Swelling and drug release behavior of poly(2-hydroxyethyl methacrylate/itaconic acid) copolymeric hydrogels obtained by gamma irradiation

Controlled drug release from hydrogels for contact lenses: Drug partitioning and diffusion

“…We should stress here that the polymer volume fraction did not reveal to be sensitive to small changes in pH and ionic strength. Changing the medium from water to PBS led to an increase in EWC of both hydrogels smaller than 3% which is in agreement with the findings of other authors relative to pHEMA (Tomic et al, 2007). Thus, the difference in the results obtained in water and in PBS must be attributed to the behavior of the drugs in solution and to their interactions with the polymeric membranes.…”

“…They may be correlated with the size of the solutes using theories that describe hindered diffusion of macromolecules in nonadsorbing hydrogels (Kim and Chauhan, 2008;Ogston et al, 1973;Phillips, 2000;Saini et al, 2005;Tomic et al, 2007). Based on the assumption of Brady (Clague and Phillips, 1996) that the relative diffusivity, defined as the ratio between the diffusion coefficients in the gel and in the dilute, bulk solution, is given by < = " • -, where F is a hydrodynamic-resistance factor and S is a steric factor, several diffusion models that have been proposed.…”

Evaluation of pH-sensitive poly(2-hydroxyethyl methacrylate-co-2-(diisopropylamino)ethyl methacrylate) copolymers as drug delivery systems for potential applications in ophthalmic therapies/ocular delivery of drugs

“…This effect is related to the swelling property of these hydrogels when changing the medium pH. At basic pH the matrix is closed and the swelling is low, by acidifying the medium, the hydrogel swells and the release rate of the Rh6G increases as well as the pore size of the hydrogel [53]. In the case of HD70/30-1 the effect of the pH on the release kinetics is much more pronounced than in HD90/10-1 copolymer due to the higher amount of DPA.…”

Macromolecular composition and drug-loading effect on the delivery of paclitaxel and folic acid from acrylic matrices

“…Solute diffusion coefficients at early (equation 3) and late (equation 4) times were evaluated as (Tomic et al, 2007):…”

“…This increase in volume rose until the thermodynamic equilibrium was reached. The thermodynamic equilibrium in the swelling process occurs when the osmotic pressure, cause of the penetration of the water in the cavities formed between macromolecules, and the elastic force of the chains become equal (Tomic et al, 2007). Because PMMA and PBMA present the same principal structure of the macromolecules, it was reasonable to hypothesize that the stiffness of the macromolecules did not significantly vary and when the swelling equilibrium was reached the elastic forces exerted by PMMA, PBMA, and their copolymers were similar.…”