In this study, the pH-driven method was employed to construct tilapia myofibrillar protein (TMP)/κ-carrageenan oligosaccharide (κCOS) nanocomplexes for encapsulating curcumin (CUR), aiming to address the issues of its low bioavailability and poor stability. The nanocomplex prepared under optimized conditions (TMP concentration = 12 mg/mL, κCOS concentration = 4 mg/mL) had the following properties: an average particle size of (291.16 ± 5.37) nm, a zeta potential of (−29.80 ± 1.67) mV, and a polydispersity index (PDI) of 0.34 ± 0.04. Furthermore, the nanocomplex formed a three-dimensional network structure. At a concentration of 0.2 mg/mL, CUR could be effectively loaded into the nanocomplex, with a high loading rate of (76.76 ± 0.04)%. The results of infrared (IR) and circular dichroism (CD) spectroscopy indicated that TMP and κCOS were combined through hydrophobic and electrostatic interactions, and the content of α-helix significantly increased after binding, from 22% (TMP) to 76% (TMP/κCOS). The in vitro release results indicated that the cumulative release rate of CUR from the TMP/κCOS/CUR complex was only (14.43 ± 0.85)% after 60 min, while it reached (74.71 ± 0.70)% after 180 min. This nanocomplex could effectively improve the ionic and thermal stability of CUR. This study provides a reliable process for the construction of TMP/κCOS nano-delivery systems and also indicates its good application potential in the field of hydrophobic active ingredient delivery.

The crude fucoidan extracted from Sargassum hemiphyllum (S. hemiphyllum) demonstrated notable immunomodulatory effects; however, its structural features and mechanistic underpinnings remained poorly understood. In this study, the crude polysaccharide from S. hemiphyllum (F) was purified to yield a product named FS, its molecular characteristics, thermal properties, and microscopic morphology were systematically examined, alongside its immunomodulatory mechanisms. The main monosaccharide components of F were fucose (22.80%), galactose (15.40%), glucuronic acid (15.95%), and mannuronic acid (14.40%), while FS were primarily composed of fucose (23.00%), mannose (13.39%), xylose (12.36%) and glucuronic acid (24.24%). All three polysaccharides exhibited favorable thermal stability. Immunostimulation assays indicated that FS significantly promoted the secretion of cytokines—TNF-α, IL-1β, and IL-6 in RAW264.7 macrophages. RNA sequencing analysis further identified 501 differentially expressed genes after FS treatment, comprising 206 up-regulated and 295 down-regulated genes. Mechanistic studies revealed that FS mediates immunomodulation mainly via activation of the TNF/IL-17 signaling pathway. These findings offer new perspectives on the immunomodulatory mechanisms of marine polysaccharides and provide a critical theoretical foundation for their application in functional foods and nutritional supplements.

In this study, the chemical compositions, structures, immunomodulatory and hypoglycemic activities of fucoidans from Sargassum zhangii (SZ-Fuc) and Sargassum hemiphylla (SH-Fuc) were analyzed and compared. The results showed that the sulfate group content and molecular mass of SZ-Fuc were (29.74 ± 0.01)% and 111.28 kDa, respectively, and SZ-Fuc had a relatively loose surface structure. The main chain of SZ-Fuc was composed of (→1) linked fucose, xylose, glucose, mannose and galactose, (1→3)- and (1→4)- linked xylose, (1→2)-linked mannose, (1→3)-, (1→4)- and (1→6)-linked galactose, and (1→4)- and (1→6)-linked glucose. Meanwhile, the sulfate group content and molecular mass of SH-Fuc were (44.11 ± 0.01)% and 1166.48 kDa, respectively, SH-Fuc had a compact surface structure, and its main chain contained (→1), (1→3)- and (1→4)-linked fucose, (→1), (1→4)- and (1→6)-linked glucose, (→1) and (1→2)-linked mannose, and (1→4)-linked galactose. Besides, both SZ-Fuc and SH-Fuc had branched structures. They significantly increased NO release from RAW264.7 cells and improved the protein expression of inducible nitric oxide synthase (iNOS) and cyclooxygenase-2 (COX-2), indicating good immunomodulatory activity. The immunomodulatory activity of SZ-Fuc was better than that of SH-Fuc, while the inhibitory effect of SH-Fuc on α-glucosidase was better than that of SZ-Fuc, suggesting that SH-Fuc had better hypoglycemic potential. This study can provide a theoretical basis for polysaccharides from S. zhangii and S. hemiphylla in the development of functional and nutritional foods with immunomodulatory and blood glucose-reducing activity.