Feasibility of Silicon Quantum Dots as a Biomarker for the Bioimaging of Tear Film

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.

Comparison of eye drop retention time using fluorophotometry in three commercially available lubricant eye drops

SIGNIFICANCE

This is the first study to evaluate the retention time of lubricating eye drops containing various concentrations of sodium hyaluronate using fluorophotometry in a symptomatic dry eye population. Information regarding eye drop retention may be useful for eye care practitioners to assist in the selection of more effective treatments for managing dry eye.

PURPOSE

This study aimed to use fluorophotometry to compare retention time on the ocular surface of three commercially available lubricating eye drops, each containing varying concentrations of sodium hyaluronic acid (HA), and their effects on tear film stability post-instillation in a population with symptoms of dry eye.

METHODS

Adults with symptoms of dry eye (Ocular Surface Disease Index score, >12) were enrolled in this prospective, double-masked comparison of eye drops containing 0.15% HA-hydroxypropyl guar (HPGuar), 0.2% HA, and 0.1% HA. Participants were randomized to the eye drop order and the study eye under evaluation. Each eye drop was admixed with a fluorescent tracer (70-kDa fluorescein isothiocyanate-dextran) at 10% wt/vol, and 10 μL volume was instilled for each evaluation. A fluorophotometer was used to measure the time for the tracer signal to return to baseline. Fluorescein tear breakup time was measured following fluorophotometry assessment.

RESULTS

Retention time for 0.15% HA-HPGuar and 0.2% HA was significantly longer compared with 0.1% HA (p=0.02 and p=0.03). Fluorescein tear breakup time was significantly longer for the 0.15% HA-HPGuar eye drop compared with both the 0.1% HA eye drop (p=0.01) and 0.2% HA eye drop (p=0.003).

CONCLUSIONS

Retention time on the ocular surface of the two eye drops containing higher concentrations of HA was longer than the eye drop with the lowest concentration of HA. The tear film was also more stable with the 0.15% HA-HPGuar eye drop compared with the eye drops containing HA alone, which may be attributable to the other components in the 0.15% HA-HPGuar eye drop.

Spectrotemporal characterization of photoluminescent silicon nanocrystals and their energy transfer to dyes

Silicon nanocrystals (SiNCs) are a promising material for applications in bioanalysis and imaging. Compared to other types of semiconductor nanocrystals, the development and characterization of energy transfer (ET) configurations with SiNCs has been far more limited, resulting in an equally limited understanding of this process and its SiNC-specific nuances. Here, we present a systematic and detailed study of ET between SiNCs and dyes. A combination of spectroelectrophoresis and time-gated and time-resolved photoluminescence measurements were used to characterize the photophysical properties of ensembles of SiNCs and gain insight into how these properties varied as a function of nanocrystal size. ET between SiNC donors and a series of non-fluorescent Black Hole Quencher (BHQ) dyes and fluorescent sulfo-Cyanine 5.5 dye acceptors was evaluated in terms of spectral properties, wavelength-resolved efficiencies, trends with spectral overlap integral, and differences between two methods of BHQ association with the SiNCs. The overall results were consistent with a Förster resonance energy transfer (FRET) mechanism where the polydispersity of the SiNCs had a significant impact on the observed ET: the choice of wavelength and timing parameters were important, and ensemble measurements represented an average of heterogeneous ET behaviors. Prospective advantages and disadvantages of SiNCs as ET donors are discussed. This study serves as a foundation for the continued and optimized development of ET configurations with SiNCs.

Advanced Nanomaterials for Quantum Technology, Sensor and Health Therapy Applications

The intense interest in nanostructured materials is fueled by the tremendous economic and technological benefits anticipated to be achieved by nanotechnology and nanodevices [...].