Bioinspired imprinted PHEMA-hydrogels for ocular delivery of carbonic anhydrase inhibitor drugs

Hydrogels with high affinity for carbonic anhydrase (CA) inhibitor drugs have been designed trying to mimic the active site of the physiological metallo-enzyme receptor. Using hydroxyethyl methacrylate (HEMA) as the backbone component, zinc methacrylate, 1- or 4-vinylimidazole (1VI or 4VI), and N-hydroxyethyl acrylamide (HEAA) were combined at different ratios to reproduce in the hydrogels the cone-shaped cavity of the CA, which contains a Zn(2+) ion coordinated to three histidine residues. 4VI resembles histidine functionality better than 1VI, and, consequently, pHEMA-ZnMA(2) hydrogels bearing 4VI moieties were those with the greatest ability to host acetazolamide or ethoxzolamide (2 to 3 times greater network/water partition coefficient) and to sustain the release of these antiglaucoma drugs (50% lower release rate estimated by fitting to the square root kinetics). The use of acetazolamide as template during polymerization did not enhance the affinity of the network for the drugs. In addition to the remarkable improvement in the performance as controlled release systems, the biomimetic hydrogels were highly cytocompatible and possessed adequate oxygen permeability to be used as medicated soft contact lenses or inserts. The results obtained highlight the benefits of mimicking the structure of the physiological receptors for the design of advanced drug delivery systems.