SERS-based lateral flow assay for the rapid and ultra-sensitive diagnosis of bacterial infection Waleed Hassanain 1 , Julia Spoors 2 , Christopher L. Johnson 2 ,Karen Faulds 1 , Neil Keegan 2 and Duncan Graham 1 1 Department of Pure and Applied Chemistry, Technology and Innovation Centre, UK. 2 Diagnostic and Therapeutic Technologies, Translational and Clinical Research Institute, UK. Clostridium difficile ( C.diff ) bacterial infection is one of the most transmissible diseases between hospitalised patients that can lead to high morbidity and mortality rates. Despite the availability of therapies, treatment failure and recurrence are common. Accurate diagnosis can help in choosing of the most effective treatment, thus reducing its spread. Currently, there are some commercially available lateral flow tests for C.diff detection that test glutamate dehydrogenase enzyme and toxins A/B simultaneously, as C.diff biomarkers. These tests enable the rapid clinical diagnosis of the infection. However, they still suffer from limitations, such as: selectivity, sensitivity and quantification capacity of the results. In 2018, our group reported the surface layer protein A (SlpA) biomarker as a new and unique species-specific biomarker for C.diff infection (CDI) which presents in all C.diff strains sequenced to-date. We have also reported the successful synthesis of SlpA antibodies, that displayed negligible cross-reactivity to other closely related species. Building on this success, we present a novel proof-of-concept duplex surface enhanced Raman scattering-based lateral flow assay (SERS-based LFA) for CDI diagnosis via the ultra-sensitive quantitative detection of its biomarkers, SlpA and toxin B, down to 0.01 pg/μL within 20 minutes. The simultaneous novel detection of toxin B and SlpA instead of glutamate dehydrogenase can indicate the presence of CDI, as well as its toxigenicity without any cross-reactivity from other species, which is a potential risk with glutamate dehydrogenase assays. Therefore, this novel SERS-based LFA platform can overcome the limitations of the conventional lateral flow tests for CDI. The integration of a portable Raman spectrometer with this duplex lateral flow test, paves the way to move the C.diff diagnostic test from centralised laboratories to points of care application. Accordingly, we believe this novel duplex test can be used in the future as an alternative diagnostic test for CDI after large scale population wide-testing study.
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