Entrapment of bacterial cellulose nanocrystals stabilized Pickering emulsions droplets in alginate beads for hydrophobic drug delivery

In this work, the interfacial assembly of amphiphilic bacterial cellulose nanocrystals (BCNs) by Pickering emulsion method was proposed to improve the compatibility between the alginate and hydrophobic drug. BCNs prepared by sulfuric acid hydrolysis of biosynthesized bacterial cellulose was used as the particulate emulsifiers, whereas the model drug, alfacalcidol, dissolved in CH2Cl2 was used as the oil phase. The oil-in-water Pickering emulsions were prepared by ultrasonic dispersion method and then they were well dispersed in alginate solution. Ultimately, the drug-loaded alginate composite beads were successfully fabricated by external gelation. The characterization results revealed that BCNs possessed good colloidal property and could form flocculated fibril network, which was beneficial to stabilize Pickering emulsions. The irreversible adsorption of BCNs at the oil water interface could make the Pickering emulsions preserve the droplets against coalescence and Ostwald ripening when they were dispersed in alginate solution. The interfacial assembly of amphiphilic BCNs and the hydrogel shells of the alginate composite beads formed by external gelation achieved the loading and sustained release of alfacalcidol. The release curves were well fitted by Korsmeyer Peppas model and the release mechanism of alfacalcidol from the composite beads was attributed to non-Fickian transport. In addition, the resultant alginate composite beads exhibited low cytotoxicity and good capabilities for osteoblast differentiation.