Soft Nanotubes Research Articles

Electrokinetic energy conversion efficiency in a polyelectrolyte-grafted nanotube

Analytical investigations are performed for pressure driven flow of an electrically conducting, incompressible and viscous fluid in a polyelectrolyte-grafted nanotube by using Bessel functions. Nanofluidic tubes whose walls are covered by polyelectrolyte materials, named the fixed charge layer (FCL), are identified as soft nanotubes. The flow relies on an externally imposed pressure gradient and an induced reverse electroosmotic force produced by the streaming potential field which is spontaneously developed due to the ionic charge migration with the fluid flow. Many parametrical ranges are determined to ensure the validity of Debye-Hckel approximation. The analysis is based on the solutions of the linearized Poissson-Boltzmann equation and modified Navier-Stokes equation. To obtain the streaming potential, we use a numerical treatment to solve an integral equation governing the streaming potential. Finally, the electrokinetic energy conversion efficiency is studied. The result shows that both the streaming potential and energy conversion efficiency monotonically increase with the FCL thickness d increasing. However, they present a monotonic decrease trend with the increase of K, which is the ratio of the characteristic scale of the mobile charges to the fixed charge within the FCL. We compare the results in a soft nanotube with those in a rigid one, whose zeta potential is equal to the electrostatic potential at the solid-polyelectrolyte interface of the soft nanotube. We find that the electric potential in a soft nanotube is higher than that in the corresponding rigid nanotube, which results in a larger streaming potential in the soft nanotue. Moreover, for the parameter ranges considered in this work, our results show that the electrokinetic energy conversion efficiency in a soft nanotube is 1.5-3 times higher than that in a rigid nanotube. These findings are important for investigating the streaming potential and electrokinetic energy conversion efficiency in soft nanotubes. They can be used as a kind of new method to enhance the energy conversion efficiency of the electrokinetic transport in nanotube.

Soft nanotubes acting as confinement effecters and chirality inducers for achiral polythiophenes.

Depending on their nanochannel sizes, soft nanotubes were able to not only control the conformation and aggregation state of encapsulated achiral polythiophene boronic acids but also induce chirality in the polythiophene chains that exhibit chiral recognition abilities for D, L-sugars.

Short polyethylene glycol chains densely bound to soft nanotube channels for inhibition of protein aggregation

Specific thermal dehydration/rehydration of short polyethylene glycol (PEG) chains densely bound to nanotube channels was useful for aggregation suppression and refolding acceleration of proteins.

Photoinduced morphological transformations of soft nanotubes.

In water, synthetic amphiphiles composed of a photoresponsive azobenzene moiety and an oligoglycine hydrogen-bonding moiety selectively self-assembled into nanotubes with solid bilayer membranes. The nanotubes underwent morphological transformations induced by photoisomerization of the azobenzene moiety within the membranes, and the nature of the transformation depended on the number of glycine residues in the oligoglycine moiety (i.e., on the strength of intermolecular hydrogen bonding). Upon UV-light irradiation of nanotubes prepared from amphiphiles with the diglycine residue, trans-to-cis isomerization induced a transformation from nanotubes (inner diameter (i.d.) 7 nm), several hundreds of nanometers to several tens of micrometers in length, to imperfect nanorings (i.d. 21-38 nm). The cis-to-trans isomerization induced by continuous visible-light irradiation resulted in the stacking of the imperfect nanorings to form nanotubes with an i.d. of 25 nm and an average length of 310 nm, which were never formed by a self-assembly process. Time-lapse fluorescence microscopy enabled us to visualize the transformation of nanotubes with an i.d. of 20 nm (self-assembled from amphiphiles with the monoglycine residue) to cylindrical nanofibers with an i.d. of 1 nm; shrinkage of the hollow cylinders started at the two open ends with simultaneous elongation in the direction of the long axis.

Two-step naked-eye detection of lectin by hierarchical organization of soft nanotubes into liquid crystal and gel phases.

Depending on the concentration of a lectin analyte, supramolecular soft nanotubes, bearing recognition sites immobilized on the outer surface through ethylene glycol chains, hierarchically organized into naked-eye-detectable liquid crystals and hydrogels.

Soft nanotube hosts for capsulation and release of molecules, macromolecules, and nanomaterials

This review article introduces soft nanotubes with controllable diameters and functionalizable surfaces, which are formed by self-organization of well-designed synthetic amphiphiles in some solvents. The soft nanotubes are able to act as meso-scale hosts, and not only encapsulate molecules, macromolecules, and nanomaterials in the nanotube hollow cylinder but also release those encapsulated guests to bulk media. Various spectroscopy and microscopy methods enable us to clarify physical features, dynamic behavior, and stabilities of confined solvents and guests in the nanotube hollow cylinder. Nanobio functions of the soft nanotubes, such as nanocontainers for biologically-responsive drug release and artificial chaperones for refolding assistances of denatured proteins, are also described, comparing with those functions of other supramolecular systems and porous materials. Furthermore, this review article covers more recent topics, photo-functional soft materials, including the soft nanotubes having light-harvesting antenna and light-triggered morphological-transformation abilities.

Stimuli‐Responsive Materials: Soft Nanotubes with a Hydrophobic Channel Hybridized with Au Nanoparticles: Photothermal Dispersion/Aggregation Control of C60 in Water (Adv. Funct. Mater. 13/2013)

Glycolipid-based soft nanotubes with a hydrophilic outer surface and hydrophobic nanochannel encapsulating C60 are reported by Naohiro Kameta and co-workers on page 1677. It is found that the photothermal effect of gold nanoparticles hybridized with the nanotube induces an unfolding of the tubular morphology and leads to compulsive release of C60 in bulk water.

Multi‐shell Soft Nanotubes from Cyclic Peptide Templates

Multi-shell nanotubes containing poly(acrylic acid) external shell and polyisoprene internal shells are prepared by exploiting the self-assembly of an alt-(d,l) cyclic peptide template. Crosslinking of the acrylic acid shell, followed by ozonolysis of the polyisoprene, gives access to nanotubes with an internal pore which can be controlled by the degree of polymerization of polyisoprene. As a service to our authors and readers, this journal provides supporting information supplied by the authors. Such materials are peer reviewed and may be re-organized for online delivery, but are not copy-edited or typeset. Technical support issues arising from supporting information (other than missing files) should be addressed to the authors. Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.

Direct measurement of single soft lipid nanotubes: Nanoscale information extracted in a noninvasive manner

We investigated the dynamics of single soft nanotubes of phospholipids to extract nanoscale information such as the size of the tube, which were several tens to hundreds of nanometers thick. The dynamic properties of the tubes obtained from direct observation by fluorescent microscopy, such as their persistence length, enable us to access the nanoscale characteristics through a simple elastic model of the membrane. The present methodology should be applicable to the nanosized membrane structure in living cells.

Soft Nanotubes with a Hydrophobic Channel Hybridized with Au Nanoparticles: Photothermal Dispersion/Aggregation Control of C60 in Water

AbstractSimple glycolipid N‐alkaroyl‐β‐D‐glucopyranosylamine 1(n) selectively self‐assembles into sheets in water, nanotubes in alcohols, and helical nanocoils in toluene. All self‐assemblies consist of bilayer membranes in which 1(n) packed in an interdigitated fashion. The outer surface of the sheet is covered with the hydrophilic glucose headgroup of 1(n), whereas those of the nanotube and helical nanocoil are covered with the hydrophobic alkyl‐chain tail of 1(n). Heat treatment of the nanotube in the presence of water induces a rearrangement of the molecular packing of the outermost surface that allows the nanotube to become an effective nanocontainer for the dispersion of fullerene (C60) in water, a result of the ability of the hydrophilic outer surface of the nanotube and the hydrophobic nanochannel to encapsulate C60. The nanotube also exhibits photothermal characteristics after being hybridized with Au nanoparticles (AuNPs). The photothermal effect of the AuNPs allows the nanotube to unfold its tubular morphology and leads to compulsive release of the encapsulated C60 to the bulk water. Application of other nanotubes with similar photostimulated transformation ability should facilitate control of the dispersion/aggregation of other carbon nanomaterials, functional aromatic compounds, and drugs with low solubility in water.

RETRACTED: Soft Nanotubes Acting as a Light-Harvesting Antenna System

Amphiphilic monomers, which were quantitatively synthesized from a dehydration reaction between a glycolipid and naphthalene-boronic acids, self-assembled in organic solvents to selectively form tape-like structures (nanotape) and tubular structures (nanotube) depending on the bond position of the boron atom in the naphthalene ring. The nanotube has a strong narrow fluorescence band attributable to the monomer species of the naphthalene group, whereas the nanotape has a weak broad fluorescence band at a relative longer wavelength region based on the excimer species of the naphthalene group. Light energy adsorbed by the naphthalene groups densely and regularly organized in the bilayer membrane wall of the nanotube was transferred, with high quantum efficiency, into anthracene as an acceptor encapsulated in the nanochannel. The supramolecular nanotube proved to be able to act as a light-harvesting antenna.

Photoresponsive soft nanotubes for controlled guest release.

Light, transformation, release! Self-assembly of a simple amphiphile with an azobenzene unit produced an organic nanotube with 20 nm inner diameter. The trans-to-cis photoisomerization of the azobenzene unit within the solid bilayer membranes of the nanotube induced the transformation to cylindrical nanofibers (see graphic). This way, the nanotube was able to precisely release encapsulated guest molecules as a response to photostimulus.

Biomimetic helical rosette nanotubes and nanocrystalline hydroxyapatite coatings on titanium for improving orthopedic implants

Natural bone consists of hard nanostructured hydroxyapatite (HA) in a nanostructured protein-based soft hydrogel template (ie, mostly collagen). For this reason, nanostructured HA has been an intriguing coating material on traditionally used titanium for improving orthopedic applications. In addition, helical rosette nanotubes (HRNs), newly developed materials which form through the self-assembly process of DNA base pair building blocks in body solutions, are soft nanotubes with a helical architecture that mimics natural collagen. Thus, the objective of this in vitro study was for the first time to combine the promising attributes of HRNs and nanocrystalline HA on titanium and assess osteoblast (bone-forming cell) functions. Different sizes of nanocrystalline HA were synthesized in this study through a wet chemical precipitation process following either hydrothermal treatment or sintering. Transmission electron microscopy images showed that HRNs aligned with nanocrystalline HA, which indicates a high affinity between both components. Some of the nanocrystalline HA formed dense coatings with HRNs on titanium. More importantly, results demonstrated enhanced osteoblast adhesion on the HRN/nanocrystalline HA-coated titanium compared with conventional uncoated titanium. Among all the HRN/nanocrystalline HA coatings tested, osteoblast adhesion was the greatest when HA nanometer particle size was the smallest. In this manner, this study demonstrated for the first time that biomimetic HRN/nanocrystalline HA coatings on titanium were cytocompatible for osteoblasts and, thus, should be further studied for improving orthopedic implants.

Coupled mechanical and conductivity measurements: Damage detection

This paper reports in situ measurements of electrical resistivity during mechanical solicitation of insulator-conductor composite. Electrical and mechanical behaviors will be discussed on 3 examples namely (i) unidirectional carbon fiber reinforced polymers (CFRP), (ii) stick-like whiskers reinforced soft thermoplastics and (iii) carbon nanotubes reinforced soft thermoplastics. Resistivity measurements are described as a useful tool to monitor the damage of these composites. In the case of composite materials consisting in reinforced insulated matrix by electrically conducting fibers or fillers, resistivity (or conductivity) measurements show classically several features such as strong anisotropy in long fiber composites or the existence of continuous direct current (DC) conducting pathway for short fiber or particulate composites. Moreover, and this is the topic discussed here, in terms of mechanical stress/strain properties, the fibers or fillers conducting network may exhibit resistivity changes due to fiber ruptures, delamination, filler-filler debonding within filler network, etc.

Soft nanotubes from amphiphilic ABA triblock macromonomers.

Soft, water-filled polymer nanotubes of several tens of microm in length have been prepared via self-assembly of amphiphilic ABA-triblock macromonomers in aqueous media; the tubes are mechanically and chemically stable and can be loaded with water-soluble substances.