Glucose-sensitive polyelectrolyte microcapsules based on (alginate/chitosan) pair

Novel chemical stimulus-responsive multilayer assemblies have been elaborated through the layer-by-layer deposition of oppositely charged polysaccharides on either flat or spherical surfaces. Concentration-dependent glucose responsiveness was obtained through chemical modification of alginate, selected as polyanion, with phenylboronic acid moieties. QCM measurements showed that the alginate derivate still self-assembles though electrostatically-driven interactions with chitosan at pH 4, and that the polysaccharides multilayer assemblies, as obtained after crosslinking, exhibit improved stability versus pH (in the range 4-9) as well as swelling ability in the presence of glucose-containing solution. Glutaraldehyde-mediated crosslinking was achieved through reaction with free primary amines of chitosan. This approach was further extended to the preparation of smart capsules using CaCO3 microparticles as dissolvable core templates. Success of the LbL deposition process, stability (pH range 4-9) of the multilayer assemblies and glucose-induced swelling were fully confirmed for the microcapsules. One of the major result of this study is that crosslinking prevents total dissolution of the capsules and enables modulating the permeability of the polysaccharide shell yielding controlled release on in-capsule entrapped low molecular weight molecules.