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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. [ABSTRACT FROM AUTHOR]

Fluorescence polarization (FP) has been applied in detecting chemicals and biomolecules for early-stage diagnosis, food safety analyses, and environmental monitoring. Compared to organic dyes, inorganic nanomaterials such as quantum dots have special fluorescence properties that can enhance the photostability of FP-based biosensing. In addition, nanomaterials, such as metallic nanoparticles, can be used as signal amplifiers to increase fluorescence polarization. In this review paper, different types of nanomaterials used in in FP-based biosensors have been reviewed. The role of each type of nanomaterial, acting as a fluorescent element and/or the signal amplifier, has been discussed. In addition, the advantages of FP-based biosensing systems have been discussed and compared with other fluorescence-based techniques. The integration of nanomaterials and FP techniques allows biosensors to quickly detect analytes in a sensitive and cost-effective manner and positively impact a variety of different fields including early-stage diagnoses. [ABSTRACT FROM AUTHOR]