Lateral flow assay with near-infrared dye for multiplex detection.
BACKGROUND
Lateral flow assays (LFAs) are popular point-of-care diagnostic tools because they are rapid and easy to use. Nevertheless, they often lack analytical sensitivity and quantitative output and may be difficult to multiplex, limiting their usefulness in biomarker measurement. As a proof-of-concept study, we detail the design of a quantitative, multiplex LFA with readily available near-infrared (NIR) detection to improve analytical sensitivity.


METHODS
NIR dye was conjugated to selected antibodies and incorporated into LFAs. We used singleplex, optimized NIR-LFAs to measure interleukin (IL)-6 from 0 to 200 pg/mL and developed duplex assays to simultaneously measure IL-6 from 0 to 100 pg/mL (0 to 4.5 pmol/L) and C-reactive protein (CRP) from 50 to 2500 ng/mL (0.4 to 20 nmol/L) on a single test strip. Assays were tested on 60 different spiked samples and compared to ELISA results.


RESULTS
NIR-LFAs detected IL-6 in a 10% plasma matrix with a limit of detection of 4 pg/mL (182 fmol/L) and a CV <7%. Duplex NIR-LFAs quantitatively measured IL-6 and CRP concentrations simultaneously. Values strongly correlated to ELISA measurements, with R(2) values of 0.9825 and 0.9711 for IL-6 and CRP, respectively.


CONCLUSIONS
NIR-LFAs exhibit quantitative measurement at pg/mL concentrations owing to a high signal-to-background ratio and robust detection antibody clearance through the test strip. Moreover, NIR-LFAs are able to detect molecules present at vastly different concentrations in multiplex format and compare favorably to ELISAs. LFAs with direct NIR detection may be a valuable tool for biomarker evaluation in the point-of-care setting.
SRI International, Menlo Park, CA, USA. christina.swanson@sri.com
Christina
C
Swanson
Annalisa
A
D'Andrea
D002097:C-Reactive Protein / Q000378:metabolism; D004396:Coloring Agents; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D015850:Interleukin-6 / Q000097:blood; D057230:Limit of Detection; D019265:Spectroscopy, Near-Infrared
D004396:Coloring Agents; D015850:Interleukin-6; D002097:C-Reactive Protein