Hydrophobic Silicon Quantum Dots for Potential Imaging of Tear Film Lipid Layer

The tear film, consisting of the aqueous and lipid layers, maintains the homeostasis of the ocular surface; therefore, when disturbed, it can cause dry eye, which affects millions of people worldwide. Understanding the dynamics of the tear film layers is essential for developing efficient drug delivery systems for dry eye disease. Quantum dots (QDs) offer the potential for real-time monitoring of tear film and evaluating its dynamics. Hydrophilic silicon QDs (Si-QDs) have already been optimised to image the aqueous layer of the tear film. This study was conducted to optimise hydrophobic Si-QDs to image the lipid layer of the tear film. Si-QDs were synthesised in solution and characterised by transmission electron microscope and spectrofluorophotometry. The fluorescence emission of Si-QDs was monitored in vitro when mixed with artificial tears. The cytotoxicity was assessed in cultured human corneal epithelial cells using an MTT assay following 24 h of exposure. Si-QDs were 2.65 ± 0.35 nm in size and were non-toxic at <16 µg/mL. Si-QDs emitted stable green fluorescence for 20 min but demonstrated aggregation at higher concentrations. These findings highlight the potential of hydrophobic Si-QDs as a biomarker for the real-time imaging of the tear film lipid layer. However, further research on surface functionalisation and preclinical evaluations are recommended for enhanced solubility and biocompatibility in the ocular surface.