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工学教育研究部 工学科化学生命プログラム担当 |
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Araki M., Matsumoto J., Kuroda K., Izawa H.
Carbohydrate Polymers 380 2026年5月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Carbohydrate Polymers
We previously reported a low molecular weight water-soluble guanidinylated chitosan (GCS) with a controlled degree of acetylation (DA). However, the effects of DA, degree of guanidinylation (DG), and molecular weight on the solubility, functions, and biocompatibility of GCS remain unclear, even though water-soluble GCSs with varying parameters would contribute to the development of novel biomaterials. Here we show the bio-interface properties of acetylated chitosans (CSs) and GCSs with systematically varied DA, DG, and molecular weight, including their solubility, antibacterial activity, and cytotoxic effects. Solubility tests revealed that guanidinylation generally reduced solubility, particularly in DA-uncontrolled samples and at higher molecular weights, whereas GCSs with DA values of 32–37% specifically exhibited improved solubility. In other words, we revealed that the control of DA represents the critical factor for enhancing the solubility of GCS. The minimum inhibitory concentration assays of representative acetylated CSs and GCSs against Escherichia coli and Staphylococcus epidermidis revealed that reduced acetyl content is more critical for antibacterial activity than positive charge, and that guanidinylation induces antibacterial activity under neutral conditions. The cytotoxicity and cell proliferation results suggest that water-soluble GCSs show low cytotoxicity, comparable to acetylated CSs, while strongly inhibiting cell proliferation, supporting their potential as anticancer agents.
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Guanidinylated nanochitins: guanidinylated chitin nanocrystals are dispersible at neutral pH 査読あり
Izawa H., Ando S., Sone K., Tajima W., Zewude D.A., Yamashita Y., Ifuku S.
Journal of Materials Chemistry B 14 ( 1 ) 144 - 152 2026年1月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Materials Chemistry B
Despite nanochitins showing favorable biological effects, the colloid stability of positively charged nanochitins by virtue of the amino group is limited to acidic pH, which is different from biological conditions. Here, we show that guanidinylated chitin nanocrystals (GChNCs) are dispersible at neutral pH. The GChNCs are prepared by guanidinylation of partially deacetylated chitin nanocrystals (ChNCs) with 1-amidinopyrazole hydrochloride. The degrees of guanidinylation and acetylation of the GChNCs are 4.6% and 75.7%, respectively. A 1.0 wt% GChNC dispersion is prepared with 0.5 wt% acetic acid solution by sonication treatment. Although slight white turbidity is observed due to scattering, no visible macroscopic precipitates are observed. The average diameter of the GChNCs estimated by DLS analysis is 327.2 nm. When the GChNC dispersion is neutralized by adding 0.1 M NaOH solution, the transmittance of the GChNC dispersion is decreased by aggregation. However, the transmittance of the GChNC dispersion is higher than that of the ChNC dispersion, suggesting that the GChNC particles are less aggregated than the ChNC particles due to the positive charge by virtue of the high basicity of the guanidino group. Interestingly, we find that the GChNCs homogeneously disperse in 0.1 M HEPES buffer (pH 7.4) up to 0.5 wt% by sonication treatment, even though the average diameter of the GChNCs in the solution is 3.4-fold higher (1115.1 nm) than that prepared at pH 3.0. We additionally find no observation of this improved dispersibility of guanidinylated chitin nanofibers due to the guanidino group. This result indicates that the guanidinylation is effective in improving the dispersion of nanochitins with smaller aspect ratios, like ChNCs. Furthermore, we demonstrate that the dispersibility of GChNCs at neutral pH can be utilized for material development, where a gelatin–GChNF composite hydrogel displaying enhanced mechanical properties is successfully prepared by adding 10% (w/w) GChNCs.
DOI： 10.1039/d5tb01771h
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Guanidinylated Chitosan as a Multifunctional Enhancer for Improved Flurbiprofen Delivery 査読あり
Khan N.F., Nakamura H., Izawa H., Ikeda T., Ifuku S., Otagiri M., Anraku M.
Biological and Pharmaceutical Bulletin 48 ( 8 ) 1246 - 1254 2025年8月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Biological and Pharmaceutical Bulletin
In this study, we investigated guanidinylated chitosan (GCS), a chemically modified derivative of unmodified low-molecular-weight chitosan (CS), as a multifunctional excipient to enhance the solubility and absorption of poorly water-soluble drugs. Flurbiprofen (FP) was selected as a model drug to compare the performance of kneaded dispersions GCS-based (FP-GCS) and CS-based (FP-CS). Both GCS and CS increased the solubility of FP in a concentration-dependent manner, with no significant differences between them. However, dissolution testing showed that FP-GCS kneaded dispersion significantly enhanced the dissolution rate of FP alone in water and simulated gastric fluid (pH 1.2), but not under simulated intestinal conditions (pH 6.8). In vivo pharmacokinetic studies in rats demonstrated that FP-GCS kneaded dispersion achieved the highest plasma concentration of FP, suggesting enhanced gastrointestinal permeability. Moreover, FP-GCS kneaded dispersion markedly reduced gastric ulceration in a rat ulcer model. These results indicate that GCS is an effective oral drug delivery excipient capable of improving both the bioavailability and gastrointestinal safety of FP.
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Preparation of Fully Guanidinylated ε-Polylysine and Its Antibacterial Activity 査読あり
Izawa H., Baba N., Araki M., Ifuku S.
Journal of Fiber Science and Technology 81 ( 4 ) 58 - 63 2025年
掲載種別：研究論文（学術雑誌） 出版者・発行元：Journal of Fiber Science and Technology
ε-Poly-L-lysine (PL) is a natural polymer bearing a key amino group that provides it with a cationic nature, high reactivity in water, and consequent broad applicability. Here we prepared a guanidinylated PL (GPL) exhibiting an enhanced cationic nature by guanidinylation of the amino group with 1-amidinopyrazole hydrochloride (AP) and trimethylamine (TEA) (AP-TEA system). In the AP-TEA system using 3 eq of AP for 2 days at room temperature, a GPL with the degree of guanidinylation (DG) of 100% was achieved. The DG value could be controlled by the AP amount. The lower acidity of the GPL relative to PL was confirmed by pH titration; the reduced acidity resulted in enhanced antibacterial activity of the GPL under an alkaline condition (pH 8.0 and 9.0).
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Yanagi E., Akamatsu M., Suezawa T., Kaminaka H., Izawa H., Ifuku S.
Colloids and Surfaces A: Physicochemical and Engineering Aspects 700 2024年11月
掲載種別：研究論文（学術雑誌） 出版者・発行元：Colloids and Surfaces A: Physicochemical and Engineering Aspects
Partially deacetylated nanochitin (DAcNC) exhibits amphiphilicity owing to the hydrophilic protonated amino groups and hydrophobic surface planes of DAcNC. Although DAcNCs possess emulsifying abilities, their role and versatility as emulsifiers remain unclear. In this study, we investigated oil-in-water (O/W) type Pickering emulsions stabilized with DAcNCs. Stable emulsions were formed using a variety of oils such as vegetable oils, decane, and ether oils. Measurements of the interfacial tension and adsorption of DAcNC showed that formation of tolerant interfacial films stabilized the emulsions. Furthermore, the pH-triggered release of ibuprofen, an antipyretic drug, was demonstrated using the emulsion. Enhanced ibuprofen release was observed upon increasing the pH from 2.0 to 6.0. This phenomenon can be attributed to the deprotonation of ammonium moieties on the DAcNC, which induced the desorption of DAcNC from oil/water interfaces. The DAcNC emulsion can be useful for the oral administration of ibuprofen as an antipyretic agent, facilitating intestinal release.
講演・口頭発表等 【 表示 ／ 非表示 】
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酸性pHの制約を受けにくい高機能キトサン誘導体の開発
井澤浩則
令和6年度高分子学会九州支部講演会
開催年月日： 2024年12月6日
会議種別：口頭発表（招待・特別）
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水溶性グアニジル化キトサン：置換度と分子量が溶解性に与える影響
荒木 美穂、井澤 浩則
2024年 繊維学会秋季研究発表会
開催年月日： 2024年11月28日 - 2024年11月29日
会議種別：口頭発表（一般）
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Solubility of Chitosan-Oligomers Having Different Degrees of Acetylation
Miho Araki, Hironori Izawa
International Symposium on Fiber Science and Technology
開催年月日： 2024年11月25日 - 2024年11月28日
会議種別：ポスター発表
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アセチル化度の異なるキトサンの溶解性とイオンコンプレックス形成挙動
荒木 美穂、井澤 浩則
第14回CSJ化学フェスタ２０２４
開催年月日： 2024年10月22日 - 2024年10月24日
会議種別：ポスター発表
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中性で均一分散するグアニジル化ナノキチンの開発
井澤 浩則、曽根 健聖、田嶋 航
第7３回高分子討論会
開催年月日： 2024年9月25日 - 2024年9月27日
会議種別：ポスター発表
科研費（文科省・学振・厚労省）獲得実績 【 表示 ／ 非表示 】
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多機能性キトサンを基盤とした抗酸化型機能食品と製剤特性改善素材に関する包括的研究
研究課題/領域番号：24K09953 2024年04月 - 2027年03月
独立行政法人日本学術振興会 科学研究費基金 基盤研究(C)
担当区分：研究分担者
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微細構造表面を誘起するスキン層の科学の開拓
研究課題/領域番号：19K05616 2019年04月 - 2022年03月
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
担当区分：研究代表者
その他競争的資金獲得実績 【 表示 ／ 非表示 】
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再生ナノキチンの社会実装
2025年08月 - 2026年07月
宮崎大学、福岡銀行、九州オープンイノベーションセンター 「九州・大学発ベンチャー振興会」ギャップ資金
担当区分：研究代表者
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グアニジル化キトサンライブラリの構築
2024年08月 - 2026年03月
国立研究開発法人新エネルギー・産業技術総合開発機構 （NEDO） 官民による若手研究者発掘支援事業／マッチングサポートフェーズ（NEDO）
担当区分：研究代表者