A novel fluorescent detection strategy for lysozyme in tears based on glycoside bond hydrolysis†

Dry eye disease (DED) is a prevalent condition characterized by a multifaceted etiology, with its incidence exhibiting an upward trajectory. Consequently, it is imperative to develop a sensitive, straightforward, and convenient method for the analysis of biomarkers associated with DED to facilitate its auxiliary diagnosis. Lysozyme (LYZ), produced by the lacrimal gland, is an antibacterial enzyme believed to play a crucial role in immunity and is associated with DED. In this study, a novel fluorescent sensing platform utilizing neutral red-heparin sodium (NR-HS) was developed with LYZ as the target. The platform operates on the principle of static quenching, where HS effectively quenches the fluorescence of NR. As a hydrolase, LYZ can catalyze the hydrolysis of the glucoside bond in HS, thereby modulating the transformation of the NR-HS fluorescence signal. This provides a straightforward fluorescence method for monitoring LYZ levels. Under optimal conditions, the developed “on–off–on” NR-HS sensing platform demonstrated the capability to detect LYZ within a range of 0.5 to 10 μg mL⁻¹, with a detection limit of 0.42 μg mL⁻¹, and exhibited enhanced selectivity for LYZ. In conclusion, a cost-effective, rapid, and efficient LYZ sensing platform was established, which facilitates the diagnosis of DED and shows potential as a diagnostic detection technique.