Structural characterization of a novel fucoidan from Sargassum horneri for anticancer drug delivery

A fucoidan SHF from Sargassum horneri was obtained. Nanoparticles were prepared using SHF (F) and chitosan (Cs) at F/Cs mass ratios of 1.0/3.0, 1.0/1.5, 1.0/1.0, 1.5/1.0 and 3.0/1.0. The nanoparticles showed a high binding affinity for P-selectin, especially at the ratio of 1.5/1.0. The pH-responsive drug release of doxorubicin (DOX)-loaded nanoparticles was evaluated to select the nanoparticle with low DOX release in blood (pH 7.4) but high release upon entering the endosome/lysosome (pH 4.5-5.5) of cancer cells. Results indicated that the DOX release rate significantly increased at 1.5/1.0 when the medium pH decreased from 7.4 to 5.5. Moreover, DOX-loaded nanoparticles showed improved inhibitory effects against a metastatic breast cancer cell line (MDA-MB-231) compared to free DOX at equivalent concentrations. Therefore, nanoparticles based on SHF achieved efficient delivery of DOX. SHF is an excellent material for the tumor-targeting drug delivery systems. To further understand the structural characteristics of tumor-targeting fucoidan, the fine structure of SHF was analyzed. The main chain of SHF might be cross-linked by →4)-α-l-Fucp(2,3SO₄)-(1→ and →3,2)-β-d-Galp-(1→, with the →4,6)-β-d-Manp-(1 → 3,2)-β-d-Galp-(1 → 4,6)-β-d-Manp-(1→ fragment interspersed between them. Notably, dual-sulfated fucose residues accounted for a large proportion.