Feeling of an Eye When It Meets the Unseen "Nano"

Nanomedicine is increasingly being utilized in addressing various eye ailments and holds immense potential in rectifying ocular diseases; however, the interactions between nanomedicines and their route of administration via tear fluid remain poorly understood. When nanoparticles are introduced into the tear fluid, a layer of protein corona is formed on their surface that not only influences the properties and biological fate of nanoparticles but also potentially interferes with the function of endogenous proteins. To investigate the interactions between gold nanoaprticles (AuNPs) and tear fluid, focusing on the physicochemical changes of the particles, and to quantitatively and qualitatively identify the key proteins involved in the corona formation, we employed label-free techniques for material and biophysical characterizations along with proteomic analyses and mass spectrometry. The AuNPs remained stable without forming aggregates, showing only an ∼31 nm increase in hydrodynamic diameter after interacting with tear fluid. Notably, their overall zeta potential increased significantly from -12 to -23 eV due to the supplemented charge by the adsorbed proteins. Proteomic analysis and liquid chromatography/mass spectrometry (LC-MS/MS) identified 31 proteins that were bound with the nanoparticles from a total of 174 proteins that were detected in the tear fluid. Bioinformatic classification revealed an enrichment of specific proteins essential for ocular health; proteins such as clusterin, lactotransferrin, adenosine triphosphate (ATP) synthase, lysozyme, alpha enolase, keratin, apolipoprotein, and epidermal growth factor receptor (EGFR) with pivotal roles in anti-inflammatory, immune response, cell adhesion, cellular organization, plasminogen activation, cell signaling, stress response, and corneal epithelial homeostasis. Overall, our study provides an unresolved comprehensive map of the tear protein corona landscape and its impact on nanoparticle behavior in the tear fluid. These insights must be considered and are valuable for designing safer and more effective nanomedicines for the treatment of various eye diseases.