MUCOADHESION OF POLY(2-HYDROXYETHYL METHACRYLATE) IS IMPROVED WHEN LINEAR POLY(ETHYLENE OXIDE) CHAINS ARE ADDED TO THE POLYMER NETWORK

The mucoadhesive capacity of poly(2-hydroxyethyl methacrylate) (PHEMA) microspheres was studied in contact with Sprague-Dawley rat jejunum a t pH=6 and at 22 degrees C. Dry PHEMA microparticles exhibited adequat e mucoadhesive capacity, which was independent of nominal crosslinking ratio. When PHEMA microparticles were loaded with linear PEO chains o f molecular weight 1000, the mucoadhesive capacity increased significa ntly, almost doubling. This behavior was attributed to a significant i ncrease of the PEO chains penetrating across the mucosal tissue. Howev er, very long pendant chains could have a detrimental effect on interp enetration, as was shown with PHEMA microparticles loaded with PEO cha ins of molecular weight 100 000 which exhibited only a limited mucoadh esive capacity. This was the result of extensive entanglements by the long PEO chains and impediment of chain mobility across the PHEMA/muco sal interface.