Two Robust Strategies toward Hydrogels from Quenched Block Copolymer Nanofibrillar Micelles.

While the formation of (tri)block copolymer hydrogels has been extensively investigated, such studies mostly focused on equilibrium self-assembling whereas the use of preformed structures as building blocks such as out of equilibrium, quenched, nanofibrillar micelles is still a challenge. Here, we demonstrate that quenched, ultralong polystyrene-b-poly(ethylene oxide) (PS-b-PEO) micelles can be used as robust precursors of hydrogels. Two cross-linking strategies, (i) thermal fusion of micellar cores and (ii) chemical cross-linking of preformed micellar coronas were studied. The gelation process and the structure of the micellar networks were investigated by in situ rheological measurements, confocal microscopy and transmission electron microscopy. Direct observation of core fusion of preformed quenched micelles is provided validating this method as a robust gelation route. Using time sweep rheological experiments, it was found for both cross-linking methods that these 3D "mikado" gels are formed in three different stages, containing (1) initiation, (2) transition (growth), and (3) stabilization regimes.

Chemical physics of electroactive materials - the oft-overlooked faces of electrochemistry.

Electroactive materials and their applications are enjoying renewed attention, in no small part motivated by the advent of nanoscale tools for their preparation and study. While the fundamentals of charge and mass transport in electrolytes on this scale are by and large well understood, their interplay can have subtle manifestations in the more complex situations typical of, for example, integrated microfluidics-based applications. In particular, the role of faradaic processes is often overlooked or, at best, purposefully suppressed via experimental design. In this introductory article we discuss, using simple illustrations from our laboratories, some of the manifestations of electrochemistry in electroactive materials.

A facile approach for the fabrication of 2D supermicelle networks.

A novel and facile approach to fabricating well-organized macroscopic 2D networks of cylindrical micelles is reported, based on transfer printing and thermal welding of aligned supramolecular micelles of block copolymers. This versatile approach provides a new strategy for fabricating functional 2D superstructures with a higher level of order.

Nonendocytic delivery of lipoplex nanoparticles into living cells using nanochannel electroporation.

The delivery of biomolecules, including siRNAs (≈21 bp) and large plasmids (≈10 kbp), into living cells holds a great promise for therapeutic and research applications. Lipoplex nanoparticles are popular nanocarriers for gene delivery. In conventional transfection methods, the cellular uptake of lipoplex nanoparticels occurs through the endocytosis process. The entrapment of lipoplex nanoparticles into endocytic vesicle is a major barrier in achieving efficient gene silencing and expression. Here, a novel nanochannel electroporation (NEP) method is employed to facilitate the cellular uptake and release of siRNAs/DNAs from lipoplexes. First, it is demonstrated that in a NEP device, lipoplex nanoparticles can be injected directly into the cell cytoplasm within several seconds. Specifically, it is found that lipoplexes containing MCL-1 siRNA delivered by NEP can more efficiently down-regulate the expression of MCL-1 mRNA in A549 cancer cells than conventional transfection. Quantum dot-mediated Förster resonance energy transfer (QD-FRET) reveals that lipoplexes delivered via NEP can directly release siRNA in the cytoplasm without going through the endocytosis route, which unravels the responsible mechanism for efficient gene delivery. Furthermore, the advantage of combining NEP with lipoplex nanoparticles by the successful delivery of large plasmids (pCAG2LMKOSimO, 13 kbp) into CHO cells is demonstrated.