Evaluation of poly(2-hydroxyethyl methacrylate) gels as drug delivery systems at different pH values

Studies of dynamic and equilibrium swelling, structural characterisation an d solute transport in swollen poly(2-hydroxyethyl methacrylate) gels (pHEMA ) cross-linked with tripropyleneglycol diacrylate (TPGDA) were done for a w ide range of TPGDA concentrations. The influence of the pH on these pHEMA p roperties was evaluated. In swelling studies it was found that in changing the pH from 6.5 to 12.0, a large increase in swelling occurred. from approx imately 48 to 55%, for the lowest concentration of TPGDA (1 mol%), and from 40 to 80% for the highest concentration (10mo1%). Fourier transform infrar ed (FTIR) and differential scanning calorimetry (DSC) measurements were mad e after the equilibrium swelling of the gels at different pH values, to exp lain these results. The advantage of using these gels as controlled drug de livery systems is illustrated using salicylic acid (SA) as a model drug. Th e loading and the release of the SA were made at different pH values and th e results obtained showed that it is possible to modulate the hydrogel perf ormance by controlling an external factor, the pH at which the drug loading and release were performed. (C) 2000 Elsevier Science B.V. All rights rese rved.