On the formation of uniform alginate-silica microcomposites with ordered hierarchical structures

The hierarchical ordering at micro- and nano-scales in hybrid composites of alginate and silica nanoparticles was observed when uniform microparticles were formed in a single step via a micro-fluidic jet spray drying. A polymer-mediated 'bricks and mortar' strategy initially aligned silica nanoparticles into nano-clusters in the dispersion with sizes depending on the ratio of polymer to silica. Evaporation induced self-assembly during spray drying then formed uniform microparticles with shells enriched with silica nanoparticles, enclosing arrays of close-packed spherical aggregates of these nano-clusters. The final structures of particles were determined by the drying temperature and the ratio of alginate to silica, indicating that this approach could be used to fabricate diverse structural motifs. The combination of polymer-mediated self-assembly with a moderate temperature spray drying could be a versatile route to synthesize thermal sensitive, ordered biomaterials for food and pharmaceutical-related applications.