Supramolecular assembly of cyclodextrin-based nanoparticles on solid surfaces for gene delivery

In this work, a new approach for surface-mediated gene delivery based on inclusion complex formation between the solid surface and delivery vehicles is presented. beta-Cyclodextrin (CD) molecules form high-affinity inclusion complexes with adamantane. This complexation ability was used to specifically immobilize beta-CD-modified poly(ethylenimine) (CD-PEI) nanoparticles on adamantane- (AD-) modified self-assembled monolayers. To investigate the nanoparticle/surface interaction, CD-PEI-based and PEI-based nanoparticles were passed through a surface plasmon resonance flow cell containing the monolayers. CD-PEI nanoparticles are specifically immobilized on the chip surface by cyclodextrin-adamantane inclusion complex formation. Minimal nanoparticle adsorption was detected with PEI-based nanoparticles or on control surfaces. Competition studies with free cyclodextrins reveal that the multivalent interactions between CD-PEI nanoparticles and the adamantane-modified surface results in significantly higher binding affinity than single cyclodextrin-adamantane complexes. Immobilized nanoparticles were characterized by atomic force microscopy and quantified by fluorescence assay. Thus, the ability of CD-PEI nanoparticles to form inclusion complexes can be exploited to attain specific, high-affinity loading of delivery vehicles onto solid surfaces.     

Controlled assembly of mesoscale structures using DNA as molecular bridges

Mesoscale polyhedral structures from binary mixtures of microspheres of specific size ratios were prepared by using DNA as a molecular bridge. Carboxy-modified polystyrene beads were decorated with fluorescently labeled single-stranded DNA via carboxydiimide chemistry. Fluorescent resonance electron transfer in a confocal microscopy setting was utilized to corroborate DNA hybridization. Tetrahedrons were made by combining DNA-containing 0.818 and 0.211 mum beads, while octahedrons were obtained by bridging 0.818 and 0.364 mum beads. Confocal data in the reflection mode and SEM provide evidence for the formation of mesoscale building blocks.     

Supramolecular structures and assembly and luminescent properties of quinacridone derivatives

The synthesis and single-crystal X-ray structures of two quinacridone derivatives, N,N'-di(n-butyl)quinacridone (1) and N,N'-di(n-butyl)-1,3,8,10-tetramethylquinacridone (2), are reported, and the 1H NMR, absorption, photoluminescent (PL), and electroluminescent (EL) characteristics are presented. Both these crystal structures are characterized by intermolecular pi...pi and hydrogen bonding interactions. The intermolecular pi...pi interactions lead to the formation of molecular columns in the solids of 1 and 2, and the interplanar contact distances between two adjacent molecules are 3.48 and 3.55 angstroms, respectively. Crystals of 1 display shorter intermolecular pi...pi contacts and higher density than 2. These results suggest that tighter intermolecular interactions exist in 1. The 1H NMR, absorption, and PL spectra of 1 and 2 in solutions exhibit concentration-dependent properties. The PL quantum yields of 1 in solutions decrease more quickly with the increase of concentration compared to that of 2 in solutions. For solid thin films of Alq3:1 (Alq3 = tris(8-hydroxyquinolinato)aluminum), emission intensities dramatically decrease and obvious red shifts are observed when the dopant concentration is above 4.2%, while for films of Alq3:2, a similar phenomenon occurs when the concentration is above 6.7%. EL devices with Alq3:1 as emitting layer only show high efficiencies (20.3-14.5 cd/A) within the narrow dopant concentration range of 0.5-1.0%. In contrast, high efficiencies (21.5-12.0 cd/A) are achieved for a wider dopant concentration range of 0.5-5.0% when Alq3:2 films are employed as emitting layer. The different PL and EL concentration-dependent properties of the solid thin films Alq3:1 and Alq3:2 are attributed to their different molecular packing characteristics in the solid state.     

Supramolecular assembly system depended on guest species based on bis-naphthane modified β-cyclodextrin dimer

The supramolecular assembly system based on bis naphtahlene modified β-cyclodextrin dimer linked with ethylenediamine unit was studied. The synthesis of the titled compound (β-1) was succeeded in a 7% synthetic yield. It was observed that β-1 showed monomer emission, which was decreased concurrently with appearance of excimer emission in an addition of guest species such as 1-adamantanol or ursodeoxycholic acid. When γ-CyD was added to the system, two types of fluorescent spectra were obtained, which was depended on guest species. It was indicated that both of naphthalene units of β-1 were included in the γ-CyD cavity in the presence of 1-adamantanol in a fashion of 2:1 complex. On the other hand, an addition of ursodeoxycholic acid gave disappearance of the excimer emission as well as increase of monomer emission. In the system, each of the appended units was trapped by the each of two γ-CyDs, which is 2:2 complex formation.     

Supramolecular [60]fullerene chemistry on surfaces

This critical review documents the exceptional range of research avenues in [60]fullerene-based monolayers showing unique and spectacular physicochemical properties which prompted such materials to have potential applications in several directions, ranging from sensors and photovoltaic cells to nanostructured devices for advanced electronic applications, that have been pursued during the past decade. It illustrates how progress in covalent [60]fullerene functionalisation led to the development of spectacular surface-immobilised architectures, including dyads and triads for photoinduced electron and energy transfer, self-assembled on a wide variety of surfaces. All of these molecular assemblies and supramolecular arrays feature distinct properties as a consequence of the presence of different molecular units and their spatial arrangement. Since the properties of [60]fullerene-containing films are profoundly controlled by the deposition conditions, substrate of adsorption, and influenced by impurities or disordered surface structures, the progress of such new [60]fullerene-based materials strongly relies on the development of new versatile and broad preparative methodologies. Therefore, the systematic exploration of the most common approaches to prepare and characterise [60]fullerene-containing monolayers embedded into two- or three-dimensional networks will be reviewed in great detail together with their main limitations. Recent investigations hinting at potential technological applications addressing many important fundamental issues, such as a better understanding of interfacial electron transfer, ion transport in thin films, photovoltaic devices and the dynamics associated with monolayer self-assembly, are also highlighted.     

Combining magnetic field induced locomotion and supramolecular interaction to micromanipulate glass fibers: toward assembly of complex structures at mesoscale

The formation of ordered complex structures is one of the most challenging fields in the research of biomimic materials because those structures are promising with respect to improving the physical and mechanical properties of man-made materials. In this letter, we have developed a novel approach to fabricating complex structures on the mesoscale by combining magnetic-field-induced locomotion and supramolecular-interaction-assisted immobilization. We have employed a magnetic field to locomote the glass fiber, which was modified by the layer-by-layer self-assembly of magnetic nanoparticles, to desired positions and have exploited the supramolecular interaction to immobilize glass fiber onto the appointed position. By magnetically induced micromanipulation, we can drive another fiber across the former one and finally obtain a crossing structure, which can lead to more complex structures on the mesocale. Moreover, we have constructed a mesoscale structure, termed "CHEM", to demonstrate further the application of this method.     

Supramolecular structures in nanocomposite multilayered films

We investigate the multilayered structures of poly(ethylene)oxide/montmorillonite nanocomposite films made from solution. The shear orientation of a polymer-clay network in solution combined with simultaneous solvent evaporation leads to supramolecular multilayer formation in the film. The resulting films have highly ordered structures with sheet-like multilayers on the micrometer length scale. The polymer covered clay platelets were found to orient in interconnected blob-like chains and layers on the nanometer length scale. Inside the blobs, scattering experiments indicate the polymer covered and stacked clay platelets oriented in the plane of the film. The polymer is found to be partially crystalline although this is not visible by optical microscopy. Atomic force microscopy suggests that the excess polymer, which is not directly adsorbed to the clay, is wrapped around the stacked platelets building blobs and the polymer also interconnects the polymer-clay layers. Overall our results suggest the re-intercalation of clay platelets in films made from exfoliated polymer-clay solutions as well as the supramolecular order and hierarchical structuring on the nanometer, via micrometer to the centimeter length scale.     

Supramolecular assembly in a polymer/ low-molar-mass system

Thermal analysis and infra-red spectroscopy have been used to study the interactions between poly (N-vinylpyrrolidone) and low-molar-mass, hydrogen-bonding-active aromatics. A remarkably strong interaction is observed between the polymer and 3,5-dihydroxybenzoic acid, which is consistent with the crosslinking of the polymer by acid dimers.     

Supramolecular assembly of three d10 metal coordination polymers based on the naphthalene-1,8-dicarboxylate ligand: Syntheses, structures and luminescent properties

Three d¹⁰ tetranuclear complexes, [Cd₄(1,8-nap)4(2,2′-bipy)₄(H₂O)8]·6H₂O (1,8-nap = naphthalene-1,8-dicarboxylate and 2,2′-bipy = 2,2′-bipyridine) (1), [Cd₄(1,8-nap)4(2,2′-bipy)₄(H₂O)8]·6H₂O (2) and [Zn₄(1,8-nap)₄(2,2′-bipy)₄(H₂O)4]·2H₂O (3), have been synthesized under hydrothermal conditions and characterized by elemental analyses, IR and X-ray diffraction techniques. Complexes 1 and 2 are isomers showing one-dimensional ribbon-like structures connected by O-H…O hydrogen bonds, and the one-dimensional ribbons are further linked into the three-dimensional network by π-π stacking. In complex 3, the intramolecular O-H…O hydrogen bonds just exist in the inner of the single molecule ring to consolidate its structure, and the single molecules are further linked into a two-dimensional layer structure by the π-π stacking interactions. The luminescent properties reveal that all the complexes display luminescent properties in the violet region.     

Supramolecular structures and conformational transitions in polyelectrolyte gels

Three actual problems connected with the collapse transition of polyelectrolyte gels in poor solvent are reviewed. (i) The first topic is the appearance of microstructures for polyelectrolyte gels in poor enough solvents. Three reasons for microsegregation are discussed: effect of polyelectrolyte – hydrophobic competition, effect of the formation of multiplets from ionic pairs in the ionomer regime and the effect of partial formation of glassy kinetically frozen polymer rich regions. (ii) Second we analyze the interaction of the gels with polymers which are capable to form complexes with the gel chains. Main experimental results are presented for poly(methacrylic acid) gels interacting with poly(ethylene oxide), (iii) Finally, we consider the problem of interaction of polyelectrolyte gels with the sufactants. The micelle formation of surfactants inside the gel and its consequences for the conformational properties of the gel are discussed in detail.     

Supramolecular pseudopolymorphs: double helix and planar structures with channels

3,5-Dinitrobenzamide (DNBA) and 4,4′-bipyridyl (BP) co-crystallize to yield different types of channel structure from methanol and water, constituting supramolecular pseudopolymorphs. While, in the methanol adduct, DNBA and methanol molecules form a double helix network, in the water adduct, DNBA and water molecules yield a planar layer structure. However, in both the adducts, BP molecules sit in the channels created in the three-dimensional packing of the double helix or layers.     

Molecular ordered structures on solid surfaces

Problems involved in producing perfect, two-dimensionally ordered Langmuir-Blodgett films (LBF) are examined. In particular, the role of the physicochemical state of a semiconductor substrate in the formation of the planar structure of Langmuir-Blodgett layers is studied. The method of slow-electron diffraction was used to record the hexagonal structure of a bilayer of stearic acid on an atomically pure (111) surface of Cd_xHg_1–xTe semiconductor. LBF of certain types of amphophilic phthalocryanines were obtained. The relationship between the structure and the electric and optical properties of these films is established and explained. The possibilities of specifically changing the magnitude of electrical conductivity, band shape of optical absorption, and optical planar dichroism of LBF of phthalocyanines are demonstrated. A sensitive nitrogen oxide sensor can be designed, based on the planar conductivity modulation effect of LBF.Translated from Teoreticheskaya i. Éksperimental'naya Khimiya, Vol. 29, No. 4, pp. 291–305, July–August, 1993.     

Magnetic nanoparticle assembly on surfaces using click chemistry

Controlled assembly of ferromagnetic nanoparticles on surfaces is of crucial importance for a range of spintronic and data storage applications. Here, we present a novel method for assembling monolayers of ferromagnetic FePt nanoparticles on silicon oxide substrates using "click chemistry". Reaction of alkyne-functionalized FePt nanoparticles with azide-terminated self-assembled monolayers (SAMs), on silicon oxide, leads to the irreversible attachment of magnetic nanoparticles to the surface via triazole linkers. Based on this covalent interaction, well-packed monolayers of FePt nanoparticles were prepared and nanoparticle patterns are generated on surfaces via microcontact printing (μCP).     

Peculiarities of polyelectrolyte multilayer assembly on patterned surfaces

The layer-by-layer assembly of poly(diallyldimethylammonium chloride) and poly(sodium 4-styrenesulfonate) is studied on templates with imprinted arrays of microwells ranging from 2 to 25 μm and different aspect ratios. The thickness and microstructure of polyelectrolyte multilayers (PEMs) are measured using scanning electron microscopy. At 0.2 M ionic strength, the PEM film evenly coats the template both inside and outside the microwells. If the film is thinner than the critical value of about 400 nm, PEM microstructures collapse upon dissolving the template. Euler's model of critical stress is used to describe the collapse. At 2 M ionic strength, a substantially thinner PEM film is assembled inside the 25 μm wells than outside. If the well diameter is reduced to 7 and 2 μm, a much thicker PEM film is formed inside the microwells. These observations have been attributed to the changing of polyelectrolyte conformation in the solutions.     

Signal-directed sequential assembly of biomolecules on patterned surfaces

The signal-guided and sequential assembly of biomolecules onto patterned surfaces is demonstrated. Readily transmittable electric signals are used to guide spatially selective deposition of the pH-responsive polysaccharide, chitosan, and functionalized chitosan conjugates, by generating localized pH gradients. The nucleophilic primary amine groups of chitosan enable facile conjugation of proteins and nucleic acids by two approaches, one an enzymatic approach and the other a standard chemical modification, thus providing flexibility when sequentially assembling biomolecules in a spatially selective manner. Moreover, we developed an agarose gel "biomask" for the sequential assembly of single-stranded DNA and confirmed its functionality through nucleic acid hybridization assays.     

NaBH4-induced assembly of immobilized Au nanoparticles into chainlike structures on a chemically modified glass surface

A facile method of obtaining chainlike assemblies of gold nanoparticles (AuNPs) on a chemically modified glass surface based on NaBH(4) treatment is developed. Citrate-stabilized AuNPs (17 nm) are immobilized on a glutaraldehyde-functionalized glass surface and assembled into chainlike structures after treatment with aqueous sodium borohydride (NaBH(4)) solution. The production and morphology of the AuNP chainlike assemblies are controlled by the density of the immobilized NPs, the concentration of NaBH(4) solution, and the treatment time. The AuNP assemblies are stable in water and can undergo drying. X-ray photoelectron spectroscopic data show that the number of citrate ions on the AuNPs decreased by 43% after treatment with 5 mg/mL NaBH(4) solution. The NaBH(4)-induced partial removal of the citrate ions and the roughness of the glass surface greatly affect the binding force of AuNPs on the substrate. The immobilized AuNPs begin to move at the solid-liquid interface without desorbing when the strength of the binding force was decreased. These mobile NPs form chainlike assemblies under the driving force of van der Waals interaction and diffusion. This interface-based formation of chainlike assemblies of AuNPs may provide a simple protocol for the 1D assembly of other Au-coated colloidal nanoparticles.     

Supramolecular porphyrinic prisms: coordinative assembly and solution phase X-ray structural characterization

Supramolecular porphyrin prisms have been obtained via coordinative self-assembly and characterized by 1H NMR, PFG NMR, electronic absorption spectroscopy and synchrotron-based measurements of solution phase X-ray scattering and diffraction.