Dual lateral flow assay using quantum nanobeads for quantitative detection of BDNF and TNF-α in tears†

Abstract

Glaucoma is a group of neurodegenerative eye diseases characterized by progressive damage to the optic nerve which is typically asymptomatic until irreversible vision loss has occurred. Early screening is essential for timely treatment to prevent visual impairment. However, existing detection methods struggle to achieve a balance between accuracy, time efficiency, and portability. The lateral flow assay (LFA) is a well-established immunoanalytical tool for point-of-care (POC) analysis. Here, we have developed a unique dual-testing, quantum nanobeads-based fluorescence LFA, allowing for the simultaneous and quantitative detection of two glaucoma biomarkers: tumor necrosis factor-α (TNF-α) and brain-derived neurotrophic factor (BDNF). By coating quantum dots on the surface of a SiO₂ core, the fluorescent intensity of the quantum nanobeads was enhanced enabling an accurate, efficient, and high-throughput bioanalytical performance, with low detection limits of 3.39 pg mL⁻¹ for TNF-α and 4.13 pg mL⁻¹ for BDNF. The LFA also demonstrated superior selectivity, reproducibility, and stability to the standard enzyme-linked immunosorbent assay (ELISA). Using a 3D-printed readout box, the analysis of the LFA requires only a readily accessible smartphone and image processing software, making it an ideal POC detection tool. This ultrasensitive, economical, and user-friendly LFA demonstrates significant potential as an alternative for glaucoma screening.