Development of a surface enhanced Raman scattering lateral flow immunoassay with prolonged reproducibility and stability over time

Abstract

Lateral flow immunoassays (LFIAs) coupled to surface enhanced Raman scattering (SERS) measurements can produce quantitative outputs with excellent sensitivity. Despite this, they have not been adopted into point-of-care (POC) scenarios, due to the perceived lack of reproducibility and stability in SERS measurements over time. To address this, the performance, stability and reproducibility of a newly developed SERS-LFIA designed for the detection of liver injury has been assessed to investigate if the tests could yield the same results six-months after preparation. The SERS-LFIA incorporated silica coated Raman active gold nanoparticles to increase the stability when used with human serum samples and the SERS signals of the test and control lines were analysed using a handheld Raman reader to mimic its use at the POC. The relative standard deviations of key metrics, including reproducibility and variation in signal were assessed over the course of a 6-month stability study using a range of methods that aimed to standardise the output. Test line intensity, test/control ratio and slope linear regression outputs were all used to assess the SERS-LFIA results with the best reproducibility being achieved when normalising the test via the slope linear regression method. After 5 months the output only decreased by 11 % for a sample spiked with a clinically relevant concentration of liver injury biomarker, demonstrating the test was still performing as intended. Overall, we have shown that SERS-LFIA can produce similar outputs after 5 months of storage at room temperature demonstrating their stability and robustness.