A research team led by Prof. JIANG Changlong from the Hefei Institutes of Physical Science of the Chinese Academy of Sciences has developed a wearable fluorescent eye patch sensor capable of non-invasively detecting lysozyme levels in human tears. By integrating a multi-emission metal-organic framework hydrogel (Eu-Dy MOF gel) with smartphone-based color recognition, the system offers a promising tool for real-time eye health monitoring.

The findings were recently published in Analytical Chemistry.

Lysozyme, commonly known as "the body's own antibiotic," plays a crucial role in protecting the eyes from infection. As an important biomarker for various eye diseases, monitoring its levels in tears can offer valuable insights into eye health. However, traditional methods for detecting lysozyme are often invasive or require complex equipment.

To address these limitations, the researchers proposed a non-invasive fluorescent visualization detection method, expanding the application range of eye patch fluorescent sensors: the functionalized Eu-Dy MOF gel probes integrated into the eye patch sensors are used as sensing units. Tear fluids secreted by the eyes are collected via the eye patches applied to the skin beneath the eyes. The color signal generated by the sensing area on the eye patch under ultraviolet light are then captured using the camera function of a smartphone, and analyzed using color recognition software on the device. 

The MOF material was chosen for its "antenna effect," in which organic ligands absorb light and transfer energy to lanthanide ions such as Eu³⁺ and Dy³⁺, leading to visible fluorescence. This efficient energy transfer makes MOF gels ideal for sensitive optical sensing.

In the presence of lysozyme, the Eu-Dy MOF gel forms complexes with the protein, leading to a quenching of blue fluorescence through static quenching and local electron transfer. The system demonstrated a detection limit as low as 1.5 nanomolar, enabling highly sensitive, real-time measurement of lysozyme levels in tears.

"Our finding holds great potential for non-invasive detection of lysozyme in tears, promoting the widespread application of functionalized MOF fluorescent sensors in personal health monitoring, disease early warning, diagnosis and treatment fields," said Prof. JIANG. 

Design of the eye patch fluorescent sensor based on Eu-Dy MOF gel and real-time detection and quantitative analysis of lysozyme using a smartphone. (Image by PAN Lei)

 Actual image of Eu-Dy MOF gel eye patch and fluorescence color changes after adding different concentrations of lysozyme. (Image by PAN Lei)