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Uncoated chitosan beads and chitosan beads coated with hyaluronic acid/chitosan (HA/Ch) multilayers, were used to investigate the controlled release of gentamicin sulphate (GS). Greater encapsulation efficiency was observed for the layer—by-layer multilayer coated beads. The in vitro drug release was in a slower sustained manner compared with noncoated chitosan beads. The differences in in vitro drug release results may be explained by the barrier effect of the coating that impedes diffusion of GS and supporting complementary water uptake. These findings indicated that a slower sustained release of gentamicin can be obtained using multilayer coatings of HA/Ch on chitosan beads and that this process could be used as a drug delivery system. In addition, agglomerates of these bead could provide a porous support in tissue engineering applications.

Chitosan (Ch) microspheres have been developed by precipitation method, cross-linked with glutaraldehyde and used as a template for layer-by-layer (LBL) deposition of two natural polyelectrolytes. Using a LBL methodology, Ch microspheres were alternately coated with hyaluronic acid (HA) and Ch under mild conditions. The roughness of the Ch-based crosslinked microspheres was characterized by atomic force microscopy (AFM). Morphological characterization was performed by environmental scanning electron microscopy (ESEM), scanning electron microscopy (SEM) and stereolight microscopy. The swelling behaviour of the microspheres demonstrated that the ones with more bilayers presented the highest water uptake and the uncoated cross-linked Ch microspheres showed the lowest uptake capability. Microspheres presented spherical shape with sizes ranging from 510 to 840 mum. ESEM demonstrated that a rougher surface with voids is formed in multilayered microspheres caused by the irregular stacking of the layers. A short term mechanical stability assay was also performed, showing that the LBL procedure with more than five bilayers of HA/Ch over Ch cross-linked microspheres provide higher mechanical stability.