Sunflower oil-assisted conversion of α-cellulose into mesoporous cellulose II microbeads for size-influenced protein loading

Mesoporous cellulose II microbeads (CMBs) were prepared from α-cellulose through a water-in-oil emulsion–gelation process using sunflower ( Helianthus annuus L.) oil as a representative crop-derived plant-oil continuous phase and 60 wt% aqueous LiBr as the cellulose dissolution medium. This study addresses the need for renewable, structurally tunable cellulose microcarriers by linking plant-oil-assisted emulsion processing with cellulose II regeneration, mesopore formation, and size-influenced protein-loading functionality. To establish a plant-oil-based processing route for value-added porous cellulose particles, Span 80 concentration and stirring speed were investigated in relation to bead morphology, crystalline transformation, and mesopore formation. The optimized condition produced spherical regenerated cellulose II microbeads with a Type IV mesoporous network, a high BET surface area of 205.71 m²/g, and an average pore diameter of 16.5 nm. X-ray diffraction confirmed complete transformation of cellulose I into cellulose II, with crystallinity indices ranging from 44.5% to 56.0% depending on the emulsion–gelation conditions. The mesoporous cellulose network was further evaluated as a size-influenced protein-loading platform by separately immobilizing fibrinogen and thrombin. Based on protein dimensions and complementary post-loading evidence, fibrinogen loading was more surface-dominant, whereas thrombin showed greater access to the internal mesopore network, with desorption efficiencies exceeding 70%. As an application-oriented demonstration, a dry powder composed of fibrinogen-loaded and thrombin-loaded CMBs showed rapid fluid absorption recovery and fibrin-forming functionality. These results demonstrate that sunflower oil-assisted emulsion–gelation provides a feasible route for converting α-cellulose into mesoporous cellulose II microbeads with tunable structure and size-influenced biomolecule carrier functionality.