Mucoadhesion of copolymers and mixtures containing polyacrylic acid.

Water-soluble polymers were synthesized from dextran and polyacrylic acid and their ocular mucoadhesion was evaluated. One series had polyacrylic acid grafted onto the polysaccharide backbone of dextran, and another series had dextran grafted onto the polyacrylic acid backbone. Mucoadhesion of these copolymers was investigated using a tensile apparatus and compared with that of polyacrylic acid/dextran mixtures prepared in different proportions. Whatever the copolymer structure, no synergistic effects were seen and mucoadhesion was not markedly increased compared to dextran. The adhesion of copolymers was the same as that of mixtures having a similar polyacrylic acid content and was always less than that of polyacrylic acid alone. Formation of an interpolymer complex occurred at concentrations up to 60% polyacrylic acid, and only above this value did bioadhesion increase above that of dextran. When this complex was dissociated by neutralization of the carboxyl groups of polyacrylic acid, the mucoadhesion of the copolymers and the mixtures was improved. These experiments demonstrated that copolymers and mixtures of dextran and polyacrylic acid did not produce polymers with improved ocular mucoadhesion.

Effects of acetylcysteine on rabbit conjunctival and corneal surfaces. A scanning electron microscopy study.

Conjunctival and corneal epithelial surfaces of normal rabbit eyes with their associated mucus were studied by scanning electron microscopy before and after treatment with the mucolytic agent N-acetylcysteine (AC). Four groups received topically one 50-microliters drop of either (Group A) 0.1 MAC, (Group B) 0.1 M AC every 5 min for 1 hr, (Group C) 0.1 M AC every 5 min for 2 hr, or (Group D) three drops of 20% AC over 15 min. The effects of the instillation of AC on mucus removal and cellular lesions increased in the order (A) less than (B) less than (C) less than (D). Treatment A had no effect on cornea and conjunctiva. Treatment B cleaned away mucosal debris without alteration of either conjunctival or corneal epithelium. Treatment C had a similar effect on the mucus but was associated with focal necrosis, and treatment D produced widespread necrosis, desquamation of epithelial cells, and inflammation.