In vivo assessment of topically applied silver nanoparticles on entire cornea: comprehensive FTIR study

Silver nanoparticles (AgNPs) have gained attention in medicine for their potent antibacterial, antiviral, and anti-inflammatory properties. The use of silver nanoparticles in ophthalmic solutions raises concerns regarding potential toxicity of nanoparticles to ocular tissues, such as the cornea, conjunctiva, and retina, which necessitates further toxicity assessments aiding in the development of safer ophthalmic solutions. This study investigates the impact of AgNPs on corneal tissue using ophthalmic investigations, Fourier transform infrared (FTIR) spectroscopy, and chemometric analyses. Three concentrations of AgNPs (0.48 µg/mL, 7.2 µg/mL, and 15.5 µg/mL) were topically applied twice daily for 10 days, synthesized biologically by reducing silver nitrate with almond kernels water extract. Corneas, obtained by cutting 2-3 mm below the ora serrata, were analyzed with FTIR spectroscopy and subjected to chemometric analyses. Results reveal AgNPs' influence on constituents with OH and NH groups, affecting corneal lipids and reducing the lipid saturation index. AgNPs alter both bulk and interfacial water, leading to changes in corneal hydration thus modifying corneal physico-chemical properties. The influence extends to the water environment around proteins and lipids, releasing bound water from phospholipids and disrupting hydrogen bonding networks around proteins. In conclusion, the applied AgNPs concentrations can be linked to dry eye onset.