levels than erythrocytes. Vroemen and coworkers fromHeerlen and Maastricht, The Netherlands (this issue, page672) investigated differences in ITPase levels in different leu-kocyte subsets of human volunteers. To this end, they devel-oped the first polychromatic flow cytometry assays to identifycell phenotypes and quantitate their ITPase expression levels.The authors found that all leukocyte subsets express ITPase.However, expression level was higher in activated monocytesand granulocytes as compared to lymphocytes. These assaysmay help in diseases where ITPase polymorphism plays a rolein order to improve our understanding of disease mechanismsand potentially produce new diagnostic tools for individua-lized therapy.The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazoliumbromide) (MTT) assay is a very commonly used cell-basedvitality assay for high-throughput drug screening. It is based onthe reduction of the yellow water soluble dye MTT into a blueviolet water insoluble dye, formazane (3). Now, Lim and co-workers from the Universities of Seoul and Kongju in Korea(this issue, page 691) developed a microfluidic image cytome-try-based method. Their measurements are multiplexed in thatthey do not only quantitate (on the single cell basis) the meta-bolization of MTT but in addition, also detect cell morphologi-cal changes. This assay was used to test cadmium (Cd

Characterization and encapsulation efficiency of rhamnolipid vesicles with cholesterol addition

The effect of cholesterol on the vesicle formation of a rhamnolipid biosurfactant extracted from the liquid culture of Pseudomonas aeruginosa SP4 was investigated. The rhamnolipid vesicles were prepared in a phosphate-buffer saline (PBS) solution (pH 7.4) at a biosurfactant concentration of 2.6mM, or 6.5 times the critical micelle concentration (CMC), with various amounts of cholesterol. The biosurfactant solution was characterized using turbidity, zeta potential, and dynamic light scattering (DLS) measurements. The morphology of the rhamnolipid vesicles formed at different cholesterol concentrations was examined with the use of transmission electron microscopy (TEM). The results showed that the rhamnolipid biosurfactant formed spherical vesicles both in the absence and presence of cholesterol, but the incorporation of the cholesterol into the bilayer membrane reduced the vesicle size. Sudan III, a water-insoluble dye, was used as a model hydrophobic compound in the encapsulation experiment. The encapsulation efficiency (E%) of the rhamnolipid vesicles was affected by the cholesterol concentration and the initial Sudan III concentration. The maximum E% of nearly 90% was achieved at the cholesterol concentration of 100μM and the initial Sudan III concentration of 8.8μM.

NUCLEATION PROCESS AND NUCLEATION MECHANISM OF MMA/BA SEEDED SEMI-CONTINUOUS EMULSION POLYMERIZATION

A water-insoluble dye(BL-S)was used as a probe to study the influence of some factors on the process of nucleation and nucleation mechanism in seeded semi-continuous emulsion polymerization.Some parameters were analysed for quantitative study on nucleation mechanisms,the parameters include the amount of dye incorporated into the resultant latex particles(P_dye),number of the resultant latex particles(Nc_p)and the different numbers of particles which are formed by micellar nucleation(N_m)and homogeneous nucleation(N_h).The results of the study and analysis show that P_dye,N_h,N_m and N_h/Nc_p all increase with increasing initiator concentration [I],but N_m/Nc_p decreases as N_m/Nc_p=-0.0262[I]+0.8833,which can illuminate the proportion of homogeneous nucleation increases while micellar nucleation decreases with increasing [I].The influence of the emulsifier concentration [E] on nucleation mechanisms is different at different concentration range,when [E] equals to 0.7216×10-2 mol·L-1,the proportion of homogeneous nucleation is equal to micellar nucleation,both of them are 50%.When [E] is greater than 0.7216×10-2 mol·L-1,the nucleation time t_1,2 decreases and N_m/Nc_p increases with increasing [E],N_h/Nc_p decreases accordingly,and the proportion of micellar nucleation is larger than homogeneous nucleation,so that the micellar nucleation mechanism predominates gradually in the particle nucleation process;when [E] is less than 0.7216×10-2 mol·L-1,the proportion of micellar nucleation is less than homogeneous nucleation,the main nucleation mechanism becomes to homogeneous nucleation.In the system of MMA/BA copolymerization,when f_MMA increases from zero to 0.6,the value of N_m/Nc_p decreases from 80.93%to 50%,which means that the proportion of micellar nucleation is larger than that of homogeneous nucleation,so that micellar nucleation plays a key role in the particle formation period.When f_MMA increases from 0.6 to 1,N_m/Nc_p is reduced to 40% and N_h/Nc_p is raised to 60%,but homogeneous nucleation is more important than micellar nucleation in this system.In addition,the t_1,2 is 12 min and 6 min for the conventional and seeded semi-continuous emulsion polymerization,respectively,but P_dye change is less.All these show that the both semi-continuous emulsion polymerization techniques only have some effect on the formation process of particles and the neculeation time,but little effect on their specific nucleation.

Solution properties and vesicle formation of rhamnolipid biosurfactants produced by Pseudomonas aeruginosa SP4

A biosurfactant produced by Pseudomonas aeruginosa strain SP4 was previously reported as a mixture of 11 types of rhamnolipid compounds. Among them, the major component in the biosurfactant was characterized as l-rhamnosyl-3-hydroxydecanoyl-3-hydroxydecanoate, or monorhamnolipid (Rha–C 10–C 10). In this present study, solution properties of the biosurfactant were investigated in a phosphate-buffer saline (PBS) solution (pH 7.4) by using surface tension, turbidity, electrical conductivity, and dynamic light scattering (DLS) measurements. It was found that spherical biosurfactant vesicles of various sizes (ranging from 50 to larger than 250 nm) were spontaneously formed at a biosurfactant concentration greater than its critical micelle concentration (CMC), which was 200 mg/l. The encapsulation efficiency ( E%) of the biosurfactant vesicles was preliminarily studied by using Sudan III, a water-insoluble dye, as a model hydrophobic substance. The obtained results showed that the vesicle formed in the PBS solution at a biosurfactant concentration of 1280 mg/l could entrap about 10% of the initial hydrophobic dye concentration. The effects of salt and alcohol on the vesicle formation of the biosurfactant and its encapsulation efficiency were also observed by using sodium chloride (NaCl) and ethanol (C 2H 5OH), respectively. In the presence of either NaCl or C 2H 5OH, the vesicle size was reduced from larger than 250 nm to 50–250 nm. The encapsulation efficiency of the biosurfactant vesicle was slightly influenced by the addition of NaCl, but was significantly increased, up to nearly 30%, in the presence of C 2H 5OH.