RESUMO
Polysaccharide/silica hybrid microcapsules were prepared using ionic gelation followed by spray-drying. Chitosan and alginate were used as biopolymer matrices, and in situ prepared silica was used as a structuring additive. The prepared microparticles were used in two very different applications: the encapsulation of hydrophilic molecules, and as a support for palladium nanoparticles used as catalysts for a model organic reaction, namely the reduction of p-nitrophenol by sodium borhydride. In the first application, erioglaucine disodium salt, taken as a model hydrophilic substance, was encapsulated in situ during the preparation of the microparticles. The results indicate that the presence of silica nanostructures, integrated within the polymer matrix, affect the morphology and the stability of the particles, retarding the release of the encapsulated substance. In the second application, chloropalladate was complexed on the surface of chitosan microparticles, and palladium(II) was subsequently reduced to palladium(0) to obtain heterogeneous catalysts with an excellent performance.
RESUMO
Nanoemulsions are kinetically stabilized emulsions with droplet sizes in the nanometer scale. These nanodroplets are able to confine spaces in which reactions of polymerization or precipitation can take place, leading to the formation of particles and capsules that can act as nanocarriers for biomedical applications. This review discusses the different possibilities of using nanoemulsions for preparing biomedical nanocarriers. According to the chemical nature, nanocarriers prepared in nanoemulsions are classified in polymeric, inorganic, or hybrid. The main synthetic strategies for each type are revised, including miniemulsion polymerization, nanoemulsion-solvent evaporation, spontaneous emulsification, sol-gel processes, and combination of different techniques to form multicomponent materials.
