Mucoadhesive poly(vinyl alcohol) hydrogels produced by freezing/thawing processes: applications in the development of wound healing systems.

Ultrapure poly(vinyl alcohol) (PVA) hydrogels were prepared by exposing an aqueous solution of 15 or 20 wt% PVA to repeated cycles of freezing for 6 or 12 h at -20 degrees C and thawing for 2 hours at 25 degrees C. The adhesive characteristics of the PVA gels in contact with a reconstituted mucus surface were quantified using a tensile technique. As the number of freezing/thawing cycles increased, the work of fracture (adhesion) decreased due to the increase in the PVA degree of crystallinity. Crystallinity was determined using differential scanning calorimetry. PVA gels prepared from the 20 wt% solution and exposed to two cycles of freezing/thawing exhibited the largest work of adhesion. Drug delivery studies were conducted with ketanserin, a wound healing enhancer. Release studies were conducted using PVA samples prepared from a 20-wt% solution that were exposed to two or three freezing cycles for 12 h followed by thawing for 2 h. Results from the release of the drug from the PVA sample exposed to two cycles showed that approximately 80% of the ketanserin was released within 4 h.