Preparation and evaluation of the in vitro drug release properties and mucoadhesion of novel microspheres of hyaluronic acid and chitosan

Rapid mucociliary clearance of intranasally administered drugs is often a key factor in determining the bioavailability of such therapeutic agents. The use of mucoadhesive microparticles provide a potential strategy for improving retention of drugs within the nasal cavity, and thereby improve the resultant pharmacokinetic profile. This study describes the comparison of a number of novel, potentially mucoadhesive microspheres, prepared by solvent evaporation, composed of hyaluronic acid (HA), chitosan glutamate (CH) and a combination of the two with microcapsules of HA and gelatin prepared by complex coacervation. The microspheres had a mean particle size of 19.91 +/- 1.57 mu m (HA), 28.60 +/- 1.34 mu m (HA/CH), 29.47 +/- 3.58 mu m (CH). The incorporation of a model drug, gentamicin sulphate (%) was 46.90 +/- 0.53 (HA), 28.04 +/- 1.21 (HA/CH) and 13.32 +/- 1.04 (CH). The in vitro release profiles of microsphere formulations prepared by solvent evaporation were determined. The release of gentamicin from HA and HA/CH was 50% longer than CH and was best modelled as a release from a matrix. The degree of mucoadhesion of each formulation was investigated by determining the mucociliary transport rate (MTR) of the microparticles across an isolated frog palate. Acacia/gelatin microcapsules were used as a positive control. The rank order of mucoadhesion for the microspheres and the microparticles was HA=HA/CH>CH>HA/ gelatin>CHins. The entrapment of gentamicin did not affect the mucoadhesive properties (P>0.05, Mann-Whitney U-test). The combination of HA with chitosan may afford additional advantages in combining the mucoadhesive potential of HA with the penetration enhancing effect of chitosan. (C) 2000 Elsevier Science B.V. All rights reserved.