Nanoparticle-Based Membrane Assembly and Silicificationin Coacervate Microdroplets as a Route to Complex Colloidosomes.

The chemical construction of complexcolloidosomes consisting ofa molecularly crowded polyelectrolyte-enriched interior surroundedby a continuous shell of closely packed silica nanoparticles is studiedusing optical and fluorescence microscopy, high-resolution X-ray microcomputedtomography, and synchrotron radiation X-ray tomographic microscopy.The colloidosomes are prepared by addition of partially hydrophobicsilica nanoparticles to dodecane dispersions of positively or negativelycharged coacervate microdroplets consisting of aqueous mixtures ofpoly(diallyldimethylammonium chloride) (PDDA) and adenosine 5′-triphosphate(ATP) or PDDA and poly(acrylic acid) (PAA), respectively. Interfacialassembly of the nanoparticles produces a polydisperse population ofwell-defined PDDA/PAA droplets with diameters ranging from 50 to 950μm. In contrast, reconstruction of the PDDA/ATP coacervate interioroccurs on addition of the silica nanoparticles to produce a nanoparticle-stabilizedoil-in-coacervate-in-oil multiphase emulsion. Transfer of the coacervate-containingcolloidosomes into water and replication of their internal structureare achieved by addition of tetramethoxysilane, which serves as botha cross-linking and silicification agent to produce mineralized PDDA/PAAor PDDA/ATP microstructures with a uniform solidified texture or multichamberedinterior, respectively. The integration of colloidosome and coacervatetechnologies offers a route to a new type of multifunctional microcompartmentalizedsystem based on the membrane-mediatedincarceration of molecularly crowded chemical environments. [ABSTRACT FROM AUTHOR]