Cationic Micelles Research Articles

Formation of N-nitrosamines by micelle-catalysed nitrosation of aliphatic secondary amines.

N-Nitrosamines are an important class of potent human carcinogens and mutagens that can be present in water and wastewater. For instance, N-nitrosamines can be formed by reaction of nitrosating agents such as NO+ or N2O3 formed from nitrite under acidic conditions with secondary amine precursors by an acid-catalysed nitrosation pathway. This study investigates the catalytic effect of cationic and anionic micelles on the nitrosation of secondary aliphatic amines in the presence of nitrite at different pH values. The results of this study demonstrate that the nitrosation of hydrophobic secondary amines (e.g., dipropylamine and dibutylamine) by nitrite was significantly enhanced in the presence of micelles of the cationic surfactant cetyltrimethylammonium chloride whereas anionic micelles formed by sodium dodecylsulfate did not significantly enhance the formation of N-nitrosamines. Rate enhancements of up to 100-fold were observed for the formation of N-nitrosodibutylamine in the presence of cetyltrimethylammonium chloride. The magnitude of the catalytic effect of cationic micelles on the nitrosation reaction depended mainly of the hydrophobicity of the amine precursors (i.e., alkyl chain length), the stability and the charge of the micelles and pH. One important enhancement factor is the lowering of the pKa of the precursor alkylammonium ion due to the electrical potential at the micelle-water interface by up to ∼2.5 pH units. These results suggest that cationic micelle-forming surfactants might play a role in the formation of N-nitrosamines in wastewater, consumer products and in industrial processes using high concentrations of cationic surfactants.

Delivery of interleukin-22 binding protein (IL-22BP) gene by cationic micelle for colon cancer gene therapy.

Gene therapy has provided an alternative strategy for cancer therapy. As an important cytokine, interleukin-22 (IL-22) is not only critical in reinforcing innate immune defenses and tissue regeneration, but also involved in the initial establishment of tumors. A soluble-secreted receptor of the cytokine IL-22, IL-22 binding protein (IL-22BP), binds IL-22 and prevents its binding to the functional transmembrane receptor IL-22R1 complex, inhibiting IL-22-based intracellular cancer proliferation signal. In this work, a novel IL-22BP-based cancer gene therapy strategy was reported for the first time. It was established by delivering IL-22BP gene with a newly developed non-viral gene vector DMP. The DMP cationic micelles were prepared by modifying monomethoxy poly(ethylene glycol)-poly(ε-caprolactone) with DOTAP lipid through self-assembling. The anti-cancer efficacy of the DMP/IL-22BP complex was studied on a colon cancer model by intraperitoneal administration. Our results demonstrated that the secretory expressed IL-22BP cytokine effectively inhibited cancer growth both in vitro and in vivo. Multiple anti-cancer mechanisms including IL-22 blocking, apoptosis inducing, lymphocyte infiltration and angiogenesis inhibition were indicated to be involved while no pathology changes were observed in healthy tissues. These results suggest the DMP/IL-22BP complex to be a potential candidate for cancer gene therapy.

Quinolinium bound chromium(VI) reagents for efficient electrophilic aromatic nitration and thiocyanation reactions using sodium nitrate and ammonium thiocyanate

Quinolinium dichromate (QDC) and quinolinium chlorochromate (QCC) were studied as efficient reagents for electrophilic aromatic nitration using sodium nitrite and thiocyanation by using ammonium thiocyanate under conventional, ultrasonic and solvent-free microwave assisted conditions. The microwave-assisted protocols exhibited remarkable rate acceleration and offered selective thiocyanation of the aromatic and heteroaromatic compounds with good yields. Addition of anionic (SDS) micelle to the reaction medium afforded considerable rate enhancements, while cationic (CTAB) and nonionic (Tx-100) micelles did not affect the rate noticeably. These protocols have were extended to regioselective thiocyanation of various aromatic compounds. Results were are completely similar to the nitration protocols. However, the reactions revealed comparatively shorter reaction times, and better yields in nitration reactions than in thiocyanation protocols. Catalytic effect of the SDS was attributed to the electrostatic stabilization of the cationic electrophile (NO2+ in nitration, and SCN+ in thiocyanation).

Study of Cationic and Nonionic Mixed Micelles with NaBr and 3,5-Cl2C6H3CO2Na by Use of Probe Nucleophilic Reaction of Piperidine with Ionized Phenyl Salicylate.

Behaviors of cationic and nonionic mixed micelles in the form of hexadecyltrimethylammonium bromide (HDABr) and hexadecyltrimethylammonium bromide-Polyethylene glycol hexadecyl ether (C16E20), in the presence of inert salts (NaBr and 3,5-dichlorosodium benzoate), by the use of reaction probe between Pp and ionized PhSH (Pp = piperidine and PhSH = phenyl salicylate), has been reported in this work. The values of RXBr (RXBr denotes ion exchange constants obtained in the presence of micelles of different structural features) or KXBr (KXBr denotes ion exchange constants obtained in the presence of micelles of the same structural features) for 3,5-Cl2C6H3CO2- were almost the same at three different [HDABr]T (0.006, 0.010 and 0.015 M). The average value of RXBr or KXBr determined, in the presence of pure HDABr micelles, using semi empirical kinetic (SEK) method appeared to be almost 2½-fold larger (RXBr or KXBr = 198) than that in the presence of mixed HDABr-C16E20 micelles (RXBr or KXBr = 78). Rheological measurements indicated the existence of wormlike/twisted micelles and vesicle at 0.015 M pure HDABr, various [3,5-Cl2C6H3CO2Na], and 25 and 35℃ whereas there were evidence of only spherical micelles in the presence of mixed HDABr-C16E20 ([HDABr]T = 0.015 M and [C16E20]T = 0.006 M) at both temperatures.

TAT-conjugated chitosan cationic micelle for nuclear-targeted drug and gene co-delivery

We developed a high-efficiency nucleus-targeted co-delivery vector that delivers genes and drugs directly into the nucleus of cancer cells. The system is based on grafted poly-(N-3-carbobenzyloxy-lysine) (CPCL) with transactivator of transcription (TAT)- chitosan on the surface. It is designed to perform highly efficient nucleus- targeted gene and drug co-delivery. Confocal laser scanning microscopy (CLSM) revealed that more TAT-CPCL entered the nucleus than does CPCL alone. The TAT-modified vector serves as a gene and drug co-delivery mechanism to achieve high gene transfection efficiency, high apoptosis and low viability in HeLa cells. TAT-CPCL may become a vector for cancer gene treatment and a template for designing better co-deliver systems.

Mechanical and Rheological Behavior of Hybrid Cross‐Linked Polyacrylamide/Cationic Micelle Hydrogels

AbstractIn this work, a hybrid cross‐linked polyacrylamide (PAM)/cationic micelle hydrogel is fabricated by introducing the cationic micelles into the chemically cross‐linked PAM network. The cationic micelles act as the physical cross‐linking points through the strong electrostatic interaction with anionic initiator potassium persulfate. Thereafter, in situ free radical polymerization is initiated thermally from the cationic micelle surface to form the hybrid cross‐linked network. The synergistic effect between chemical and physical cross‐link endows the hydrogel with excellent mechanical and recoverable properties. The resulting hydrogel exhibits tensile stress of 481 kPa and fracture toughness of 1.65 MJ m−3. It is found that the chemical cross‐linking can inhibit the hysteresis of the hybrid hydrogel, exhibiting good elasticity in the tensile loading–unloading test. Moreover, dynamic rheological measurements show that the hybrid hydrogels possess fewer defects of network and exhibit excellent self‐recovery behavior. Thus, this investigation provides a different view for the design of new high elastic and tough hydrogels containing hybrid physical and chemical cross‐linking networks.

Micellar catalyzed hydrolysis of mono-2,3-dichloroaniline phosphate

ABSTRACTThe kinetics of micellar catalyzed hydrolysis of mono-2,3-dichloroaniline phosphate in the presence of different surfactants has been studied at 303 K. The rate of reaction has been found to be first order with respect to both [substrate] and [HCl]. The cationic micelles of cetylpyridinium chloride (CPC), anionic micelles of di-octyl sodium sulphosuccinate (AOT), and non-ionic micelles of polyoxyethylene sorbitan monooleate (Tween 80) enhanced the rate of reaction to a maximum value and after that the increase in concentration of surfactant decreased the reaction rate. The applicability of different kinetic models has been tested to explain the observed micellar effects. The various thermodynamic activation parameters (Ea, ΔH≠, ΔS≠, ΔG≠) have been evaluated. The added salts viz. KCl, KNO3, K2SO4 enhanced the rate of reaction in the presence of CPC, AOT, and Tween 80 micelles. The kinetic parameters were determined from the rate (surfactant) profile and a suitable mechanism consistent with the experimental finding has been proposed.

Structure and rheology of self-assembled aqueous suspensions of nanoparticles and wormlike micelles

We present a systematic molecular dynamics (MD) simulation study of the structure and rheology of solutions consisting of cationic micelles and negatively charged nanoparticles (NPs) in the presence of a hydrotropic salt, namely, sodium salicylate. The addition of NPs to wormlike micelle (WLM) solutions results in the formation of electrostatically stabilised NP-micelle junctions, leading to a significant enhancement in the viscosity of the mixture due to effective lengthening of micelle clusters. A monotonic increase in zero-shear viscosity is observed as the NP volume fraction is increased. Branched micelles form at sufficiently large salt concentrations. Sliding motion of micelle branches along the contour of a wormlike chain provides an additional mechanism for stress relaxation. Hence, branch formation induces a non-monotonic variation in the solution viscosity as a function of the salt concentration. Reverse non-equilibrium MD simulations were performed to study the effect of uniform and steady shear flow on the viscosity of the WLM-NP mixtures. Beyond a critical shear rate, flow-induced anisotropy, which is quantified by an orientational order parameter, manifests as viscoelastic rheological behaviour. Specifically, at higher NP volume fractions and shear rates that exceed the inverse of a characteristic structure relaxation time, flow-alignment of the microstructure causes pronounced shear thinning.

Interfacial Hydration Dynamics in Cationic Micelles Using 2D-IR and NMR.

Using the thiocyanate anion as a vibrational probe chromophore in conjunction with infrared and NMR spectroscopy, we find that SCN- strongly associates with the cationic head group of dodecyltrimethylammonium bromide (DTAB) micelles, both in normal-phase and reverse micelles. In competition with chloride and iodide ions, we find no evidence for displacement of thiocyanate, in accord with the chaotropicity of the Hofmeister ordering, while lending support to a direct interaction picture of its origin. Ultrafast 2D-IR spectroscopy of the SCN- probe in a range of DTAB micelle sizes (w0 = 4 to w0 = 12) shows little if any size dependence on the time scale for spectral diffusion, which is found to be ∼3.5 times slower than in bulk water (both D2O and H2O). Normal-phase micelles studied with 2D-IR exhibit essentially the same spectral dynamics as do reverse micelles, indicating a lack of sensitivity to interfacial curvature. Combined with 1H NMR chemical shift perturbations, we conclude that the SCN- ions tightly associate with the head groups and are partially buried. The 3-4-fold slowdown in spectral diffusion is consistent with the excluded volume model for interfacial perturbation to hydrogen bond reorientation dynamics. On the basis of these observations and comparisons to previous studies of zwitterionic interfaces probed with phosphate transitions, we conclude that the SCN- spectral dynamics in both reverse- and normal-phase micelles is largely dominated by hydration contributions, and offers a promising probe of interfacial hydration at cationic interfaces. Addition of competitive anions alters neither the IR spectra nor the ultrafast dynamics, indicating that SCN- is robustly associated with the head groups.

Polymeric vehicles for transport and delivery of DNA via cationic micelle template method

This work describes the preparation of polymeric non-viral system for transport and delivery of nucleic acids. An amphiphilic poly(2-(dimethylamino)ethyl methacrylate)-block-poly(e-caprolactone)-block-poly(2-(dimethylamino)ethyl methacrylate) (PDMAEMA20-b-PCL70-b-PDMAEMA20) triblock copolymer was synthesized and used for formation of cationic micelles and subsequent complexation with DNA. Next, a protective polymer coating on the complex surface and removal of copolymer from the particle interior were conducted. In this way, polymer nanocapsules containing DNA molecules were obtained. The synthesized polymer, cationic micelles, complexes, and polymer capsules were investigated by proton nuclear magnetic resonance, gel permeation chromatography, dynamic and electrophoretic light scattering, and transmission electron microscopy. In vitro cytotoxicity assessment of the different systems revealed very good tolerance to human cells.

Elaboration on the Distribution of Hydrophobic Segments in the Chains of Amphiphilic Cationic Polymers for Small Interfering RNA Delivery.

Hydrophobization of cationic polymers, as an efficient strategy, had been widely developed in the structure of cationic polymer micelles to improve the delivery efficiency of nucleic acids. However, the distribution of hydrophobic segments in the polymer chains is rarely considered. Here, we have elaborated three types of hydrophobized polyethylene glycol (PEG)-blocked cationic polymers with different distributions of the hydrophobic segments in the polymer chains PEG-PAM-PDP (E-A-D), PEG-PDP-PAM (E-D-A), and PEG-P(AM/DP) (E-(A/D)), which were synthesized by reversible addition-fragmentation chain transfer polymerization of methoxy PEG, cationic monomer aminoethyl methacrylate, and pH-sensitive hydrophobic monomer 2-diisopropylaminoethyl methacrylate, respectively. In aqueous solution, all of the three copolymers, E-A-D, E-D-A, and E-(A/D), were able to spontaneously form nanosized micelles (100-150 nm) (ME-A-D, ME-D-A, and ME-(A/D)) and well-incorporated small interfering RNA (siRNA) into complex micelles (CMs). The effect of distributions of the hydrophobic segments on siRNA delivery had been evaluated in vitro and in vivo. Compared with ME-D-A and ME-(A/D), ME-A-D showed the best siRNA binding capacity to form stable ME-A-D/siRNA CMs less than 100 nm, mediated the best gene-silencing efficiency and inhibition effect of tumor cell growth in vitro, and showed better liver gene-silencing effect in vivo. In the case of ME-(A/D) with a random distribution of cationic and hydrophobic segments, a gene-silencing efficiency higher than Lipo2000 but lesser than ME-A-D and ME-D-A was obtained. As the mole ratio of positive and negative charges increased, ME-D-A/siRNA and ME-A-D/siRNA showed similar performances in size, zeta potential, cell uptake, and gene silencing, but ME-(A/D)/siRNA showed reversed performances. In addition, ME-A-D as the best siRNA carrier was evaluated in the tumor tissue in the xenograft murine model and showed good anticancer capacity. Obviously, the distribution of the hydrophobic segments in the amphiphilic cationic polymer chains should be seriously considered in the design of siRNA vectors.

Spectral and chromatographic characterization of fixed dose combination norfloxacin and metronidazole interacting with cetyltrimethylammonium bromide

Surfactant molecular self-assemblies solubilize and shelter the drugs from adverse conditions. As membrane mimetic they serve as a powerful tool to understand the consequences of drug membrane interactions. In this study the interaction modulation of fixed dose combination (FDC) having norfloxacin (NOR) and metronidazole (MET) with quaternary ammonium disinfectant (cetyltrimethylammonium bromide) has been described at physiological condition (pH7.4). The spectral and physiochemical characteristic of NOR and MET interacting with cationic micelles were investigated by electronic spectroscopy as function of cetyltrimethylammonium bromide (CTAB) concentration from pre-micellar to post-micellar region. Magnitudes of binding constant and related Gibbs free energies were optimized using differential absorption spectrometry and micellar liquid chromatography (MLC). The results indicate potential solubilization of drugs in the peripheral region of micelles that may be helpful to their control release. The values of the binding capacities of drug-micelle system have verified these results.

Efficient separation and reuse of CI Reactive Blue 19 from dyeing effluent by solvent extraction

In order to reduce environmental pollution from dyeing effluent, the cationic reverse micelles were prepared and used for removal of anionic Color Index (CI) Reactive Blue 19. The effect of surfactants, dyes, temperature and ultrasonic treatment on dye removal was investigated, respectively. The conductivity of CI Reactive Blue 19 aqueous solution was measured during removal process. In addition, the photograph of CI Reactive Blue 19 was also obtained. Finally, the removed dyes were backward extracted and reused for dyeing cotton fabrics. The results indicated that the removal of dyes was increased with increasing surfactants concentration and temperature, while the dye concentration exhibited the reverse trend. The higher removal of dyes could be caused by using ultrasonic treatment. The conductivity of dye aqueous solution was decreased with increasing surfactant concentration for the removal of dyes. The CI Reactive Blue 19 from backward extraction was reused for dyeing cotton fabrics, which exhibited the good property.

Fluorescence Behavior of Schiff Base-N, N'-bis(salicylidene) Trans 1, 2-Diaminocyclohexane in Proteinous and Micellar Environments.

Fluorescence properties of N, N'-bis(salicylidene) trans 1, 2-diaminocyclohexane (H 2 L) is used to probe the anionic (SDS), cationic (CTAB) and nonionic (TX-100) micelles as well as in serum albumins (BSA and HSA) and chicken egg white lysozyme (LYZ) by steady state and picosecond time-resolved fluorescence spectroscopy. The fluorescence band intensity was found to increase with concomitant blue-shift with gradual addition of different surfactants. All the experimental results suggest that the probe molecule resides in the micelle-water interface rather than going into the micellar core. However, the penetration is more towards the micellar hydrocarbon core in nonionic surfactant (TX-100) while comparing with ionic surfactants (SDS and CTAB). Several mean microscopic properties such as critical micelle concentration, polarity parameters and binding constant were calculated in presence of different surfactants. The decrease in nonradiative decay rate constants in micellar environments indicates restricted motion of the probe inside the micellar nanocages with increasing fluorescence emission intensity and quantum yields. Further in this work, we also investigated the interaction behavior of the probe with different proteins at low concentrations under physiological conditions (pH = 7.4). Stern-Volmer analysis of the tryptophan (Trp) fluorescence quenching data in presence of probe reveals Stern-Volmer constant (Ksv) as well as bimolecular quenching rate constant (Kq). The binding constant as well as the number of binding sites of the probe with proteins were also monitored and found to be 1:1 stoichiometry ratio.

EGFR-Targeted Cationic Polymeric Mixed Micelles for Codelivery of Gemcitabine and miR-205 for Treating Advanced Pancreatic Cancer.

Gemcitabine (GEM), a first-line chemotherapy for pancreatic cancer undergoes rapid metabolism and develops chemoresistance after repeated administration. We previously demonstrated that the combination of GEM and miR-205 provides an effective therapeutic strategy to sensitize GEM-resistant pancreatic cancer cells. Since epidermal growth factor receptor (EGFR) is overexpressed in pancreatic cancer cells, in this study, we aimed to deliver mixed micelles containing GEM and miR-205 decorated with EGFR-targeting cetuximab (C225) monoclonal antibody for targeted therapy. Cetuximab C225 was conjugated to malemido-poly(ethylene glycol)-block-poly(2-methyl-2-carboxyl-propylene carbonate-graft-dodecanol (C225-PEG-PCD) to prepare mixed micelles with mPEG-b-PCC-g-GEM-g-DC-g-TEPA for targeted codelivery of GEM and miR-205. This mixed micelle formulation showed a significant enhancement in EGFR-mediated cellular uptake in GEM-resistant MIA PaCa-2R cells. Further, an enhanced tumor accumulation of C225-micelles conjugated with near-infrared fluorescent Cy7.5 dye and Dy677-labeled miR-205 in orthotopic pancreatic tumor bearing NSG mice was evident after systemic administration. In addition, inhibition of tumor growth was also observed with increased apoptosis and reduced EMT after treatment with C225-micelles containing GEM and miR-205. Therefore, we believe that the targeted delivery of GEM and miR-205 in combination could be a novel strategy for treating advanced pancreatic cancer.

Influence of micellar aggregates on oxidative degradation of β-cyclodextrin by alkaline permanganate: A kinetic and mechanistic study of inclusion complex

Kinetics of MnO4−-β-cyclodextrin (BCD) redox reaction has been studied spectrophotometrically in presence of anionic surfactant micelles of sodium dodecyl sulfate (SDS) and cationic surfactant micelles of cetyltrimethylammonium bromide (CTAB) in alkaline medium. The rate of the reaction shows first order dependence on [MnO4−] and fractional order dependence on [BCD], [OH−] in the presence of both CTAB and SDS. Both the surfactants CTAB and SDS shows rate inhibition effects. Inhibition effect of CTAB was observed above critical micelle concentration (CMC) while that of SDS was observed below the CMC. Oxidised products were confirmed by FT-IR and 1H NMR spectral techniques. Reaction between SDS and BCD shows inclusion complex formation which was confirmed by conductivity measurements. The observed results were discussed in terms of Menger and Portnoy’s model for micellar inhibition. Activation parameters have been evaluated using Eyring equation. The effect of added salts (KCl, KBr, NaNO3 and Na2SO4) on the reaction has been studied. The effect of ionic strength and dielectric constant on the rate of reaction has been studied in the absence of surfactants. Probable reaction mechanism, in agreement with the observed kinetic results has been proposed and discussed.

Anomalous diffusion and stress relaxation in surfactant micelles.

We investigate the mechanisms of anomalous diffusion in cationic surfactant micelles using molecular dynamics simulations in the presence of explicit salt and solvent-mediated interactions. Simulations show that when the counterion density increases, saddle-shaped branched interfaces manifest. In experiments, branched structures exhibit lower viscosity as compared to linear and wormlike micelles. This has long been attributed to stress relaxation arising from the sliding motion of branches along the main chain. Our simulations reveal a mechanism of branch motion resulting from an enhanced counterion condensation at the branched interfaces and provide quantitative evidence of stress relaxation facilitated by branched sliding. Furthermore, depending on the surfactant and salt concentrations, which in turn determine the microstructure, we observe normal, subdiffusive, and superdiffusive motions of surfactants. Specifically, superdiffusive behavior is associated with branch sliding, breakage and recombination of micelle fragments, as well as constraint release in entangled systems.

Complexation of Linear DNA and Poly(styrenesulfonate) with Cationic Copolymer Micelles: Effect of Polyanion Flexibility.

The complexation of linear double stranded DNA and poly(styrenesulfonate) (PSS) with cationic poly(dimethylamino ethyl methacrylate)-block-poly(n-butyl methacrylate) micelles was compared in aqueous solutions at various pH values and ionic strengths. The complexation process was monitored by turbidimetric titration, as a function of the ratio (N/P) of amine groups in the micelle corona to the number of phosphates (or sulfonates) in the polyanion. The size, structure and stability of the resulting micelleplexes were studied by dynamic light scattering (DLS) and cryogenic transmission electron microscopy (cryo-TEM). In the short chain regime, where the contour lengths of the polyanions are shorter than or comparable to the micelle corona thickness, micelleplexes with DNA oligomers show very similar behavior to complexes with short PSS chains, in terms of titration curves and structural evolution of the complexes as a function of charge ratio. However, in the long chain regime, where the contour length of the polyanion far exceeds the micelle radius, micelleplexes of linear DNA show titration curves shifted toward lower N/P ratios, reduced stability at N/P < 1, and a higher percentage of small complexes at N/P > 1 compared to complexes with long chain PSS. Furthermore, at 1 M ionic strength, the cationic micelles could still complex with long chain PSS, but not with DNA of the same total charge. These differences are attributed to the flexibility difference between the polyanion chains, and possible mechanisms are proposed. This work highlights the importance of chain flexibility in complexation of dissimilar polyelectrolyte pairs, a factor that could therefore help guide the future design of micelleplexes for various applications.

Molecular dynamics study of the aggregation rate for zwitterionic dodecyldimethylamine oxide and cationic dodecyltrimethylammonium chloride micelles

We studied dynamic scaling law for the early stage domain growth in the micelle aggregation process of dispersed surfactant molecules in water for zwitterionic dodecyldimethylamine oxide (DDAO) and cationic dodecyltrimethylammonium chloride (DTAC) based on all-atomistic molecular dynamics calculations. For both surfactants, the aggregation number N increases in proportion to tα′, where t and α′ are the simulation time and exponent of the dynamic scaling, respectively. When the aggregation is controlled by diffusion, it follows the well-known Lifshitz–Slyozov (LS) law giving the exponent α′ = 1. The values of α′ obtained for DDAO and DTAC are 0.6 and 0.3, respectively, indicating that the aggregation rate is suppressed compared with purely diffusion controlled LS process. The aggregation of DDAO and DTAC may be partly controlled by electrostatic interaction between the aggregates.

Double Sweeping: Highly Effective Sample Preconcentration Using Cationic and Anionic Micelles and Its Application to a Multiple Enzyme Activity Assay.

In conventional microfluidic bioassays, short optical path length and extremely small quantities of analytes sometimes can significantly reduce detectability. Various sample preconcentration techniques have been reported for improving the detectability of bioassays. In the present study, we developed a novel preconcentration technique, "double sweeping", utilizing cationic and anionic micelles simultaneously. Microscopic observations demonstrated that double sweeping enabled a sample solution, which initially filled a capillary, to be focused into an extremely narrow band. Initially, the sample molecules are swept from cathode to anode, or anode to cathode, based on conventional sweeping with an anionic or cationic micellar solution, respectively. Then, the fronts of the swept bands collide with each other in the capillary and halt at the interface between the bands. The sample molecules in the micellar solutions continue to move toward the interface because of the electrophoretic migration of the micelles, which results in further focusing and suppression of the band broadening due to molecular diffusion. We demonstrated that higher preconcentration efficiency was achieved using double sweeping than using conventional sweeping. In addition, double sweeping was successfully incorporated into a multiple enzyme activity assay using an arrayed reagent-release capillary, resulting in simple, rapid, simultaneous, and highly sensitive assays of caspase-3, alkaline phosphatase, and trypsin.