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.

Polymeric micelles of single and mixed poloxamines (Tetronic) were evaluated regarding their ability to host the antiglaucoma agent ethoxzolamide (ETOX) for topical ocular application. Three highly hydrophilic varieties of poloxamine (T908, T1107 and T1307) and a medium hydrophilic variety (T904), possessing a similar number of propylene oxide units but different contents in ethylene oxide, were chosen for the study. The critical micellar concentration and the cloud point of mixed micelles in 0.9 per cent NaCl were slightly greater than the values predicted from the additive rule, suggesting that the co-micellization is hindered. Micellar size ranged between 17 and 120 nm and it was not altered after the loading of ETOX (2.7-11.5 mg drug g -1 poloxamine). Drug solubilization ability ranked in the order: T904 (50-fold increase in the apparent solubility) . T1107 ffi T1307 . T908. Mixed micelles showed an intermediate capability to host ETOX but a greater physical stability, maintaining almost 100 per cent drug solubilized after 28 days. Furthermore, the different structural features of poloxamines and their combination in mixed micelles enabled the tuning of drug release profiles, sustaining the release in the 1-5 days range. These findings together with promising hen's egg test-chorioallantoic membrane biocompatibility tests make poloxamine micelles promising nanocarriers for carbonic anhydrase inhibitors in the treatment of glaucoma.

Abstract. The aim of this study is to confirm the formation of inclusion complexes between miconazole (MCZ) and two derivatives of beta-cyclodextrin, methyl-beta-cyclodextrin (MβCD) and 2-hydroxypropyl-beta-cyclodextrin (HPβCD) in aqueous solution by phase solubility studies. Inclusion complexes with MβCD in the solid state were then prepared by different methods, i.e., kneading, coevaporation (COE), spray-drying (SD), and lyophilization (LPh). The physicochemical properties of these complexes were subsequently studied by means of differential scanning calorimetry, Fourier transform infrared spectroscopy, scanning electron microscopy, and X-ray diffraction techniques. Phase solubility diagrams with MβCD and HPβCD were classified as A P type, indicating the formation of 1:1 and 1:2 stoichiometric inclusion complexes. The apparent stability constants (K S ) calculated from the phase solubility diagram were 145.69 M −1 (K 1:1 ) and 11.11 M −1 (K 1:2 ) for MβCD and 126.94 M −1 (K 1:1 ) and 2.20 M −1 (K 1:2 ) for HPβCD. The method of preparation of the inclusion complexes in the solid state was shown to greatly affect the properties of the formed complex. Hence, the LPh, SD, and COE methods produce true inclusion complexes between MCZ and MβCD. In contrast, crystalline drug was still clearly detectable in the kneaded (KN) product.

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-Purpose. Conventional ophthalmic systems present very low corneal systemic bioavailability due to the nasolacrimal drainage and the difficulty to deliver the drug in the posterior segment of ocular tissue. For these reasons, recent advances have focused on the development of new ophthalmic drug delivery systems. This review provides an insight into the various constraints associated with ocular drug delivery, summarizes recent findings in soft contact lenses (SCL) and the applications of novel pharmaceutical systems for ocular drug delivery. Among the new therapeutic approaches in ophthalmology, SCL are novel continuous-delivery systems, providing high and sustained levels of drugs to the cornea. The tendency of research in ophthalmic drug delivery systems development are directed towards a combination of several technologies (bio-inspired and molecular imprinting techniques) and materials (cyclodextrins, surfactants, specific monomers). There is a tendency to develop systems which not only prolong the contact time of the vehicle at the ocular surface, but also at the same time slow down the clearance of the drug. Different materials can be applied during the development of contact lenses and can be combined with natural inspired strategies of drug immobilization and release, providing successful tools for ocular drug delivery systems.

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