Realization of rapid diabetic retinopathy screening with lipocalin 1 in tear using enhanced immunofluorescence photonic crystal microchip

Diabetic retinopathy (DR) is a major cause of preventable blindness, but current diagnostic tools rely on expensive imaging devices, specialized expertise, and, in some cases, invasive procedures, limiting accessibility in resource-constrained settings. There is an unmet need for rapid, non-invasive, and affordable point-of-care methods for early DR detection. We developed a portable lateral flow microfluidic chip integrated with a photonic crystal (PhC) biosensor to enhance immunofluorescence detection of lipocalin-1 (LCN-1), a biomarker associated with DR. The PhC surface provided a 2.7-fold fluorescence enhancement compared to non-PhC substrates, and the microfluidic flow was optimized using an absorbent paper design to ensure uniform fluid distribution and sufficient antigen-antibody interaction time. Analytical performance was validated using sandwiched immunoassays with carboxylate-modified particles, followed by clinical evaluation in 30 tear samples from healthy individuals, non-proliferative DR (NPDR), and proliferative DR (PDR) patients. The PhC microchip achieved a detection limit of 136 pg μL^-1 and delivered quantifiable results within 15 min. In clinical testing, elevated LCN-1 levels were observed in both NPDR and PDR patients compared with healthy controls. The biosensor achieved 100% sensitivity, specificity, and accuracy in distinguishing PDR from healthy individuals, as well as 100% sensitivity with 90% specificity for NPDR <i>versus</i> healthy individuals, resulting in an overall diagnostic accuracy of 95%. The PhC-integrated microchip enables rapid and non-invasive detection of DR from tear samples. Its high sensitivity, specificity, and capability to differentiate between NPDR and PDR demonstrate strong potential for future adaptation into a portable point-of-care screening platform, particularly suited for low-resource settings to facilitate early intervention and reduce vision loss in diabetic patients.