Rapid detection of tear lactoferrin for diagnosis of dry eyes by using fluorescence polarization-based aptasensor

Differentiating dry eye disease (DED) from allergic or viral conjunctivitis rapidly and accurately is important to ensure prompt diagnosis and treatment. Tear lactoferrin (LF), a multi-functional glycoprotein found in tears, decreases significantly in patients with DED, and has been considered as a DED diagnostic biomarker. Measuring tear LF level, however, takes time and requires the use of bulky instruments. Herein, a homogeneous carbon nanostructure-based aptasensor with high sensitivity and selectivity has been developed by applying fluorescence polarization (FP) technology. The FP of carbon dots (CDs) bioconjugated with LF aptamers (CDs-aptamer) is 21.2% higher than that of CDs, which can be further amplified (1.81 times) once interacting with graphene oxide nanosheets (GONS). In the presence of LF, GONS separates from CDs-aptamer because of the stronger binding affinity between CDs-aptamer to LF, resulting in the decrease of FP value. A linear relationship is observed between FP value and LF concentration in spiked tear samples from 0.66 to 3.32 mg/mL. The selectivity of the aptasensor has been investigated by measuring other proteins. The results indicate that the FP-based aptasensor is a cost-effective method with high sensitivity and selectivity in detection of tear LF.