Graphene oxide coatings enhance fluorescence signals in a lateral flow immunoassay for the detection of UCH-L1, a marker for trauma brain injury

We present a lateral flow immunoassay (LFA) for the quantitative, fluorescence-based detection of the trauma brain injury (TBI) biomarker ubiquitin carboxyl-terminal hydrolase-L1 (UCH-L1) that features a layer of graphene oxide (GO) particles over the test zone of nitrocellulose (NC) strips. The introduction of 80 ng of GO at test lines increased fluorescence signals 2-3-fold. This was attributed to an increase in the immobilization of capture antibodies in the top layer of NC, which increased the density of recognition complexes at the surface and hence the signals reaching the reader used. A linear concentration-response relationship was observed in the 0-200 pg/ mL UCH-L1 range with an inter assay CoV of 2.65 %. The LOD and LOQ values of 11.1 pg/mL and 33.5 pg/mL were compatible with threshold levels of UCH-L1. Finally, mock plasma samples with UCH-L1 levels characteristic of TBI patients with negative (60 pg/mL) and positive (130 pg/mL) CT scans were successfully analyzed. Storage stability testing further showed that GO did not affect the biological activity of the capture antibody. In summary, we demonstrate that the use of GO particles in the top layers of the test zone of NC strips improves signal intensity, which could potentially enhance the accuracy and efficiency of LFA-based diagnosis.