N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activity

Partially deacetylated nanochitins (NH2NCs) possess cationic properties that allow their stable dispersion in acidic water. Their surface charge plays a crucial role in their antibacterial functions, which occur through electrostatic interactions. However, NH2NCs lose their positive charge upon depr...

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Main Authors: Masaki Kawamoto, Toshifumi Mizuta, Hironori Kaminaka, Masaaki Akamatsu, Shinsuke Ifuku
Format: Article
Language:English
Published: Elsevier 2025-03-01
Series:Carbohydrate Polymer Technologies and Applications
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Online Access:http://www.sciencedirect.com/science/article/pii/S2666893925000271
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author Masaki Kawamoto
Toshifumi Mizuta
Hironori Kaminaka
Masaaki Akamatsu
Shinsuke Ifuku
author_facet Masaki Kawamoto
Toshifumi Mizuta
Hironori Kaminaka
Masaaki Akamatsu
Shinsuke Ifuku
author_sort Masaki Kawamoto
collection DOAJ
description Partially deacetylated nanochitins (NH2NCs) possess cationic properties that allow their stable dispersion in acidic water. Their surface charge plays a crucial role in their antibacterial functions, which occur through electrostatic interactions. However, NH2NCs lose their positive charge upon deprotonation under basic conditions, leading to aggregation and significant reductions in their effectiveness. Thus, a strategy to maintain the positive charge of the material regardless of the pH must be developed. In this study, NH2NCs were modified by N-trimethylation to prevent the loss of their positive charge. The total degree of substitution for methyl groups was 0.96, while that for N-trimethylamino groups was 0.15, as determined by 13C NMR spectroscopy, FT-IR spectroscopy, elemental analysis, and conductivity titration. The structure of the modified NH2NCs contained N-methyl, N-dimethyl, and O-methyl groups. Methylated nanochitins (MeNCs) maintained a positive zeta potential regardless of the pH owing to the presence of quaternary ammonium salts. Thus, they remained stably dispersed, even under basic conditions. Furthermore, their high surface charge improved their grinding efficiency and reduced their proportion of large agglomerated particles. Whereas the NH2NCs lost their antibacterial properties against Staphylococcus aureus at neutral to basic pH levels, the MeNCs retained their high antibacterial effectiveness. The improvement of dispersibility and antibacterial properties through chemical modification will promote the use of nanochitin, derived from waste crab shells, in cosmetics and health foods.
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spelling doaj-art-325d264ad6e3485fa4abcb1e7f1149f52025-08-20T02:52:21ZengElsevierCarbohydrate Polymer Technologies and Applications2666-89392025-03-01910068810.1016/j.carpta.2025.100688N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activityMasaki Kawamoto0Toshifumi Mizuta1Hironori Kaminaka2Masaaki Akamatsu3Shinsuke Ifuku4Department of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552, JapanTechnical Department, Tottori University, 4-101 Koyama-Minami, Tottori 680-8550, JapanFaculty of Agriculture, Tottori University, 4-101 Koyama-Minami, Tottori 680-8553, JapanDepartment of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552, Japan; Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Koyama-Minami, Tottori 680-8550, JapanDepartment of Engineering, Graduate School of Sustainability Science, Tottori University, 4-101 Koyama-Minami, Tottori 680-8552, Japan; Center for Research on Green Sustainable Chemistry, Tottori University, 4-101 Koyama-Minami, Tottori 680-8550, Japan; Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji 611-0011, Japan; Corresponding author at: Research Institute for Sustainable Humanosphere, Kyoto University, Gokasho, Uji 611-0011, Japan.Partially deacetylated nanochitins (NH2NCs) possess cationic properties that allow their stable dispersion in acidic water. Their surface charge plays a crucial role in their antibacterial functions, which occur through electrostatic interactions. However, NH2NCs lose their positive charge upon deprotonation under basic conditions, leading to aggregation and significant reductions in their effectiveness. Thus, a strategy to maintain the positive charge of the material regardless of the pH must be developed. In this study, NH2NCs were modified by N-trimethylation to prevent the loss of their positive charge. The total degree of substitution for methyl groups was 0.96, while that for N-trimethylamino groups was 0.15, as determined by 13C NMR spectroscopy, FT-IR spectroscopy, elemental analysis, and conductivity titration. The structure of the modified NH2NCs contained N-methyl, N-dimethyl, and O-methyl groups. Methylated nanochitins (MeNCs) maintained a positive zeta potential regardless of the pH owing to the presence of quaternary ammonium salts. Thus, they remained stably dispersed, even under basic conditions. Furthermore, their high surface charge improved their grinding efficiency and reduced their proportion of large agglomerated particles. Whereas the NH2NCs lost their antibacterial properties against Staphylococcus aureus at neutral to basic pH levels, the MeNCs retained their high antibacterial effectiveness. The improvement of dispersibility and antibacterial properties through chemical modification will promote the use of nanochitin, derived from waste crab shells, in cosmetics and health foods.http://www.sciencedirect.com/science/article/pii/S2666893925000271NanochitinTrimethylationQuaternary ammonium saltAntibacterial propertyHigh dispersibility
spellingShingle Masaki Kawamoto
Toshifumi Mizuta
Hironori Kaminaka
Masaaki Akamatsu
Shinsuke Ifuku
N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activity
Carbohydrate Polymer Technologies and Applications
Nanochitin
Trimethylation
Quaternary ammonium salt
Antibacterial property
High dispersibility
title N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activity
title_full N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activity
title_fullStr N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activity
title_full_unstemmed N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activity
title_short N-Trimethylation of nanochitin for high dispersibility and pH-independent antibacterial activity
title_sort n trimethylation of nanochitin for high dispersibility and ph independent antibacterial activity
topic Nanochitin
Trimethylation
Quaternary ammonium salt
Antibacterial property
High dispersibility
url http://www.sciencedirect.com/science/article/pii/S2666893925000271
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