Fucoidan-based PEGylated MnFe₂O₄ Nanocomposites: Characterization, in vitro release behavior, and anticancer activity against A549 cells

Sulfated polysaccharides (SPs) derived from marine brown algae have gained considerable attention due to their diverse biological activities and potential biomedical applications. In the present study, SPs were isolated and purified from Padina tetrastromatica, followed by comprehensive biochemical and structural characterization. Sequential purification resulted in an enriched fraction (F3) with increased carbohydrate and sulfate content, which exhibited potential antioxidant activity across DPPH, FRAP, ABTS, and reducing power assays. Structural characterization using FTIR, HPLC, and NMR confirmed the presence of fucose-rich SPs, characteristic of fucoidan. Manganese ferrite (MnFe₂O₄) NPs were synthesized via a hydrothermal method and subsequently functionalized with polyethylene glycol (PEG) and fucoidan (FU) to enhance stability and biocompatibility. Physicochemical characterization using UV–Vis spectroscopy, FTIR, dynamic light scattering (DLS) analysis revealed an increase in hydrodynamic size from 62.6 nm for MnFe₂O₄ NPs to 179.8 nm for PEGylated MnFe₂O₄-FU NPs, while zeta potential shifted from −6.1 mV to −10.9 mV, indicating successful surface modification., X-ray diffraction (XRD), SEM analysis showed particle sizes ranging from 9.2 to 49.8 nm for MnFe₂O₄ NPs and 11.6–158.9 nm for PEGylated MnFe₂O₄-FU NPs, indicating successful surface modification and energy-dispersive X-ray spectroscopy (EDAX) confirmed successful synthesis, surface modification, and structural integrity of the nanocomposites. UV–Vis stability studies demonstrated enhanced colloidal stability of PEGylated MnFe₂O₄-FU NPs over 11 weeks. In vitro fucoidan release studies showed a sustained release profile with 99.23% cumulative release at pH 7.4, following first-order kinetics. Cytotoxicity assessment against A549 lung cancer cells revealed IC₅₀ values of 54.02 µg/mL for free FU and 43.94 µg/mL for PEGylated MnFe₂O₄-FU NPs. Furthermore, AO/EtBr staining indicated apoptosis-associated morphological changes in treated cells. These findings suggest that PEGylated MnFe₂O₄-FU nanocomposites possess improved antioxidant activity, sustained fucoidan release, and enhanced anticancer activity against A549 cells.