Photoacoustic lateral flow assay for point-of-care testing of thrombin in human whole blood without background interference

Nanomaterial-based lateral flow assay (LFA) has broad prospect in point-of-care testing (POCT) owning the advantages of simplicity and portability. However, the detection sensitivity and accuracy are often affected by the interferences of complex sample matrices. Herein, we describe a gold nanorods (Au NRs)-labeled LFA for background-free detection of thrombin (TB) in human whole blood. The near-infrared (NIR) absorption of Au NRs coupled with photoacoustic (PA) readout eliminate background signal, empowering a high-sensitivity detection without complicated procedures. With the increasement of TB concentrations, the PA signal changes of detection zones on LFA test strip driven by a modulated 808 nm laser beam could be conveniently collected through the handheld oscilloscope. Thanks to the combination of economic LFA strip and portable PA device, it not only greatly simplifies the operation steps but also dramatically reduces the size and cost of the instrument to achieve POCT of TB. There is a favorable linear relationship between the PA signal and TB concentration in whole blood matrix ranging from 0.5 to 18 U/mL (R 2  = 0.9929), and a detection limit of 0.2 U/mL is obtained. This NIR absorption PA probe labeling approach has direct implications for ultrasensitive and background-free POCT of other blood biomarkers in resource-limited clinical settings.