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Nobuhiko Yui

Publications and source records attributed to Nobuhiko Yui.

34 records · Page 2Linked to original sources
PubMed2004

Design of polyrotaxanes as supramolecular conjugates for cells and tissues.

This research focuses on the supramolecular challenge of enhancing multivalent binding between ligands and proteins or biological receptors on cell surfaces. Our special interest is using supramolecular-structured polymers, namely, polyrotaxanes consisting of ligand-immobilized alpha-cyclodextrins (alpha-CDs) threaded onto a poly(ethylene glycol) (PEG) chain capped at both terminals with bulky end groups via biodegradable linkages. The structural characteristics of these polyrotaxanes involve sliding and rotational motion of the ligands immobilized on alpha-CDs along a PEG chain, thus facilitating access to binding sites on proteins. This approach provides a novel biomaterial design in the field of drug delivery and tissue engineering.

Animals↗
PubMed2004

Novel biodegradable cholesterol-modified polyrotaxane hydrogels for cartilage regeneration.

Cholesterol was introduced to a hydrolyzable polyrotaxane (PRx), not only to improve cell proliferation and glycosaminoglycan (GAG) production, but also to control the degradation rate of the hydrogels. The cholesterol was introduced to hydrolyzable PRx species by threading many alpha-cyclodextrins (alpha-CDs) on a poly(ethylene glycol) (PEG) chain having hydrolyzable ester linkages at the terminals; the PRx species were then cross-linked with other PEGs to prepare cholesterol-modified PRx hydrogels. The degree of cholesterol substitution was varied in the range of 1-25%. These hydrogels were examined to clarify the effect of cholesterol groups on mechanical properties, erosion time and chondrocyte proliferation. Highly porous biodegradable cholesterol-modified PRx hydrogels were fabricated using a combination of potassium hydrogen carbonate (as an effervescent salt) and citric acid. This fabrication process enabled the homogeneous expansion of pores within the polymer matrices, leading to well-interconnected macroporous hydrogels with a mean pore size of around 200-400 microm, ideal for high-density chondrocyte seeding. Time to complete degradation of the hydrogels was shortened by increasing the degree of substitution due to the aggregation of alpha-CDs through hydrophobic interaction of cholesterol groups. The presence of approx. 10% cholesterol improved the chondrocyte proliferation and GAG production. The modification of cholesterols to PRx is a good approach for creating new biodegradable hydrogels in terms of chondrocyte culture and controlling degradation time of the hydrogels.

Animals↗
PubMed2003

Novel poly(ethylene glycol) scaffolds crosslinked by hydrolyzable polyrotaxane for cartilage tissue engineering.

Highly porous poly(ethylene glycol) (PEG) hydrogel scaffolds crosslinked with hydrolyzable polyrotaxane for cartilage tissue engineering were prepared by a solvent casting/salt leaching technique. The resultant scaffolds have well interconnected microporous structures ranging from 87 to 90%. Pore sizes ranging from 115.5-220.9 microm appeared to be dependent on the size of the sieved sodium chloride particulates. Moreover, a dense surface skin layer was not found on either side of the scaffold surfaces. Using microscopic Alcian blue staining of the chondrocyte-seeded scaffolds, well adhered cells and newly produced glycosaminoglycans (GAG) were confirmed. Following the initial chondrocyte seeding onto the hydrogel scaffolds, the cell number was significantly increased, reaching 149, 877, and 1228 cells/mg of tissue at 8, 15, and 21 days in culture, respectively. The micrograph shows well adhered and spread chondrocytes in the interior pores and a cartilaginous extracellular matrix with a GAG fraction produced from the chondrocytes. Results suggest that the PEG hydrogel scaffolds crosslinked with the hydrolyzable polyrotaxane are a promising candidate for chondrocyte culture.

Absorbable Implants↗
PubMed2003

Supramolecular design for multivalent interaction: maltose mobility along polyrotaxane enhanced binding with concanavalin A.

High molecular mobility of maltose-conjugated alpha-cyclodextrins (alpha-CDs) along a poly(ethylene glycol) (PEG) chain due to the mechanically locked structure of polyrotaxanes enhanced multivalent interactions between maltose and concanavalin A (Con A). When maltose groups are conjugated with alpha-CDs that were threaded onto a PEG capped with benzyloxycarbonyl l-tyrosine (polyrotaxane), Con A-induced hemagglutination was greatly inhibited by polyrotaxanes with a certain threading % of alpha-CDs. Such an inhibitory effect was significantly superior to the other type of conjugates, in which poly(acrylic acid) was used as a backbone for maltose conjugation. The spin-spin relaxation time (T2) of the maltose C(1) proton in the polyrotaxane at a typical alpha-CD threading % was significantly larger than that of any other conjugate, which was well related to the inhibitory effect. Therefore, we concluded that the high mobility of maltose groups along the polyrotaxane structure contributes to enhanced Con A recognition.

Concanavalin A↗
PubMed2003

In vitro biocompatibility assessment of sulfonated polyrotaxane-immobilized polyurethane surfaces.

Sulfonated polyrotaxanes (PRx-SO(3)'s), in which sulfonated alpha-cyclodextrins (alpha-CDs) were threaded onto the poly(ethylene glycol) (PEG) segments in a PEG-b-poly(propylene glycol) (PPG)-b-PEG triblock copolymer (Pluronic) capped with benzyloxycarbonyl (Z)-L-phenylalanine (Z-L-Phe), were prepared as a novel surface-modifying biomaterial. Surface modification of the polyurethane (PU) was carried out by blending the PRx-SO(3)'s with a PU solution, followed by solution casting. The incorporated PRx-SO(3)'s led to the enhanced hydrophilicity by changing the surface properties of the PU matrix. Modified PUs showed the stable entrapment of the PRx-SO(3)'s with little extraction into water and enhanced mechanical properties after exposure to water compared to the PU control. The incorporated PRx-SO(3)'s repelled the proteins and kept them from closely approaching the surface areas, prevented platelet activation by thrombin, and effectively repelled bacteria. These results suggest that both the supramolecular structure of the polyrotaxanes and exposure of the sulfonated groups onto the surfaces contribute to these phenomena. Thus, surface modification with PRx-SO(3)'s is suggested to be useful for the fabrication of biocompatible medical devices.

Biocompatible Materials↗
PubMed2003

pH- and thermosensitive supramolecular assembling system: rapidly responsive properties of beta-cyclodextrin-conjugated poly(epsilon-lysine).

beta-Cyclodextrin-conjugated poly(epsilon-lysine) (beta-CDPL) was synthesized as a novel polymeric host for constructing a smart supramolecular assembling system. Systematic studies on the inclusion complexation between the polymeric host with an alpha- or beta-CD cavity and a model guest molecule provided evidence that dual cooperative interactions, specific host-guest interaction and intermolecular ionic interaction, played a dominant role in leading to a fast aggregation phenomenon. In addition, a rapid phase transition induced by the supramolecular assembly was observed reversibly in response to a small change in pH or temperature.

Biomimetic Materials↗
PubMed2003

A study of compatibility between cells and biopolymeric surfaces through quantitative measurements of adhesive forces.

The mechanism of cell adhesion to biomaterials or components of the extracellular matrix is an important topic in the field of tissue engineering and related biotechnological processes. Many factors affect cell adhesion, and many biochemical and biological studies have attempted to identify their roles in the adhesion mechanism. Systematic studies of this nature require quantification of the adhesive force of a cell to identify the effect of a specific factor. However, most studies of cell adhesive force have used qualitative approaches. We propose a new technique for quantifying the force by which cells adhere to various biomaterial surfaces, which utilizes the relationship between the deflection of a cantilever beam and the required force. A micropipette was used as the cantilever beam. This technique was used to measure the attachment forces of chondrocytes seeded on three different biodegradable polymers commonly used in tissue engineering and medicine: poly epsilon-carprolactone (PCL), poly(L-lactide) (PLLA) and poly(lactic-co-glycolic acid) (PGLA, L/G = 75:25). The bond between the cells and the three polymers was evaluated using the quantified adhesive forces. The adhesive forces were also measured 8, 12, 24 h and 5 days after seeding the chondrocytes on the polymer surfaces. Results of statistical analysis showed that the cells attached to the PLLA had the strongest average attachment force for up to 24 h after seeding (P < 0.05).

Animals↗
PubMed2003

Preparation of porous hydrolyzable polyrotaxane hydrogels and their erosion behavior.

We have prepared porous polyrotaxane hydrogels by using the salt leaching technique. Porous hydrogels were found to have a uniform and highly porous structure. The size of pores in each hydrogel was directly proportional to the size of the sodium chloride particle used. Structural uniformity of the hydrogels is useful not only for uniform cell distribution, but also for well-controlled material properties. Uniform pore size and distribution may ensure the diffusion of nutrients throughout of the gel and the removal of metabolic wastes from the system. The results of an erosion study in phosphate-buffered saline showed that the erosion time of porous polyrotaxane hydrogels was controlled by the poly(ethylene glycol) (PEG) content in the hydrogels. The erosion time of the porous polyrotaxane hydrogel was observed to be almost the same with the non-porous polyrotaxane hydrogel with the same PEG content. From the erosion study, the erosion time of the polyrotaxane hydrogel may be independent of its morphology. Easy control of the erosion time in the polyrotaxane hydrogels is useful in the preparation of scaffolds for tissue engineering.

Biocompatible Materials↗
PubMed2002

Carboxyethylester-polyrotaxanes as a new calcium chelating polymer: synthesis, calcium binding and mechanism of trypsin inhibition.

A carboxyethylester-polyrotaxane was synthesized as a novel calcium chelating polymer in the field of oral drug delivery and characterized in terms of mechanism of trypsin inhibition. Here, carboxyethylester (CEE) groups are introduced to all the primary hydroxyl groups in alpha-cyclodextrins (alpha-CDs), which are threaded onto a poly(ethylene glycol) chain capped with bulky end-groups (polyrotaxane). The solubility of the CEE-polyrotaxane in physiological conditions increased with pH, indicating ionization-related solubility similar to conventional polyacrylates. The ability of calcium (Ca2+) chelation was found to increase in the order of poly(acrylic acid) (PAA)>CEE-polyrotaxanez.Gt;CEE-alpha-CD, suggesting that the increased density of carboxyl groups enhances the Ca2+ chelating ability. The activity of trypsin was inhibited by these compounds in the same order of the calcium chelation. However, the inhibitory effect of CEE-polyrotaxane was reduced by adding excess Ca2+ without precipitation that was observed in the presence of PAA. Such the reduced inhibition and precipitation by CEE-alpha-CD was not observed. Therefore, the inhibitory effect of CEE-polyrotaxane is due to Ca2+ chelation from trypsin without non-specific interaction.

Acrylic Resins↗
PubMed2002

Multivalent interactions between biotin-polyrotaxane conjugates and streptavidin as a model of new targeting for transporters.

Kinetic analysis of interactions between biotin-polyrotaxane or biotin-alpha-cyclodextrin (biotin-alpha-CD) conjugates and streptavidin was carried out as a model of new targeting to transporters using the surface plasmon resonance (SPR) technique. The biotin-polyrotaxane conjugates, in which biotin-introduced alpha-CDs are threaded onto a poly(ethylene oxide) chain capped with bulky end-groups, are expected to increase the valency of biotin from monovalent to multivalent binding. The number of biotins conjugated with one polyrotaxane molecule varied from 11 to 78, and apparently increased the association equilibrium constant (K(a)), assuming pseudo-first-order kinetics. A detailed dissociation kinetics was analyzed and the re-binding of the biotin-polyrotaxane conjugates was observed on the streptavidin-deposited SPR surface. The magnitude of the re-binding is likely to become larger with increasing the number of biotins, suggesting multivalent interaction on the SPR surface. To quantify the effect of valency, competitive inhibition assay was performed in terms of the supramolecular structure of the polyrotaxane. The inhibitory potency of the biotin-polyrotaxane conjugate was found to be 4-5 times greater than that of the biotin-alpha-CD conjugate. Therefore, the biotin-polyrotaxane conjugates by supramolecular formation of the biotin-alpha-CD conjugate significantly switches from monovalent to multivalent bindings to the model binding protein, streptavidin.

Biotin↗
PubMed2002

Anticoagulant activity of sulfonated polyrotaxanes as blood-compatible materials.

Polyrotaxanes, in which alpha-cyclodextrins (alpha-CDs) are threaded onto poly(ethylene glycol)-b-poly(propylene glycol)-b-poly(ethylene glycol) triblock copolymers (Pluronic) capped with benzyloxycarbonyl(Z)-L-phenylalanine (Z-L-Phe), were prepared, and sulfopropyl groups were introduced to hydroxyl groups of alpha-CDs in the polyrotaxanes. The supramolecular structure and the chemical composition of the polyrotaxanes after the sulfonation were confirmed by 1H-NMR, 13C-NMR, and elemental analysis. Anticoagulant activity of the polyrotaxanes and sulfonated polyrotaxanes was measured by activated partial thromboplastin time (APTT). It was found that the polyrotaxanes and the sulfonated polyrotaxanes showed greater anticoagulant activity than Pluronic itself, suggesting that both the supramolecular structure of the polyrotaxanes and the sulfonated groups contribute to the inhibition of intrinsic coagulation factors. Finally, our designed polyrotaxanes are suggested to be a promising candidate when fabricating blood-compatible medical devices by blending with or coating on clinically used polymers.

Anticoagulants↗
PubMed2002

Fibroblast adhesion and proliferation on poly(ethylene glycol) hydrogels crosslinked by hydrolyzable polyrotaxane.

Fibroblast culture was performed to evaluate cell adhesion and proliferation on poly(ethylene glycol) (PEG) hydrogels crosslinked by a hydrolyzable polyrotaxane. The polyrotaxane consisting of alpha-cyclodextrins (alpha-CDs) and PEG terminated by benzyloxycarbonyl (Z)-L-phenylalanine (L-Phe) via ester linkage was used as a multi-functional crosslinker in the PEG hydrogels. From the results of contact angle and small angle light scattering measurements, it was suggested that the surface and bulk structure of the PEG hydrogels were heterogeneous. Fibroblast adhesion and proliferation on the hydrogels was observed. The number of fibroblast adhesion on the hydrogels crosslinked by the polyrotaxane was proportional to contact angle values and correlation length, and was significantly higher than those crosslinked by alpha-CDs in spite of similar contact angle and correlation length. These findings suggest that the cells recognize the surface heterogeneity due to the polyrotaxane structure, and the number of cell adhesion and proliferation is controllable by the polyrotaxane content in feed.

3T3 Cells↗
PubMed2002

Synthesis and characterization of nitric oxide generative polyrotaxane.

L-Arginine was immobilized into a supramolecular-structured polyrotaxane to examine the generation of nitric oxide, with a view to improving antithrombosis and the blood compatibility of polymeric biomaterials. L-Arginine was immobilized to the hydroxyl groups of alpha-cyclodextrins in the polyrotaxane via an ester linkage, and the nitric oxide generation and L-arginine release behavior were characterized. L-Arginine-immobilized polyrotaxane was insoluble in water, but was found to generate nitric oxide when placed in Tris-HCI buffer supplemented with activators. L-Arginine-immobilized polyrotaxane exhibited sustained nitric oxide generation for a period of 250 h. L-Arginine was completely released by non-enzymatic hydrolysis from 200 h to 700 h, with a lag-time for the first 200 h. Consequently, after the generation of nitric oxide and the release of L-arginine from the L-arginine-immobilized polyrotaxane, the residual component will be a polyrotaxane with superior biocompatibility and mechanical properties. These results suggest that L-arginine-immobilized polyrotaxane can be useful in a wide range of medical applications, including use as a nitric oxide generative system for antithrombosis, coating and blending materials of hydrophobic extracorporeal circuits, and implantable catheters.

Arginine↗
PubMedDate not supplied

Inhibitory effect of supramolecular polyrotaxane-dipeptide conjugates on digested peptide uptake via intestinal human peptide transporter.

The effect of polyrotaxane-dipeptide (Val-Lys) conjugates on the uptake of a model dipeptide (Gly-Sar) was examined via human peptide transporter (hPEPT1) on HeLa cells. Here, Val-Lys groups are introduced to alpha-CDs, which are threaded onto a poly(ethylene oxide) chain capped with bulky end-groups (polyrotaxane). The Gly-Sar uptake via hPEPT1 was significantly inhibited in the polyrotaxane conjugates, and this inhibitory effect was not explained by the sum of interaction between hPEPT1 and alpha-CD-Val-Lys conjugates. Further, the inhibition was significantly greater than those observed in dextran-Val-Lys conjugates. Therefore, our data clearly suggests that supramolecular structure in the polyrotaxane conjugates contributes considerably to the inhibitory effect via multivalent binding of Val-Lys groups with hPEPT1.

Biological Transport↗
PubMedDate not supplied

Rapid binding of concanavalin A and maltose-polyrotaxane conjugates due to mobile motion of alpha-cyclodextrins threaded onto a poly(ethylene glycol).

Maltose-polyrotaxane conjugates (Mal-PRXs), in which maltose-conjugated alpha-cyclodextrins (alpha-CDs) are threaded onto a poly(ethylene glycol) (PEG) chain capped with benzyloxycarbonyl-L-tyrosine, were characterized in terms of their molecular motion and the relation to multivalent interactions between the maltose moiety and concanavalin A from Canavalia ensiformis (Con A). Spin-lattice relaxation time (T1) and spin-spin relaxation time (T2) of alpha-CD C(1), maltosyl C(1), and PEG methylene protons in the Mal-PRXs revealed that the mobile motion of alpha-CDs in the polyrotaxane governed the molecular motion of maltosyl groups in alpha-CDs and threading PEG chain. The association constant (Ka) of the Mal-PRXs with 22, 38 and 53% of alpha-CD threading was 5.7 x 10(4), 1.1 x 10(6), and 5.3 x 10(5) (M(-1)-maltose), respectively. The largest Ka value of the Mal-PRX with 38% of alpha-CD threading was well correlated with the T1 and T2 values of maltosyl groups and alpha-CD, suggesting that the mobile motion of maltose-conjugated alpha-CDs in the Mal-PRX contributes to the highest affinity with Con A. Initial rate of binding with Con A was also governed by the mobile motion of maltose-conjugated alpha-CDs. Therefore, we concluded that both highly molecular motion due to the mobile motion of maltose-conjugated alpha-CDs and multivalency of the Mal-PRXs contributes to inducing rapid Con A binding.

Concanavalin A↗