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所属 |
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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職名 |
特別助教 |
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関連SDGs |
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学位 【 表示 ／ 非表示 】
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博士（工学） （ 2025年9月 鹿児島大学 ）
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修士（工学） （ 2023年3月 鹿児島大学 ）
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学士（工学） （ 2021年3月 鹿児島大学 ）
研究分野 【 表示 ／ 非表示 】
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ナノテク・材料 / ナノ材料科学
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ものづくり技術（機械・電気電子・化学工学） / 移動現象、単位操作
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ものづくり技術（機械・電気電子・化学工学） / バイオ機能応用、バイオプロセス工学
論文 【 表示 ／ 非表示 】
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Yamashita Y., Ohzuno Y., Saito Y., Fujiwara Y., Yoshida M., Takei T.
Gels 9 ( 4 ) 280 2023年3月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Gels
Moist wound healing is known to heal wounds faster than dry wound healing. Hydrogel wound dressings are suitable for moist wound healing because of their hyperhydrous structure. Chitosan, a natural polymer, promotes wound healing by stimulating inflammatory cells and releasing bioactive compounds. Therefore, chitosan hydrogel has great potential as a wound dressing. In our previous study, physically crosslinked chitosan hydrogels were successfully prepared solely by freeze-thawing of chitosan-gluconic acid conjugate (CG) aqueous solution without using any toxic additives. Furthermore, the CG hydrogels could be sterilized by autoclaving (steam sterilization). In this study, we showed that autoclaving (121 °C, 20 min) of a CG aqueous solution simultaneously achieved gelation of the solution and sterilization of the hydrogel. Hydrogelation of CG aqueous solution by autoclaving is also physically crosslinking without any toxic additives. Further, we showed that the CG hydrogels retained favorable biological properties of the CG hydrogels prepared by freeze-thawing and subsequent autoclaving. These results indicated that CG hydrogels prepared by autoclaving were promising as wound dressings.
DOI： 10.3390/gels9040280
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Yamashita Y., Ohzuno Y., Yoshida M., Takei T.
Macromol 4 ( 2 ) 376 - 386 2024年5月
担当区分：筆頭著者, 責任著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Macromol
Conventionally, chitosan hydrogels are acidic and contain toxic chemicals because chitosan is soluble only in acidic solvents and requires toxic additives such as chemical crosslinkers and polymerization agents to fabricate chitosan hydrogels. These properties prevent chitosan hydrogels from being used for medical applications. In this study, chitosan hydrogels were prepared by a simple and versatile process using urea hydrolysis by autoclaving (steam sterilization, 121 °C, 20 min). When autoclaved, urea hydrolyzes in an acidic chitosan aqueous solution, and ammonia is produced, which increases the pH of the solution, and chitosan becomes insoluble, leading to the formation of a chitosan hydrogel. The pH and osmotic concentration of chitosan hydrogels could be adjusted to be suitable for physiological conditions (pH: 7.0–7.5, and osmotic concentration: 276–329 mOsm/L) by changing the amount of urea added to chitosan solutions (chitosan: 2.5% (w/v), urea: 0.75–1.0% (w/v), pH: 5.5). The hydrogels had extremely low cytotoxicity without the washing process. In addition, not only pure chitosan hydrogels, but also chitosan derivative hydrogels were prepared using this method. The autoclaving technique for preparing low-toxic and wash-free sterilized chitosan hydrogels in a single step is practical for medical applications.
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Yamashita Y., Hosoya K., Fujiwara Y., Saito Y., Yoshida M., Matsune S., Okubo K., Takei T.
Gels 11 ( 1 ) 60 2025年1月
担当区分：筆頭著者 記述言語：英語 掲載種別：研究論文（学術雑誌） 出版者・発行元：Gels
After endoscopic sinus surgery (ESS), nasal packing is often used to stop bleeding and promote wound healing. Because maintaining a moist environment is important to enhance wound healing, hydrogel-based wound dressings are effective to promote wound healing. Chitosan is used in the medical field because of its high hemostatic and wound healing properties. We developed a pH-neutral and non-toxic chitosan hydrogel, which was difficult to achieve using conventional methods. In this study, we show in animal experiments that the chitosan hydrogel (hydrogel particles) had higher wound healing properties than a commercially available solid wound dressing (dry state) composed of the same polymer. Additionally, we applied the injectable chitosan hydrogel particles as nasal packing materials to patients with bilateral chronic sinusitis undergoing ESS in a pilot clinical study. Concerning symptom scores, though the results narrowly missed statistical differences (p < 0.05), the average scores of our chitosan hydrogel were superior to those of a commercially available wound dressing (especially p = 0.09 for nasal bleeding). These findings suggest that the injectable chitosan hydrogel could be a viable option as a packing material following ESS.
DOI： 10.3390/gels11010060
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Guanidinylated nanochitins: guanidinylated chitin nanocrystals are dispersible at neutral pH 査読あり 国際誌
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
記述言語：英語 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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Yuji Nagase , Yusuke Yamashita , Takuma Yoshinaga , Yoshihiro Ohzuno , Masahiro Yoshida , Kei Hosoya , Masaki Kawabata , Masaru Yamashita , Shoji Matsune , Takayuki Takei
Eng 7 ( 1 ) 53 2026年1月
科研費（文科省・学振・厚労省）獲得実績 【 表示 ／ 非表示 】
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研究課題/領域番号： 26K24704 2026年07月 - 2028年03月
日本学術振興会 科学研究費助成事業 研究活動スタート支援
担当区分：研究代表者 資金種別：競争的資金
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オートクレーブ滅菌をトリガーとしてゲル化するキトサンヒドロゲルの創傷治療への応用
研究課題/領域番号：25KJ1985 2025年04月 - 2025年09月
日本学術振興会 科学研究費助成事業 特別研究員奨励費
担当区分：研究代表者 資金種別：競争的資金