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Ultrafine and carboxylated β-chitin nanofibers prepared from squid pen and its transparent hydrogels

Ma, Qinyan, Pang, Kai, Wang, Kai, Huang, Shasha, Ding, Beibei, Duan, Yongxin, Zhang, Jianming
Carbohydrate polymers 2019 v.211 pp. 118-123
acetic acid, ammonium persulfate, aqueous solutions, calcium carbonate, carboxylation, chitin, coagulation, crabs, hydrogels, nanofibers, oxidation, shrimp, squid, tube worms, ultrasonics
TEMPO-mediated oxidation has been successfully used to prepare carboxylated chitin nanofibers (ChNFs) with purified chitins originating from the outer shells of crab and shrimp (α-form) or tubeworm (β-form). However, the method for obtaining carboxylated ChNFs with squid pen chitin (hydrated β-form) has not been developed yet. It might be due to the existence of the small amount of partial deacetylation (DD ≈ 9%) in the squid pen β-chitins. Herein, ultrafine (2–4 nm in width and several micrometers in length) and carboxylated β-ChNFs were fabricated directly from the squid pen with simultaneously removing of protein, CaCO3 and other non-chitin components by one-step oxidation procedure using ammonium persulfate (APS) and followed ultrasonic disintegration under acid conditions. When 45 wt% APS was used to react with squid pen, the carboxylate content of ChNFs reaches 0.802 mmol/g. Therefore, the β-ChNFs with anionically charged groups (COO−) can be dispersed stably in aqueous solution under basic conditions. Meanwhile, thus-obtained β-ChNFs aqueous solution even with very low concentration (0.8%) can be transformed to transparent, robust and moldable hydrogels by gas coagulation of acetic acid.