Biomedical subjects

Katsuhiko Nakamae

Publications and source records attributed to Katsuhiko Nakamae.

5 recordsLinked to original sources

PubMed2005

Surface properties and structures of diblock copolymer and homopolymer with perfluoroalkyl side chains.

The surface free energy of diblock copolymer, composed of methyl methacrylate and 2-perfluorooctylethyl methacrylate (PMMA-b-PFEMA), was compared with that of PFEMA homopolymer (P-PFEMA) in correlation with their structures in the solid state and in the solution using dynamic contact angle, X-ray photoelectron spectroscopy, X-ray diffraction, and dynamic light scattering. The PMMA-b-PFEMA film cast from chloroform solution was found to possess very low surface free energy (7.8 mJ/m(2)) compared with the surface free energies of the P-PFEMA (8.5 mJ/m(2)) and the PMMA-b-PFEMA (9.8 mJ/m(2)) films cast from CF(3)CF(2)CHCl(2) solutions. These differences in the surface free energy were brought about by the variations in their surface structures. The very low surface free energy was considered to have originated from the surface segregation of the PFEMA segments highly self-assembled by the presence of chloroform.

Fluorocarbons↗

PubMed2004

Surface properties and structures of diblock and random copolymers with perfluoroalkyl side chains.

Polymers with perfluoroalkyl side chains have recently attracted a great deal of interest as additives to surface hydrophobicity to values higher than these corresponding to polytetrafluoroethylene. The structure and surface free energy of random and diblock copolymers of methyl methacrylate and 2-perfluorooctylethyl methacrylate (PMMA-r-PFEMA and PMMA-b-PFEMA, respectively) were compared using dynamic contact angle, X-ray photoelectron spectroscopy, X-ray diffraction, and reflection-adsorption FT-IR spectroscopy. The PMMA-b-PFEMA solution cast film showed a surface free energy of 7.8 mJ/m2. This value was lower than that of PMMA-r-PFEMA solution cast film (13.4 mJ/m2) but is comparable to the lowest value (6.7 mJ/m2) reported in literature. The surface of PMMA-b-PFEMA was almost covered with the CF3 groups of self-assembled perfluoroalkyl side chains. On the other hand, more CF2 groups and methacrylate main chain were exposed on the PMMA-r-PFEMA film surface due to parallel orientation of the perfluoroalkyl side chains, which determined the relatively higher surface free energy of the PMMA-r-PFEMA film.

Fluorocarbons↗

PubMed2004

Preparation of reversibly glucose-responsive hydrogels by covalent immobilization of lectin in polymer networks having pendant glucose.

Glucose-responsive hydrogels were prepared by copolymerization of a monomer having a pendant glucose with modified lectin (concanavalin A (ConA)) having vinyl groups. Swelling behavior of ConA-copolymerized glucosyloxyethyl methacrylate (GEMA) hydrogels was discussed from the viewpoint of their synthetic condition and structures. The swelling ratio of the ConA-copolymerized GEMA hydrogels was strongly dependent on the glucose concentration in a buffer solution. As free glucose resulted in the dissociation of the complex between ConA and pendant glucose in the networks and the cross-linking density in the hydrogel decreased, the hydrogels swelled gradually in the presence of free glucose. Leak of ConA from the ConA-entrapment hydrogel and ConA-copolymerized hydrogel was examined in order to discuss the reversible changes of their glucose-responsive behavior. During swelling in the presence of free glucose, ConA leaked out of the ConA-entrapment GEMA hydrogel but did not out of the ConA-copolymerized GEMA hydrogel. As a result, the ConA-copolymerized GEMA hydrogel showed the reversible swelling changes in response to a stepwise change in the glucose concentration. This study revealed that covalent immobilization of ConA in the GEMA networks is very important for development of reversibly glucose-responsive hydrogels.

Biocompatible Materials↗

PubMed2004

Synthesis and characterization of stimuli-sensitive hydrogels having a different length of ethylene glycol chains carrying phosphate groups: loading and release of lysozyme.

In order to prepare a polymer matrix capable of loading protein at high density, anionic hydrogels were synthesized by copolymerizing a monomer carrying a pendant phosphate group, methacryloyl-polyoxyethyl phosphate, with N-isopropylacrylamide and N,N'-methylene-bis-acrylamide, and the stumuli-sensitivity of hydrogels was characterized. The number of repeating ethylene glycol units in the phosphate carrying monomer was 1, 2, 5 or 8. Lysozyme bearing a positive net charge was immobilized in the hydrogel through formation of polyelectrolyte complex. It was shown that the amount of complexed lysozyme reached to 1.7 g/g dry gel, when high content of a phosphate-carrying monomer with 5 ethylene glycol units was incorporated into a hydrogel. It was further found that lysozyme complexed with phosphate-carrying network could be released by immersion of the lysozyme/hydrogel composite in a phosphate buffer solution of pH 7.4 owing to the pH-sensitivity of the hydorgel but no lysozyme was released at pH 1.4. The initial rate of lysozyme release was varied depending on the length of the ethylene glycol chains possessed by a network polymer and the content of the phosphate-carrying monomer unit. Lysozyme released from the phosphate-carrying hydrogel was proved to retain enzymatic activity at a level similar to the activity of lysozyme, which had been kept in buffer solution.

Ethylene Glycol↗

PubMed2002

Biomolecule-sensitive hydrogels.

Stimuli-sensitive hydrogels have attracted considerable attention as intelligent materials in the biochemical and biomedical fields, since they can sense environmental changes and induce structural changes by themselves. In particular, biomolecule-sensitive hydrogels that undergo swelling changes in response to specific biomolecules have become increasingly important because of their potential applications in the development of biomaterials and drug delivery systems. This article provides an overview of the important and historical research regarding the synthesis and applications of glucose-sensitive hydrogels which exhibit swelling changes in response to glucose concentration. Enzymatically degradable hydrogels and antigen-sensitive hydrogels are also described in detail as protein-sensitive hydrogels that can respond to larger biomolecules. The synthetic strategies of other biomolecule-sensitive hydrogels are summarized on the basis of molecular imprinting and specific interaction. The biomolecule-sensitive hydrogels reviewed in this paper are expected to contribute significantly to the exploration and development of newer generations of intelligent biomaterials and self-regulated drug delivery systems.

Biocompatible Materials↗