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We have synthesized novel water-soluble anionic porphyrin monomers that undergo pH-regulated ionic supramolecular polymerization in aqueous media. By tuning the total charge of the monomer, we selectively produced two different supramolecular polymers: J- and H-stacked. The main driving force toward the J-aggregated supramolecular polymers was the ionic interactions between the sulfonate and protonated pyrrole groups, ultimately affording neutral supramolecular polymers. In these J-aggregated supramolecular polymers, amide groups were aligned regularly along polymer wedges, which further assembled in an edge-to-edge manner to afford nanosheets. In contrast, the H-aggregated supramolecular polymers remained anionic, with their amide NH moieties acting as anion receptors along the polymer chains, thereby minimizing repulsion. For both polymers, varying the steric bulk of the peripheral ethylene glycol (EG) units controlled the rates of self-assembly as well as the degrees of polymerization. This steric effect was further tunable, depending on the solvation state of the EG chains. Accordingly, this new family of supramolecular polymers was created by taking advantage of unique driving forces that depended on both the pH and solvent.

This work reports a basic microflow system capable of performing multistep supramolecular polymerization. In this system, injection of the monomer, directional supramolecular copolymerization, removal of the unreacted monomer, and purification of the product supramolecular diblock copolymers are realized along a three-stream flow. When injecting a supramolecular polymer into the central stream of the three-stream flow, the supramolecular polymerization always occurs in the central flow, with the two lateral flows serving as supply and removal lines for the monomer. Employing two kinds of perylene bisimide derivatives as monomers, we confirmed that the reaction occurred selectively at the forward-facing terminus of the supramolecular polymer, along with recovery of the unreacted monomer, ultimately leading to a high-purity supramolecular diblock copolymer. Diblock copolymers are basic units for preparing multicomponent supramolecular block copolymers. Thus, connecting the present system in series would, in principle, result in a "microplant" capable of producing supramolecular polymers having desired inner complexity.

The anisotropic properties of one-dimensional (1D) supramolecules have generally been the sole way to input molecular information along a structure of high density. Although the chain reaction of a...

It is known that interfaces have various impacts on crystallization from a solution. Here, we describe crystallization of acetaminophen using a microflow channel, in which two liquids meet and form a liquid–liquid interface due to laminar flow, resulting in uniform mixing of solvents on the molecular scale. In the anti‐solvent method, the microflow mixing promoted the crystallization more than bulk mixing. Furthermore, increased flow rate encouraged crystal formation, and a metastable form appeared under a certain flow condition. This means that interface management by the microchannel could be a beneficial tool for crystallization and polymorph control.

The macromolecular structure of highly 1,6-glucose-branched β-1,3-glucan (6BG3) was elucidated spectroscopically by modification and complexation with chromophoric reporters. The circular dichroism spectra of 4-(dimethylamino)benzoic acid (DABz)-modified 6BG3 showed a relatively small but obvious bisignate couplet in an aqueous DMSO solution; however, in DMSO, 6BG3 forms a random coil. These chiroptical properties and the AFM images revealed that reporter-modified 6BG3 goes through a random coil-to-globule conversion process upon solvent switching. The macromolecular structure of native, nonchromophoric 6BG3 was further examined by complexation with 2,5-poly(3-(6-pyridiniohexyl)thiophene) (PyPT) in situ. The 6BG3 random-coil strand complexed with PyPT to afford a heteroduplex with a small amount of a heterotriplex, showing a large exciton coupling for the π,π* transition of PyPT. The amount of the heteroduplex hybridization was enhanced at higher pH due to further complexation of single strands of partially deprotonated 6BG3 with free PyPT. The solution-state macromolecular structure of highly 1,6-glucose-branched β-1,3-glucan (6BG3) was elucidated by modifying and complexing with chromophoric reporters. The reporter-modified 6BG3 forms the globule through the random coil-to-globule conversion process. Hybridizing 6BG3 with the polythiophene reporter affords the loose heteroduplex rather than the tight heterotriplex, indicating the formation of the loose homoduplex of 6BG3.

A series of porphyrin-curdlan conjugates 1-5 of varying degree of substitution (DS) were synthesized to examine their morphological features, chiroptical properties, and oligosaccharide sensing in aqueous media, particularly for tetrasaccharide acarbose, which is a drug to treat type-2 diabetes. The random coil state of compounds 1-5 in DMSO becomes the globule curdlan-saccharide coaggregate upon interaction of acarbose in aqueous DMSO solution to induce various circular dichroism (CD) responses. The high cooperativity and positive homotropic allosterism were observed in the acarbose recognition, enabling the allosteric signal-amplification sensing, for which the DS, stacking character, and microenvironmental polarity changes of the tethered porphyrin reporters are likely to be responsible.

Very rapid, uniform and vector diffusion of solvent molecules can be coupled with up-hill self-assembly from less active molecules and/or under low concentration conditions. We have demonstrated in this paper that perylene bisimide derivatives undergo effective supramolecular polymerization in microflow channels coupling with solvent diffusion. The resultant nanofibers were highly aligned along the stream line of laminar flow.

The absorption spectra of bromothymol blue (BTB) solution introduced in microfluidic devices were reproduced by principal component analysis (PCA)-based xyz-spectrum conversion methods for geometric mapping of the pH values of fluids. We fabricated PDMS-made microfluidic devices with a channel depth of 1 mm to overcome the lower detection limits of transmittance image acquisition. Aqueous solutions of pH indicators under various pH conditions were hydrodynamically introduced into the channel, and RGB values of the region of interest (ROI) were obtained via image analysis. The xyz values were then converted into absorption spectral data of the pH indicator using the PCA-based spectral reproduction previously proposed by the authors. The high reproducibility of the spectra was confirmed to be comparable to that of the conventional method using a spectrophotometer. We applied the present method to elucidate the pH gradient at an aqueous biphasic interface in the microfluidic channels generated by contacting multiple laminar flows of two or three buffered solutions. We confirmed that the pH gradient ranged from approximately 70 to 140 μm, which is consistent with the results reported using other approaches. The results demonstrate the applicability of the present method to the fluctuation field in micro/nanospaces to acquire spectrophotometric information in the order of milliseconds without monochromating equipment.

Constructing a versatile self-assembly system that enables chemists to control molecular interactions will lead to technological innovations in the field of supramolecular chemistry. From the viewpoint of creating new materials, this approach can take the form of a new reaction or a new catalyst to be used in synthetic organic chemistry. We have proposed a novel, practical supramolecular assembly system that enables the control of intermolecular or interpolymer interactions through the precise regulation of a flowing self-assembly field at a micrometer scale. The potential use of microflow channels as a self-assembly field was explored by utilizing various simple model compounds. We found that the rapid activation of molecules under a nonequilibrium state caused by uniform solvent diffusion drastically enhanced the interactions in the microflow channel. This resulted in the synthesis of a variety of novel supramolecules, such as discrete microstructures, hierarchical assemblies, and supramolecules with a time-delayed action (metastable assemblies), which were previously inaccessible.

In a microflow environment, the sizes of guest-binding pockets constructed by chlorophyll units can be regulated precisely through linking to the spring-like dynamic motion of a polymer backbone. Very rapid host/guest interactions at the polymer surface enabled isolation of metastable conformers having different helical pitches.

Control over the self-assembly pathways of small functional molecules is a current trend in supramolecular chemistry, as a variety of metastable self-assemblies with nanostructures distinct from those of thermodynamically stable assemblies can be formed as kinetic products. If such kinetically formed assemblies can be trapped under non-equilibrium conditions, diverse self-organized structures beyond the immediate molecular design may be accessible. The self-assembly of specifically designed amphiphilic π-conjugated molecules in water represents a promising strategy to realize such conditions, wherein strong hydrophobic molecular interactions play an important role. Based on the alkyl-tethered covalent perylene bisimide (PBI) dyad scaffold that can potentially aggregate into one-dimensional supramolecular polymers, herein we demonstrate that an amphiphilic molecular design can open up new self-assembly pathways, which can potentially afford distinct nanostructures in aqueous media. We synthesized amphiphilic PBI dyads that contain one PBI unit functionalized with hydrophobic branched alkyl chains, and one PBI unit functionalized with hydrophilic branched alkyl chains. By changing the composition ratio of the THF/water mixtures, we obtained one-dimensional fibrous and vesicular aggregates as a result of increasing hydrophobic effects. Increasing the temperature of the THF/water mixtures in which fibrous aggregates are preferentially formed subdued the aggregation to entropy control and resulted in the formation of coil- and ring-shaped kinetic nanoaggregates.

In this article, we have demonstrated that π–π stacking interactions can be synchronized through the rapid hydration of π-conjugated molecules, generating a sort of metastable state. The self-assem...

Supramolecular polymerization of TPPS, a kind of self-assembling porphyrin, was investigated in a pressure-adjustable microflow channel. We found that the nucleation process of TPPS was accelerated...

The morphologies and functionalities of supramolecular architectures are governed entirely by the molecular design and the self-assembling field. Herein, we demonstrate that use of a microflow syst...

Self-assembly of porphyrin molecules can be controlled kinetically to form structures with lengths extending from the nano- to the micrometer scale, through a programmed solvent-diffusion process in designed microflow spaces. Temporal solvent structures generated in the microflow were successfully transcribed into molecular architectures.

Fine hydrogen-bonded networks over the micrometer scale were spontaneously constructed in microflow through the synchronized protonation of porphyrin having four carboxylic acid groups. The obtaine...

To date, little attention has been paid to the positive control of the self-assemble process itself. Rapid activation and synchronous growth of PCBM, a kind of fullerene derivative, in a precisely ...

We demonstrate that the kinetics of supramolecular polymerization of TPPS, a type of self-assembling porphyrins, is controllable in a designed microflow space through regulation of the flow distanc...

Constructing new and versatile self-assembling systems in supramolecular chemistry is much like the development of new reactions or new catalysts in synthetic organic chemistry. As one such new technology, conventional supramolecular assembly systems have been combined with microflow techniques to control intermolecular or interpolymer interactions through precise regulation of a flowing self-assembly field. The potential of the microflow system has been explored by using various simple model compounds. Uniform solvent diffusion in the microflow leads to rapid activation of molecules in a nonequilibrium state and, thereby, enhanced interactions. All of these self-assembly processes begin from a temporally activated state and proceed in a uniform chemical environment, forming a synchronized cluster and resulting in effective conversion to supramolecules, with precise tuning of molecular (or polymer) interactions. This approach allows the synthesis of a variety of discrete microstructures (e.g., fibers, sheets) and unique supramolecules (e.g., hierarchical assemblies, capped fibers, polymer networks, supramolecules with time-delayed action) that have previously been inaccessible.

This chapter focuses on dynamic polymer–polymer interactions triggered by the boronic acid–diol interaction. General polymer–polymer interactions, except for those occurring in biological systems, take place in a random fashion. In view of the creation of polymer based materials, any comprehensive strategy for overcoming this limitation would be attractive and applicable. By introducing boronic acid groups into a polymer, it acquires precise molecular recognition ability based on dynamic boronic acid–diol interactions, thus affording stimulus-responsive supramolecular architectures in combination with various molecules or polymers. This strategy is powerful and introduces new opportunities for the sciences of polymer-based materials.

We recently revealed that β-1,3-glucans act as unique natural nanotubes, which can accept functional polymers and molecular assemblies in an induced-fit manner. A variety of individual conjugated polymers or molecular assemblies can be incorporated into the one-dimensional hollow constructed by the helical superstructure of β-1,3-glucans to create water-soluble one-dimensional nanocomposites. The advantageous point of the present hosting system is that the selective modification of β-1,3-glucans leads to the creation of various functional one-dimensional nanocomposites in a supramolecular manner. Furthermore, the composites with functional surfaces can act as one-dimensional building blocks toward further hierarchical self-assembles, leading to the creation of two- or three-dimensional nanoarchitectures, which are applicable for fundamental nanomaterials.

It is known that an achiral water-soluble polythiophene (PT-1) is chirally twisted by complexation with a natural helix-forming polysaccharide, shizophyllan (SPG). We found that the chirality can b...

Much attention has been focused on exploiting novel strategies for the creation of hierarchical polymer assemblies by the control of the assembling number or the relative location among neighboring polymers. We here propose a novel strategy toward the creation of "hierarchical" single-walled carbon nanotube (SWNT) architectures by utilizing SWNT composites with cationic or anionic complementary semi-artificial beta-1,3-glucans as "building blocks". These beta-1,3-glucans are known to wrap SWNTs helically, to create one-dimensional superstructural composites. If the cationic composite is neutralized by an anionic composite, a well ordered SWNT-based sheet structure was created. Transmission electron microscopy (TEM) observation revealed that this sheet structure is composed of highly-ordered fibrous assemblies of SWNTs. This suggests that the cationic and anionic composites are tightly packed through electrostatic interactions. Moreover, both of the final assembly structures are readily tunable by adjusting the cation/anion ratio. The self-assembling modulation of functional polymers is associated with the progress in ultimate nanotechnologies, thus enabling us to create numerous functional nanomaterials. We believe, therefore, that the present system will extend the frontier of SWNT research to assembly chemistry including "hierarchical" superstructures.

It has been demonstrated that a chiral, insulated poly(p-phenylene ethynylene) (PPE) nano-wire can be created by a polymer wrapping method utilizing natural β-1,3-glucan polysaccharide schizophyllan (SPG). Spectroscopic and microscopic measurements have revealed that PPE adopts a rigid conformation and exists as one piece in the helical hollow constructed by two SPG chains. Moreover, the inherent helical structure of SPG can induce the chiral twisting of the insulated PPE backbone. It is believed that the present system is really applicable for designing novel chiral sensors based on PPE.

Constructing new and versatile self-assembling systems in supramolecular chemistry is much like the development of new reactions or new catalysts in synthetic organic chemistry. As one such new technology, conventional supramolecular assembly systems have been combined with microflow techniques to control intermolecular or interpolymer interactions through precise regulation of a flowing self-assembly field. The potential of the microflow system has been explored by using various simple model compounds. Uniform solvent diffusion in the microflow leads to rapid activation of molecules in a nonequilibrium state and, thereby, enhanced interactions. All of these self-assembly processes begin from a temporally activated state and proceed in a uniform chemical environment, forming a synchronized cluster and resulting in effective conversion to supramolecules, with precise tuning of molecular (or polymer) interactions. This approach allows the synthesis of a variety of discrete microstructures (e.g., fibers, sheets) and unique supramolecules (e.g., hierarchical assemblies, capped fibers, polymer networks, supramolecules with time-delayed action) that have previously been inaccessible.

We have demonstrated that one-dimensional supramolecular dye assemblies with a uniform diameter can be created by utilizing schizophyllan (SPG) as a one-dimensional host. In the supramolecular nanofibers, the dye molecules are assembled into the different aggregation modes depending on the preparation procedures. The findings establish that SPG is useful for creating the supramolecular nanofibers, where temporal superstructures can be stabilized by the SPG-specific helical higher-order structure. [structure: see text].

Antisense oligonucleotides (AS ODNs) are applied to silence a particular gene, and this approach is one of the potential gene therapies. However, naked oligonucleotides are easy to be degraded or absorbed in biological condition. Therefore, we need a carrier to deliver AS ODNs. This paper presents galactose moieties that were conjugated to the side chain of SPG to enhance cellular ingestion through endocytosis mediated by asialoglycoprotein receptor specifically located on parenchymal liver cells. We introduced galactose with two types of chemical bonds; amide and amine, and the amine connection showed lower ingestion and more toxicity than the amide one. Since PEG was known to induce endocytosis escape, we combined PEG and galactose aiming to provide both cellular up-take and subsequent endocytosis escape. We designed lactose or galactose moieties to attach to the end of the PEG chain that connects to the SPG side chain. When the PEG had the molecular weight of 5000-6000, the antisense effect reached the maximum. We believe that this new type of galactose and PEG dual conjugation broaden the horizon in antisense delivery.

(1→3)-β- d -Glucans having various functional appendages (lactoside, ferrocene, pyrene, and porphyrin) can be prepared in an convenient, quantitative, and regioselective manner through regioselective bromination–azidation of curdlan to afford 6-azido-6-deoxycurdlan followed by chemoselective [3+2]-cycloadditions with various functional modules bearing a terminal alkyne group. The ability to monitor reaction conversions is an additional advantage of this synthetic approach over the conventional direct modifications on polysaccharides; the reaction can be readily monitored based on the intensity of azido peaks in the in situ attenuated total reflection infrared spectra.

β-Lactosylated 5,15-meso-diphenylporphyrinatoiron(III) chloride was prepared by ironization of the corresponding free base porphyrin having acetylated lactoside-units followed by deacetylation with ammonia in a water–methanol mixture. The resultant 5,15-meso-bis(β-lactosylphenyl)porphyrinatoiron(III) chloride showed unique colorimetric response to calcium cation. This colorimetric response is calcium-specific and no other cations, such as sodium, potassium, or magnesium ions induced such colorimetric response. Lines of evidence including UV–vis spectra under different conditions and TEM images strongly indicate that interdigitations of the corresponding μ-oxo-dimers are responsible for this colorimetric change.

Schizophyllans carrying poly(N-substituted-acrylamide)-branches were synthesized from native schizophyllan through Ce(IV)-initiated radical homo- or co-polymerization of N-iso-propyl- and N-sec-butyl-acrylamide. A series of structural analyses including elemental analysis, gel permeation chromatography, 1H NMR, and enzymatic degradation using β-1,3-glucanase revealed that schizophyllans (150 kDa) bearing long poly(N-substituted-acrylamide)-branches (ca. 290 kDa) are obtained. These SPG-conjugates form macromolecular complexes with certain homopolynucleotides such as poly(C), poly(dA), and poly(A) and then efficiently co-precipitate them on heating. For example, schizophyllan carrying poly(N-iso-propylacrylamide)-branches can selectively recover poly(C) from a mixture of poly(C) and poly(U) by simple heating (36 °C) followed by centrifugation. HPLC analysis of the recovered polynucleotide revealed the high poly(C)-selectivity (poly(C):poly(U) = 95:5). Similarly, schizophyllan carrying more hydrophobic poly(N-iso-propylacrylamide-co-N-sec-butylacrylamide)-branches precipitates at lower temperature (ca. 20 °C) and is applicable to isolation of poly(A) that forms less stable macromolecular complexes with SPG and SPG-derivatives (the dissociation temperatures are around 30 °C).

It was found that DNAs can act as attractive templates for oxidative polymerization of pyrrole and result in novel higher-order superstructures composed of the DNA padding and the conjugate polymer outer layer. Furthermore, the resultant DNA/poly(pyrrole) composite can be deposited on an ITO electrode. The TEM and SEM observations have shown that oxidative polymerization creates a variety of superstructural poly(pyrrole) assemblies such as nanosized rodlike, circular, or supercoiled structures, reflecting the higher-order conformations of DNAs acting as the templates. The findings establish that the morphology of the conjugate polymer assemblies are controllable by a change in the DNA morphology used as their templates. The deposition of DNAs onto the ITO electrode was characterized by (1) ATR IR absorption bands assignable to DNA, (2) XPS binding energy of the phosphate group assignable to DNAs, and (3) binding of ethidium bromide (EB) to DNAs as detected by UV−vis spectroscopy and confocal laser scannin...

Schizophyllan having folate-appendages was synthesized from native schizophyllan through NaIO 4 -oxidation and the subsequent reductive amination in aqueous ammonia followed by amido-coupling with folic acid. The resulting folate-appended schizophyllan can form stable complex with poly(dA), show specific affinity toward folate binding protein, and mediate effective antisense activity in cancer cells.

Schizophyllan (SPG) is a natural β-(1→3)-D-glucan existing as a triple helix in water and as a single chain in dimethylsulfoxide (DMSO), respectively. As we already reported, when a homo-phosphodiester polynucleotide [for example, poly(dA) or poly(C)] is added to the SPG/DMSO solution and subsequently DMSO is exchanged for water, SPG forms a complex with the polynucleotide. One of the potential applications of this novel complex is an antisense-oligonucleotide (AS ODN) carrier. The present paper describes a modification technique which enables us to introduce transferrin to the reducing end of SPG (Tf-SPG). We made a complex from Tf-SPG and AS ODN and carried out an in vitro antisense assay. We found that Tf-SPG dramatically enhances the antisense effect. Their superiority can be ascribed to enhancement of endocytosis due to the attached transferrin. One of the peculiar features of our system is that the complex (i.e., carrier + AS ODN) is charged negatively in total, because SPG itself is a neutral polysaccharide. This feature is different from the conventional systems such as cationic liposomes and polycations. The present work has thus clarified that SPG can act as a new potential candidate for AS ODN carriers. [DOI: 10.1380/ejssnt.2005.195]

Two kinds of polymeric nanoarchitectures, i.e., one-dimensional polymer composites and two-dimensional sheet-like structures, can be created using a semiartificial helical polysaccharide with one-d...

The water solubility of curdlan was enhanced by partial sulfation at O-6. Circular dichroism measurements suggest that the sulfated curdlan with the degree of substitution (DS) from 0 to 8.7 mol % forms macromolecular complexes with polycytidylic acid (poly(C)). Although the thermal stability of the complexes decreased with increase in DS, this could be overlapped by addition of NaCl in the concentration above that of serum. The results clearly indicate that the drawback arising from the electrostatic repulsion between the anionic charges can be partially compensated by the presence of salt. Furthermore, the polynucleotide chain complexed with the sulfated curdlan was protected from the enzymatic hydrolysis, corroborating the assumption that the sulfated curdlan has an ability to bind poly(C).