Micellar Molecular Weight Research Articles

A Comprehensive Review on the Creation, Description, and Utilization of Surfactants Containing Multiple Hydroxyl Groups

The stereoselective synthesis of biobased nonionic sugar surfactants (polyhydroxy surfactants), which are thought to be safer, more affordable, plentiful, biodegradable, biocompatible, and possess mildness and performance in formulation, is becoming increasingly popular as people become more aware of the potential negative effects of conventional surfactants on the environment and human health. Reviewing the stereoselective synthesis of polyhydroxy surfactants is the objective of this article. Additionally, it emphasizes the synthesis and application of sugar‐based surfactants in everyday life, as well as their description and the influence of outside factors. A thorough assessment of the literature on biobased polyhydroxy surfactants including alkyl polyglycosides, sorbitol esters, sucrose esters, fatty acid glucamides, and methyl glucosides was studied for methodology. The characterization of the surfactants shows an exponential increase in electrical conductivity when there is an increase in the water volume fraction. The surface tension also showed a linear relationship with surfactant concentration, such that as the concentration increases, the surface tension of the solution decreases. The effect of external parameters on polyhydroxy surfactants was also studied, which shows that increasing temperature favors micellization initiation at a lower concentration. Likewise, the micellar molecular weight and the hydration per unit mass of the surfactants decrease with an increase in the pH value. Evidence to further support these biobased surfactants as substitutes for their petrochemical counterparts is advantageous as worldwide legislation and user requirements for sustainability and safety expand.

Some relations between dissolution rates and physical parameters of a drug in aqueous micellar solutions of a non-ionic surfactant

Dissolution rates of salicylic acid from a constant surface area into a series of aqueous micellar polysorbate 20 solutions at pH 1-0 to 4-0 have been measured using two different methods; a stirred beaker and a rotating disc technique. The micellar molecular weight of polysorbate 20 has been obtained from light scattering and differential refractometry data and used with other independently determined physical data to calculate diffusion coefficients of the diffusing species. Linear multiple regression analysis was used to assess the dependence of drug dissolution rate on the diffusion coefficient and the viscosity of the dissolution medium.

Membrane osmometry of solubilized systems.

Abstract The solubilization of decane, ethyl p-hydroxybenzoate, methyl anisate and p-hydroxybenzoic acid by aqueous micellar solutions of cetomacrogol 1000 has been examined by membrane osmometry and viscosity techniques. The effect of the solubilizates on the number-average micellar molecular weight, Mn, has been related to their site of incorporation in the micelle. Decane and methyl anisate are solubilized in the hydrocarbon core of the micelles and both compounds produce an increase in Mn up to a maximum value of 2·0 times 105, at a solubilizate concentration of approximately 80% of the saturation limit for each compound. This increase is shown to result from an increase in the number of molecules of both solubilizate and of surfactant per micelle. Further addition of solubilizate, to produce a saturation level in excess of 80%, results in a decrease in micellar size in both systems. The solubilization of ethyl p-hydroxybenzoate and p-hydroxybenzoic acid is thought to involve the oxyethylene region of the micelle and both solubilizates cause an increase in Mn owing to the inclusion of solubilizate into the micelle, the number of molecules of surfactant per micelle being unaffected by the solubilization process. Viscosity studies on the decane-ceto-macrogol-water system are interpreted as indicating no change in either micellar symmetry or hydration as a result of solubilization. A spherical model for the micelles is shown to be consistent with the experimental data.

Prediction of the micellar molecular weight and thermodynamics of micellization of mixtures of alkyltrimethylammonium salts

Journal Article Prediction of the micellar molecular weight and thermodynamics of micellization of mixtures of alkyltrimethylammonium salts Get access B W BARRY, B W BARRY School of Pharmacy, Portsmouth Polytechnic, Park Road, Portsmouth, PO1 2QQ, UK Search for other works by this author on: Oxford Academic Google Scholar G F J RUSSELL G F J RUSSELL School of Pharmacy, Portsmouth Polytechnic, Park Road, Portsmouth, PO1 2QQ, UK Search for other works by this author on: Oxford Academic Google Scholar Journal of Pharmacy and Pharmacology, Volume 23, Issue Supplement_1, December 1971, Pages 241S–242S, https://doi.org/10.1111/j.2042-7158.1971.tb08829.x Published: 12 April 2011

PH-triggered block copolymer micelles based on a pH-responsive PDPA (poly[2-(diisopropylamino)ethyl methacrylate]) inner core and a PEO (poly(ethylene oxide)) outer shell as a potential tool for the cancer therapy

The potential of a novel pH-triggered block copolymer as a promising drug delivery platform for the cancer therapy has been explored. The block copolymer poly(ethylene oxide)-b-poly(glycerol monomethacrylate)-b-poly[2-(diisopropylamino)ethyl methacrylate] herein referred to as PEO113-b-PG2MA30-b-PDPA50 upon dissolution in ethanol followed by single-step nanoprecipitation in phosphate buffered saline (PBS) self-assembled into highly regular spherical micelles whose structure was characterized in detail by static (SLS), dynamic (DLS) and electrophoretic (ELS) light scattering, small angle X-ray scattering (SAXS), fluorescence spectroscopy and transmission electron microscopy (TEM). The micellar size (2RH = 42 nm) and micellar molecular weight (Mw(micelles) > 106 kDa) were found to be in the range to avoid renal clearance providing a long blood circulation time. Their size is below the cut-off size of the leaky pathological vasculature (DH < 200 nm), making them candidates for the use in cancer therapy based on the EPR effect. The pH-responsive PDPA core could be loaded with the poorly water-soluble anti-cancer drug paclitaxel (PTX) with encapsulation efficiency ∼70% and drug loading content ∼7% wdrug/wpolymer. The pKa of the diisopropylamino group of the PDPA block was determined as pKa = 6.8 in the simulated physiological condition, which is remarkably close to the pH microenvironment of tumoral cells. The release experiments evidenced that approximately 90% of the encapsulated PTX was sustained at the PDPA micellar core within the first 9 h at pH 7.4 whilst only 18 h were required for complete drug release at pH 5.0. These results suggest that the micellar dissociation might be triggered at the slightly acid tumoral extracellular environments (pH < pKa(PDPA)). The nanostructures were further placed in contact with human plasma or human serum albumin (HSA) diluted in PBS. The DLS experiments revealed that the micelles are especially stable for up to at least 48 h in such conditions, attesting the possibly long blood circulation time of the nanoparticles at serum environments which is a pre-requisite for the drug delivery applications. The cell viability experiments demonstrated that the drug-free block copolymer micelles are non-toxic and the number of viable cells is always greater than 85% compared to the survival number of a control group.

Self-association properties of 4-[1-hydroxy-1-methylethyl]-2-propyl-1-[4-[2-[tetrazole-5-yl]phenyl]phenyl] methylimidazole-5-carboxylic acid monohydrate (CS-088), an antiglaucoma ophthalmic agent

Self-association properties of CS-088, an antiglaucoma ophthalmic agent, were investigated. Various analytical methods, such as surface tension measurement, demonstrated that CS-088 is a self-associating compound with critical micellar concentration (CMC) of approximately 10 mg/mL. Light scattering analysis revealed that the micellar molecular weight (MMW) of CS-088 aggregates well above the CMC was approximately 2260, corresponding to a pentamer. In addition, the MMW corresponding to a dimer was detected by NMR spectroscopy, indicating that self-association of monomers to pentamers is via the formation of dimers. According to the Stokes–Einstein equation, hydrodynamic radii of the dimer and pentamer were calculated to be 0.87 and 1.16 nm, respectively. The concentration-dependent change in the NMR chemical shift indicated that hydrophobic interaction between biphenyl groups is an important factor in the self-association of CS-088 molecules. Furthermore, measurement of particle size distribution using a Nicomp Submicron Particle-Sizer revealed that the addition of either n-propanol or urea to CS-088 solution led to monomerization of the dimers and pentamers, suggesting that not only hydrophobic interaction but also hydrogen bonding is involved in stabilizing CS-088 aggregates. No bigger aggregate than a pentamer was formed in the absence of NaCl, whereas further aggregation was observed with increasing concentrations of NaCl.

Polyion complex micelles from plasmid DNA and poly(ethylene glycol)–poly( l-lysine) block copolymer as serum-tolerable polyplex system: physicochemical properties of micelles relevant to gene transfection efficiency

Polyion complex (PIC) micelles composed of the poly(ethylene glycol)–poly( l-lysine) (PEG–PLL) block copolymer and plasmid DNA (pDNA) were investigated in this study from a physicochemical viewpoint to get insight into the structural feature of the PIC micellar vector system to show practical gene transfection efficacy particularly under serum-containing medium. The residual ratio ( r) of the lysine units in PEG–PLL to the phosphate units of pDNA in the system significantly affects the size of the PIC micelles evaluated from dynamic light scattering, being decreased from approximately 120 to 80 nm with an increase in the r value for the region with r⩾1.0. The zeta potential of the complexes slightly increased with r in the same region, yet maintained a very small absolute value and leveled off to a few mV at r≈2.0. These results suggest that the micelles are most likely to take the core-shell structure with dense PEG palisades surrounding the PIC core to compartmentalize the condensed pDNA. Furthermore, an increasing r value in the region of r⩾1 induces a rearrangement of the stoichiometric complex formed at r=1.0 to the non-stoichiometric complex composed of the excess block copolymer. The association number of pDNA and the block copolymer in the micelle was estimated from the apparent micellar molecular weight determined by static light scattering measurements, indicating that a single pDNA molecule was incorporated in each of the micelles prepared from the PEG ( M w=12,000 g/mol)–PLL (polymerization degree of PLL segment: 48) (12-48) block copolymer at r=2.0. These 12-48/pDNA micelles showed a gene expression comparable to the lipofection toward cultured 293 cells, though 100 μ m chloroquine was required in the transfection medium. Notably, even in the presence of serum, the PIC micelles achieved appreciable cellular association to attain a high gene expression, which is in sharp contrast with the drastic decrease in the gene expression for lipoplex system in the presence of serum. A virus-comparable size (∼100 nm) with a serum-tolerable property of the PIC micelles indeed suggests their promising feasibility as non-viral gene-vector systems used for clinical gene therapy.

Influence of Hydrophobic Cosolutes on the Associative/Segregative Phase Separation of Aqueous Cationic Surfactant−Polymer Systems

The effect of hydrophobic cosolutes on the phase behavior for a cationic surfactant and charged polymer in water has been studied. With a similarly charged polymer (cationic), the phase separation is of the segregative type with one surfactant-rich phase in equilibrium with a polymer-rich phase. Addition of small amounts of octane to such a system significantly increases the compatibility; that is, the two-phase region is reduced. If a long-chain alcohol like octanol is added, the incompatibility is enhanced. The effect is attributed to changes in the micellar aggregation number and is essentially a molecular weight effect. Octane reduces the micellar molecular weight, while octanol causes an increase. With an oppositely charged polymer (anionic), the phase separation is associative with a concentrated polymer/surfactant phase in equilibrium with a water phase. For a system that has phase-separated associatively, the addition of hydrophobic cosolutes produces little effect.

Correlation between Micellar Structure and Cloud Point in Long Poly(oxyethylene)n Oleyl Ether Systems

Phase behavior, micellar structure, and cloud point have been investigated in water/long poly(oxyethylene)n oleyl ether (C18:1EOn) (n = 10.7, 19.2, 30.1, and 50.8) systems. With increasing n, the discontinuous micellar cubic phase (I1) becomes increasingly stable, effectively replacing hexagonal and lamellar liquid crystalline phases. From NMR self-diffusion measurements in the liquid micellar phase at lower concentrations, we found that micelles at larger n remain spherical and interact to a good approximation as hard spheres up to crystallization. In the cubic phase, small-angle X-ray data indicate a body-centered cubic arrangement. The aggregation number of the micelles monotonically decreases with increasing EO chain length, but the micellar molecular weight first decreases and then turns to increase at a certain EO chain length because of the increase of molecular weight of the surfactant molecule. As a result, the cloud point first increases with increasing EO chain length, reaches a maximum, and th...

Electrolyte-Induced Structural Evolution of Triton X-100 Micelles

The long-time self-diffusion coefficients of Triton X-100 micelles have been determined as a function of surfactant and electrolyte concentrations using rotating disk electrode voltammetry in conjunction with ferrocene acting as an electroactive probe. Micellar diffusion conforms to the linear interaction theory and yields micellar hydrodynamic radii values and interaction parameters as a function of electrolyte concentration. The interaction parameters varied from 3.4 to 3.6 over the electrolyte concentration range 0.01−0.8 mol dm-3 KCl, which is consistent with excluded volume interactions and indicated the absence of significant micellar shape changes with the addition of electrolyte. Micellar hydrodynamic radii varied linearly with respect to [KCl] from 4.22 to 6.21 nm, indicating the progressive evolutionary growth of the oblate micelles due to increasing aggregation number and “hydration”. The semimajor to semiminor axial ratio (a/b) increased from 2.0 to 3.5, indicating evolution to a more asymmetric structure. Micellar molecular weights increased from 77 700 to 326 000 over the electrolyte concentration range studied, which is predominantly due to water entrapment at the periphery of the self-assembled structures. Intrinsic viscosities were found to decrease from 6.09 to 4.61 cm3 g-1, indicating a decrease in specific micellar volume, which may be attributed to ethylene oxide chain collapse due to dehydration. The decrease in micellar specific volume was found to correlate precisely with the electrolyte induced decrease of the cloud point.

Effect of Anions from the Hofmeister Series and Urea on the Binding of the Charged and Uncharged Forms of the Local Anesthetic Tetracaine to Zwitterionic Micelles*

ABSTRACTIt is widely known that ions in the aqueous phase affect the binding of charged solutes to membranes. Here we report the effect of ions and urea on the interaction of both the charged and uncharged forms of the local anesthetic tetracaine (TTC, an aminoester derivative of ben‐zoic acid) to zwitterionic micelles. Binding was monitored by the increase in TTC fluorescence. Shifts in the emission wavelength maximum (δmax) indicated that the anesthetic was located in an environment of lower polarity. The neutral form of TTC bound to micelles to a larger extent than the protonated form, in agreement with results found for lipid bilayers (Boulanger, Leitch, Schreier and Smith, Can. J. Biochem. 58, 986–995, 1980). When ions from the Hofmeister series and urea were compared in their ability to affect the partitioning of the anesthetic, binding of both the charged and uncharged forms was found to increase upon addition of SO42– and CI− but was seen to decrease in the presence of SCN−, CIO4−‐ and urea. Solubility measurements revealed that the solubility of uncharged TTC increases in solutions containing the additives in the following order: SO42– &lt; CI− &lt; CIO4−‐ &lt; dilute buffer &lt; SCN− &lt; urea. Spin label EPR spectra indicated that, except for CIO4−‐, the ions had little effect on micellar structure. Static light scattering measurements corroborated this result indicating a large increase in micellar molecular weight in the presence of CIO4−‐ and lesser increases for CI.‐ and SCN−. The results show that, besides affecting the binding of ionic species through an electrostatic mechanism, ions also act by altering water structure and, as a consequence, the water solubility and the tendency to partition into the less polar micellar environment of polar charged or uncharged small organic solutes such as the benzoic acid ester derivative. Moreover, evidence suggests that the ions bind directly to the zwitterionic polar groups of the micelles, leading to changes in structure and size.

Effect of Inorganic Additives on Solutions of Nonionic Surfactants: X. Micellar Properties

The study of the interaction between electrolytes and nonionic surfactants was extended to the micellar properties of octoxynol 9 at 25°C. Density, surface tension, viscosity, and static and dynamic light scattering were measured in water (where dilute octoxynol solutions had a cloud point of 64°C), in a salting-out electrolyte, 0.40 m Na 2SO 4 (cloud point lowering = 28°C), and in the salting-in electrolytes 1.80 m NaSCN (cloud point increase = 27°C) and 2.00 m Mg(NO 3) 2 (cloud point increase = 14°C). The intrinsic viscosity of octoxynol in Na 2SO 4 was twice as large as in water and NaSCN, the diffusion coefficient was 2.5 times smaller, the micellar molecular weight was 5 and 14 times larger than in water and NaSCN, respectively, and the micellar hydration was at least twice as large. The micellar properties in Mg(NO 3) 2 differed from those in the other three media: The partial specific volumes in the latter were independent of surfactant concentration and had comparable values, while decreasing significantly with increasing surfactant concentration in the former. The micellar molecular weights and aggregation numbers were nearly the same in Mg(NO 3) 2 and NaSCN and amounted to ≈ 1 3 of the corresponding values in water; the intrinsic viscosities were 98 and 83% of that in water, respectively, while the micellar diffusion coefficients at infinite dilution were 59 and 120%. The apparent diffusion coefficients in Mg(NO 3) 2 increased slightly with increasing surfactant concentration while decreasing in the other three media. Only in Mg(NO 3) 2 did the micellar hydration increase with increasing surfactant concentration. These observations point to micellar binding of Mg(NO 3) 2, presumably via complexation of Mg 2+ ions by the ether oxygens of the micellar polyoxyethylene moieties, which rendered the surfactant somewhat cationic.

Spherical and Rod SDS Micelles

Experimental procedure using light-scattering intensity measured with a spectrofluoroimeter to determine micellar molecular weight, shape, and dimensions; includes data and analysis.

Aggregation properties of GD1b, II 3Neu5Ac 2GgOse 4Cer, and of GD1b-lactone, II 3[α-Neu5Ac-(2→8, 1→9)-α-Neu5Ac]GgOse 4Cer, in aqueous solution

The relevance of the presence of an inner ester in the oligosaccharide chain on the aggregative properties of gangliosides is investigated. Micellar molecular weight and hydrodynamic radius of natural GD1b and of semisynthetic GD1b-lactone are measured by the laser light scattering technique. The presence of the lactone ring causes an increase of 36% for the molecular weight and 16% for the hydrodynamic radius. Measurements on mixtures of GD1b and GD1b-lactone show that mixed micelles are formed with microdomain structure. The results are interpreted in terms of the geometrical packing model for the aggregation of amphiphilic molecules and are correlated to membrane processes.

Purification of octyl β- d-glucopyranoside and re-estimation of its micellar size

The commercial non-ionic detergent octyl β- d-glucopyranoside is often contaminated by significant amounts of UV absorbing and/or ionic compounds that can associate with membrane proteins. Such impurities can be monitored by several techniques (i.e., spectrophotometry, size exclusion chromatography, and pH, conductivity, and surface tension measurements) and can be removed using mixed-bed ion exchange chromatography. High performance of size exclusion chromatography, dynamic light scattering, and ultracentrifugation have been used to re-estimate the size of micelles of octyl β- d_glucopyranoside since previously published data varied over a wide range. Aggregation numbers were 27 to 100 for micellar molecular weights 8000 to 29 000. Direct physical methods that do not perturbate the sample indicated a large size for the micelles (hydrodynamic radius 23 ± 3 A ̊ ; M r 22 000 ± 3000; aggregation number 75 ± 10 for a 34 mM aqueous solution). In contrast the chromatographic micellar size appeared to be smaller (hydrodynamic radius 15 ± 1 A ̊ ; M r 8000 ± 1000; aggregation number 27). This underestimation may be the result of adsorption and/or alteration of the micelles.

Solution properties of association colloids of twelve aluminum monohydroxy disoaps in nonaqueous solutions

This paper reports the micellar properties of 12 aluminum disoaps in nonaqueous solutions, many of which have not been synthesized previously. Measurements of light scattering, sedimentation velocity in an ultracentrifuge, and viscosity were made on various concentrations of six straight-chain and six branched monohydroxy aluminum disoaps in toluene or trichloroethylene. All these soaps formed association colloids in toluene solutions. Molecular weights of the micelles formed by these soaps ranged from 3 million to 45 million. Sedimentation velocity experiments showed that each soap forms a monodisperse micelle. Light mattering measurements pointed out the importance of the structure of the organic soap molecule in establishing micellar properties. The two most stable soaps prepared were the aluminum dioctoate and the di-2-methylundecanoate, which formed elongated micelles. Soaps with methyl groups near the tail were less asymmetric and less stable. For example, di-3-ethylheptanoate was less stable than the dioctoate (di-2-ethylhexanoate). The micellar molecular weight and CMC for solutions of the six straight chain disoaps increased gradually as the number of carbon atoms increased. Viscosity measurements of aluminum distearate in toluene were used to determine the relative strength of peptizing agents and to quantify time-dependent behavior. Amines were the strongest peptizing agents, followed by alcohols and acids. The presence of water decreased the solution viscosity over several days throughout the concentration range investigated.

In vitro effect of Triton WR-1339 on canine plasma high density lipoproteins.

We studied the effect in vitro of various concentrations of Triton WR-1339 on normolipidemic canine plasma and on the high density lipoproteins (HDL) isolated from this plasma by ultracentrifugation. As a preamble to this study, we established that Triton WR-1339 has a unimer molecular weight of 4,500, a micellar molecular weight of 180,000, and a critical micellar concentration (CMC) of 0.018 mM or 0.008 g/dl. Above its CMC, Triton WR-1339 in concentrations between 2 and 10 mg/ml induced concentration-dependent structural changes in HDL which were characterized by a progressive displacement of apoA-I from the HDL surface without loss of lipids. The addition of Triton WR-1339 to the HDL particles modified their electrophoresis mobility and caused an increase in size (95 +/- 5 A to 114 +/- 7 A). At the extreme Triton WR-1339 concentrations utilized in these studies (10 mg/ml) disruption of the HDL particles occurred; at this stage, the original, relatively homogeneous, spherical HDL particles were replaced by a heterogeneous population ranging in size between 50 and 250 A, representing complexes of Triton WR-1339 with lipids essentially free of apoA-I which could be sedimented by ultracentrifugation. The effects of Triton WR-1339 on whole plasma or isolated HDL were comparable. These studies indicate that Triton WR-1339 in vitro alters HDL in a concentration-dependent manner and that these changes vary from a displacement of apoA-I from the HDL surface to a state where all lipids are solubilized into the Triton WR-1339 micellar phase and are driven away from the protein moiety.(ABSTRACT TRUNCATED AT 250 WORDS)

Temperature dependences of micellar molecular weight and radius of nonionic surface active agent in the aqueous solution

The molecular weight and diffusion constant of poly(oxyethylene) dodecyl ether (C 12OE 9·3) micelles with an average of 9.3 oxyethylene group were determined from light-scattering measurements and free boundary experiments over a wide temperature range. It was found that micelles formed by C 12OE 9·3 were monodisperse in the temperature range studied. Plots of the logarithms of micellar molecular weight and micellar radii estimated from the diffusion constants against the temperature have a break point around 45°C. This temperature agrees with a theta point where the second virial coefficient obtained from light-scattering measurements is zero. Although the number of the molecules participating in micelle formation increases with temperature, the size of the micelle remains constant up to the temperature corresponding to the theta point, because the spherical micelle is packed with increasing tightness. The increase in the size and weight beyond that point may be attributed to a departure from spherical shape.

Effect of pH on the rate of emulsion polymerization of styrene initiated by potassium persulfate

AbstractThe influence of pH on the emulsifier property (micellar molecular weight) of sodium dodecyl sulfate has been studied in conjunction with the effect of pH on the rate of emulsion polymerization of styrene initiated by potassium persulfate. The rate of polymerization was found to be pH dependent. The micellar weight of sodium dodecyl sulfate has been determined at various pH values. The miceller weight was found to increase with decrease in pH. On the basis of the result, a suggestion was made that the effect of pH on micellar molecular weight can account for the observed behavior of the rate of polymerization.

Partial molal volume and light scattering studies on certain polyoxyethylene monohexadecyl ethers, and the effect of added aromatic solutes

An examination of volumetric properties of polyoxyethylene monohexadecyl ethers at and below the critical micelle concentration shows that there is an increase in the partial molal volume (V̄) of the monomer with increasing ethylene oxide chain length. Micelle formation is accompanied by an increase in V̄. Micellar molecular weight and critical micelle concentration determined by light scattering decreased as the ethylene oxide chain length was increased. The addition of phenol and aromatic alcohols to polyoxyethylene monohexadecyl ether (C 16E 18) solutions increased the critical micelle concentration and micellar molecular weight which became large in size as the concentration increased. This indicates that C 16E 18 forms rigid rod-like micelle in aqueous solutiosn of aromatic solutes at concentrations higher than 0.03 M for phenol and 0.02 M for aromatic alcohols. However at higher concentrations of additive, the critical micelle concentration decreased. This is attributed to changes in solvent composition and dielectric constant of the environment together with solubilization of the aromatic solute.