Soft contact lenses (SCLs) constitute a promising vehicle for ocular drug delivery due to their biocompatibility, prolonged contact with the eye and general acceptance. Soaking in the drug solution is the simplest method to load the drug into the SCLs. However, by itself, it usually does not allow ensuring a controlled drug release, compatible with the therapeutic needs. Thus, additional approaches, such as the application of coatings on the SCLs, have been tried to achieve that purpose.
In this work, a lab-made silicon based hydrogel intended for SCLs was loaded by soaking with an anti-inflammatory drug (diclofenac, DCF) and coated, using a layer-by-layer (LbL) coating strategy, with alginate, chitosan and hyaluronic acid (ALG/CHI/HA). Material properties such as transmittance, wettability, ionic permeability and swelling were studied. In all cases, the material presented adequate characteristics to be used in therapeutic SCLs. Drug release experiments were carried out under sink conditions. The results demonstrated that DCF release can be regulated by the coating. A mathematical model was applied to predict the in vivo efficacy of the coated lenses, indicating that the studied system may ensure a controlled release of the drug within therapeutic levels for more than 2 weeks. Chorioallantoic membrane (HET-CAM) tests suggest that the coated material shall not induce ocular irritation.
The interaction of lysozyme (one of the most abundant protein in lacrimal fluid) with the coating was evaluated by quartz-crystal microbalance with dissipation (QCM-D). It was concluded that the coating has an antifouling properties.
In sum, the LBL coating of the DCF loaded silicon based hydrogel is pointed out as an efficient strategy to get efficient therapeutic SCLs, without impairing relevant properties for the intended application.