Development of a low-cost optical device for imaging lateral flow nitrocellulose membranes

Lateral flow nitrocellulose membranes are commonly used in full assay designs. They provide a suitable surface for loading the detection particles without decreasing the adsorption ability. In point-of-care applications, various diseases can be detected by an optical reader imaging the fluorescently dyed disease markers. Therefore, there is a need for a low-cost optical reader device for imaging the membranes with fluorescent dyes. In this study, two versions of the optical reader are developed for imaging nitrocellulose membranes, including fluorescein sodium salt and rhodamine B dyes. The preliminary device is mainly composed of a minicomputer, a stand-alone camera, two different power light-emitting diodes matching the spectral characteristics of the dyes, an optical filter, and additional electronic components. The preliminary version underscores the need for further refinements to improve image quality and portability, leading to the development of the final version. The portable final optical reader, powered by the batteries, is designed using a minicomputer with improved features and a high-quality camera. The components of both readers are positioned and housed by the designed mechanical components. Also, the device operation is controlled by the developed graphical user interface. The samples are prepared by loading the different concentration solutions of fluorescein sodium salt and rhodamine B dyes onto the membranes. The prepared samples are imaged in both versions of the optical reader. According to the measured mean intensity values, the green and red channels are the primary channels for fluorescein sodium salt and rhodamine B, respectively. The captured images of the dyes, especially rhodamine B, are partially affected by the excitation lights from the power light-emitting diodes. During the experiments, the environmental conditions that the samples are exposed to, are monitored and recorded from the sensor. The designed compact and lightweight optical reader with the dimensions of 13×14×24cm3 (W×H×L) raises the usability of devices across various settings, from clinical laboratories to field applications. In the future, the optimization of the imaging settings and sample properties, re-imaging of the new samples with unused membranes, and validation of the results will be carried out to improve the reliability and repeatability of the optical reader.