An enzyme-responsive polymeric superamphiphile

UV-responsive polymeric superamphiphile based on a complex of malachite green derivative and a double hydrophilic block copolymer

We have prepared a UV-responsive polymeric superamphiphile, formed by a malachite green derivative and the double hydrophilic block copolymer methoxy-poly(ethylene glycol)(114)-block-poly(l-lysine hydrochloride)(200) (PEG-b-PLKC) on the basis of electrostatic interactions. The malachite green derivative undergoes photo-ionization upon UV irradiation, which makes it more hydrophilic, resulting in changes in the self-assembly behavior of the polymeric superamphiphile. For this reason, the polymeric superamphiphile originally self-assembles to form sheetlike aggregates, which disassemble after UV irradiation because of the increased solubility of the malachite green derivative. By use of Nile red as a probe, the polarity of the polymeric superamphiphile solution is confirmed to be increased after UV irradiation by fluorescence spectra, which also explains the disassembly of the polymeric superamphiphile.

Enzyme-directed assembly and manipulation of organic nanomaterials

Enzymes are the prime protagonists in the chemistry of living organisms. As such, chemists and biologists have long been fascinated by the array of highly selective transformations possible under biological conditions that are facilitated by enzyme-catalyzed reactions. Moreover, enzymes are involved in replicating, repairing and transmitting information in a highly selective and organized fashion through detection and signal amplification cascades. Indeed, because of their selectivity and potential for use outside of biological systems, enzymes have found immense utility in various biochemical assays and are increasingly finding applications in the preparation of small molecules. By contrast, the use of enzymatic reactions to prepare and build supramolecular and nanoscale materials is relatively rare. In this article, we seek to highlight efforts over the past 10 years at taking advantage of enzymatic reactions to assemble and manipulate complex soft, organic materials on the nanoscale. It is tantalizing to think of these processes as mimics of natural systems where enzymes are used in the assembly and transformation of the most complex nanomaterials known, for example, virus capsid assemblies and the myriad array of nanoscale biomolecular machinery.

Bolaform superamphiphile based on a dynamic covalent bond and its self-assembly in water

We have employed a dynamic covalent bond to fabricate a bolaform superamphiphile, which can be used as building blocks for controlled assembly and disassembly. In alkaline environment, one building block bearing a benzoic aldehyde group can react with the other building block bearing an amino group to form a bolaform superamphiphile. It is found that the bolaform superamphiphiles can self-assemble in water to form micellar aggregates. When the pH is tuned down to slightly acidic values, the benzoic imine bond can be hydrolyzed, leading to the dissociation of the superamphiphile. The micellar aggregates will also disassemble, and the loaded guest molecules are released subsequently. This line of research has enriched the family of bolaform amphiphiles, and the resulting assemblies may find application in the field of controlled and targetable drug-delivery in a biological environment.

Multistimuli responsive micelles formed by a tetrathiafulvalene-functionalized amphiphile

An electroactive tetrathiafulvalene (TTF)-functionalized amphiphile 1 was designed and synthesized to investigate its self-assembling behavior in water. Dynamic light scattering (DLS), (1)H NMR, fluorescence spectrum, and cryogenic transmission electron microscopy (cryo-TEM) studies revealed that amphiphile 1 can form micelle-like aggregates via direct dissolution into water, and the micellar architectures could be disrupted either by addition of chemical oxidant Fe(ClO(4))(3) or by complexation with electron-deficient cyclobis(paraquat-p-phenylene) tetracation cyclophane (CBPQT(4+)) to release encapsulated hydrophobic dye Nile Red from the interior of micelles.

Photocontrollable J-aggregation of a diarylethene-phthalocyanine hybrid and its aggregation-stabilized photochromic behavior

The photocontrollable J-aggregation of a diarylethene-phthalocyanine hybrid (T-ZnPc) and its aggregation-stabilized photochromic behavior were investigated by various techniques. T-ZnPc initially exhibited slight J-aggregation tendency in solvents such as chloroform and toluene through conformational planarization effect, but formed much stronger J-aggregates upon the illumination of 254 nm UV light. In darkness, the UV-irradiated solutions gradually returned to their initial state. These phenomena can be explained by the pronounced change in molecular planarity accompanying the reversible isomerization of the diarylethene units of T-ZnPc. Besides, we have found that the thermal stability of the closed-ring diarylethene isomers in molecularly dispersed T-ZnPc is much poorer than that in aggregates. As long as the aggregates were broken, they converted to corresponding open-ring form instantly. This study provided an example of fully photocontrollable aggregation of phthalocyanines and paved a new way for improving the stability of the photochromic systems.

Superamphiphiles as building blocks for supramolecular engineering: towards functional materials and surfaces

Superamphiphiles refer to amphiphiles that are constructed on the basis of noncovalent interactions or dynamic covalent bonds. Superamphiphiles are a new kind of building block for well-defined nanostructured soft materials. This article summarizes different ways to fabricate superamphiphiles, including low-molecular-weight and polymeric superamphiphiles. In addition, the noncovalent nature of superamphiphiles facilitates the incorporation of functional groups, thus opening a new avenue for supramolecular engineering of functional soft materials.