Iron-oxide nanoparticle-integrated soft contact lenses: optical optimization, catalytic functionality, and biocompatibility.

Abstract

Millions of people suffer from corneal infections and inflammatory conditions, and a contact lens that not only corrects vision but also continuously protects against microbes and inflammation could transform ocular therapeutics. Compared with plasmonic metal nanoparticles, such as silver or gold, iron oxide nanoparticles are well known for their biocompatibility, low toxicity, and low cost. To our knowledge, this work is the first to demonstrate the integration of iron oxide nanoparticles into commercial contact lenses. Nanoparticles were characterized using X-ray diffraction, X-ray photoelectron spectroscopy, scanning electron microscopy and transmission electron microscopy. Optical properties were assessed using UV-Vis spectroscopy and COMSOL simulations. Catalytic activity was evaluated by methylene blue degradation in the presence of H₂O₂. Lens's biocompatibility, anti-inflammatory and anti-bacterial properties were investigated using fibroblast cell viability assays and antibacterial testing. X-ray diffraction verified the structure with a lattice parameter of 8.37 Å, while XPS shows that the obtained nanoparticles (NPs) consisted of a mixture of both Fe₃O₄/γ-Fe₂O₃ NPs. SEM and transmission electron microscope confirmed that the NPs are uniformly dispersed and have an average size of ∼8 nm. UV-vis spectroscopy results showed significant optical transmission after embedding the NPs. The COMSOL simulation data indicated that smaller nanoparticle radii maintain high transparency and larger radii reduce transmission. At higher nanoparticle loading, the lenses exhibited 96.7% methylene blue degradation in the presence of H₂O₂ over 2 weeks. Biocompatibility testing showed >70% fibroblast cell viability with normal morphology, along with anti-inflammatory and antibacterial activity against Staphylococcus aureus. Findings show the potential of iron-oxide nanoparticle-embedded contact lenses as transparent, catalytically active, and biologically safe platforms for future therapeutics and wearable optics applications.