Encapsulation of glucose oxidase microparticles within a nanoscale layer-by-layer film: immobilization and biosensor applications.

We report on an immobilization strategy utilizing layer-by-layer encapsulated microparticles of enzymes within a nanoscale polyelectrolyte film. Encapsulation of glucose oxidase (GOD) microparticles was achieved by the sequential adsorption of oppositely charged polyelectrolytes onto the GOD biocrystal surface. The polyelectrolyte system polyallylamine/polystyrene sulfonate was used under high salt conditions to preserve the solid state of the highly water soluble GOD biocrystals during the encapsulation process. The resulting polymer multilayer capsule of about 15 nm wall thickness is permeable for small molecules (glucose), but non-permeable for macromolecules thus preventing the enzyme from leakage and at the same time shielding it from the outer environment e.g., from protease or microbial activity. Decrease of the buffer salt concentration leads to the dissolution of the enzyme under formation of mu-bioreactors. The spherical mu-bioreactors are bearing an extremely high loading of biocompound per volume. Encapsulated GOD was subsequently used to construct a biosensor by nanoengineered immobilisation of mu-bioreactor capsules onto an electrode surface. The presented approach demonstrates a general method to encapsulate highly soluble solid biomaterials and an immobilization strategy with the potential to create highly active thin and stable films of biomaterial.