Smartphone-based fluorescent sensing platforms for point-of-care ocular lactoferrin detection

Lactoferrin is a critical glycoprotein that accounts for the major component in tear protein composition. Tear lactoferrin has been indicated as a potential biomarker in ocular health screening, such as dry eye disease diagnosis. Fluorescent biosensors are a desirable alternative to current diagnostic methods, due to their high selectivity and sensitivity, and rapid and cost-effective detection technologies at point-of-care (POC) platforms. Herein, fluorescent lactoferrin sensing is examined and applied on nitrocellulose membrane, capillary tube, and contact lens platforms in cooperation with a developed smartphone software for data collection and analysis. Fluorescent sensors based on trivalent terbium (TbCl3) are integrated into different platforms, including nitro-cellulose membranes, capillary tubes, and contact lenses, and tested in artificial tear fluid. A bespoke 3D printed readout device integrated with a smartphone camera was employed for image acquisition and readout. The detection range of the lactoferrin sensors could be varied from 0 to 5 mg mL-1 with a strong linear relation and yielded a limit of detection (LOD) of 0.57 mg mL-1 for lateral flow sensing, 0.12 mg mL-1 for capillary tube sensing, and 0.44 mg mL-1 for contact lens sensing. The contact lens sensor obtained the highest linear regression, while the capillary tube sensor achieved a lowest LOD. This work could pave the way towards accessible lactoferrin monitoring at POC and could induce hospitalization at the UK national health service (NHS) for future clinical trials and examinations.