Rapid and quantitative detection of tear MMP-9 for dry eye patients using a novel silicon nanowire-based biosensor

Dry eye disease (DED) is the most common chronic eye disease characterized by ocular surface inflammation that affects hundreds of millions of people worldwide. The diagnosis and monitoring of DED require fast and reliable tools in the clinical setting. Matrix metalloproteinase 9 (MMP-9) has been proven to be a reliable indicator of DED owing to its close relationship with inflammation. A novel biosensor based on silicon nanowire-based field-effect transistor (SiNW FET) devices was fabricated for the quantitative measurement of MMP-9 in human tears. A modified controllable process was applied to improve the uniformity of the SiNWs in size and stabilize their performance with optical calibration at low salt concentrations for clinical application. With this protocol, correlation analysis proved the high agreement between the biosensor and enzyme-linked immunosorbent assay (correlation coefficient of 0.92 for DED patients and 0.90 for healthy controls). A diagnostic sensitivity of 86.96% and specificity of 90% were achieved in human tear samples from DED patients and healthy subjects in real-world clinical settings. Furthermore, the tear MMP-9 concentrations monitored using the device correlated with the therapeutic response of the patients with DED. Our enhanced SiNW biosensor device demonstrated its potential as an alternative tool for real-time diagnosis and monitoring for prognostic prediction toward point-of-care testing for DED.