海藻酸盐是线性阴离子多糖,以其生物相容性、无毒和可生物降解的性质而闻名。该聚合物由β-(1→4)-连接的D-甘露糖醛酸(M)和α-(1→4)-连接的L-古洛糖醛酸(G)交替单元组成,以羟基和羧基为主要官能团组。由于聚合物链中存在大量游离羧基和羟基,因此聚合物主要是亲水性的。食品和制药行业是海藻酸盐生产胶凝剂和增稠剂最广泛的用途。然而,通过赋予藻酸盐疏水性,可以拓宽应用范围。尽管有关于藻酸盐及其化学修饰的评论,但尚未提出针对疏水性相关藻酸盐的评论。常用的引入疏水性的化学修饰包括酯化、Ugi反应、还原胺化和接枝共聚。疏水改性海藻酸盐在疏水性药物和农药的递送中发挥着重要作用,因为改性增加了对疏水性成分的亲和力并有助于其持续释放。由于其无毒和可食用的性质,它们在食品工业中用作乳液稳定剂,以稳定水包油乳液并提高乳化能力。此外,对基于藻酸盐的材料(例如膜、气凝胶和薄膜)进行疏水改性,以改善其功能以及在水处理和食品包装中的适用性。 本综述旨在强调重要的化学修饰和赋予藻酸盐疏水性的方法,并讨论疏水修饰藻酸盐在从药物输送到食品包装等不同领域的应用。
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A Review on Hydrophobically Associated Alginates: Approaches and Applications
Alginates are linear anionic polysaccharides, which are well-known for their biocompatible, nontoxic, and biodegradable nature. The polymer consists of alternating units of β-(1 → 4)-linked D-mannuronic acid (M) and α-(1 → 4)-linked L-guluronic acid (G) that have hydroxyl and carboxyl groups as the main functional groups. As a large number of free carboxyl and hydroxyl groups are present in the polymeric chain, the polymer is predominantly hydrophilic. The food and pharmaceutical industries have been the most extensive utilizers of alginates to produce gelling and thickening agents. However, by imparting hydrophobicity to alginates, the range of applications can be widened. Although there are reviews on alginate and its chemical modifications, reviews focusing on hydrophobically associated alginates have not been presented. The commonly used chemical modifications to incorporate hydrophobicity include esterification, Ugi reaction, reductive amination, and graft copolymerization. The hydrophobically modified alginates play an important role in delivery of hydrophobic drugs and pesticides as the modification increases the affinity toward hydrophobic components and helps in their sustained release. Due to their nontoxic and edible nature, they find use in the food industry as emulsion stabilizer to stabilize oil-in-water emulsions and to improve creaming ability. Further, alginate-based materials such as membranes, aerogels, and films are hydrophobically modified to improve their functionality and applicability to water treatment and food packaging. This Review aims to highlight the important chemical modifications and methods that are done to impart hydrophobicity to alginate, and the applications of hydrophobically modified alginates in different sectors ranging from drug delivery to food packaging are discussed.