Honeycomb-patterned Films Research Articles

Honeycomb-Patterned Film Segregated with Phenylboronic Acid for Glucose Sensing

Phenylboronic acid (PBA)-functionalized materials have attracted considerable attention because of their potential applications in many fields. In this paper, we report a PBA-segregated honeycomb-patterned porous film (HPPF) for glucose sensing. Polystyrene-block-poly(acrylic acid-co-acrylamidophenylboronic acid) with different contents of PBA pendants was synthesized via atom transfer radical polymerization (ATRP) followed by a coupling reaction. PBA-functionalized HPPFs were then fabricated by the breath figure method. Results indicate that the composition of the copolymers and the relative humidity play key roles in pore size and regularity of the films. Using Alizarin Red S (ARS) that does not emit fluorescence itself as a fluorescent probe, it is confirmed that PBA pendants are mainly distributed at the pore wall, instead of at the outer surface of HPPFs. This distribution is caused by the segregation of hydrophilic PBA-blocks toward the condensed water droplets, which act as templates for the pore formation. Quartz crystal microbalance results demonstrate that the PBA-functionalized HPPFs show high sensitivity in glucose sensing, which is owing to the segregation of PBA pendants at the pore wall as well as the large specific surface area of the porous films.

Dimensional Architecture of Ferrocenyl-Based Oligomer Honeycomb-Patterned Films: From Monolayer to Multilayer

We report a fabrication of highly ordered honeycomb-patterned films by the breath figure method from ferrocenyl-based oligomer with ferrocene units in the main chain and hydrophobic cholesteryl groups as side chains and investigate their dimensionality nature, i.e., the array of pores varying from monolayer to multilayer structure. A tentative model, including several key influencing parameters, is described to illustrate the varying layer numbers in the one film. The formation of the multilayer structure is ascribed to the Marangoni convection, thermocapillary effects, wet thickness, and evaporation speed.

Tunable Morphology of 2D Honeycomb-Patterned Films and the Hydrophobicity of a Ferrocenyl-Based Oligomer

Honeycomb-patterned polymer films with tunable pore size and regularity of ordered two- or three-dimensional hexagonal arrays have met with widespread interest in recent years in different areas, for instance as separation and superhydrophobic materials. Herein, 2D honeycomb-patterned films of amphiphilic ferrocenyl-based oligomer with cholesterol as side chains were prepared by the breath-figure method on solid surfaces and their surface-wetting behavior were tested. These films can be simply prepared by spreading a mixture of polymer and organic solvents on a solid surface under moist airflow and at an air/water interface without any extra moist airflow. An ordered 2D hexagonal array of pores with monodisperse size distribution can be obtained over a large area by changing various influencing factors, including humidity, wet volume, concentration, selective solvent, and spreading method, which provides a facile route to regulate the morphology of patterned porous films. The surface-wetting behavior indicates that a higher hydrophobicity of the ferrocenyl-based oligomer honeycomb films can be obtained by modulating the pore size and regularity. It is expected that this could promote the potential application of ordered porous polymer films in hydrophobic materials and biochemistry.

Fabrication and Wettability Patterning of Nano-structured Silicon Surface by using Self-organized Polymer Structures

We demonstrate here a creation of superhydrophobic and superhydrophilic patterned surface by using reactive ion etching (RIE) of silicon with a self-organized porous polymer structures and UV-O3 treatments through the photo-mask. Honeycomb-patterned films of polystyrene and amphiphilic polymer were prepared by casting of their chloroform solution. After UV-O3 treatment, honeycomb-patterned films were fixed on silicon substrates up side down with Poly (vinyl alcohol) solution. After peeling of the bottom layer of the honeycomb-patterned films, porous polymer masks were formed on the silicon substrate. After RIE, the silicon nanospike-array structure was obtained. Water contact angles on the silicon nanospike-array structures were c. a. 165 degree. From the results of X-ray photoelectron spectrum of the silicon nanospike-structures, fluorine was detected. The result suggests that superhydrophobicity was originated by absorbed fluorocarbons on the surface of the silicon nanospike-array structures and their surface structures. After UV-O3 treatment with photo-masks, fluorine was partially removed at irradiation area, and the area shows superhydrophilicity. These results suggest that we can easily design superhydrophobic and superhydrophilic patterned surfaces by UV-O3 treatment through photo-masks.

Selective layer-by-layer self-assembly on patterned porous films modulated by Cassie–Wenzel transition

We describe a robust and facile approach to the selective modification of patterned porous films via layer-by-layer (LBL) self-assembly. Positively charged honeycomb-patterned films were prepared from polystyrene-block-poly(N,N-dimethyl-aminoethyl methacrylate) (PS-b-PDMAEMA) and a PS/PDMAEMA blend by the breath figure method followed by surface quaternization. Alginate and chitosan were alternately deposited on the films via LBL self-assembly. The assembly on the PS-b-PDMAEMA film exhibits two stages with different growth rates, as elucidated by water contact angles, fluorescence microscopy, and quartz crystal microbalance results. The assembly can be controlled on the top surface or across all surfaces of the film by changing the number of deposition cycles. We confirm that there exists a Cassie-Wenzel transition with an increase in deposition cycles, which is responsible for the tunable assembly. For the PS/PDMAEMA film, the pores can be completely wetted and the polyelectrolytes selectively assemble inside the pores, instead of on the top surface. The controllable selective assembly forms unique hierarchical structures and opens a new route for surface modification of patterned porous films.

Effect of amphiphilic copolymer containing ruthenium tris(bipyridyl) photosensitizer on the formation of honeycomb-patterned film

A new functional amphiphilic polymer (AP) containing ruthenium tris(bipyridyl) photosensitizer was synthesized and a honeycomb-patterned film was fabricated by casting a polystyrene solution and different concentrations of AP under humid conditions. The amphiphilic copolymer was obtained by the radical copolymerization of ruthenium (4-vinyl-4′-methyl-2,2′-bipyridine)bis(2,2′-bipyridine)bis(hexaflurophosphate) with N-dodecylacrylamide and N-isopropylacrylamide. Without the addition of AP, irregularly ordered porous films were obtained, while adding AP in the casting solution resulted in highly ordered honeycomb-patterned films. In addition, the pore diameter and height of the porous structure increased with the increase of AP amount in the solution. However, an excessive amount of AP induced an irregularly structured pattern with small pore sizes.

Controlled synthesis of linear and comb-like glycopolymers for preparation of honeycomb-patterned films

Honeycomb-patterned films can be facilely prepared by the breath figure method. However, it is still ambiguous how the polymer structure affects the morphologies of the films. In this work, poly(styrene- co-2-(2-,3-,4-,6-tetra- O-acetyl-β- d-glucosyloxy) ethyl methacrylate) (PS- co-AcGEMA) with well-defined linear and/or comb-like structures were synthesized by atom transfer radical polymerization (ATRP). These glycopolymers were used as precursors for the fabrication of pattern films by the breath figure method. The regularity and pore size of the films are greatly influenced by the polymer structure and the solution concentration. Highly ordered pattern films can be prepared from the comb-like glycopolymer and the linear block glycopolymers with relatively long PAcGEMA segment. Further studies of lectin recognition on the honeycomb-patterned films demonstrate that the glucose-containing films can specifically recognize Con A. These bioactive honeycomb-patterned films have potential applications as templates, picoliter beakers for bioanalysis and cell culture materials.

Controllable Construction of Carbohydrate Microarrays by Site-Directed Grafting on Self-Organized Porous Films

Carbohydrate-protein interactions are critical in many biological processes. However, the interactions between individual carbohydrates and proteins are often of low affinity and difficult to study. Recent development of carbohydrate microarrays provides an effective tool to explore the interaction. In this work, carbohydrate microarrays were controllably constructed by grafting of a carbohydrate-containing monomer on self-organized honeycomb-patterned films. The films were prepared from an amphiphilic block copolymer, poly(styrene-block-(2-hydroxyethyl methacrylate)), by a breath figure method. Three-dimensional fluorescence results demonstrate that the hydroxyl groups aggregate mainly inside the pores, which afford a chance of site-directed surface modification. 2-(2,3,4,6-Tetra-O-acetyl-beta-D-glucosyloxy)ethyl methacrylate was selectively grafted in the pores by a surface-initiated atom transfer radical polymerization. Characterization by attenuated total reflectance Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy, atomic force microscopy, and contact angle measurements confirms the site-directed growth of the glycopolymer chains. Further specific recognition of the carbohydrate microarrays to lectin (concanavalin A) leads to an organized microarray of protein, and hence this approach also opens a new route to fabricating other functional microarrays such as protein-patterned surfaces.

自己組織化ハニカムフィルムに対するラット骨髄間葉系幹細胞の応答

自己組織化ハニカムフィルムに対するラット骨髄間葉系幹細胞の応答

B134 水の凝縮を利用したポーラス有機薄膜生成(OS-4:マイクロ・ナノ熱工学(I))

B134 水の凝縮を利用したポーラス有機薄膜生成(OS-4:マイクロ・ナノ熱工学(I))

Proliferation of Periodontal Ligament Cells on Biodegradable Honeycomb Film Scaffold with Unified Micropore Organization

Tissue-engineered grafts using a scaffold can be used in treating periodontal disease; however, previous scaffolds for the cultivations of the periodontal ligament cells have been structurally incompatible with the morphological requirements of human periodontal tissue. Here, we describe a self-organized honeycomb-patterned film (honeycomb film) that acted as an appropriate scaffold for periodontal tissue regeneration. The honeycomb films were prepared from biodegradable poly(e-caprolactone) with highly regular three-dimensional micropatterned surface topography by casting a polymer solution of water-immiscible solvent under humid conditions. To evaluate its performance in activating the proliferation and organizing of cells, we have demonstrated specific behaviors of the cultured periodontal ligament cells on the self-organized honeycomb structures in vitro. Fibroblast-like cells derived from the periodontal ligament of extracted human molar teeth were cultivated on three types of honeycomb films with 5-, 10-, and 15-µm pore sizes for 4 h to 42 d. Morphological observation of the cultured tissues at 4—72 h revealed that the pseudopodiums of cell bodies were attached to the pillars in the honeycomb structure. A certain number of cells shifted their cell bodies into the honeycomb structural lumen through the oscula of 10- and 15-µm pores. After 28 and 42 d, the cells were observed to have formed multiple layers; further, each cell had penetrated through the 10- and 15-µm pores in the honeycomb film. The morphological examination of the honeycomb film along with the pillar structures revealed that the scaffold was clusteringly arrayed with interconnected structures, remarkably enhanced proliferation, and extension of the cultured cells. We consider that the film can be applied in periodontal therapy for use as a scaffold for periodontal tissue regeneration.

Quantum-dot-embedded ionomer-derived films with ordered honeycomb structures via breath figures

A new approach for fabricating a series of multi-functional honeycomb-patterned films was successfully achieved using ionomers via breath figures.

Effect of Honeycomb-Patterned Surface Topography on the Function of Mesenteric Adipocytes

Excessive accumulation of visceral adipose tissue, particularly mesenteric adipose tissue, is one of the most important factors in the pathogenesis of the metabolic syndrome. We previously developed a system for physiologically differentiating rat mesenteric-stromal vascular cells (mSVCs) to mesenteric-visceral adipocytes (mVACs) and are currently implementing various approaches to elucidate the details of the pathophysiology of mVACs. However, there is a critical problem to overcome, namely, that mature mVACs detach from the culture dishes and lose their function after approx. 10 days in culture. Therefore, we examined a culture of mSVCs on self-organized honeycomb-patterned films (honeycomb films) in order to establish a long-term culture for mVACs. The honeycomb films with highly regular porous structures can be prepared under humid casting conditions. These films can be prepared with ease, at a low cost and without any limitations pertaining to the availability of materials for the scaffold. As a result, mSVCs differentiated to mVACs and maintained their function for the secretion of adiponectin on the honeycomb films for at least 40 days. In addition, we investigated the influence of the pore size of the honeycomb films on mVAC behavior. We found that a honeycomb film with a pore size of 20 μm showed the highest mVAC function and optimum size for the long-term culture of mVACs. Thus, we established a long-term culture system for mVACs using the honeycomb films. We believe that this culture system will contribute to the understanding of the pathophysiology of mVACs and to the evaluation of drug candidates for the metabolic syndrome.

Self-Organized Honeycomb Structures of Mn12 Single-Molecule Magnets

In this paper, Mn(12)-based ordered honeycomb structures were successfully constructed from a simple solution casting process at high relative humidity through the modification of fatty acids to Mn(12) clusters. Mn(12)-fatty acid complexes maintain typical features of a single-molecule magnet as confirmed by IR spectra and magnetization hysteresis studies. Investigation of the effects of concentration, velocity of humid airflow, solvent, substrate, and alkyl chain length of the Mn(12) complex on the morphology of the honeycomb structures demonstrated wide generality and high reproducibility of the formation of Mn(12)-based self-organized honeycomb-patterned films. Both two-dimensional and three-dimensional honeycomb structures were obtained by adjusting the concentration of the complex solution. Mn(12)-based, honeycomb-patterned films maintain a paramagnetic response at room temperature, and thus give rise to a spatially distributed magnetic pattern on the substrate, which can be imaged by magnetic force microscopy. Importantly, the single-molecule magnetic property of the Mn(12) complex at low temperature is well maintained in the honeycomb-patterned film, which represents a promising outlook for high-density information storage and quantum computing applications.

Honeycomb-Patterned Films Fabricated by Self-Organization of DNA−Surfactant Complexes

In this paper, DNA-based honeycomb films were successfully constructed from a simple solution casting process at high relative humidity, through the encapsulation of DNA with a cationic surfactant ditetradecyldimethylammonium (DTDA). Cationic surfactants electrostatically attach to phosphate anions of DNA in a molar ratio of 1:1 in the DNA-DTDA complex. Investigation of the effects of substrate, concentration, and solvent on the morphology of the microporous films demonstrated the wide generality and high reproducibility of the formation of DNA-DTDA self-organized microporous films. The morphology of the microporous structures can be adjusted by slightly changing the concentration of the complex solution. DNA exists in the double helical B-form in the microporous film confirmed by circular dichroism spectrum. Dye molecule rhodamine B was loaded into the DNA-DTDA complex, presenting a fluorescent microporous film. DNA-DTDA complex as a host material provides a new method for tailoring fluorescent microporous films. The DNA-based ordered honeycomb films should be attractive for use in optical and optoelectronic devices, separation, ion transportation, and biosensors.

A Thin Honeycomb-patterned Film as an Adhesion Barrier in an Animal Model of Glaucoma Filtration Surgery

To evaluate the effectiveness and safety of a thin honeycomb-patterned biodegradable film for glaucoma filtration surgery in rabbits. A 7 microm-thick film made from poly(L-lactide-co-epsilon-caprolactone) was placed in the subconjunctival space in one eye of rabbits, with or without full thickness filtration surgery. The film had a honeycomb-patterned surface that faced the subconjunctival Tenon tissue and the other side was smooth. Filtration surgery was also performed in the fellow eye, which received either no adjunctive treatment or 0.4 mg/mL mitomycin C (MMC; n=6 each). Intraocular pressure (IOP) measurements and bleb evaluations using ultrasound biomicroscopy were performed periodically for 28 days after surgery followed by histologic observation. Postoperative IOPs of the film-treated eyes were significantly lower than that of control eyes from day 10 to day 28 (P<0.05), but were not significantly different from those of MMC-treated eyes. The subconjunctival filtration space, detected by ultrasound biomicroscopy, disappeared in 5 control eyes, 1 MMC-treated eye, but none of the film-treated eyes. A bleb leak occurred postoperatively in 2 MMC-treated eyes. Histologically, in eyes without filtration surgery, fibrotic tissue with the film partly attached to it was noted on the honeycomb side, but was minimal on the sclera that faced the smooth side of the film. In eyes with filtration surgery, the honeycomb-patterned film lined the inner bleb wall with minimal inflammatory reaction. The thin honeycomb-patterned film that attached to the inner bleb wall worked as an adhesion barrier in glaucoma filtration surgery in rabbits, which is worthy of further investigation.

Honeycomb-patterned films of polystyrene/poly(ethylene glycol): preparation, surface aggregation and protein adsorption

Highly ordered honeycomb-patterned polystyrene (PS)/poly(ethylene glycol) (PEG) films were prepared by a water-assisted method using an improved setup, which facilitated the formation of films with higher regularity, better reproducibility, and larger area of honeycomb structures. Surface aggregation of hydrophilic PEG and adsorption of bovine serum albumin (BSA) on the honeycomb-patterned films were investigated. Field emission scanning electron microscopy (FESEM) and atomic force microscopy (AFM) were used to observe the surface morphologies of the films before and after being rinsed with water. As confirmed by the FESEM images and the AFM phase images, PEG was enriched in the pores and could be gradually removed by water. The adsorption of fluorescence-labeled BSA on the films was studied in visual form using laser scanning confocal microscopy. Results clearly demonstrated that the protein-resistant PEG was selectively enriched in the pores. This water-assisted method may be a latent tool to prepare honeycomb-patterned biofunctional surfaces.

The Effects of Interfacial Tensions of Amphiphilic Copolymers on Honeycomb-Patterned Films

A honeycomb-patterned film is formed by casting a polymer solution of polystyrene and amphiphilic copolymer under humid condition. Amphiphilic copolymers stabilize condensed water droplets as temporal templates. Therefore, physical properties of the amphiphilic copolymer are important factors for stability of condensed water droplets and the structure of the honeycomb-patterned film. In order to verify the effect of the interfacial tension between water and chloroform solution of the amphiphilic copolymer, which is one of the important physical properties, amphiphilic copolymers were synthesized from hydrophobic monomer and hydrophilic monomer at various copolymerization ratios. The interfacial tension decreased with increasing the copolymerization ratio of the hydrophilic comonomer. Uniformity of micropores of the honeycomb-patterned film increased with decreasing the value of the interfacial tension. Moreover, polymer frame of honeycomb-patterned film became thinner with decreasing the value of the interfacial tension. These results indicate that the structure of honeycomb-patterned film can be controlled by the interfacial tension between water and polymer solution.

Enhanced Cell Survival and Yield of Rat Small Hepatocytes by Honeycomb-Patterned Films

Surface designing of substrate to regulate cell adhesion and function in nano and micro scale is a critical issue in biomaterial science. In this study, we describe the fabrication of highly regular patterned porous films (honeycomb-patterned film) formed by a simply casting technique, and the culture of mature hepatocytes and small hepatocytes on the films. The pore size of the honeycomb-patterned films used was 6, 12, and 16 µm. We evaluated the effect of the honeycomb-patterned films on the morphology, cell yield, survival and the differentiated hepatic function (albumin production) of the both hepatocytes. Both hepatocytes attached on the flat films appeared to spread well, showing a typical monolayer morphology. They peeled off from the films at 7 days in culture on the flat films. On the other hand, spreading of the each hepatocytes was restricted on the honeycomb-patterned films at 3 and 7 days in culture. The cell yield and survival of the each hepatocytes increased with increasing culture time. Small hepatocyte on the pore sizes of 16 µm showed the highest cell yield (approximately 3 times). Albumin production of mature hepatocyte on the pore sizes of 16 µm (224.1.3 ±157 ng ml-1 well-1 at 1 day in culture, 369.5 ±222 ng ml-1 well-1 at 3 days in culture) was higher than that of the hepatocytes on the flat films (119.3 ±9.3 ng ml-1 well-1 at 1 day in culture, 262.8 ±47.3 ng ml-1 well-1 at 3 days in culture), although that of small hepatocytes on the honeycomb-patterned films (pore size: 16 µm) was similar on the flat film. These results indicated that both the surface topography and the pore size of the honeycomb-patterned film affected the hepatic metabolic function.

Electroless deposition of zinc oxide on pincushion films prepared by self-organization

This report describes the electroless deposition of zinc oxide on pincushion-like polymer structures prepared by self-organization. By using condensed water droplet arrays as templates, a honeycomb-patterned film was formed after evaporation of solvent and template water droplets from casting polymer solution. Well-ordered pincushion structures were prepared by peeling off the top layer of the honeycomb-patterned film. Thin catalytic gold layer was sputtered onto the pincushion film of polystyrene and amphiphilic copolymer, and the gold-coated pincushion film was dipped in an aqueous solution containing zinc ion and reducer. The scanning electron microscopy and X-ray photoelectron spectroscopy revealed that zinc oxide layer was formed on the gold-coated pincushion film.