Alkali/urea, a green dissolution system for chitosan, have been widely used in preparation of chitosan-derived materials. However, there are no related reports detail the structure stability and biocompatibility of chitosan in alkali/urea, which are important for its large-scale application. In this work, chitosan was dissolved in KOH/urea solution and stored at different temperature for different time. The structure, viscosity, molecule weight (Mw), degree of deacetylation (DD), and biocompatibility of chitosan were determined. The Mw of chitosan decreased from 1011 KDa to 827-834 KDa, and DD increased from 76.9% to 85.7-93.5% after been stored at 25 °C and 4 °C for 5 weeks. Incomplete dissolution of chitosan and increase of DD enhanced its thermal stability by forming new crystallization zone. In contrast, chitosan stored in -20 °C for 5 weeks was stable without obvious change of Mw and DD. Moreover, the processed chitosans were no-toxic and safety for the biomedicine applications.

中文翻译：

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壳聚糖在碱/尿素溶解体系中的结构转化和生物相容性的大规模应用评价

碱/脲，一种壳聚糖的绿色溶解系统，已被广泛用于制备壳聚糖衍生的材料。然而，尚无相关报道详述壳聚糖在碱/尿素中的结构稳定性和生物相容性，这对其大规模应用至关重要。在这项工作中，将脱乙酰壳多糖溶解在KOH /尿素溶液中，并在不同的温度下保存了不同的时间。测定了壳聚糖的结构，粘度，分子量（Mw），脱乙酰度（DD）和生物相容性。在25°C和4°C下保存5周后，壳聚糖的Mw从1011 KDa降低到827-834 KDa，DD从76.9％升高到85.7-93.5％。壳聚糖的不完全溶解和DD的增加通过形成新的结晶区而提高了其热稳定性。相反，在-20°C下储存5周的壳聚糖稳定，Mw和DD没有明显变化。此外，加工后的壳聚糖对生物医学应用无毒且安全。