•The phase behavior of stearic acid and alkali in water was observed.•Multi-responses of the emulsion stabilized by bilayers were achieved.•The ability of stabilizing the emulsion by the bilayers and micelles was compared.Stearic acid (SA) mixed with alkali in water can form different fascinating aggregates in solution. The phase behavior of SA and alkali in water was observed in this work, and the apparent viscosity was measured by rheological measurements. Fatty acid self-assembled into bilayers at pH ≈ pKa and the structure was determined by cryogenic transmission microscopy (cryo-TEM) observations. The ability of stabilizing the emulsion by the bilayers and micelles was compared. The homogeneous emulsion formed by bilayers was gained, indicating that the bilayers have a better emulsion stability. By adjusting the conditions and external stimuli, emulsification and demulsification can be achieved. Based on this background, we carried out the experiments of multi-responses of the emulsion stabilized by bilayers, including pH, CO2, light, and temperature.Download high-res image (155KB)Download full-size image

•Completely compacted DNA by zwitterionic surfactants with adding acids.•Decompacted DNA by using β-CD was realized.•The release of DNA from the CnDMAOH+/DNA precipitates can be controlled.Controlled compaction and decompaction of DNA by zwitterionic surfactants, alkyldimethylamine oxides (CnDMAO, n = 10, 12, and 14), were investigated by various analytical tools. It was found that DNA could effectively be compacted by cationic micelles of CnDMAOH+ which were produced by the protonation of CnDMAO in acidic media leading to the formation of water-insoluble CnDMAOH+/DNA complexes. The DNA molecules were compacted at pH 4–5 when the concentration of C10DMAOH+, C12DMAOH+, and C14DMAOH+ reached 8.0, 1.6, and 0.9 mmol L−1, respectively. Interestingly, the precipitates of CnDMAOH+/DNA complexes can re-dissolve which indicated that the DNA molecules were released from the complexes by regulating the pH of the solution to ∼4 and increasing the surfactant concentration to 40, 9.0, and 1.8 mmol L−1 for C10DMAOH+, C12DMAOH+, and C14DMAOH+, respectively. This phenomenon was attributed to the hydrogen bonding formed between cationic CnDMAOH+ and zwitterionic CnDMAO species. These hydrogen-bonded species screen the electrostatic forces between the positively charged CnDMAOH+ micelles and the negatively charged backbones of DNA. Our results demonstrated that the release of DNA from the CnDMAOH+/DNA precipitates depended on the concentration of cationic CnDMAOH+ and the pH of the solution. Compared with the conventional release of DNA by the addition of β-cyclodextrin, the present strategy allowed for a specific controlled release, which favored the penetration of DNA into cells and could protect the DNA molecules from nucleases degradation.Compaction and decompaction of DNA by zwitterionic surfactants with adding acids and β −CD were investigated.

A dual-responsive cationic surfactant, 4-ethoxy-4′-(trimethyl- aminoethoxy) azobenzene trichloromonobromoferrate (azoTAFe), which contains both a light-responsive moiety azobenzene and a paramagnetic counterion, [FeCl3Br]−, was designed and synthesized. Not only does this cationic surfactant abundantly utilize inexhaustible and clean sources, i.e., light and magnetic field, but it also serves as a powerful dual-switch molecule for effectively controlling the capture and release of DNA. Our results could provide potential applications in gene therapy for creating smart and versatile machines to control the transport and delivery of DNA more intelligently and robustly. It was proved that the light switch can independently realize a reversible DNA compaction. The introduction of a magnetic switch can significantly enhance the compaction efficiency, help compact DNA with a lower dosage and achieve a magnetic field-based targeted transport of DNA. In addition, the light switch can make up the irreversibility of magnetic switch. This kind of self-complementation makes the cationic azoTAFe be useful as a potential tool that can be applied to the field of gene therapy and nanomedicine.Keywords: capture and release; cationic surfactant; DNA; dual-switch; light and magnet;

A multiresponsive hydrogel material consisting of a commercial cationic surfactant and an azobenzene derivative functionalized with four carboxylic acid groups was constructed. The achiral azobenzene molecule as a gelator produces chirality at the supramolecular level in the presence of H+. The acid-induced gelation and morphology change of supramolecular gels were investigated in detail by cryogenic transmission electron microscopy (cryo-TEM), rheological measurements, circular dichroism (CD), and 1H NMR spectra. Based on the results, a mechanism of the intermolecular H-bond-directed gelation and supramolecular chirality was proposed. Other than the pH sensitivity, the microstructure and the chirality of the hydrogel demonstrate reversible switching behavior in response to photoirradiation, on account of the photoisomerization of the azobenzene derivative. Accordingly, a chiroptical switch comprising four different states in response to pH and light stimuli is strategically constructed. Not only does the present system provide a good opportunity for investigating the gelation-induced supramolecular chirality by symmetry breaking totally based on achiral molecules, but it also proposes a new strategy to build multiresponsive supramolecular switches as particularly attractive for the future development of functional materials.

Cationic and anionic (catanionic) vesicles were constructed from the mixtures of sodium laurate (SL) and alkyltrimethylammonium bromide (CnTAB, n = 12, 14, and 16) and were used to control the loading capacity of DNA. The binding saturation point (BSP) of DNA to catanionic vesicles increases with the chain length of cationic surfactants, which is at 1.0, 1.3 and 1.5 for CnTAB with n = 12, 14, and 16, respectively. Our measurements showed that the loading capacity and affinity of DNA can be controlled by catanionic vesicles. It increases with the chain length of cationic surfactants. Because of a large reduction in surface charge density, catanionic vesicles are prone to undergo re-aggregation or fusion with the addition of DNA. DNA molecules can still maintain original coil state during the interaction with catanionic CnTAL vesicles. 1H NMR data reveals that the obvious dissociation of anionic ions, L−, from catanionic C14TAL vesicles is due to the interaction with DNA; however, this phenomenon cannot be observed in C12TAB–SL vesicles. Agarose gel electrophoresis (AGE) results demonstrate that the electrostatic interaction between the two oppositely charged cationic and anionic surfactants is stronger than that between DNA and cationic surfactant, CnTAB (n = 12, 14, and 16). Not only is the dissociation of L− simply determined by the charge competition, but it also depends largely on the variations in the surface charge density as well as the cationic and anionic surfactant competing ability in geometry configuration of catanionic vesicles. The complicated interaction between DNA and catanionic vesicles induces the deformation of cationic vesicles. Our results should provide clear guidance for choosing more proper vectors for DNA delivery and gene therapy in cell experiments.

The interaction of DNA with salt-free tetradecyltrimethylammonium hydroxide and lauric acid lamellar vesicles with positive charges was investigated to probe potential applications of vesicles in DNA transfection. The aggregation morphology of the vesicles changes greatly with the addition of DNA due to the dissociation of anionic surfactants, as indicated by 1H nuclear magnetic resonance, and the expelled surfactant molecules self-assemble into micelles at high concentrations of DNA. Salt-free cationic and anionic (catanionic) vesicles have a much higher binding saturation point with DNA at R = 2.3 (the ratio of DNA to the excess positive charge in vesicles) than formerly reported salt-containing systems, implying high transfection efficiency. DNA retains its native stretched state during the interaction process. This very interesting result shows that catanionic vesicles could help transport undisturbed and extended DNA molecules into the target cells, which is of great importance in gene delivery, nanomedicine field, and controlling the formation of certain morphological aggregates.