SAW immunosensors for HBsAb detection

This paper presents the implementation of a surface acoustic wave (SAW) immunosensor system for real sample detection of antibody to hepatitis B surface antigen (HBsAg). The SAW sensor device was based on the mass detection using LOVE wave with the central frequency of 200 MHz. The thickness of the SiO₂ guiding layer was optimized both theoretically and experimentally to obtain the maximum sensitivity. A detection circuitry using a differential scheme measured the frequency difference by subtracting the resonant frequency of the sample SAW from that of the reference SAW. The sensitivity of the sensor was 0.74 Hz/(pg/mulscr) and the detection limit was 10 pg/mulscr. Our SAW sensor successfully detected natural anti-HBsAg antidbody (HBsAb) of the real whole blood samples, which opens up a possibility of label-free protein detection without any pretreatment procedures.