Tear biosensor detects diabetic retinopathy biomarkers for early diagnosis

Tear fluid is emerging as an attractive source of diagnostic information because it can be collected easily and non-invasively. Changes in tear composition often reflect underlying physiological conditions, making tears a valuable medium for monitoring eye diseases.

The newly developed biosensor targets two proteins associated with diabetic retinopathy:

• Lipocalin-1 (LCN1) — linked to inflammation and changes in tear composition

• Vascular endothelial growth factor (VEGF) — a key driver of abnormal blood vessel growth in advanced stages of the disease

By detecting both biomarkers simultaneously, the system provides a more comprehensive picture of retinal health compared with conventional single-target tests.

A miniature fiber-optic sensing platform

The technology is based on semi-distributed interferometer (SDI) sensors fabricated from optical fibers. These miniature devices are lightweight, resistant to electromagnetic interference, and suitable for in-situ monitoring.

After fabrication, the researchers functionalized the fiber tips with specific antibodies, enabling selective binding to the target biomarkers. When proteins attach to the sensor surface, the optical signal changes — allowing real-time monitoring without fluorescent labels or complex sample preparation.

Laboratory tests demonstrated strong performance:

• Detection of LCN1 down to 5.98 ng/mL

• Detection of VEGF as low as 26.6 fg/mL

Importantly, the system was evaluated not only in static laboratory conditions but also in dynamic experiments simulating natural tear flow — an essential step toward real-world clinical applications.

Multiplex sensing for improved diagnostics

A key innovation of the study is the use of a three-sensor configuration: two biosensors for LCN1 and VEGF detection, and a reference sensor monitoring background signals. This design improves measurement stability and reduces the risk of false readings.

Simultaneous measurement of multiple biomarkers, known as multiplexed detection. May help clinicians assess disease progression more accurately while reducing analysis time and costs.

Toward accessible and personalized eye care

Current diagnostic tools for diabetic retinopathy, such as retinal imaging and optical coherence tomography, require specialized equipment and trained personnel. The research team believes that compact fiber-optic biosensors could complement these methods by enabling rapid screening and personalized monitoring, particularly in settings with limited resources.

Because the sensing element is small and inexpensive, future versions could be integrated into wearable devices or point-of-care systems, potentially supporting continuous monitoring of tear biomarkers.

Next steps

While the present work demonstrates proof-of-concept performance in artificial tear fluid, future research will focus on testing diluted clinical samples and exploring practical clinical deployment.

The study was funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan and Nazarbayev University.