IZAWA Hironori



Engineering educational research section Department of Applied Chemistry Program



Research Areas 【 display / non-display

  • Nanotechnology/Materials / Bio chemistry

  • Nanotechnology/Materials / Polymer chemistry

  • Nanotechnology/Materials / Polymer materials

  • Nanotechnology/Materials / Functional solid state chemistry


Papers 【 display / non-display

  • Evaluation of the Safety and Gastrointestinal Migration of Guanidinylated Chitosan after Oral Administration to Rats Reviewed

    Khan N.F., Nakamura H., Izawa H., Ifuku S., Kadowaki D., Otagiri M., Anraku M.

    Journal of Functional Biomaterials   14 ( 7 )   2023.7

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    Publishing type:Research paper (scientific journal)   Publisher:Journal of Functional Biomaterials  

    Arginine-rich membrane-permeable peptides (APPs) can be delivered to cells by forming complexes with various membrane-impermeable bioactive molecules such as proteins. We recently reported on the preparation of guanidinylated chitosan (GCS) that mimics arginine peptides, using chitosan, a naturally occurring cationic polysaccharide, and confirmed that it enhances protein permeability in an in vitro cell system. However, studies on the in vivo safety of GCS are not available. To address this, we evaluated the in vivo safety of GCS and its translocation into the gastrointestinal tract in rats after a single oral administration of an excessive dose (500 mg/kg) and observed changes in body weight, major organ weights, and organ tissue sections for periods of up to 2 weeks. The results indicated that GCS causes no deleterious effects. The results of an oral administration of rhodamine-labeled chitosan and an evaluation of its migration in the gastrointestinal tract suggested that the disappearance of rhodamine-labeled GCS from the body appeared to be slower than that of the non-dose group and pre-guanidinylated chitosan due to its mucoadhesive properties. In the future, we plan to investigate the use of GCS to improve absorption using Class III and IV drugs, which are poorly water-soluble as well as poorly membrane-permeable.

    DOI: 10.3390/jfb14070340


  • Water-soluble guanidinylated chitosan: a candidate material for protein delivery systems Reviewed

    Izawa H., Yagi A., Umemoto R., Ifuku S.

    Polymer Journal   55 ( 8 )   885 - 895   2023

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    Publishing type:Research paper (scientific journal)   Publisher:Polymer Journal  

    Here, we introduce water-soluble guanidinylated chitosan (WGCS) as a candidate material for protein delivery systems to enhance the cellular internalization of protein/peptide drugs. A WGCS composed of 48.2% guanidinylated chitosan, 20.6% chitosan, and 31.2% chitin units was prepared with a low-molecular-weight chitosan (CS) lactate via a guanidinylation reaction with 1-amidinopyrazole hydrochloride. The Mn of WGCS was estimated by gel permeation chromatography analysis to be 7.6 × 103 (Mw /Mn = 1.5). The higher chitin content in WGCS than in common CS (<20%) is an important factor in achieving water solubility. WGCS showed ca. 2.5-fold higher internalization into HeLa cells than CS does. This clearly indicated that guanidinylation enhances internalization. In addition, endocytic pathways were suggested as a mechanism underlying internalization. Moreover, WGCS significantly enhanced the internalization of bovine serum albumin (BSA) in transport medium at pH 7.4 containing BSA: the internalized amount of BSA in the presence of WGCS was ca. 2-fold higher than in the presence of CS. This higher internalization was caused by efficient binding between WGCS and BSA via electrostatic interactions owing to the guanidino groups. Indeed, the affinity of the binding sites of WGCS is more than 10-fold higher than that of the binding sites of CS.

    DOI: 10.1038/s41428-023-00787-4


  • Preparation of Nanochitin from Crickets and Comparison with That from Crab Shells Reviewed

    Kishida K., Mizuta T., Izawa H., Ifuku S.

    Journal of Composites Science   6 ( 10 )   2022.10

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:Journal of Composites Science  

    Crickets are gaining worldwide attention as a nutrient source with a low environmental impact. We considered crickets as a new source of chitin raw material. Chitin isolated from crickets was successfully converted to nanochitin by pulverization. First, chitin was obtained from cricket powder in a 2.6% yield through a series of chemical treatments. Chitin identification was confirmed by FT-IR and 13C NMR. The chitin had an α-type crystal structure and a deacetylation degree of 12%. Next, it was pulverized in a disk mill to obtain nanochitin. Cricket nanochitin was of a whisker shape, with an average fiber width of 10.1 nm. It was larger than that of crab shells, while the hydrodynamic diameter and crystal size were smaller. Such differences in shape affected the physical properties of the dispersion. The transmittance was higher than that of crab nanochitin due to the size effect, and the viscosity was smaller. Moreover, the dry non-woven cricket nanochitin sheets were more densely packed, and their modulus and breaking strength were greater.

    DOI: 10.3390/jcs6100280


  • Drying-Induced Surface Wrinkles Generated on Chitosan Films Having Polyion Complex Skin Layers: Effects of Physical Properties of Skin Layers and Substrates on Surface Wrinkling upon Drying Reviewed

    Hironori Izawa, Shota Ishisaka, Hiroyuki Saimoto, Shinsuke Ifuku

    Bulletin of the Chemical Society of Japan   95 ( 9 )   1289 - 1295   2022.9

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    Authorship:Lead author, Corresponding author   Language:Japanese   Publishing type:Research paper (scientific journal)  

    The effects of the physical properties of skin layers and substrates on drying-induced surface wrinkling are investigated with a system using chitosan films having polyion complex (PIC) skin layers. The PIC layers are fabricated with diverse anionic polymers having similar molecular weights on a chitosan (CS) film surface, and the films are dried. In all cases, surface wrinkles form but their sizes vary widely depending on the molecular structure. In particular, wrinkles formed with ligninsulfonate are much larger than those formed with the others. The skin layers differ significantly in surface hardness but not in thickness, indicating that wrinkle sizes induced by PIC skin layers are predominately determined by the hardness of the layers or by physical properties affected by hardness, such as shrinkage volume. The effects of the elastic moduli and shrinkage volume of the substrates are evaluated with higher molecular weight CS and surface-deacetylated chitin nanofiber composite CS films that have different elastic moduli but show very similar swellingdrying behaviors. The wrinkle sizes and skin layer thicknesses also suggest that wrinkle size in this system depends on the hardness of the skin layers or on the physical properties affecting the hardness.

    DOI: 10.1246/bcsj.20220177


  • Optimization of Chitin Nanofiber Preparation by Ball Milling as Filler for Composite Resin Reviewed

    Dagmawi Abebe Zewude, Hironori Izawa, Shinsuke Ifuku

    JOURNAL OF COMPOSITES SCIENCE   6 ( 7 )   2022.7

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    Language:Japanese   Publishing type:Research paper (scientific journal)   Publisher:MDPI  

    Chitin nanofiber is a nanomaterial produced by pulverizing chitin, the main component of crab shells. Since it has excellent mechanical properties, it is expected to be used as a reinforcing material to strengthen materials. Chitin was mechanically ground in water using a ball mill to prepare nanofibers. The ball size, total ball weight, and milling time were varied, and the resulting water dispersion and the cast film were analyzed to optimize the conditions for efficient preparation. The length and width of the nanofibers were also measured by SEM and AFM observations. The size of the balls affected the level of grinding and the intensity of impact energy on the chitin. The most efficient crushing was achieved when the diameter was 1 mm. The total ball weight directly affects the milling frequency, and milling proceeds as the total weight increases. However, if too many balls occupy the container, the grinding efficiency decreases. Therefore, a total ball weight of 300 g was optimal. Regarding the milling time, the chitin becomes finer depending on the increase of that time. However, after a specific time, the shape did not change much. Therefore, a milling time of approximately 150 min was appropriate.

    DOI: 10.3390/jcs6070197

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Grant-in-Aid for Scientific Research 【 display / non-display

  • 微細構造表面を誘起するスキン層の科学の開拓

    Grant number:19K05616  2019.04 - 2022.03

    日本学術振興会  科学研究費助成事業 基盤研究(C)  基盤研究(C)

    井澤 浩則

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    Authorship:Principal investigator