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In the field of tissue engineering and biomaterials, controlling the surface properties and mechanical properties of scaffold materials is crucial and has attracted much attention. Here, two types of bilayer polymer brushes composed of a hydrophilic underlying layer and a cationic surface layer [made of poly(2-aminoethyl methacrylate)] with a thickness gradient were prepared by surface-initiated atom-transfer radical polymerization. To investigate the influence of the stiffness as a mechanical property of the polymer brush on cell behavior, the underlayer was prepared from either 2-methacryloyloxyethyl phosphorylcholine or oligo(ethylene glycol) methyl ether methacrylate, with the bilayers designated as gradient poly(2-methacryloyloxyethyl phosphorylcholine)

We investigate the response speed of thermoresponsive poly(N-isopropylacrylamide) (PNIPAAm) brushes by in situ electrical monitoring, which are grafted by surface-initiated activators regenerated b...

Temperature is a key indicator of infection and disease, however, it is difficult to measure at a cellular level. Nanoparticles are applied to measure the cellular temperature, and enhancement of the stability and reliability of the signal and higher biocompatibility are demanded. We have developed fluorescent polymeric nanoparticles loaded with temperature-sensitive units (as rhodamine B) and internal reference units (as coumarin) for imaging and ratiometric sensing of the cellular temperature in the physiological range. The fluorescence signal of the nanoparticles was stable in the bio-environment and the ratiometric sensing strategy could overcome the concentration effect of nanoparticles. The nanoparticles were endocytosed by cells and partially presented in mitochondria. The fluorescence intensity ratio of rhodamine B and coumarin using nanoparticles showed good linear correlations in buffer solutions, cell suspensions, and imaging of living cells. Using the fluorescent polymeric nanoparticles, the change of temperature of cells during influenza virus infection could be individually monitored.

Lipid bilayer transformations are involved in biological phenomena including cell division, autophagy, virus infection, and vesicle transport. Artificial materials to manipulate membrane dynamics play a vital role in cellular engineering and drug delivery technology that accesses the membranes of cells or liposomes. Transformation from 3D lipid vesicles to 2D nanosheets is thermodynamically prohibited because the apolar/polar interfaces between the hydrophobic bilayer edges and water are energetically unfavorable. We recently reported that cell-sized lipid vesicles (or giant vesicles) can be thoroughly transformed to 2D nanosheets by the addition of the amphiphilic E5 peptide and a cationic graft copolymer. Here, to understand the mechanisms underlying the lipid nanosheet formation, we systematically investigated the structural effects of the cationic copolymers on nanosheet formation. We found that lipid nanosheet formation is controlled in an all-or-nothing manner when the graft content of the copolymer is increased from 5.7 mol % to 7.7 mol %. This finding prompted us to obtain autonomous 2D/3D transformation system. A newly designed hetero-grafted cationic copolymers with thermoresponsive poly(

We show experimentally that chemical and mechanical self-oscillations in Belousov−Zhabotinsky hydrogels are inherently asynchronous, that is, there is a detectable delay in swelling−deswelling response after a change in the chemical redox state. This phenomenon is observable in many previous experimental studies and potentially has farreaching implications for the functionality and response time of the material in future applications; however, so far, it has not been quantified or reported systematically. Here, we provide a comprehensive qualitative and quantitative description of the chemical-tomechanical delay, and we propose to explain it as a consequence of the slow nonequilibrium swelling−deswelling dynamics of the polymer material. Specifically, standard hydrogel pieces are large enough that transport processes, for example, counterion migration and water diffusion, cannot occur instantaneously throughout the entire gel piece, as opposed to previous theoretical considerations. As a result, the volume response of the polymer to a chemical change may be governed by a characteristic response time, which leads to the emergence of delay in mechanical oscillation. This is supported by our theoretical calculations.

A modifiable, spontaneously formed and biocompatible polymer gel, composed of phosphorylcholine and N-hydroxysuccinimide ester, is reported, which can be subjected to postmodification by amine-cont...

Nanoparticle-based probes have great potential for imaging specific biomolecules in signal distinguishing and amplification via Forster resonance energy transfer (FRET). Protein-specific sialylatio...

We prepared the chemically crosslinked, cylindrical thermoresponsive poly(N-isopropylacrylamide) gels with changing the contents of reversible addition-fragmentation chain transfer (RAFT) agent. The environment in the gel was estimated by using a hydrophobic fluorescence probe. While the equilibrium swelling ratios were comparable, the deswelling response became fast as the content of RAFT agent increased with the formation of “bubble pattern”. This result indicates that the PNIPAAm gels prepared by RAFT still have spatial defects. In addition, the cooperative diffusion coefficients in swelling process of the gels prepared by RAFT polymerization were estimated.

Bacterial adhesion on material surfaces is a significant problem in many areas, especially on medical devices. Upon colonizing a surface, bacteria tend to form biofilms and become difficult to eradicate. A multistep process is involved in bacterial biofilm formation, including primary adhesion to material surface and accumulation of bacterial cells. Controlling the primary adhesion of bacteria is an efficient way to manage biofilms. This study focused on the primary adhesion of bacteria on a copolymer thin-film composed of 2-methacryloyloxyethyl phosphorylcholine (MPC), 3-methacryloxypropyl trimethoxysilane (MPTMSi), and 3-(methacryloyloxy) propyl-tris(trimethylsilyloxy) silane (MPTSSi), which has anti-biofouling and thickness and stiffness tunable properties. We modulated the thickness (5-90 nm) and stiffness of the thin-film via changing the polymer concentration in the coating solution (dip coating). All polymer thin-films inhibited Gram-positive

Hydrophilic surfaces with antifouling properties are in demand for medical and environmental applications, especially for ready-to-use purposes. In the present study, a simple and effective surface modification of ceramic surfaces via amphiphilic block polymers with zwitterionic group was developed. Block copolymers with polymer chains containing hydrophilic segments of poly(2-methacryloyloxyethyl phosphorylcholine) (MPC) and random copolymer chains of hydrophobic segments of poly(3-(methacryloyloxy)propyl-tris(tri(methylsilyloxy))silane) (MPTSSi) and silane coupling segments of poly(3-methacryloxypropyl trimethoxysilane) (MPTMSi) were synthesized and successfully applied uniformly on glass substrates. For the block polymer chains with longer hydrophilic segments, the surfaces exhibited high hydrophilicity under dry conditions and excellent antifouling properties without hydration pretreatment. The zwitterionic block copolymer-modified surface showed good durability and protein inhibition properties for pH of 2–9. The hydrophilic surface coating based on the developed block copolymers is suitable for medical, healthcare, sanitary, and environmental applications because it requires no pre-hydration.

Soft interface materials have an immense potential for the improvement of biointerfaces, which are the interface of biological and artificially designed materials. Controlling the chemical and physical structures of the interfaces at the nanometer level plays an important role in understanding the mechanism of the functioning and its applications. Controlled radical polymerization (CRP) techniques, including atom transfer radical polymerization (ATRP) and reversible addition-fragmentation chain-transfer (RAFT) polymerization, have been developed in the field of precision polymer chemistry. It allows the formation of well-defined surfaces such as densely packed polymer brushes and self-assembled nanostructures of block copolymers. More recently, a novel technique to prepare polymers containing biomolecules, called biohybrids, has also been developed, which is a consequence of the advancement of CRP so as to proceed in an aqueous media with oxygen. This review article summarizes recent advances in CRP for the design of biointerfaces.

The Belousov–Zhabotinsky (BZ) self-oscillation reaction is an important chemical model to elucidate nonequilibrium chemistry in an open system. However, there are only a few studies on the electrical behavior of pH oscillation induced by the BZ reaction, although numerous studies have been carried out to investigate the mechanisms by which the BZ reaction interacts with redox reactions, which results in potential changes. Needless to say, the electrical characteristic of a self-oscillating polymer gel driven by the BZ reaction has not been clarified. On the other hand, a solution-gated ion-sensitive field-effect transistor (ISFET) has a superior ability to detect ionic charges and includes capacitive membranes on the gate electrode. In this study, we carried out the electrical monitoring of self-oscillation behaviors at the chemoelectrical interface based on the BZ reaction using ISFET sensors, focusing on the pH oscillation and the electrical dynamics of the self-oscillating polymer brush. The pH oscillation induced by the BZ reaction is not only electrically observed using the ISFET sensor, the electrical signals of which results from the interfacial potential between the solution and the gate insulator, but also visualized using a large-scale and high-density ISFET sensor. Moreover, the N-isopropylacrylamide (NIPAAm)-based self-oscillating polymer brush with Ru(bpy)3 as a catalyst clearly shows a periodic electrical response based on the swelling–deswelling behavior caused by the BZ reaction on the gate insulator of the ISFET sensor. Thus, the elucidation of the electrical self-oscillation behaviors induced by the BZ reaction using the ISFET sensor provides a solution to the problems of nonequilibrium chemistry.

Cell-surface sialic acids can be metabolically labeled and subsequently modified using bioorthogonal chemistry. The method has great potential for targeted therapy and imaging; however, distinguishing the sialylation of specific cells remains a major challenge. Here, we described a cell-selective metabolic sialylation labeling strategy based on water-soluble polymer carriers presented with pH-responsive N-azidoacetylmannosamine (ManNAz) release. 2-Methacryloyloxyethyl phosphorylcholine contributed to increased water solubility and reduced nonspecific attachment to cells. Lactobionic acid residues, used for cell selectivity, recognized overexpressed receptors on target hepatoma cells and mediated cellular internalization. ManNAz caged by acidic pH-responsive carbonated ester linkage on the polymer was released inside target cells and expressed as azido sialic acid. Additionally, longer copolymer carriers enhanced the metabolic labeling efficiency of sialylation. This approach provides a platform for cell-selective labeling of sialylation and can be applied to high-resolution bioimaging and targeted therapy.

Liposomes are self-assembled vesicles of amphiphilic lipid molecules, which have been investigated as models of cells, or tools for drug delivery systems. In these systems, the surface property of the liposomes plays an important role. In this study, we demonstrated a novel polymer modification of liposome surfaces using a controlled radical polymerization, "activators regenerated by electron transfer for atom transfer radical polymerization", in aqueous media without a deoxygenation step. Dynamic light scattering and 1H NMR measurement indicated the successful modification of the polymer on the liposome surface. The molecular weight of the grafted polymer chain was systematically controlled by changing the monomer concentrations in the "grafting from" polymerization. Moreover, the modification resulted in a notable increase in surface softness as indicated by electrophoretic behavior, which was comparable to the surface of cells. The preparation method and the characterization presented in this study would be a helpful guideline in designing the polymer/liposome hybrid having target surface properties.

Membrane-active peptides have potential as drug delivery tools for control of lipid bilayer structures in cells and liposomes. In a previous study, we reported that a cationic comb-type copolymer, poly(allylamine)-graft-dextran (PAA-g-Dex), forms a soluble interpolyelectrolyte complex with an anionic peptide, E5, and enhances its membrane-disrupting activity. Furthermore, the E5/PAA-g-Dex complex augments the cellular membrane permeability of other proteins. In this study, the affinities of the E5/PAA-g-Dex complex for lipid membranes with various compositions were determined. Secondary structure analysis of E5 and analyses of binding of E5 to liposomes revealed that lipid composition strongly influenced the interaction. No significant folding of E5 alone was observed at either pH 5.4 or pH 7.4 and folding into the functional conformation, which is both N-terminal and C-terminal helix, was observed only at pH 5.4 in the presence of liposomes having liquid-disordered phase (Ld). PAA-g-Dex induced partial f...

An autonomous swelling-deswelling oscillation of polymer gels in a hydrated protic ionic liquid (PIL) as a proton source for the Belousov-Zhabotinsky (BZ) reaction is presented. Methylammonium hydrogen sulfate ([maH+ ][HSO4- ]) was employed as the PIL because it provides stable redox oscillation in the BZ reaction. Due to the significantly higher pKa for [maH+ ][HSO4- ] than those for conventional proton sources for the BZ reaction, chemomechanical oscillation can be expected under weaker acidic conditions. The self-oscillating polymer was designed as a ternary random copolymer of N-isopropylacrylamide, N-(3-aminopropyl)methacrylamide, and the Ru(bpy)3 moiety as a catalyst for the BZ reaction. The copolymer exhibited spontaneous soluble-insoluble oscillation in hydrated [maH+ ][HSO4- ] containing NaBrO3 and malonic acid. Macroscopic swelling-deswelling oscillation of the porous bulk gel prepared by covalently connecting microgel particles was also observed.

An autonomous swelling-deswelling oscillation of polymer gels in a hydrated protic ionic liquid (PIL) as a proton source for the Belousov-Zhabotinsky (BZ) reaction is presented. Methylammonium hydrogen sulfate ([maH

Biomimetic phospholipid copolymer films are known to possess antifouling properties against protein adsorption and biofilm formation. However, the interactions between bacterial cells and material surfaces are not fully understood. This work investigated the bacterial adhesion strength of phospholipid copolymer films using a shear stress-tunable microfluidic device. The copolymer, comprising 2-methacryloyloxyethyl phosphorylcholine (MPC), 3-methacryloxypropyl trimethoxysilane (MPTMSi), and 3-(methacryloyloxy) propyl-tris(trimethylsilyloxy) silane (MPTSSi), formed crosslinked films on glass substrates; the thickness of the coating film was controlled by the polymer concentration during dip-coating. Polymer films with two typical thicknesses, 20 and 40 nm (denoted as C-20 and C-40, respectively), were prepared on the bottom wall of the microfluidic device. After seeding S. aureus in the microfluidic device, several shear stresses were applied to evaluate the adhesion strength of the polymer films. S. aureus was found to have weaker adhesion strength on the C-40 surface than on the C-20 surface; numerous bacterial cells detached from the C-40 surface on application of identical shear stress. To mimic the presence of plasma protein, fibrinogen (Fg) was introduced into the device before performing the bacterial adhesion assay. The results showed that the adsorption of Fg promoted S. aureus adhesion and strong interactions under shear stress. However, the adhesion strength of S. aureus did not affect the Fg adsorption for both the C-20 and C-40 surfaces. Using the shear stress-tunable microfluidic device, we found that the adhesion of S. aureus on the thicker and softer phospholipid copolymer was weak, and the cells easily detached under high shear stress.

We prepared poly(N-isopropylacrylamide-r-N-3-(aminopropyl)methacrylamide) (poly(NIPAAm-r-NAPMAm)) gels with poly NIPAAm (PNIPAAm) grafted only in the surface region (so-called thermoresponsive surface-grafted gels) with various graft densities and investigated the effect of the graft density on the bulk volume change properties, shrinking and swelling, in response to temperature changes. Initiators for atom-transfer radical polymerization (ATRP) and structurally analogous compounds were introduced at certain ratios onto the surface regions of the gels, and a subsequent activator regeneration by electron transfer ATRP of NIPAAm was conducted in aqueous media. The graft densities and molecular weights of the grafted polymers were evaluated from the increment in the dry mass of the gels and the amount of introduced ATRP initiators, which was measured by elemental analyses. Three-dimensional measuring laser microscopy revealed that the prepared gels had graft-density-dependent fine wrinkle structures on their surfaces. The surface-grafted gels induced the formation of skin layers during the shrinking process in response to a temperature increase, and their permeability strongly depended on the graft density. The graft density also controlled the kinetics of the swelling behavior in response to a temperature decrease. These physical properties were discussed on the basis of Young's modulus of the surface determined by an atomic force microscopy force curve measurement and the homogeneity of the surface polymer network observed by cryo-scanning electron microscopy. This makes it possible to arbitrarily control the characteristics of gels as open or semiclosed systems, which was uniquely determined by the designs of the surface gel networks.

Herein, we designed an upper critical solution temperature (UCST)-type self-oscillating polymer that exhibited rhythmic soluble-insoluble changes induced by Belousov-Zhabotinsky (BZ) reaction. The target polymers were prepared by conjugating Ru(bpy)3, a catalyst for the BZ reaction, to ureido-containing poly(allylamine-co-allylurea) (PAU) copolymers. The Ru(bpy)3-conjugated PAUs exhibited UCST-type phase transition behavior, and the solubility of the polymer changed in response to the alternation in the valency of Ru(bpy)3. The ureido content influence the temperature range of self-oscillation, and the oscillation occurred at higher temperatures than conventional LCST-type self-oscillating polymers. Further, the self-oscillating behavior of the Ru-PAU could be regulated by addition of urea, which is a unique tuning strategy. We envision that novel self-oscillating polymers with widely tunable soluble-insoluble behaviors can be rationally designed based these UCST-type polymers.

Herein, a thermoresponsive polymer, poly(N-isopropylacrylamide) (PNIPAAm) was grafted on a Ta2O5 gate surface by surface-initiated atom transfer radical polymerization. We found that the phase transition behaviour from swelling state to deswelling state in response to temperature change was electrically detected in real time by using the PNIPAAm-grafted gate FET.

We developed an autonomous functional surface, named a "self-oscillating polymer brush surface", which exhibits swelling-deswelling of the modified polymer chains synchronized with the Belousov-Zhabotinsky (BZ) reaction. The grafted polymer chain is a random copolymer composed of thermoresponsive N-isopropylacrylamide, N-(3-aminopropyl)methacrylamide, and ruthenium tris(2,2'-bipyridine) [Ru(bpy)3]. To provide stable oscillations over a long period of time, suppression of the dilution of the BZ reactants inside the polymer surface and the increase in the amount of immobilized Ru(bpy)3 are important. Here, we modified the self-oscillating polymer brush on a porous glass substrate and characterized its dynamic behavior. The increased surface area of the porous glass allowed for an efficient introduction of the metal catalyst, which resulted in a stable BZ reaction observable by optical microscopy. Compared with an aqueous BZ solution and the self-oscillating polymer modified on a glass coverslip, the wave velocity and diffusion coefficient were significantly lower for the porous glass system, which suggested that the reaction-diffusion of the reactants was markedly different than those of the other two systems. Moreover, the wave velocity was unchanged on the porous glass system for 1 h, whereas that of the solution dropped by 30 μm s-1. Waveform analyses based on the Field-Koros-Noyes mechanism revealed that densely packed Ru(bpy)3 in the porous glass system affects the duration of the key processes in the BZ reaction. These findings can help with understanding the dynamic behavior of the self-oscillating polymer brush on a porous glass substrate. Stable self-oscillations on the polymer brush-grafted porous glass substrate will aid future applications such as mass transport systems.

A surface-grafted hydrogel was successfully synthesized by immobilization of the ATRP initiator at the surface region of the gel and the subsequent ARGET ATRP step. This is the first example of a bulk hydrogel with a dense surface-localized layer of a grafted polymer and "active" permeation control of the gel.

In protein adsorption on material surfaces, the surface structure at the nanometer-scale is one of the most important factors; however, the relationship between the size of the hydrophobic protein-adsorptive domain and that of the protein in protein adsorption remains unclear. In this study, we prepared phase-separated surfaces with different hydrophobic domain sizes (10 or 19 nm) using amphiphilic ABA-type block copolymers composed of hydrophilic poly(2-methacryloyloxyethyl phosphorylcholine) (PMPC) and hydrophobic poly(3-methacryloyloxy propyltris(trimethylsilyloxy) silane) (PMPTSSi) to investigate the adsorption behavior of proteins, including fibronectin, fibrinogen, and lysozyme. The hydrophobic PMPTSSi domain promotes protein adsorption, whereas the PMPC domain suppresses this. Compared with the uniform hydrophobic PMPTSSi surface, fibronectin and fibrinogen were not adsorb on the phase-separated surfaces, while lysozymes adsorbed only partly, indicating that proteins smaller than nanoscale hydrophobic domains adsorbed on the phase-separated surface. Moreover, the protein adsorption behavior and circular dichroism spectra analysis suggest that lysozyme densely adsorbed on the hydrophobic domain like a multi-layer, and that denature on the surface was promoted. This study contributes to the understanding of protein adsorption at nanoscale interfaces and designing biomaterials.

Control of protein conformation and function, induced by the binding of an effector, plays significant roles in modulating biochemical reaction. Although the DNAzymes catalytic activity is similar to protein-based enzymes, reports of allosterically controlled DNAzymes are still limited except for aptamer-DNAzymes hybrrids. Here, we report allosteric control of peroxidase-mimicking DNAzyme activity using cationic copolymers. The DNAzyme requires a structured G-quadruplex core and hemin for activity, and the DNAzyme with a parallel G-quadruplex core has higher DNAzyme activity than DNAzymes based on other types of structure. We previously reported that a cationic copolymer composed of a cationic backbone and hydrophilic dextran side chains selectively stabilizes parallel G-quadruplex structures. In this study, we investigated effects of the cationic copolymer on peroxidase-mimicking DNAzyme activity. The cationic copolymer enhanced the DNAzyme activity by more than 30-fold by stabilizing the parallel G-quadruplex structure. Furthermore, reversible allosteric control of DNAzyme activity was achieved by adding cationic and anionic polymers.

Membrane active peptides (MAPs) have potential applications in drug delivery systems and as antimicrobials. We previously showed that a cationic comb-type copolymer, poly(allylamine)- graft-dextran (PAA- g-Dex), forms a soluble inter-polyelectrolyte complex with an anionic MAP, the E5 peptide, resulting in significant enhancement of the membrane disruption activity of E5. In this study, we designed a novel comb-type cationic copolymer composed of a PAA main chain and thermoresponsive poly( N-isopropylacrylamide) graft chains (PAA- g-PNIPAAm). We hypothesized that the thermoresponsive hydrophilic/hydrophobic transition of the grafted polymer would regulate the membrane disruption activity of E5 peptide. Both the binding affinity of the complex and the membrane disruption activity of E5/PAA- g-PNIPAAm were found to be enhanced above the phase transition temperature of the grafted chain. Our analysis suggests that the hydrophilic/hydrophobic environment around the cationic polymer chain plays important roles in the enhancement of the activity of the anionic peptide.

We have developed a novel polymer brush surface exhibiting autonomous swelling–deswelling changes driven by the Belousov–Zhabotinsky (BZ) reaction, that is, the self-oscillating polymer brush. In this system, the ruthenium tris(2,2′-bipyridine) [Ru(bpy)3] catalyst-conjugated polymer chains are densely packed on the solid substrate. It is expected that the BZ reaction in the polymer brush would be influenced by the immobilization effect of the catalyst. To clarify the effect of the immobilization of the catalyst on the self-oscillating polymer brush, the self-oscillating behavior of the polymer brush was investigated by comparing it with that of other self-oscillating polymer materials, the free polymer, and the gel particle under various initial substrate concentrations. The initial substrate dependency of the oscillating period for the polymer brush was found to be different from those for the free polymer and the gel particle. Furthermore, the oscillatory waveform was analyzed on the basis of the Field–...

A polymer brush surface with autonomous function has been designed by using a self-oscillating polymer that we developed. The self-oscillation is induced by chemomechanical energy conversion from an oscillating chemical reaction (the Belousov–Zhabotinsky (BZ) reaction) to conformational changes of polymer chains. In this study, the surface nanostructure of polymer brushes were regulated and the spatiotemporal behaviors of self-oscillation were investigated. The target polymer brush surfaces were prepared through surface-initiated atom transfer radical polymerization (SI-ATRP) of N-isopropylacrylamide (NIPAAm) and N-(3-aminopropyl) methacrylamide (NAPMAm), and the subsequent conjugation of Ru(bpy)3 to the amino group of NAPMAm. The characterization of the prepared polymer brush and the free polymer was determined by X-ray photoelectron spectroscopy, atomic force microscopy, attenuated total reflection Fourier transform infrared spectroscopy, UV–vis spectrophotometry, gel permeation chromatography, and 1H N...

We have developed a novel “self-oscillating” gel that exhibits an autonomous mechanical oscillation without any external stimuli. Here the ternary self-oscillating polymer composed of N-isopropylacrylamide and N-(3-aminopropyl)methacrylamide and Ru(bpy)3 was newly synthesized by atom transfer radical polymerization (ATRP) and the gel was prepared. For the self-oscillating polymers and gels with various compositions, their phase transition and self-oscillating behaviors were investigated considering the potential for biomedical application. It was demonstrated that the swelling–deswelling behavior of the self-oscillating gels can be controlled by changing the composition ratio of the free amino group present in the polymer and the conjugated Ru(bpy)3 moieties. Therefore the hydrophilic/hydrophobic balance is controllable and adjustable by this composition ratio.

Herein, we describe the physicochemical aspects of the Belousov–Zhabotinsky (BZ) reaction in hydrated protic ionic liquids (PILs) combined with different cations with a hydrogen sulfate ([HSO4–]) anion. PILs were prepared from the neutralization reactions of sulfuric acid with 13 different aliphatic amines. The amine structure was selected to investigate the effect of the number of active protons, alkyl chain length (hydrophilicity), and cationic linearity on the mechanism of the BZ reaction. The pKa values of PILs were significantly higher (pKa = 1.0–2.5) than those of inorganic acids (H2SO4 = −3.0; HNO3 = −1.4), the conventional proton source in a BZ reaction. A periodic redox oscillation was observed in Ru(bpy)3 when appropriate amounts of BZ reaction substrates (NaBrO3 oxidant; malonic acid reductant) were added to the hydrated PILs. A long-lasting BZ oscillation was realized when hydrophilic cations (ammonium, ethylammonium, and dimethylethylammonium) were employed. Interestingly, a large ΔA5000 (osc...

The propagation control of chemical waves via a pentagonal patterned structure in a self-oscillating polymer brush composed of N-isopropylacrylamide and a metal catalyst for the Belousov–Zhabotinsky (BZ) reaction is reported. The patterned self-oscillating polymer brush is prepared by combining surface-initiated atom transfer radical polymerization and maskless photolithography. Surface modification is confirmed by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, 3D measuring laser microscopy, and fluorescence microscopy. The polymer brush patterns are fabricated with gaps between the pentagonal regions, and investigations on the effect of the gap distance on the BZ reaction reveal that at the appropriate distance, chemical waves propagate across the array from the plane to the corner between the patterns. Unidirectional control is achieved not only in the 1D array, but also in a 2D curved array. This patterned self-oscillating polymer brush is a novel and advantageous approach for creating an autonomous dynamic soft interface.

Nanosheets have thicknesses on the order of nanometers and planar dimensions in the micrometer range. Nanomaterials that are capable of converting reversibly between 2D nanosheets and 3D structures in response to specific triggers can enable construction of nanodevices. Supra-molecular lipid nanosheets and their triggered conversions to 3D structures including vesicles and cups are reported. They are produced from lipid vesicles upon addition of amphiphilic peptides and cationic copolymers that act as peptide chaperones. By regulation of the chaperoning activity of the copolymer, 2D to 3D conversions are reversibly triggered, allowing tuning of lipid bilayer structures and functionalities.

An autonomous functional surface has been designed by using self-oscillating polymers that convert the chemical energy of the Belousov-Zhabotinsky reaction into conformational changes of the polymer chains (see picture: red: hydrophobic/collapsed, green: hydrophilic/extended). Self-oscillating polymer brushes were grafted onto the inner surface of a glass capillary, and autonomous propagation of a chemical wave was observed.

A gradient self-oscillating polymer brush has been designed to achieve controlled unidirectional motion., A gradient self-oscillating polymer brush surface with ordered, autonomous, and unidirectional ciliary motion has been designed. The self-oscillating polymer is a random copolymer composed of N-isopropylacrylamide and ruthenium tris(2,2′-bipyridine) [Ru(bpy)3], which acts as a catalyst for an oscillating chemical reaction, the Belousov-Zhabotinsky reaction. The target polymer brush surface was designed to have a thickness gradient by using sacrificial-anode atom transfer radical polymerization. The gradient structure of the polymer brush was confirmed by x-ray photoelectron spectroscopy, atomic force microscopy, and ultraviolet-visible spectroscopy. These analyses revealed that the thickness of the polymer brush was in the range of several tens of nanometers, and the amount of Ru(bpy)3 increased as the thickness increased. The gradient polymer brush induced a unidirectional propagation of the chemical wave from the region with small Ru(bpy)3 amounts to the region with large Ru(bpy)3 amounts. This spatiotemporal control of the ciliary motion would be useful in potential applications to functional surface such as autonomous mass transport systems.

“Self-oscillating” gels that undergo spontaneous periodic swelling–deswelling changes without any on/off switching of external stimuli, as with heart muscle, have been developed. The self-oscillating gels were designed by utilizing the Belousov–Zhabotinsky reaction, as a chemical model for understanding several autonomous phenomena in biological systems. These polymer gels have been systematically studied since the first report in 1996 by the author’s group. Several kinds of autonomous functional soft materials utilizing the self-oscillating polymer and gel, such as biomimetic soft actuators, mass transport systems, functional fluids, etc., are expected. Herein, our recent progress on the self-oscillating polymer gels and the development of functional material systems are summarized based on the polymer nanoarchitectures.

Amphiphilic peptides are great focus owing to potential applications including drug delivery systems and antimicrobials. E5 peptide, one of amphiphilic peptides, forms amphiphilic α-helix at low pH, and exhibits membrane permeabilizing activity.1,2) However, the activity of E5 peptide is low attributed to low solubility in aqueous media. In the previous paper, we showed that the cationic comb-type copolymer, poly(allylamine)-graft-dextrane (PAA-g-Dex) formed soluble inter-polyelectrolyte complex (sIPEC) with E5 peptide at both low and natural pH, and E5/PAA-g-Dex exhibited strong membrane disruptive activity.3) In this study, we designed a novel comb-type cationic copolymer composed of a PAA main chain and thermoresponsive poly(N-isopropylacrylamide) graft chains (PAA-g-PNIPAAm). We hypothesized that the thermoresponsive hydrophilic/hydrophobic transition of the grafted polymer would regulate the membrane disruption activity of E5 peptide. The target copolymer was prepared by activators regenerated by electron transfer atom transfer radical polymerization (ARGET ATRP). The ratio of AA units to Initiator to NIPAAm units was estimated to be 100:9:421 by 1H NMR. Thus, the number-averaged molecular weight (M n) of PNIPAAm and the PNIPAAm contents were 1.0 × 104 and 94.3 wt %, respectively. Circular dichroism (CD) spectra measurement revealed that PAA-g-PNIPAAm formed sIPEC with E5 peptide, resulting in α-helix formation of E5 peptide. Furthermore, the complex formation of E5 and PAA-g-PNIPAAm was investigated by measuring the fluorescence spectra of triptophan residure in E5 peptide. From these investigations, we found that the interaction between E5 peptide and PAA-g-PNIPAAm at 35 °C (above LCST) was stronger than that at 25 °C (below LCST). These results suggest that the hydrophobicity of the environment around the cationic polymer chain influences complex formation. E5 peptide in the presence of PAA-g-PNIPAAm induced the leakage from liposomes, whereas E5 peptide alone did not. Importantly, E5/PAA-g-PNIPAAm induced more significant leakage at 35 °C than at 25 °C. Thus, membrane disruptive activity of E5/PAA-g-PNIPAAm sIPEC was regulated in response to temperature coupled with the phase transition of the thermo-responsive grafted chain.4) References: 1) M. Murata, et al., Ohnishi, J. Biol. Chem. 1991, 266, 14353. 2) M. Murata, et al., Biophys. J. 1993, 64, 724. 3) N. Shimada et al., J. Controlled Release 2015, 218, 45. 4) T. Masuda et al., Biomacromolecules 2018, 19, 1333. Figure 1