Point of use SERS-based lateral flow test for pathogenic infections

Lateral flow immunoassays are paper-based tests that can be used to detect different pathogenic biomarkers at the point-of-use. Conventionally, detection antibodies labelled with gold nanoparticles form sandwich immunoassays between the target antigen and capture antibody on the test line/spot when the biomarker is present in a sample. They provide rapid, visual and yes/no answers based on the appearance of the gold nanoparticles on the strip. However, lateral flow tests suffer from poor sensitivity which can lead to false negative results when the biomarker concentration is below the visual threshold of the test, especially at early infection stages. They also can't accurately quantify the biomarker concentration which is important in monitoring the progression of an infection or the effectiveness of a treatment. Accordingly, lateral flow test should be combined with a read-out system that is convenient for points of use and could enable the accurate, sensitive and rapid quantification of the test results. In this work, we discuss the integration of surface enhanced Raman scattering technique with the lateral flow test in one platform to improve the test sensitivity and quantification capability, while maintaining the user-friendly and point-of-use features the lateral flow test provides. We have applied this approach for the detection of Clostridioides difficile and SARS-COV-2, as demonstrators for pathogenic infections, using new recognition elements in the test as a proof-of-concept.