Point-of-care monitoring of dry eye disease using lysozyme in tear based on commercial pregnancy test strips

Dry eye disease (DED) is a common disease associated with ocular inflammation, which affects the vision of patients and the quality of their life. Therefore, it is of great significance to develop a point-of-care (POC) test for ancillary detection of DED. In this study, we designed a lysozyme (LYZ) detection method for DED diagnosis using commercial pregnancy test strips as readout. A human chorionic gonadotropin-LYZ aptamer (hCG-apt) signal probe was adsorbed by large scale of graphene oxide (GO). The LYZ specifically binds hCG-apt to form hCG-apt/LYZ complex, which could keep away from GO surface ascribed to the conformation change of hCG-apt and could be recognized by hCG test strip. Thus, the LYZ level could be estimated according to the color intensity on the hCG strip. Under the optimal conditions, LYZ could be quantitatively analyzed within 45 min with a detection limit of 0.80 µg/ml. It was observed that the average LYZ concentration (48.62 ± 11.14 μg/ml) in the tear of DED patients caused by ophthalmic surgery was lower than that in healthy people (78.42 ± 14.86 μg/ml), indicating that LYZ in tear might be as a potential biomarker for evaluating DED. In conclusion, a LYZ detection platform characterized with low-cost, fast, and efficient was established to help in DED diagnosis and provided a significant reference for other biomarkers POC detection.