Construction and characterization of a fructan functionalized gold nanoparticles and its immunopotentiation effects in zebrafish immunodeficiency model.

The construction of nanodrug delivery systems using safe, low-toxicity, biocompatible natural polysaccharides is an effective strategy for expanding the clinical applications of bioactive polysaccharides. In this study, we functionalized gold nanoparticles (AuNPs) with fructan (AAP70-1), a previously reported immunomodulatory active polysaccharide from A. Asphodeloides, with the aim of developing a potential clinical immunostimulant (AAP-SH-AuNPs) that can broaden the application of AAP70-1 and address the issues of poor stability and biocompatibility of AuNPs. The constructed AAP-SH-AuNPs mainly appeared as monodisperse spherical particles in aqueous solution (30.3 ± 13.2 nm) and could be stored at 4 °C for 28 days. In vitro cell assays revealed that the formation of AAP-SH-AuNPs effectively enhances the capacity of AAP70-1 to stimulate macrophages, as evidenced by elevated phagocytosis, increased ROS content, and increased secretion of cytokines (IL-6, IL-1β, TNF-α, and IL-18) by macrophages. These results can also be confirmed by the chloramphenicol-induced zebrafish immunodeficiency model, which revealed that AAP-SH-AuNPs can effectively increase the numbers of macrophages and neutrophils, the production of chemokines (NO and ROS), and the secretion of cytokines (IL-6, IL-1β, and TNF-α) in zebrafish through the TLR4/MyD88/NF-κB pathway. This research establishes a theoretical foundation for advancing the applications of both AAP70-1 and AuNPs.