A Surface Enhanced Raman Scattering Lateral Flow Immunoassay Approach for the Detection of Bacteria in Point of Care Settings

In fifteen words or less, explain the significance of this contribution (Novel Aspect).: Use of different plasmonic substrates for lateral flow applications.

Abstract Text:

Cameron Gale^a, Hayleigh May^a, Neil Shand^b, Duncan Graham^a, Karen Faulds^a 

^aDepartment of Pure and Applied Chemistry, Technology and Innovation Centre, University of Strathclyde, 99 George Street, Glasgow, G1 1RD.

^bDSTL, Porton Down, Salisbury, Wiltshire, SP4 0JQ.

Recent research efforts have sought to harness the simplicity, ease of use and portability of lateral flow immunoassays (LFIAs) for the detection of an array of targets from biomolecules such as biomarkers for disease to pathogens such as bacteria and viruses. The paper-based detection platform provides a simple colorimetric response, however the sensitivity is limited to what the eye can see, the optical limit of detection (LOD). Surface-enhanced Raman scattering (SERS) is a powerful spectroscopic technique that can be incorporated into LFIAs via the functionalisation of plasmonic nanoparticles with Raman reporters and target-specific targeting species such as aptamers, peptides or antibodies to yield SERS tags. Spectroscopic analysis allows for analyte quantification by correlating its concentration to the SERS intensity from a gold nanoparticle functionalised with a Raman reporter and subsequently provides sensitive detection beyond the optical LOD. With technological advances, hand-held Raman spectrometers provide the possibility of moving spectroscopic analysis away from the laboratory and into point of care (POC) settings, allowing for rapid, onsite testing. A SERS-LFIA has been constructed and optimised for the detection of one of the leading causes of nosocomial infections, the bacterium Staphylococcus aureus, with an optical LOD of 10⁴ CFU mL^-1 and through spectroscopic analysis, a SERS LOD of 57 CFU mL^-1. SERS substrates employed in these assays vary in composition, size and shape with efforts made to synthesise and incorporate bright substrates into SERS tags with the aim of improving assay sensitivity. Historically, such substrates have suffered from reproducibility issues and sometimes rely on the controlled formation of localised areas of intense field enhancements with intrinsic hot spots formed in core-shell structures and at interparticle junctions which have been explored for applications towards the development of sensitive SERS-LFIAs.