Mechanical properties of carriers based on natural polymers: Polysaccharides, proteins, and lipids as wall materials

Traditional synthetic polymer carriers are restricted due to microplastic pollution, whereas, natural polymer materials have gained widespread use as wall materials for carriers due to their biodegradability, availability, ease of modification, and biocompatibility. The mechanical properties of carriers are particularly crucial for formulation design, storage stability, and practical performance. However, there is currently a lack of reviews on the mechanical properties of natural polymer-based carriers (NPC). This paper delves into the mechanical properties of NPC from five aspects: First, natural polymer wall materials are classified into polysaccharide-based, protein-based, lipid-based, and composite materials, focusing on polysaccharide-dominated systems, and the mechanical properties of NPC constructed from materials of different origins are summarized. Second, various preparation techniques for NPC are introduced, summarizing the mechanical properties of carriers constructed by each method. The paper then examines regulation strategies of the mechanical properties of NPC, including modification techniques, encapsulated substances, morphology, and particle size. Next, methods for characterizing mechanical properties of NPC are introduced. Finally, there is a summary of the progress of NPCs with different mechanical properties in fields, highlighting the challenges faced and proposing future research directions. This review links mechanical optimization to performance, bridging research and applications with eco-friendly NPC strategies.