Rapid particle concentration for immunofluorescence enhancement by a surface acoustic wave microchip

At the initial stages of pathogenesis, biomarkers are generated in an insignificant concentration. Hence, the rapid screening for these low-abundance indicators is immensely critical for early disease diagnosis. Enhancement of the immunofluorescence signal emitted from little concentrated biomarkers can aid their detection among other molecules in complex body fluids. Here, we developed an advanced bead-based immunosensing technique combining surface acoustic wave (SAW) for a rapid and sensitive on-chip detection of the diabetic retinopathy biomarker lipocalin 1. As a result, the implementation of the SAW microchip-enabled particle mixing, separation, and concentration in the droplet delivered a 3.6-fold enhanced immunofluorescence signal within 5 s. The integration of fluorescent signal enhancement by SAW, along with the high sensitivity of the immunoassay, featured a limit of detection of 40 pg/mL in 3 min with a sample volume as low as 4 µL. A simple addition of cover glass on the SAW microchip allowed the immuno-sensing process to be completed without any direct sample contact with the interdigital transducer, minimizing the risk of cross-contamination and damage to the chip due to frequent washing. This study demonstrated the potential of the developed SAW device and insights into its utility as an early diagnostic tool.