Once the CL is inserted into the eye, proteins and other tear components adsorb onto its surface, which facilitates the adhesion of bacteria. Bacteria can come into contact with the eye through the fingers when inserting and removing the lens or through the CL itself if the care solutions or storage cases are contaminated. The risk increases in the following order: daily wear rigid gas permeable CLs < daily wear soft CLs < extended (overnight) wear CLs. CL wearing continues to be the most relevant risk factor for the development of microbial keratitis, although not all CLs are the same in terms of being prone to bacterial growth. Approximately 4.2 out of 10,000 CL wearers suffer from microbial keratitis, mainly caused by bacteria (>90%). Although CL materials have undergone a profound evolution over the last few years, the incidence of microbial-related ocular diseases has not decreased. The surfaces of contact lenses (CLs) and intraocular lenses (IOLs) are quite prone to the formation of bacterial biofilms, which may cause severe infections in the ocular structures. Overall, the designed hydrogels can host therapeutically relevant amounts of resveratrol to be sustainedly released on the eye, providing antibiofilm and antioxidant performance. In addition, importantly, the loading of resveratrol in the hydrogels preserved the antioxidant activity, even against photodegradation. Preferential adsorption of lysozyme, compared to albumin, might also contribute to the antimicrobial activity. The antibiofilm tests against Pseudomonas aeruginosa and Staphylococcus aureus evidenced that, in general, resveratrol decreased biofilm formation, which correlated with its concentration-dependent antibacterial capability. Ex vivo cornea and sclera permeability tests revealed that resveratrol released from the hydrogels readily accumulated in both tissues but did not cross through. Silicone hydrogels had stronger affinity for resveratrol, with higher loading and a slower release rate. All hydrogels showed physical properties adequate for CLs and successfully passed the hen’s egg-chorioallantoic membrane (HET-CAM) test. Both poly(hydroxyethyl methacrylate) (HEMA) and silicone hydrogels were prepared with MPC covering a wide range of concentrations (from 0 to 101 mM). MPC has, so far, been used to increase water retention on the CL surface (Proclear ® 1 day CLs). Since the use of antibiotics is associated with resistance concerns, here, two alternative strategies were evaluated to endow CLs with antibiofilm features: copolymerization with the antifouling monomer 2-methacryloyloxyethyl phosphorylcholine (MPC) and loading of the antioxidant resveratrol with known antibacterial activity. Contact lenses (CLs) are prone to biofilm formation, which may cause severe ocular infections.
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