MODULATION OF DRUG PERMEATION THROUGH INTERPOLYMER COMPLEXED HYDROGELS FOR DRUG-DELIVERY APPLICATIONS

Grafted poly(methacrylic acid-g-ethylene glycol) (P(MAA-g-EG)) copolym ers exhibit pH-sensitive, reversible complexation. Equilibrium swellin g ratios and mesh sizes of uncomplexed gels were much higher than thos e of the complexed states and varied according to copolymer compositio n and PEG graft length. Swelling under oscillatory pH conditions revea led the dynamic sensitivity of P(MAA-g-EG) gels and showed that networ k collapse (complexation) occurred more rapidly than network expansion (decomplexation). The rates of diffusion of specific ions caused the responses. Solute diffusivity was higher in uncomplexed than in comple xed P(MAA-g-EG) membranes and decreased as solute size increased. Lowe r diffusivities resulted in membranes containing longer PEG grafts sin ce in the uncomplexed state the PEG grafts dangled into the polymer me sh space.