Facile encapsulation of nanoparticles in nanoorganized bio-polyelectrolyte microshells

We present a facile method for the encapsulation of nanoparticles' (NPs) systems within the interior space of bio-polyelectrolyte microshells. The microshells, constructed by alternate adsorption of alginate sodium (ALG) and chitosan (CHI) onto the surface of colloidal templates and subsequent removal of cores, allow the polystyrene (PS) or SiO2 nanoparticles (NPs) adsorbed into the internal shells through a simple mix process, as confirmed by confocal laser scanning microscopy (CLSM), and scanning electron microscopy (SEM) analysis. The NPs-filled microshells form the rigid spherical shape in contrast to the flat and folded structure of microshells at the dry state prior to filling. The interior of NPs-encapsulated microshells was directly visualized by transmission electron microscopy (TEM) image of microtomed slices and cross-section SEM image. The loading amount of NPs in a shell composed of (ALG/CHI)5 was determined in two media i.e. H2O and 0.1 M NaCl, and the results showed that the loading amount of the former is greater than that of the latter. The possible encapsulation mechanism is also discussed. The hybrid materials with NPs core and bio-polyelectrolyte shells have potential application for controlled-release drug delivery and catalysis.