Self-assembled multimicellar vesicles via complexation of a rigid conjugated polymer with an amphiphilic block copolymer

A viable method of encapsulating block copolymer micelles inside vesicles using a conjugated polymer is reported in this study. Self-assembly and complexation between an amphiphilic block copolymer poly(methyl methacrylate)-b-poly(acrylic acid) (PMMA-b-PAA) and a rod-like conjugated polymer polyaniline (PANI) in aqueous solution were studied using transmission electron microscopy, atomic force microscopy and dynamic light scattering. The complexation and morphology transformation were driven by electrostatic interaction between PANI and the PAA block of the block copolymer. Addition of PANI to PMMA-b-PAA induced the morphology transformation from micelles to irregular vesicles through vesicles, thick-walled vesicles (TWVs) and multimicellar vesicles (MMVs). Among the observed morphologies, MMVs were observed for the first time. Morphology transformation was studied as a function of aniline/acrylic acid molar ratio ([ANI]/[AA]). Micelles were observed for the pure block copolymer, while vesicles and TWVs were observed at [ANI]/[AA] = 0.1 and 0.3, respectively. MMVs were observed at [ANI]/[AA] = 0.5 and irregular vesicles were observed for molar ratios at 0.7 and above. Clearly, a conjugated polymer like polyaniline can induce a morphology transformation even at its lower concentrations and produce complex morphologies.

Giant tubular and toroidal vesicles from self-assembled triblock copolymer-polyaniline complexes in water

An ABA type amphiphilic triblock copolymer was synthesized via ATRP and sulfonation. New self-assembled morphologies such as toroidal vesicles, giant tubular vesicles, and perforated spherical vesicles were observed from triblock copolymer-polyaniline complexes in water. The mechanism of morphology transformation at different compositions was discussed.

Control of partial coalescence of self-assembled metal nano-particles across lyotropic liquid crystals templates towards long range meso-porous metal frameworks design

The formation of purely metallic meso-porous metal thin films by partial interface coalescence of self-assembled metal nano-particles across aqueous solutions of Pluronics triblock lyotropic liquid crystals is demonstrated for the first time. Small angle X-ray scattering was used to study the influence of the thin film composition and processing conditions on the ordered structures. The structural characteristics of the meso-structures formed demonstrated to primarily rely on the lyotropic liquid crystal properties while the nature of the metal nano-particles used as well as the their diameters were found to affect the ordered structure formation. The impact of the annealing temperature on the nano-particle coalescence and efficiency at removing the templating lyotropic liquid crystals was also analysed. It is demonstrated that the lyotropic liquid crystal is rendered slightly less thermally stable, upon mixing with metal nano-particles and that low annealing temperatures are sufficient to form purely metallic frameworks with average pore size distributions smaller than 500 nm and porosity around 45% with potential application in sensing, catalysis, nanoscale heat exchange, and molecular separation.

Self-assembled peptide nanostructures for the fabrication of cell scaffolds

The fabrication of artificial scaffolds that effectively mimic the host environment of the cell have exciting potential for the treatment of many diseases in regenerative medicine. In particular, appropriately designed scaffolds have the capacity to support, replace, and mediate the transplantation of therapeutic cells in order to regenerate damaged or diseased tissues. To achieve these goals for regeneration, the engineering of an environment structurally similar to the native extracellular matrix (ECM) is necessary in order to closely match the chemical and physical conditions found within the extracellular niche. Recently, self-assembled peptide (SAP) hydrogels have shown great potential for such biological applications due to their inherent biocompatibility, propensity to form higher order structures, rich chemical functionality and ease of synthesis. Importantly, it is possible to control the organization and properties of the target materials as the chemical structure is determined by amino acid sequence. Here, the development of SAP hydrogels as functional cell scaffolds and useful tools in tissue engineering is reviewed.

Tuning the mechanical and morphological properties of self-assembled peptide hydrogels via control over the gelation mechanism through regulation of ionic strength and the rate of pH change

Hydrogels formed by the self-assembly of peptides are promising biomaterials. The bioactive and biocompatible molecule Fmoc-FRGDF has been shown to be an efficient hydrogelator via a π-β self-assembly mechanism. Herein, we show that the mechanical properties and morphology of Fmoc-FRGDF hydrogels can be effectively and easily manipulated by tuning both the final ionic strength and the rate of pH change. The increase of ionic strength, and consequent increase in rate of gelation and stiffness, does not interfere with the underlying π-β assembly of this Fmoc-protected peptide. However, by tuning the changing rate of the system's pH through the use of glucono-δ-lactone to form a hydrogel, as opposed to the previously reported HCl methodology, the morphology (nano- and microscale) of the scaffold can be manipulated.

Self-assembled V2O5 interconnected microspheres produced in a fish-water electrolyte medium as a high-performance lithium-ion-battery cathode

Interconnected microspheres of V2O5 composed of ultra-long nanobelts are synthesized in an environmental friendly way by adopting a conventional anodization process combined with annealing. The synthesis process is simple and low-cost because it does not require any additional chemicals or reagents. Commercial fish-water is used as an electrolyte medium to anodize vanadium foil for the first time. Electron microscopy investigation reveals that each belt consists of numerous nanofibers with free space between them. Therefore, this novel nanostructure demonstrates many outstanding features during electrochemical operation. This structure prevents self-aggregation of active materials and fully utilizes the advantage of active materials by maintaining a large effective contact area between active materials, conductive additives, and electrolyte, which is a key challenge for most nanomaterials. The electrodes exhibit promising electrochemical performance with a stable discharge capacity of 227 mAh·g–1 at 1C after 200 cycles. The rate capability of the electrode is outstanding, and the obtained capacity is as high as 278 at 0.5C, 259 at 1C, 240 at 2C, 206 at 5C, and 166 mAh·g–1 at 10C. Overall, this novel structure could be one of the most favorable nanostructures of vanadium oxide-based cathodes for Li-ion batteries. [Figure not available: see fulltext.]

Enhancement of ‘dry’ proton conductivity by self-assembled nanochannels in all-solid polyelectrolytes

Proton transport has been recognized as an essential process in many biological systems, as well as electrochemical devices including fuel cells and redox flow batteries. In the present study, we address the pressing need for solvent-free proton conducting polymer electrolytes for high-temperature PEM fuel cell applications by developing a novel all-solid polyelectrolyte membrane with a self-assembled proton-channel structure. We show that this self-assembled nanostructure endows the material with exciting ‘dry’ proton conductivity at elevated temperatures, as high as 0.3 mS cm−1 at 120 °C, making it an attractive candidate for high-temperature PEM fuel cell applications. Based on the combined investigation of solid-state NMR, FTIR and conductivity measurements, we propose that both molecular design and nano-scale structures are essential for obtaining highly conductive anhydrous proton conductors.

Self-assembled core-satellite gold nanoparticle networks for ultrasensitive detection of chiral molecules by recognition tunneling current

Chirality sensing is a very challenging task. Here, we report a method for ultrasensitive detection of chiral molecule l/d-carnitine based on changes in the recognition tunneling current across self-assembled core-satellite gold nanoparticle (GNP) networks. The recognition tunneling technique has been demonstrated to work at the single molecule level where the binding between the reader molecules and the analytes in a nanojunction. This process was observed to generate a unique and sensitive change in tunneling current, which can be used to identify the analytes of interest. The molecular recognition mechanism between amino acid l-cysteine and l/d-carnitine has been studied with the aid of SERS. The different binding strength between homo- or heterochiral pairs can be effectively probed by the copper ion replacement fracture. The device resistance was measured before and after the sequential exposures to l/d-carnitine and copper ions. The normalized resistance change was found to be extremely sensitive to the chirality of carnitine molecule. The results suggested that a GNP networks device optimized for recognition tunneling was successfully built and that such a device can be used for ultrasensitive detection of chiral molecules.

Desymmetrization of an octahedral coordination complex Inside a self-assembled exoskeleton

The synthesis of a centrally functionalized, ribbon-shaped [6]polynorbornane ligand L that self-assembles with PdII cations into a (Pd2L4) coordination cage is reported. The shape-persistent (Pd2L4) cage contains two axial cationic centers and an array of four equatorial H-bond donors pointing directly towards the center of the cavity. This precisely defined supramolecular environment is complementary to the geometry of classic octahedral complexes [M(XY)6] with six diatomic ligands. Very strong binding of [Pt(CN)6]2- to the cage was observed, with the structure of the host-guest complex ([Pt(CN)6]@Pd2L4) supported by NMR spectroscopy, MS, and X-ray data. The self-assembled shell imprints its geometry on the encapsulated guest, and desymmetrization of the octahedral platinum species by the influence of the D4h-symmetric second coordination sphere was evidenced by IR spectroscopy. [Fe(CN)6]3- and square-planar [Pt(CN)4]2- were strongly bound. Smaller octahedral anions such as [SiF6]2-, neutral carbonyl complexes ([M(CO)6]; M=Cr, Mo, W) and the linear [Ag(CN)2]- anion were only weakly bound, showing that both size and charge match are key factors for high-affinity binding.

Designing self-assembled multicomponent scaffolds for regenerative medicine

This project demonstrated novel approaches to incorporate multiple bioactive peptide sequences polysaccharides and proteoglycans. Demonstrated applications for both in vitro 3D cell culture and in vivo applications; highlighting the significance of this class of biomaterial for a range of therapeutic applications and use as a new generation of regenerative materials.