金纳米棒自组装的研究进展

金纳米棒具有独特的光电性能,其自组装形成的功能组装体能够展现出更加优异的整体协同性能,在纳米材料科学和生物医学领域中有广泛而重要的应用前景.本文从诱导自组装各种驱动作用力的角度,综述了金纳米棒自组装的最新研究进展,具体内容包括:表面张力引发的自组装、化学作用驱动如静电作用或氢键作用等引发的自组装以及生物分子识别作用引发的自组装.     

Temperature-triggered self-assembly of ZnO: from nanocrystals to nanorods to tablets

ZnO nanocrystals, nanorods, and tablets were prepared at 110, 140, and 180 degrees C in a water-ethanol system. Nanorods (~2 x 40 nm) arranged in serpentine morphologies formed by the oriented coalescence of anhedral ZnO nanocrystals (~3.5 nm diameter), while tabular ZnO grew by [1210] textural attachment of the nanorods. The development of these crystal habits is believed to proceed via a dissolution and growth mechanism mediated by a transient amorphous phase. Materials synthesized at intermediate temperatures (125 and 160 degrees C) possessed microstructures containing mixed crystal forms in the expected orientation relationship. Photoluminescent spectra of the nanocrystals and nanorods showed blue shifts of 0.16 and 0.13 eV with respect to the bulk ZnO band gap (3.26 eV) due to quantum confinement, with the narrow emission peaks typical of particles possessing uniform size and shape. The larger tablets displayed a less energetic emission (3.10 eV) ascribed to exciton-exciton collisions.     

Spontaneous self-assembly of cerium oxide nanoparticles to nanorods through supraaggregate formation

Self-assembly of cerium oxide nanoparticles to nanorods is reported. Such nanorods have an aspect ratio of 6 with a diameter of approximately 40 nm. The formation of cylindrical supraaggregates and their subsequent growth by preferential assembling of ceria nanocrystallites along the longitudinal direction was proposed to be the probable mechanism of spontaneous self-assembly of nanorods. The supraaggregate formation was facilitated by influencing the local curvature of the micelle surface in the presence of nitrate ions as a precursor solution. The nanorods were characterized using high-resolution transmission electron microscopy with energy dispersive spectroscopy and selected area electron diffraction for their morphology, chemistry, and crystal structure.     

Formation of organometallic polymer nanorods using a nanoporous alumina template and the conversion to magnetic ceramic nanorods

Polyferrocenylsilane nanorods were prepared using a porous anodic aluminium oxide template followed by chemical etching; pyrolysis was used to obtain magnetic iron oxide-containing ceramic nanorods.     

Anion template effect on the self-assembly and interconversion of metallacyclophanes

Reactions of 3,6-bis(2-pyridyl)-1,2,4,5-tetrazine (bptz) with solvated first-row transition metals M(II) (M(II) = Ni, Zn, Mn, Fe, Cu) have been explored with emphasis on the factors that influence the identity of the resulting cyclic products for Ni(II) and Zn(II). The relatively small anions, namely [ClO4]- and [BF4]-, lead to the formation of molecular squares [{M4(bptz)4(CH3CN)8} subsetX][X]7, (M = Zn(II), Ni(II); X = [BF4]-, [ClO4]-), whereas the larger anion [SbF6]- favors the molecular pentagon [{Ni5(bptz)5-(CH3CN)10} subsetSbF6][SbF6]9. The molecular pentagon easily converts to the square in the presence of excess [BF4]-, [ClO4]-, and [I]- anions, whereas the Ni(II) square can be partially converted to the less stable pentagon under more forcing conditions in the presence of excess [SbF6]- ions. No evidence for the molecular square being in equilibrium with the pentagon was observed in the ESI-MS spectra of the individual square and pentagon samples. Anion-exchange reactions of the encapsulated ion in [{Ni4(bptz)4(CH3CN)8} subsetClO4][ClO4]7 reveal that a larger anion such as [IO4]- cannot replace [ClO4]- inside the cavity, but that the linear [Br3]- anion is capable of doing so. ESI-MS studies of the reaction between [Ni(CH3CN)6][NO3]2 and bptz indicate that the product is trinuclear. Mass spectral studies of the bptz reactions with Mn(II), Fe(II), and Cu(II), in the presence of [ClO4]- anions, support the presence of molecular squares. The formation of the various metallacyclophanes is discussed in light of the factors that influence these self-assembly reactions, such as choice of metal ion, anion, and solvent.     

Grazing incidence X-ray scattering to probe the self-assembly of phthalocyanine nanorods on a liquid surface

The structural properties of Langmuir monolayers on aqueous substrates of a metal free phthalocyanine, 2,9,16,23-tetrakis(phenylthio)-29H,31H-phthalocyanine and an Aluminum centered phthalocyanine, Aluminum 2,9,16,23-tetrakis(phenylthio)-29H,31H-phthalocyanine chloride are reported here. Their structure is investigated under progressive lateral compression by grazing incidence diffuse X-ray scattering out of the specular plane to determine specular reflectivity-like information where the phase change of the molecules from "flat-lying" on the surface to "edge-standing" perpendicular to the surface was directly observed. Furthermore grazing incident X-ray diffraction is used to investigate the in-plane ordering of the system where it has been found that at high density states the systems can be considered as monolayers consisting of arrays of side-by-side cofacially aggregated cylindrical rodlike entities.     

Tumor microenvironment-oriented adaptive nanodrugs based on peptide self-assembly

The aberrant metabolism of tumor cells creates an inimitable microenvironment featuring acidic pH, high glutathione (GSH) levels, and overexpression of certain enzymes, which benefits the overwhelming progress of a tumor. Peptide self-assembly, emerging as a biofriendly and versatile fabrication strategy, harnesses multiple noncovalent interactions to obtain a variety of nanostructures tailored on demand. Orchestrating the reversible nature of noncovalent interactions and abnormal physiological parameters in the tumor microenvironment enables peptide-based nanodrugs to be targetable or switchable, thereby improving the drugs’ bioavailability and optimizing the treatment outcome. This review will focus on peptide-modulated self-assembly of photosensitizers, chemotherapeutic drugs, immunoactive agents for tumor microenvironment-oriented adaptive phototherapy, chemotherapy, immunotherapy and combinatorial therapy. We will emphasize the building block design, the intermolecular interaction principle, adaptive structural transformation in the tumor microenvironment and corresponding therapeutic efficacy, and aim to elucidate the critical role of peptide-modulated, tumor microenvironment-oriented adaptive assemblies in improving the therapeutic index. Challenges and opportunities will be covered as well to advance the development and clinical application of tumor therapies based on peptide self-assembly materials and techniques.

The tumor microenvironment is of significance to promote release or reorganization of peptide-modulated nanodrugs, optimizing drug bioavailability and therapeutic outcome.     

Intramolecular diels-alder reaction by self-assembly of the components on a lewis acid template

Diels-Alder reactions of 2,4-hexadienol or its O-methyl ether with acrylate derivatives at 120 degrees C give mixtures of the four possible adducts with low selectivity. At ambient temperature and in the presence of Mg(II) or Al(III) Lewis acids, reactions of the dienol (but not the ether) are highly selective. Control experiments suggest that the Lewis acid serves both to tether the diene and dienophile and to induce an "intramolecular" reaction of the resulting "self-assembled" intermediate.     

Diene-transmissive cycloadditions: control of monocycloaddition by self-assembly on a Lewis acid template

The sequential control of diene-transmissive Diels-Alder reactions to expand their versatility for natural product synthesis and the preparation of diversity oriented libraries is described. Self-assembly of the components (trienol 5 and methyl acrylate) via a Lewis acid template proceeds with regio-, diastereo-, and enantioselective [(S)-BINOL added] control to the monoadduct. In contrast, no cycloaddition reaction occurred at 22 degrees C in the absence of catalyst. This protocol obliterates the necessity of tether installation for an intramolecular cyclization. [reaction: see text].     

Size selective assembly of colloidal particles on a template by directed self-assembly technique

We report a simple and effective approach to organize micron- and submicron-sized particles in a size selective manner. This approach utilizes the template assisted directed self-assembly technique. A topographically patterned photoresist surface is fabricated and used to create an ordered array of colloidal particles from their aqueous suspensions. Assembly of particles on this template is then achieved by using a conventional spin coating technique. Feasibility of this technique to form a large area of patterned particle assemblies has been investigated. To arrange the particles on the template, the physical confinement offered by the surface topography must overcome a joint effect of centrifugal force and the hydrophobic nature of the photoresist surface. This concept has been extended to the size selective sorting of colloidal particles. The capability of this technique for sorting and organizing colloidal particles of a particular diameter from a mixture of microspheres is demonstrated.     

Catalytic enantioselective Diels-Alder reaction by self-assembly of the components on a Lewis acid template

Thermal Diels-Alder reaction of 2,4-hexadienol with methyl acrylate is unselective. By simultaneous coordination of diene and dienophile to a chiral bimetallic Lewis acid catalyst, a LACASA-DA reaction occurs with complete control of regio-, diastereo-, and enantioselectivity to give a single adduct. [reaction: see text]     

Effects of oligoDNA template length and sequence on binary self-assembly of a nucleotide bolaamphiphile

Templated self-assembly of nucleotide bolaamphiphile 1 (in which a 3'-phosphorylated thymidine moiety is connected to each end of a long oligomethylene chain) with a 10-, 20-, 30-, or 40-meric single-stranded oligoadenylic acid (2, 3, 4, or 5) led to the formation of right-handed helical nanofibers in 0.1x Tris/EDTA (TE) buffer solutions. The helical pitch increased as the length of the oligoadenylic acid template increased. DNA composed of oligoadenylic and oligocytidylic acid sequences (6, 7, and 8) also acted as templates to induce the formation of helical nanofiber structures. The diameter of the nanofibers remained constant (6-6.6 nm) irrespective of the template used. The binary self-assembly of 1 with 4 also produced higher-order, double-stranded nanofibers.     

Effect of NaCl and peptide concentration on the self-assembly of an ionic-complementary peptide EAK16-II

Previous work has examined the effects of such factors as pH and peptide concentration on the self-assembly of ionic-complementary peptides. This work focused on the effect of sodium chloride on the molecular self-assembly of an ionic-complementary peptide EAK16-II (AEAEAKAKAEAEAKAK). Surface tensions and dimensions of the self-assembled nanostructures were determined for a wide range of peptide and sodium chloride concentrations using axisymmetric drop shape analysis-profile (ADSA-P) and atomic force microscopy (AFM), respectively. The critical aggregation concentration, or critical self-assembly concentration (CSAC), of EAK16-II was not significantly affected by the presence of NaCl. However, the analysis of size variations in self-assembled nanostructures in response to changes in NaCl concentration indicated that the presence of NaCl does influence the resulting dimensions of the peptide nanostructures when the peptide concentration is below its CSAC. A critical NaCl concentration was identified at approximately 20mM, below which the equivalent radius of the peptide fibrils increased with increasing salt concentration, and above which the opposite response was observed. This critical NaCl concentration was further confirmed in the surface tension measurements, where the equilibrium surface tension and induction time of the peptide at low concentrations (相似文献   

Effect of PEG crystallization on the self-assembly of PEG/peptide copolymers containing amyloid peptide fragments

The effect of poly(ethylene glycol) PEG crystallization on beta-sheet fibril formation is studied for a series of three peptide/PEG conjugates containing fragments modified from the amyloid beta peptide, specifically KLVFF, FFKLVFF, and AAKLVFF. These are conjugated to PEG with M n = 3300 g mol (-1). It is found, via small-angle X-ray scattering, X-ray diffraction, atomic force microscopy, and polarized optical microscopy, that PEG crystallinity in dried samples can disturb fibrillization, in particular cross-beta amyloid structure formation, for the conjugate containing the weak fibrillizer KLVFF, whereas this is retained for the conjugates containing the stronger fibrillizers AAKLVFF and FFKLVFF. For these two samples, the alignment of peptide fibrils also drives the orientation of the attached PEG chains. Our results highlight the importance of the antagonistic effects of PEG crystallization and peptide fibril formation in PEG/peptide conjugates.     

Ex situ atomic force microscopy analysis of beta-amyloid self-assembly and deposition on a synthetic template

The beta-amyloid (Abeta) deposition, which is the conversion of soluble Abeta peptides to insoluble plaques on a surface, is an essential pathological process in Alzheimer's disease (AD). The identification and characterization of possible environmental factors that may influence amyloid deposition in vivo are important to unveil the underlying etiology of AD. According to the amyloid cascade hypothesis, diffuse plaques are initial and visual deposits in the early event of AD, leading to amyloid plaques. To study amyloid deposition and growth in vitro, we prepared a synthetic template by immobilizing Abeta seeds on an N-hydroxysuccinimide ester-activated solid surface. According to our analysis with an ex situ atomic force microscope, the formation of amyloid plaque-like aggregates was mediated by the interaction between Abeta in a solution and on a synthetic template, suggesting that Abeta oligomers function well as seeds for amyloid deposition. It was observed that insoluble amyloid aggregates formed on the template surface serve as a sink of soluble Abeta in a solution as well as mediate the formation of intermediates in the pathway of amyloid fibrillization in a solution. Relative seeding efficiencies of fresh monomers, oligomers, and fully grown fibrils were analyzed by measuring the deposited plaque volume and its height distribution through atomic force microscopy. The result revealed that oligomeric forms of Abeta act more efficiently as seeds than monomers or fibrils do. Fluorescence spectroscopy with thioflavin T confirmed that amyloid aggregate formation proceeds in a concentration-dependent manner. Analysis with Fourier transform infrared spectroscopy indicated a progressive transition of soluble Abeta42 monomer to amyloid fibrils having antiparallel beta-sheet structure on the template. Furthermore, studies on the interaction between Abeta40 and 42, two major variants of Abeta derived from the amyloid precursor protein, showed that amyloid aggregate formation on the surface was accelerated further by the homogeneous association of soluble Abeta42 onto Abeta42 seeds than by other combinations. A slightly acidic condition was found to be unfavorable for amyloid formation. This study gives insight into understanding the effects of environmental factors on amyloid formation via the use of a synthetic template system.     

Recent advances in short peptide self-assembly: from rational design to novel applications

Owing to their structural simplicity and robust self-assembled nanostructures, short peptides prove to be an ideal system to explore the physical processes of self-assembly, hydrogels, semi-flexible polymers, quenched disorder, and reptation. Rational design in peptide sequences facilitates cost-effective manufacturing, but the huge number of possible peptides has imposed obstacles for their characterization to establish functional connections to the primary, secondary, and tertiary structures. This review aims to cover recent advances in the self-assembly of designed short peptides, with a focus on physical driving forces, design rules, characterization methods, and exemplar applications. Super-resolution microscopy in combination with modern image analysis have been applied to quantify the structure and dynamics of peptide hydrogels, while small-angle neutron scattering and solid-state nuclear magnetic resonance continue to provide valuable information on structures over complementary length scales. Short peptides are attractive in biomedicine and nanotechnology, e.g., as antimicrobials, anticancer agents, vehicles for controlled drug release, peptide bioelectronics, and responsive cell culture materials.     

Temperature effect on template polymerization of methacrylic acid using stereocomplex formation on quartz crystal microbalance substrates

The radical polymerization of methacrylic acid (MAA) at 0, 20, 40, and 70 °C was achieved in porous isotactic (it‐) poly(methyl methacrylate) (PMMA) films on quartz crystal microbalance (QCM) substrates, which were prepared by layer‐by‐layer assembled stereocomplex films of it‐PMMA and syndiotactic (st‐) poly(methacrylic acid) (PMAA), followed by the subsequent extraction of st‐PMAA. The MAA polymerization yields increased from 35 to 75%, as the polymerization temperature increased from 0 to 70 °C. Furthermore, infrared spectroscopy revealed that a higher polymerization temperature is necessary to form it‐PMMA/st‐PMAA stereocomplexes via stereoregular polymerization manner that resemble native it‐PMMA/st‐PMAA stereocomplexes. X‐ray diffraction pattern of porous it‐PMMA were also investigated for reaction fields. © 2014 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2014 , 52, 3032–3036     

Congener-derived template to construct lithiophilic organic-inorganic layer/interphase for high volumetric capacity dendrite-free Li metal batteries

The development of lithium-metal batteries(LMBs) is seriously restricted by the out-of-control dendrites growth and infinite volume expansion. Herein, a pervasive organic-inorganic layer construction strategy is reported for the composite lithium metal anode with congener-derived organic-inorganic solid electrolyte interphase(SEI). In this strategy, the organic-inorganic Ag@polydopamine(Ag@PDA) layer is coated on the arbitrary substrates by a simple two-step method. The thin and stable congener-...     

Template assembled synthetic proteins: Condensation of a multifunctional peptide to a topological template via chemoselective ligation

A chemoselective ligation via oxime bond formation is used for the chemical synthesis of template assembled peptides according to the TASP (Template Assembled Synthetic Proteins) approach. Aminooxyacetylation of the multifunctional partial sequence Lys- Arg- Asp- Ser of lactoferrin and subsequent condensation in aqueous solution with a topological template containing four selectively addressable aldehyde functions as attachment sites gives readily access to the TASP molecule.